Post on 03-Apr-2018
transcript
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Expedited Permit Process
for PV Systems
with Detailed Explanationto Help Guide Thru the Process
Preparedfor:
NewMexicoStateUniversity
SolarAmericaBoardforCodesandStandards
(availableatwww.SolarABCS.org)
Preparedby:
BrooksEngineering
873KellsCircle
Vacaville,CA95688
www.brooksolar.com
Version4
May2009
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Dedication:
Thisdocumentisdedicatedtotwokeyindividualsthatrepresenttheverybestofthosewho
haveworkedonthecodesandstandardsprocessesastheyrelatetoPVsystems.Thesetwo
amazingpeople,TimOwens,ofSantaClaraBuildingDepartment,andChuckWhitaker,ofBEW
Engineering,passed
away
in
the
months
prior
to
the
release
of
this
standardized
permitting
process.
TimOwens:
TimOwenspassedawayinDecemberof2008attheageof??inthemidstofadistinguished
careerintheelectricaltradesandcodeenforcement.WhileworkingasChiefElectrical
InspectorfortheCityofSanDiegoin1999,Timwasthefirstjurisdictionalofficertoput
togetherasimplifiedpermittingprocessforPVsystems.Hisdesiretoseesuchaprocess
becomecommonplaceiswhathasdriventhisauthortoworkonimprovingpermittingand
approvalprocessesforPVsystemsforthepastdecade.Thesolarcommunity,lostatruefriend
andpartnerwhowasdedicatedtothesuccessofsolarphotovoltaicsystemsinCaliforniaand
therestoftheU.S.
ChuckWhitaker:
ChuckWhitakerpassedawayinearlyMayof2009attheageof50inthemidstofa
distinguishedcareersupportingthedevelopmentandimplementationofmostofthecodesand
standardsthegovernandsupportPVsystemsbothnationallyandinternationally.Hispassing
coincidedwiththeinitialreleaseofthisstandardizedpermittingprocess.Theauthorhadthe
privilegeofknowingChuckfortwodecadesandworkingcloselywithhimforover8yearsashis
employeeand
colleague.
It
is
difficult
to
overstate
Chucks
contribution
to
the
PV
industry
since
hisinfluenceisfoundinnearlyeverycodeandstandardthathasbeendevelopedforPV
equipmentandsystemsoverthepast25years.Itisonlyfittingthatthisdocument,which
includeshisinfluence,bededicatedtohismemory.AhugeholeisleftinthePVindustrywith
Chuckspassing,anditisthehopeofmanyofusinthecodesandstandardsarenatobeableto
carryonhistirelessworkwithasemblanceoftheskill,whit,andhumorthatwasthehallmark
ofthisamazingindividual.
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INTRODUCTION:............................................................................................................................. 3
ExpeditedPermitProcessforSmallScalePVSystems................................................................. 4
ExpeditedPermitGuidelinesforSmallScalePVSystems............................................................ 8
Section1. RequiredInformationforPermit:........................................................................... 8
Section2.
Step
1:
Structural
Review
of
PV
Array
Mounting
System
.......................................
8
Section3. Step2:ElectricalReviewofPVSystem(CalculationsforElectricalDiagram)......10
Section4. InverterInformation............................................................................................. 11
Section5. ModuleInformation.............................................................................................. 12
Section6. Arrayinformation................................................................................................. 13
a) NUMBEROFMODULESINSERIES................................................................................. 13
b) NUMBEROFPARALLELCIRCUITS.................................................................................. 13
c) LOWESTEXPECTEDAMBIENTTEMP............................................................................. 13
d) HIGHESTCONTINUOUSTEMP(ambient)...................................................................... 13
Section7. SIGNS..................................................................................................................... 14
a) PVPOWERSOURCE....................................................................................................... 14
b) WARNINGSIGNREQUIREDBYNEC690.17.................................................................. 15
c) PointofConnectionSign[NEC690.54]......................................................................... 15
Section8. WiringandOvercurrentProtection...................................................................... 16
a) DCWiringSystems:....................................................................................................... 16
b) ACWiringSystems........................................................................................................ 18
Section9. ACPointofConnection......................................................................................... 18
Section10. Grounding......................................................................................................... 19
a) SystemGrounding......................................................................................................... 19
b) EquipmentGrounding................................................................................................... 19
c) SizingofGroundingConductors................................................................................... 20
APPENDIX.....................................................................................................................................
21
APPENDIXA:EXAMPLESUBMITTAL............................................................................................ 22
APPENDIXB:STRUCTURAL.......................................................................................................... 26
STRUCTUREWORKSHEETWKS1................................................................................................... 26
B.2 SPANTABLES..................................................................................................................... 27
SpanTableR802.5.1(1),........................................................................................................ 27
SpanTableR802.5.1(2),........................................................................................................ 28
APPENDIXC:SPECIALELECTRICALTOPICS.................................................................................. 29
ModuleFrameGrounding:........................................................................................................... 29
ACConnectiontoBuildingElectricalSystems.............................................................................. 30
AC
Connection
to
Load
Side
of
Main
Service
Panel
......................................................................
30
ACConnectiontoSubpanel:......................................................................................................... 31
ACSupplySideConnection:.......................................................................................................... 32
SourceCircuitOvercurrentProtection:........................................................................................ 33
DisconnectingMeans:................................................................................................................... 34
Provisionsforthephotovoltaicpowersourcedisconnectingmeans:.........................................35
APPENDIXD:COSTSOFPERMITS................................................................................................ 36
APPENDIXE:TEMPERATURETABLES........................................................................................... 37
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INTRODUCTION:
Theonepageexpeditedpermitprocess,andtheaccompanyingdocumentexplainingeachstep,
providesameanstodifferentiatesystemsthatcanbepermittedquicklyandeasilyduetotheir
similaritywiththemajorityofsmallscalePVsystems.Asmostsystemshaveunique
characteristics,they
may
be
handled
with
small
additions
to
this
expedited
process
or
may
requiremuchmoreinformation,dependingontheuniquenessoftheinstallation.
ThediagramsshownintheExpeditedPermitProcessareavailableonlineatwww.solarabcs.org
inaninteractivePDFformatsothatthediagramscanbefilledoutelectronicallyandsubmitted
eitherinprintedformorviaemailtothelocaljurisdiction.Anelectronicformatisusedsothat
thesuppliedinformationisstandardizedandlegibleforthelocaljurisdiction.Additional
drawingswillbeaddedtothewebsiteastheybecomeavailable.
Theexpeditedprocessdoesprovideforflexibilityinthestructuralreviewincludingspantables
and
additional
information
found
in
Appendix
B
of
this
explanatory
document.
PV
systems
with
batterybackupmaybeabletouseaportionofthisinformationtoassistthepermitting
process,butarrayconfigurationsandthebatterysystemrequireamoredetailedelectrical
drawingthanthisprocessprovides.
TheappendixtothisexplanatorydocumenthasanexamplesubmittalinAppendixAalsohasa
varietyofspecialelectricaltopicsinAppendixC.ItalsoincludestemperaturetablesinAppendix
DthatareusedinapplyingtheNationalElectricalCodestemperaturedependentcriteria.This
documentisintendedtobeusablethroughouttheUnitedStatesandcanprovidestandard
installationdesigndocumentationformostlocationswithintheU.S.andotherregionsthatuse
theNationalElectricalCode.
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ExpeditedPermitProcessforSmallScalePVSystemsTheinformationinthisguidelineisintendedtohelplocaljurisdictionsandcontractorsidentifywhenPVsystem
installationsaresimple,needingonlyabasicreview,andwhenaninstallationismorecomplex.Itislikelythat
50%75%ofallresidentialsystemswillcomplywiththesesimplecriteria.Forprojectsthatfailtomeetthe
simplecriteria,aresolutionstepsmaybesuggestedtoprovideapathtopermitapproval.
RequiredInformation
for
Permit:
1. Siteplanshowinglocationofmajorcomponentsontheproperty.Thisdrawingneednotbeexactlytoscale,butitshouldrepresentrelativelocationofcomponentsatsite(seesuppliedexamplesiteplan).
PVarraysondwellingswitha3perimeterspaceatridgeandsidesmaynotneedseparatefireservice
review.
2. ElectricaldiagramshowingPVarrayconfiguration,wiringsystem,overcurrentprotection,inverter,disconnects,requiredsigns,andacconnectiontobuilding(seesuppliedstandardelectricaldiagram).
3. Specificationsheetsandinstallationmanuals(ifavailable)forallmanufacturedcomponentsincluding,butnotlimitedto,PVmodules,inverter(s),combinerbox,disconnects,andmountingsystem.
Step1:StructuralReviewofPVArrayMountingSystemIsthearraytobemountedonadefined,permittedroofstructure? Yes NoIfNoduetononcompliantrooforagroundmount,submitcompletedworksheetforthestructureWKS1.
RoofInformation:
1. Istheroofingtypelightweight(Yes=composition,lightweightmasonry,metal,etc)_____________If No,submitcompletedworksheetforroofstructureWKS1(No=heavymasonry,slate,etc).
2. Doestheroofhaveasingleroofcovering? Yes NoIfNo,submitcompletedworksheetforroofstructureWKS1.
3. Providemethodandtypeofweatherproofingroofpenetrations(e.g.flashing,caulk).____________MountingSystemInformation:
1. ThemountingstructureisanengineeredproductdesignedtomountPVmodules? Yes NoIfNo,providedetailsofstructuralattachmentcertifiedbyadesignprofessional.
2. Formanufacturedmountingsystems,filloutinformationonthemountingsystembelow:a. MountingSystemManufacturer ___________ProductNameandModel#_____________b. TotalWeightofPVModulesandRails___________lbsc. TotalNumberofAttachmentPoints____________d. WeightperAttachmentPoint(bc)_________________lbs(ifgreaterthan40lbs,seeWKS1)e. MaximumSpacingBetweenAttachmentPointsonaRail______________inches(seeproduct
manualformaximumspacingallowedbasedonmaximumdesignwindspeed)
f. TotalSurfaceAreaofPVModules(squarefeet)_________________ft2g. DistributedWeightofPVModuleonRoof(bf)_______________lbs/ft2
IfdistributedweightofthePVsystemisgreaterthan5lbs/ft2,seeWKS1.
Step2:ElectricalReviewofPVSystem(CalculationsforElectricalDiagram)InorderforaPVsystemtobeconsideredforanexpeditedpermitprocess,thefollowingmustapply:
1. PVmodules,utilityinteractiveinverters,andcombinerboxesareidentifiedforuseinPVsystems.2. ThePVarrayiscomposedof4seriesstringsorlessperinverter,and15kWSTCorless.3. Thetotalinvertercapacityhasacontinuouspoweroutput13,440Wattsorless4. Theacinterconnectionpointisontheloadsideofservicedisconnectingmeans(690.64(B)).5. Theelectricaldiagram(E1.1)canbeusedtoaccuratelyrepresentthePVsystem.
Filloutthestandardelectricaldiagramcompletely.Aguidetotheelectricaldiagramisprovidedtohelpthe
applicantunderstandeachblanktofillin.Iftheelectricalsystemismorecomplexthanthestandardelectrical
diagramcaneffectivelycommunicate,provideanalternativediagramwithappropriatedetail.
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ContractorName,
AddressandPhone:
_____
____________
_____
____________
_____
____________
_____
____________
S
ampleSitePlan
forSmall-Scale,Single-PhasePVSystems
SiteName:___
________________________
SiteAddress:_
________________________
SystemACSize:______________________
SIZE
FSCMNO
DWGNO
REV
S1.1
SCALE
NTS
Date:
SHEET
DrawnBy:
CheckedBy:
INVERTERWITH
SUPPLIED
COMBINERAND
DCDISCONNECT
3'-0"
3'-0"
3'-0"
J
EXISTINGALL-IN-ONE
SERVICEEQUIPMENT
W
ITH40-AMPPV
B
REAKERASAC
DISCONNECT
24SOLARWORLDSW175
MODULESIN2SERIESSTRINGS
OF12MODULESEACHON
EXISTINGROOFSTRUCTURE
ROOFTOPJ-BOXTO
TRANSITIONEXPOSED
USE-2TOTHWN-2
CONDUCTORSIN"EMT
10'-8"
11'-3"
12'-7"
EXISTINGFENCE
24SOLARWORLDSW175
MODULESIN2SERIESSTRINGS
OF12MODULESEACHON
EXISTINGSHADESTRUCTURE
J
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ContractorName,
Address
andPhone:
_______
__________
_______
__________
_______
__________
_______
__________
One-LineStan
dardElectricalDiagramfor
Small-Scale,Single-PhasePVSystems
SiteName:_
________________________
SiteAddress
:_______________________
SystemACS
ize:____________________
SIZE
FSCMNO
DWGNO
REV
E1.1
SCALE
NTS
Date:
SHEET
DrawnBy:
CheckedBy:
DESCRIPTIONORCO
NDUCTORTYPE
USE-2
orPVWIRE
BARECOPPEREQ.G
RD.COND.(EGC)
THWN-2
orXHHW
-2
orRHW-2
THWN-2
orXHHW
-2
orRHW-2
INSULATEDEGC
DCGROUNDINGELE
CTRODECOND.
THWN-2
orXHHW
-2
orRHW-2
INSULATEDEGC
TAG
12345
CONDUITANDCONDUCTORSCHEDULE
COND.
GAUGE
NUMBEROF
CONDUCTORS
CONDUIT
TYPE
N/A
N/A
CONDUIT
SIZE
N/A
N/A
DESCRIPTION
SOLARPVMODULE
PVARRAY
J-BOX(IFUSED)
COMBINER(IFUSED
)
DCDISCONNECT
DC/ACINVERTER
GENMETER(IFUSE
D)
ACDISCONNECT(IF
USED)
SERVICEPANEL
TAG
123456789
PARTNUMBER
NOTES
_____VAC,_
_____AMAIN,______ABUS,______AINVE
RTEROCPD
(SEENOTE5FORINVERTEROCPDs,ALSOSEEGUIDESECTION9)
FORUNUSEDSERIESSTRINGS
PUT"N/AinBLANKABO
VE
SEEGUIDEAPPENDIXB
FOR
INFORMATIONONMODUL
EAND
ARRAYGROUNDING
________MODULES
IN
SERIESSOURCE-CIRC
UIT
________MODULES
IN
SERIESSOURCE-CIRC
UIT
________MODULESIN
SERIESSOURCE-CIRC
UIT
________MODULESIN
SERIESSOURCE-CIRC
UIT
DC
DISCO
INVERTER
A
C
DIS
CO
AC
DC
M
BUILDING
GROUNDING
ELECTRODE
G
Disrega
rdif
providedwith
inverter
COMBINER
MUTILITY
SERVICE
MAINSERVICE
PANEL
MAIN
OCPD
INVERTER
OCPD
J-BOX
1
1
3
4
5
6
7
9
2
3
4
5
8
2
EQUIPMENTSCH
EDULE
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ExpeditedPermitGuidelinesforSmallScalePVSystems
Section1. RequiredInformationforPermit:
1. Siteplanshowinglocationofmajorcomponentsontheproperty.Thisdrawingneednotbe
toscale,butitshouldrepresentrelativelocationofcomponentsatsite.(seesupplied
examplesite
plan).
Explanation:Thisisasimplediagramtoshowwheretheequipmentislocatedontheproperty.
Thiscanbeazoneclearanceplotplanwiththeequipmentclearlyshownandidentifiedontheplan.If
PVarrayisgroundmounted,clearlyshowthatsystemwillbemountedwithinallowablezoned
setbacks. Seesiteplanexampledrawinginpermitprocessforreference.
2. ElectricaldiagramshowingPVarrayconfiguration,wiringsystem,overcurrentprotection,
inverter,disconnects,requiredsigns,andacconnectiontobuilding(seesuppliedstandard
electricaldiagram).
Explanation:Thecornerstoneofasimplifiedpermitprocessistheabilitytoexpresstheelectrical
designwithagenericelectricaldiagram.Thisdiagramhasbeendesignedtoaccuratelyrepresentthe
majorityofsinglephase,residentialsized,PVsystems.PVsystemsmayvarydramaticallyinPVarray
layoutandinverterselection.However,themajorityofsmallscale,residentialsizedPVsystemscanbeaccuratelyrepresentedbythisdiagram.Thisdiagrammustbefullycompletedfilledoutinorder
forthepermitpackagetobesubmitted.
3. Specificationsheetsandinstallationmanuals(ifavailable)forallmanufacturedcomponents
including,butnotlimitedto,PVmodules,inverter(s),combinerbox,disconnects,and
mountingsystem.
Explanation:Ataminimum,specificationsheetsmustbeprovidedforallmajorcomponents.In
additiontothecomponentslisted,otherimportantcomponentsmaybespecialtyfuses,circuit
breakers,oranyotheruniqueproductthatmayneedtobereviewedbythelocaljurisdiction.
Installationmanualsarealsolistedinthisitem.Thisisreferringtothebriefversionsofmanualsthat
arereviewedbythelistingagencycertifyingtheproduct.Somedetailedinstallationmanualscanbe
severaldozensorhundredsofpages.Ifthelocaljurisdictionfeelsitisnecessarytoreviewtheselargedocuments,agoodalternativewouldbeforthedocumentstobesuppliedelectronically,ratherthan
inprint.ItisworthconsiderationthatPDFsofthesecomprehensivemanualsbekeptelectronicallyby
thelocaljurisdiction.
Section2. Step1:StructuralReviewofPVArrayMountingSystem
Isthearraytobemountedonadefined,permittedroofstructure? Yes No(structure
meetsmoderncodes)
IfNo,submitcompletedworksheetforroofstructureWKS1.Explanation:Thereferencetoadefined,permittedroofstructurereferstostructuresthathavea
clearinspectionhistorysothatverificationofstructuralelementsisunnecessary.Ifstructural
modificationshavebeenmadeduetoremodeling,thosechangesshouldbedocumentedthroughthe
permitandreviewprocess.Italsorecognizesthefactthatthecodeenforcementofroofstructural
elementshasbeenmuchmoreconsistentacrosstheUnitedStatesinthelast35years.However,there
maybemanylocaljurisdictionswhohavebeencarefullyreviewingroofstructuresforamuchlonger
periodoftime.Thelocaljurisdictionshouldconsiderextendingthislimitbasedontheperiodthatroofs
havebeenconsistentlyinspected.Inareaswherejurisdictionalreviewshavenotextended35yearsinto
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thepast,thejurisdictionmayneedtogettheinformationfromWKS1tobesurewhetherornotthe
proposedPVsystemisbeinginstalledonatypicalroofstructureornot.
RoofInformation:
1. Istheroofingtypelightweight(Yes=composition,lightweightmasonry,metal,wood
shake,etc)_____________
If No,submitcompletedworksheetforroofstructureWKS1(No=heavymasonry,slate,
etc).
Explanation:Thereisaneedtodistinguishifaroofhasalightweightproduct.Heavier
roofingmaterials(e.g.slate,heavymasonry,maynothavetheassumeddeadloadingandlive
loadingcapacitiesthatarefoundwithlighterweightroofingmaterials.Thesearemuchless
commonrooftypesandoftenjustifyafurtherreviewtoclarifythattheroofstructureiseitherin
complianceorneedsenhancement.
2. Doestheroofhaveasingleroofcovering? Yes No
IfNo,submitcompletedworksheetforroofstructureWKS1.Explanation:Multiplecompositionrooflayersaretakingaportionoralloftheassumed
additionalweightallowancefoundinthe5lbs/ft2allowanceattheendofthemountingsystem
section.
3. Providemethodandtypeofweatherproofingroofpenetrations(e.g.flashing,
caulk).____________
Explanation:Theweatherproofingmethodneedstobespecificallyidentifiedsothatplan
checkersandfieldinspectorsarenotifiedaheadoftimeofthemethodbeingused.Some
jurisdictionsmayconstrainweatherproofingmethodsandmaterials.
MountingSystem
Information:
1. ThemountingstructureisanengineeredproductdesignedtomountPVmodules?Yes No
IfNo,providedetailsofstructuralattachmentcertifiedbyadesignprofessional.Explanation:Nonengineeredrackingsystemshaveundefinedcapabilities.PVsystems
shouldonlybemountedusingsystemsthatareengineeredanddesignedforthatpurpose.
However,ifaninstallerchoosestouseahybridmountingsystem,thenthesystemcannotbe
consideredforexpeditedpermitting.
2. Formanufacturedmountingsystems,filloutinformationonthemountingsystem
below:
a. MountingSystem
Manufacturer
___________Product
Name
and
Model#_____________(selfexplanatory)
b. TotalWeightofPVModulesandRails___________lbs(includetotalweightofall
hardwareusedalongwithmoduleweight)
c. TotalNumberofAttachmentPoints____________(selfexplanatory)
d. WeightperAttachmentPoint(bc)_________________lbs(ifgreaterthan40
lbs,seeWKS1)
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Explanation:40lbshasbeenusedbymanyjurisdictionsasareasonablelevelbelow
whichpointloadingofroofjoistsandtrussescanbeignored.Moststandardmounting
systemshavepointloadingsof2535lbsperattachment.
e. MaximumSpacingBetweenAttachmentPointsonaRail______________inches
(seeproductmanualformaximumspacingallowedbasedonwindloading)
Explanation:
Depending
on
the
wind
loading
requirements
of
a
particular
jurisdiction,
thespacingorattachmentsmaybedictatedbythemanufacturersdirections.Forinstance,a
particularmanufacturermayallowa72attachmentspacingfora90MPHwindspeed
design,butthespacingreducestoamaximumof48whenthedesignwindspeedexceeds
100MPH.
f. TotalSurfaceAreaofPVModules(squarefeet)_________________ft2Explanation:Takethesurfaceareaofasinglemodule,andmultiplyitbythetotal
numberofmodulesintheroofmountedsystem.
g. DistributedWeightofPVModuleonRoof(bf)_______________lbs/ft2
IfdistributedweightofthePVsystemisgreaterthan5lbs/ft2,seeWKS1.
Explanation:The5lbs/ft2limitisbasedontwothings:1)theroofistypicalofstandard
codecompliantroofstructuressothatthestructureeitherhastheproperspansandspacing,
orproperuseofengineeredtrusses(firstitemunderStep1:StructuralReview);and,2)
thereisasinglelayerofroofingsothatthenormalweightallowanceforadditionalroof
layersisunusedandavailablefortheweightofthePVsystem.Forapplicationson
lightweightmasonryroofingmaterialsandotherlightweightroofingproducts(e.g.metal,
shake,etc),thesematerialsdonotacceptmultiplelayersandthereforethe5lbs/ft2
allowanceisusedtoidentifythemaximumallowableadditionalweightforroofsthatare
exchangingtheallowableliveloadforadeadloadthatpreventsliveloadsuchaspeople
walkingontheroof.
Section3. Step2:ElectricalReviewofPVSystem(CalculationsforElectricalDiagram)
InorderforaPVsystemtobeconsideredforanexpeditedpermitprocess,thefollowingmustapply:
1. PVmodules,utilityinteractiveinverters,andcombinerboxesareidentifiedforuseinPV
systems.
Explanation:PVutilityinteractiveinvertersmustbespecificallylistedandlabeledforthis
application(asrequiredbyNEC690.60and690.4)(Numbersinbracketsrefertosectionsinthe2008
NECthroughoutthisdocument.).Withoutthisspecificidentificationprocessanunacceptable
amountofreviewwouldbenecessarytoapproveaninverter.InvertersthatpassUL1741andare
listedasutilityinteractivehavemettherequirement.Over500inverterscurrentlymeetthis
requirement.Aninclusivelistoftheseinvertersisavailableonlineat
http://gosolarcalifornia.com/equipment/inverter.php.
PVmodulesmustalsobelistedandidentifiedforuseinPVsystems(asrequiredbyNEC690.4).PV
modulesthatpassUL1703andhavea600Voltmaximumvoltagemeettherequirement.Alistof
theseinvertersisavailableonlineathttp://gosolarcalifornia.com/equipment/pvmodule.php.Source
combinersmustbelistedandlabeledtomeetthedcvoltagerequirementsofthePVsystemorbe
specificallytestedforPVsystemsandclearlystatetheallowablemaximumcurrentandvoltage(as
requiredbyNEC690.4).
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2. ThePVarrayiscomposedof4seriesstringsorless,and15kWSTCorless.Explanation:Thepurposeofthisrequirementistolimitthenumberofoptionsofwhatcan
complyasasimplesystemsothatasingleelectricaldiagramcanbeusedtodescribealarge
portionofthesystemsbeinginstalled.Theelectricaldiagramcanhandleupto4stringsinparallel.
Themaximumof15kWreferstothearraysizebasedonthetotalinstallednameplatecapacity.The
limitissettostaygenerallywithinelectricalinterconnectionsthatwouldbeconsideredsimpleand
possiblyabletomeetthe120%ofbusbarratingallowanceinNEC690.64(B)inaresidence
(Minimumbreakerfora13.44kWacPVsystemis70amps).
3. TheInverterhasacontinuouspoweroutput13,440WattsorlessExplanation:A70ampbreakerisimportantsincea225ampbusbarina200amppanelwill
allowa70ampPVbreaker.Sincethisdoeshappenfromtimetotime,andaninstallercanchooseto
installsuchapanelboard,itisconsideredthelargestsimplePVsystemforpurposesofthis
guideline.Atableofbreaker/panelboardcombinationsisinSection9ofthisGuideline.
4. Theacinterconnectionpointisontheloadsideofservicedisconnectingmeans(NEC
690.64(B)).
Explanation:Loadsideinterconnectionsarebyfarthemostcommon,particularlyinresidential
applications.AnylinesideconnectioniscoveredbyNEC690.64(A)and230.82.Althoughlineside
connectionscanbequitestraightforward,theyshouldrequireanadditionalstepintheapproval
processandrequireaslightlydifferentelectricaldrawing.
5. Theelectricaldiagram(E1.1)canbeusedtoaccuratelyrepresentthePVsystem.Explanation:Thebasisforasimplifiedpermitistheuseofthestandardelectricaldiagram.
Clearly,PVsystemscanvarysignificantlyinPVarraylayoutandinverterselection.However,the
majorityofsmallscale,residentialsizedPVsystemscanbeaccuratelyrepresentedbythisdiagram.
Thisdiagrammustbecompletelyfilledoutinorderforthepermitpackagetobeconsidered
complete.Thisdiagramisnotintendedforusewithbatterybasedsystems.
Section4. InverterInformation
Acopyofthemanufacturersspecificationsheetisrequiredforapermitsubmittal.Inaddition,
aprintedoutdigitalphotooftheinverterlistinglabelcanbeveryhelpfulforgatheringthe
ratingsoftheequipment.Aprerequisiteforacodeapprovedinstallationistheuseofalisted
inverter[NEC690.4;690.60].TodetermineifaninverterislistedbyaNationallyRecognized
TestingLaboratory(NRTL)toULStd.1741,thelistinglabelcanbeexaminedtoseeifitislabeled
UtilityInteractive.Iftheutilityinteractivelabelingisnotprovided,doestheunitcomplywith
therequirementsofIEEEStd.1547asverifiedtheinstructionmanualsvalidatedbythelisting
agency.For
acurrent
list
of
compliant
inverters,
visit
the
GoSolarCalifornia
website
at
http://gosolarcalifornia.com/equipment/inverter.php.SomeNRTLshavecurrentlisting
informationonlineaswell.
a) INVERTERMAKE:Thisisthemanufacturersname:(e.g.PVPowered,SMA,etc)
b) INVERTERMODEL#:Thisisthemodelnumberonthelistinglabel:(e.g.PVP5200,
SB7000US,etc)
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c) MAXDCVOLTAGERATING:Providedeitheronlistinglabelorspecificationsheet.
d) MAXPOWER@40C:Themaximumcontinuousoutputpowerat40
Cisrequired
informationforthelistinglabelandtheGoSolarCaliforniawebsite.Ifthespecification
sheetdoesnotclearlystatethevalue,consulteitheroftheseothertwosources.
e) NOMINALACVOLTAGE: Thisistheacoutputvoltageoftheinverterasconfiguredfor
thisproject.
Some
inverters
can
operate
at
multiple
ac
voltages.
f) MAXOCPDRATING:Thisisthemaximumovercurrentprotectivedevice(OCPD)rating
allowedfortheinverter.Thisiseitherstatedonthelistinglabelorintheinstallation
manual.Sometimesthisisalsolistedonthespecificationsheetbutnotalways.Itis
importanttocheckthattheinverterOCPDratinginthepanelislessthanorequaltothis
maximumratingtopreservethelistingoftheinverter.
Section5. ModuleInformation
Acopyofthemanufacturersspecificationsheetisrequiredforapermitsubmittal.Inaddition,
aprintedoutdigitalphotoofthemodulelistinglabelcanbeveryhelpfulforgatheringthe
ratingsoftheequipment.Aprerequisiteforacodeapprovedinstallationistheuseofalisted
PVmodules[NEC690.4]toUL1703.ForacurrentlistofmodulesthatarelistedtoUL1703,
visittheGoSolarCaliforniawebsite,http://gosolarcalifornia.com/equipment/pvmodule.php.Explanation:Thismoduleinformationisparticularlyimportantsinceitisusedtocalculate
severalcurrentandvoltageparametersrequiredbytheNationalElectricalCode(NEC).Listing
informationisnecessaryforNECtestingrequirements[90.7,100,110.3,690.4].(Numbersin
bracketsrefertosectionsinthe2008NECthroughoutthisdocument.)
a) MODULEMANUFACTURER: Thisisthemanufacturersname:(e.g.Evergreen,
SunPower,etc)
b) MODULEMODEL#:Thisisthemodelnumberonthelistinglabel:(e.g.EGS185,SP225,
etc)c) MAXIMUMPOWERPOINTCURRENT(IMP)
Explanation:TheratedIMPisneededtocalculatesystemoperatingcurrent.Thisisthecurrent
ofthemodulewhenoperatingatSTCandmaximumpower.
d) MAXIMUMPOWERPOINTVOLTAGE(VMP)Explanation:TheratedVMPisneededtocalculatesystemoperatingvoltage.Thisisthe
voltageofthemodulewhenoperatingatSTCandmaximumpower.
e) OPENCIRCUITVOLTAGE(VOC)Explanation:TheratedVOCisneededtocalculatedmaximumsystemvoltagespecifiedinNEC
690.7.
f) SHORTCIRCUITCURRENT(ISC)
Explanation:TheratedISCisneededtocalculatemaximumcurrentspecifiedinNEC690.8(A).g) MAXIMUMSERIESFUSE(OCPD)
Explanation:Maximumseriesfuse(OCPD)ratingisneededtoensurethattheproper
overcurrentprotectionisprovidedforthemodulesandarraywiring.
h) MAXIMUMPOWER(PMAX)atStandardTestConditions(STCis1000W/m2,25
Ccelltemp,
&AirMass1.5)
Explanation:MaximumpoweratSTCspecifiestheratedpowerofthePVmoduleunder
simulatedconditions.
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13
i) MAXIMUMSYSTEMVOLTAGEExplanation:Maximumsystemvoltage(often600Vdc)isneededtoshowthattheNEC690.7
voltagedoesnotexceedthisvalue.
Section6. Arrayinformation
Thissection
defines
the
configuration
of
the
PV
array.
PV
arrays
are
generally
made
up
of
severalmodulesinseries,calledsourcecircuits.Thesesourcecircuitsareoftenparalleledwith
multipleothersourcecircuitstomakeuptheentiredcgeneratingunitcalledthearray.Thelast
fouritemsrelatedtothePVarraymustbecalculatedandpostedonasignatthePVPower
Sourcedisconnect.Thefirsttwoitemsa)andb)characterizethearraydesignandprovidesthe
informationnecessarytocalculatethefouritemsneededtoproduceproperarrayidentification
forPVPowerSourcesigndiscussedinSection7thatisrequiredatthesite.
a) NUMBEROFMODULESINSERIESExplanation:Forsimplicity,thisdiagramonlyaddressesthemostcommonconfigurationofPV
modulesmultiplemodulesinseries.AlthoughsinglemodulePVpowersourcesexist,itismorecommon
toseePVarraysconfiguredwithasmanyas12or16modulesinseries.
b) NUMBEROFPARALLELCIRCUITSExplanation:Sincesinglephaseinverterscanbeaslargeas12kWormore,andthelargestPV
sourcecircuitsareonly2or3kW,itiscommonforPVarraystohavetwoormoresourcecircuitsin
parallel.FromExampleinAppendixOne:
Numberofmodulesinseries=12
Numberofparallelsourcecircuits=4
Totalnumberofmodules=12x4=48
c) LOWESTEXPECTED
AMBIENT
TEMP
Explanation:Upthroughthe2008edition,theNEChasnotclearlydefinedlowestexpectedambient
temperature.ASHRAE(AmericanSocietyofHeating,Refrigeration,andAirConditioningEngineers)has
performedstatisticalanalysisonweatherdatafromtheNationalWeatherService.Thesedatainclude
valuesforthemeanextremetemperaturesforthelocationswithtemperaturedata.Themeanextreme
lowtemperatureisthecoldestexpectedtemperatureforalocation.Halfoftheyearsonrecordhavenot
exceededthisnumber,andtheresthaveexceededthisnumber.Thesedataaresuppliedintheappendix
forreference.Aproposalislikelytoacceptedforthe2011NEC toincludeaFinePrintNoteto690.7that
specifiestheuseoftheASHRAEmeanextremevalueforlowestexpectedambienttemperature.
d) HIGHESTCONTINUOUSTEMP(ambient)
Explanation:Upthroughthe2008edition,theNEChasnotclearlydefinedhighestcontinuousambienttemperature.ContinuousisdefinedintheNECasa3hourperiod(Article100).ASHRAE
(AmericanSocietyofHeating,Refrigeration,andAirConditioningEngineers)hasperformedstatistical
analysisonweatherdatafromtheNationalWeatherService.Thesedataincludedesignvaluesof0.4%,
1%,and2%foreachmonthsignifyingthatthetemperatureonlyexceedstherecordedvalueupto2%of
thetimeforagivenlocationwithtemperaturedata.The2%valuehasbeenchosenbytheCopper
DevelopmentInstituteasthevaluethatbestrepresentsaconditionthatwouldcreatethe3hour
continuousconditionreferredtoinArticle100.Twopercentofonemonthisabout14hours.Sincehigh
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14
temperaturesusuallylastforseveraldaysinmostlocations,theassumptionisthatatleastoneortwo3
hourhightemperatureeventswillhappenduringagivenmonth.Thesedataaresuppliedintheappendix
forreference.Aproposalforthe2011NEChasbeensubmittedtoincludeaFinePrintNotetoTable
310.16thatspecifiestheuseoftheASHRAE2%dataforthehottestmonthtodeterminehighest
continuousambienttemperature.
Section7. SIGNS
a) PVPOWERSOURCE
i) RATEDMPP(MAXIMUMPOWERPOINT)CURRENT
(sumofparallelsourcecircuitoperatingcurrents)
Explanation:RatedMPPcurrentisfoundbymultiplyingthemoduleratedMPPcurrentfora
moduleseriesstringbythenumberofsourcecircuitsinparallel.
FromtheexampleinAppendixOne:
IMP=4.89amps
Numberofsourcecircuitsinparallel=44.89ampsx4=19.6amps
ii) RATEDMPP(MAXIMUMPOWERPOINT)VOLTAGE
(sumofseriesmodulesoperatingvoltageinsourcecircuit)
Explanation:OperatingvoltageisfoundbymultiplyingthemoduleratedMPPvoltagebythe
numberofmodulesinaseriessourcecircuit.
FromtheexampleinAppendixOne:
VMP=35.8Volts
Numberofmodulesinseries=12
35.8Voltsx12=430Volts
iii) MAXIMUMSYSTEM
VOLTAGE
[NEC
690.7]
Explanation:MaximumsystemvoltageiscalculatedbymultiplyingthevalueofVoconthe
listinglabelbytheappropriatevalueonTable690.7intheNEC,andthenmultiplyingthatvalue
bythenumberofmodulesinaseriesstring.ThetableintheNECisbasedoncrystallinesilicon
modulesanduseslowestexpectedambienttemperatureatasitetoderivethecorrectionfactor.
Somemodulesdonothavethesametemperaturecharacteristicsascrystallinesiliconsothe
manufacturersinstructionsmustbeconsultedtodeterminetheproperwaytocorrectvoltage
basedonlowestexpectedambienttemperature.
FromtheexampleinAppendixOne:
ModuleVOC=44.4Volts
NumberofModulesinSeries=12
Lowestexpectedambienttemperature(ASHRAE)=0C(SanJose,California)
Method1NECTable690.7:
MaximumSystemVoltage=VMAX=VOCxNo.ofModulesinSeriesxTable690.7Value
VMAX=44.4Vx12x1.10=586Volts
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PercentageMethod:
VMODMAX=VOC+VOCx VOC(%)x(TempLOWTempRATED)
VoltageMethod:
VMODMAX=VOC+ VOC(V)x(TempLOWTempRATED)
MaximumSystemVoltage=VMAX=VMODMAXxNumberofModulesinSeries
MaximumSystemVoltage=VMAX
=44.4V+44.4Vx0.0033/Cx(0C 25C)x12
VMAX=[44.4V+44.4Vx0.0033/Cx(25C)]x12=577Volts
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Section8. WiringandOvercurrentProtection
a) DCWiringSystems:
Sourcecircuit
conductors:
InExposedLocations:
PVmoduleinterconnectionsaregenerally90Cwetratedconductors(NEC690.31(A)
FPN).Thesameconductortypeistypicallyusedforallhomerunconductorsneeded
forsourcecircuitconductorsinexposedlocations.
Allowablewiretypesareasfollows:
USE2singleconductorcableforexposedlocations.[NEC690.31(B)]
PVWireorPVCableasasingleconductorforexposedlocations(requiredforall
ungroundedsystems).[NEC690.31(B)]ExplanationfortheneedforHighTemperatureConductors:Typicaltemperature
forPVmodulesinfullsunat20Coutdoortemperatureis50C.Thisisa30Criseabove
outdoortemperatures.Onthehottestdayoftheyear,outdoortemperaturescanreacha
continuoustemperatureof41CinmanyhotlocationsthroughouttheUnitedStates.This
meansthatthePVmodulecouldbeoperatingat71Conthehottestdayoftheyear
(41C+30C=71C).75CwireisinsufficientforconnectiontoahotPVmoduleunderthis
condition.
TofurthersupporttheconcernoverthehightemperatureofPVmodules,afineprint
notehasbeenaddedtothe2005NEC.
NEC690.31(A)FPN: Photovoltaicmodulesoperateatelevatedtemperatureswhen
exposedtohighambienttemperaturesandtobrightsunlight.Thesetemperaturesmay
routinelyexceed70C(158F)inmanylocations.Moduleinterconnectionconductorsare
availablewithinsulationratedforwetlocationsandatemperatureratingof90C
(194F)orgreater.
InConduitonRooftops:
TWOOPTIONSFORSOURCECIRCUITCONDUCTORTYPE(INSIDECONDUITCIRCLE
ONE)THWN2andXHHW2
Explanation:Conductorsinconduit,whenexposedtodirectsunlight,mustaccountfor
thehighertemperaturescausedbyintensesunlightandtheproximityoftheroof.The2005
NECfirstrecognizedtheissueofsunlitconduitinafineprintnoteinNEC310.10.
310.10FPNNo.2:Conductorsinstalledinconduitexposedtodirectsunlightinclose
proximitytorooftopshavebeenshown,undercertainconditions,toexperiencea
temperatureriseof17C(30F)aboveambienttemperatureonwhichtheampacityis
based.
The2008NECcodifiedthisissuebyclassifyingthetemperaturesbasedontheheightabove
theroofsurface.Onresidentialroofs,whereconduittypicallyisspacedbetweenand3
abovetheroofsurface,thetemperatureadderisstatedas22Cabovetheambient
temperatureaccordingtoNECTable310.15(B)(2)(c).Usingthisadder,alongwiththe
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17
ASHRAE2%designdataforthehottestlocationintheU.S.(PalmSprings,CAis44C),
producesadesigntemperatureof66C.andcorrectionfactorof0.58for90Cconductors
basedonNECTable690.31andTable310.16.Ifnineconductorsorlessareintheexposed
conduit(4pairsofconductorsorless),thentheconduitfillcorrectionfactoris0.7according
toNECTable310.15(B)(2)(a).Puttingallthesecorrectionfactorstogethermeansthatthe
30C.conductorampacitymustbeasfollows:
Ifonlytwostringsinparallel(nofuses):
I30C.=IMAX/0.58/0.7=2.46xIMAX
IfISC=9.6ampsorless,thenIMAX=ISCx1.25=12ampsorless.
IfIMAX=12Amps,thenI30C.=29.5Amps(12AWG,90Crequired(NECTable310.16))
IfISC=6.4ampsorless,thenIMAX=ISCx1.25=8ampsorless.
IfIMAX=8Amps,thenI30C.=19.7Amps(14AWG,90Crequired(NECTable310.16))
IffusesareneededtoprotectPVmodules(mostcases):
I30C.=IFUSE/0.58/0.7=2.46xIFUSE
IfISC=9.6ampsorless,thenIMAX=ISCx1.25=12amps.Theminimumovercurrent
protectivedevice(OCPD)asrequiredby690.8(B)is15amps(IFUSE=IMAXx1.25=15A).
IfIFUSE=15Amps,thenI30C.=2.46x15A=36.9Amps(10AWG,90Crequired(NEC
Table310.16)15Afusetoprotecttheconductor)
IfISC=7.68ampsorless,thenIMAX=ISCx1.25=9.6amps.Theminimumovercurrent
protectivedevice(OCPD)asrequiredbyNEC690.8(B)is12amps(IFUSE=IMAXx1.25=
12A).
IfIFUSE=12Amps,thenI30C.=2.46x12A=29.5Amps(12AWG,90Crequired(NEC
Table310.16)12Afusetoprotecttheconductor)
IfISC=6.4ampsorless,thenIMAX=ISCx1.25=8amps.Theminimumovercurrent
protectivedevice(OCPD)asrequiredby690.8(B)is10amps(IFUSE=IMAXx1.25=10A).
IfIFUSE=10Amps,thenI30C.=2.46x10A=24.6Amps(14AWG,90Crequired(NEC
Table310.16)10Afusetoprotecttheconductor)
Maximum
ModuleISC
RequiredFuse
Size
MinimumConductorSize
inConduit(9conductors)
MinimumConductorSizein
FreeAir(atmodules)
9.6Amps 15Amps 10AWG 10AWG
7.68Amps 12Amps 12AWG 12AWG
6.4Amps 10Amps 14AWG 14AWG
SincethehighestISCmodulecommonlyavailableasofthewritingofthisguideislessthan9
amps,10AWGconductorswillalwaysworkregardlessoflocationintheU.S.aslongasthere
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arenomorethan9currentcarryingconductorsintheconduitandtheconduitisatleast0.5
abovetheroofsurface.SmallerwirecanbeusedaccordingtotheISCofthemodulesbeing
usedandthenumberofconductorsintheconduit.Thesecalculationsareprovidedsothat
contractorsandjurisdictionswillnotneedtorepeatthesestandardcalculationsoverand
over.Asimpletablesummarizestheminimumconductorsizes.
b) ACWiringSystems
InverterOutputCircuitovercurrentprotectionshouldbesizedandprotectedaccordingthe
manufacturersdirections.Thecircuitandcorrespondingovercurrentprotectionshouldbe
sizedata125%ofthemaximumcontinuousoutputoftheinverter[NEC215.3Overcurrentfor
FeederCircuits,andNEC690.8(A)(3)and690.8(B)].The125percentincreaseoverthe
maximumInverterOutputCircuitcurrentistoaccountforthestandardlistingofovercurrent
devicesto80%ofmaximumcircuitcurrentforcontinuousduty.Theinvertermayalsohavea
maximumallowableovercurrentrequirement.
Explanation:Forinstance,theSMASB7000UShasamaximumcontinuousoutputof29.2amps
andamaximumallowableovercurrentprotectionof50amps.Thismeansthattheminimumallowableovercurrentis40amps(29.2ampsx1.25=36.5ampsrounduptothenextstandardsize,whichis40
amps)andamaximumof50amps.Normallytheminimumallowablebreakersizeisusedsincethe
panelboardsupplybreakersareconstrainedto120%ofthepanelboardbusbarrating.
FromtheexampleinAppendixOne:
Invertercontinuousoutputrating=7000Watts
Nominalinvertervoltage=240Volts
Maximumoperatingcurrent=7000Watts/240Volts=29.2Amps
Min.InverterOutputCircuitampacity=29.2Ampsx1.25=36.5Amps
Section9. ACPointofConnection
NEC690.64(B)coverstherequirementsforPointofConnectionofthePVinvertertothe
buildingelectricalsystem.Themostcommonmethodofconnectionisthroughadedicated
circuitbreakertoapanelboardbusbar.Thesumofthesupplybreakersfeedingthebusbarofa
panelcanbeupto120%ofthebusbarrating.AppendixBtreatsthissubjectindetail.
Explanation:Aservicepanelcontaininga200ampbusbaranda200ampmainbreakerwill
allowbreakerstotaling120%ofthebusbarrating(240amps).Sincethemainbreakeris200amps,the
PVbreakercanbeupto40ampswithoutexceedingthe120%allowance.Foraservicepanelwitha125
ampbusbaranda100ampmainbreaker,thisprovisionwillallowuptoa50ampbreaker(125ampsx
1.2=150amps;150amps100ampmainbreaker=50ampPVbreaker).
Aprovision
in
the
2005NEC
clarifies
the
fact
that
dedicated
circuit
breakers
backfed
from
listed
utilityinteractiveinvertersdonotneedtobeindividuallyclampedtothepanelboardbusbars.
Thishasalwaysbeenthecase,butmanyinspectorshaveemployedtheprovisionsofNEC
408.36(F)thatthebreakerbesecuredinplacebyanadditionalfastener.Utilityinteractive
invertersdonotrequirethisfastenersincetheyaredesignedtoshutdownimmediatelyshould
thededicatedbreakerbecomedisconnectedfromthebusbarunderanycondition.This
provisionisrepeatedinthe2008NECinaclearandconcisestatement:
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NEC690.64(B)(6)Fastening.Listedplugintypecircuitbreakersbackfedfromutilityinteractiveinverterscomplyingwith690.60shallbepermittedtoomittheadditionalfastenernormally
requiredby408.36(D)forsuchapplications.
NEC690.64(B)coverstherequirementsforPointofConnectionofthePVinvertertothe
buildingelectrical
system,
which
is
the
most
common
method
of
connection.
The
table
below
showsthehowthemaximumcurrentoftheinverter(column1)requiresaminimumsizeOCPD
(column2),whichrequiresaminimumsizeconductor(column3),whichrequiresacompatible
busbar/mainbreakercombinationinthepanelboard(column4).Thewaytounderstand
column4,minimumbusbar/mainbreakercombinationsistolookattherowthatcoincideswith
theparticularbreakerbeingselected(fromcolumn2)anduseanycombinationfromcolumn4
foundonthatroworhigherinthetable.Forinstance,a40Ampsinverterbreakerworkswitha
200/200panelcombination,butitalsoworkswitha125/100combinationfoundontherow
above.The40Ampbreakerdoesnotworkonthe150/150combination,sincethelargest
breakerwouldbe30ampsforthe150/150combination.
TableofNEC690.64(B)ACInterconnectionOptionsMaximum
Inverter
Current
Required
InverterOCPD
Size
Minimum
ConductorSizein
Conduit
MinimumBusbar/MainBreaker
Combinations
(BusbarAmps/MainAmps)
64Amps 80Amps 4AWG 400/400;200/150
56Amps 70Amps 4AWG 225/200;250/225
48Amps 60Amps 6AWG 300/300;200/175
40Amps 50Amps 8AWG 125/100;150/125
32Amps 40Amps 8AWG 225/225;200/200;150/125
24Amps
30
Amps
10
AWG
150/150
16Amps 20Amps 12AWG 100/100;70/60
12Amps 15Amps 14AWG 80/80
Section10. Grounding
a) SystemGrounding
TheNECrequires[690.41]thatallsystemsoperatingabove50voltshaveoneconductor
referencedtogroundunlessthesystemcomplieswiththerequirementsofNEC690.35for
ungroundedPVarrays.
b) EquipmentGrounding
Thecodealsorequiresthatallexposednoncurrentcarryingmetalpartsofmoduleframes,
equipment,andconductorenclosuresbegroundedregardlessofsystemvoltage[NEC690.43].
Thegroundingofmoduleframeshasreceivedsignificantattentioninthelastseveralyears.
Manyjurisdictions,withaheightenedconcernovertheissue,havedramaticallyrestricted
effectivegroundingoptions. AdiscussiononmoduleframegroundingisfoundintheAppendix.
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c) SizingofGroundingConductors
i) Equipmentgroundingconductor(EGC)sizing[NEC690.45]
ThesizeoftheEGCisdependentonwhetherthesystemhasgroundfaultprotection
(GFP)equipmentornot.TheprovisionsforGFPequipmentarestatedinNEC690.5.
Almostall
inverters
have
GFP
equipment
integral
to
the
inverter
and
require
that
the
PV
arraybegroundedattheinverteronly.
(1)Systemswithgroundfaultprotectionequipment
SizeequipmentgroundingconductoraccordingtoNECTable250.122.
(2)Systemswithoutgroundfaultprotectionequipment
TheNECrequiresthatequipmentgroundingconductorsforsystemswithoutGFP
equipmentbesizedfortwicethecircuitshortcircuitcurrent[NEC690.45].
ii) Systemgroundingconductorsizing
(1)ACSystem
Sizegroundingelectrodeconductor(GEC)accordingtoNECTable250.66.
Normallythesitealreadyhastheconductorandelectrodeinstalledfortheac
buildingwiring.
(2)DCSystem
Sizegroundingelectrodeconductor(GEC)accordingtoNEC250.166.Thisresults
inaminimumsizeof8AWG.ThemaximumsizeoftheGECisdependentupon
thetypeofgroundingelectrodeorthemaximumsizeconductorinthesystem,
whicheverissmaller.
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APPENDIX
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APPENDIXA:EXAMPLESUBMITTAL
Step1:StructuralReviewofPVArrayMountingSystem
Isthearraytobemountedonadefined,permittedroofstructure? Yes No
(structuremeetsmoderncodes)
IfNoduetononcompliantrooforgroundmount,submitcompletedworksheetforroofstructureWKS1.
RoofInformation:
1. Istheroofingtypelightweight(Yes=composition,lightweightmasonry,metal,etc)_Yescomposition
If No,submitcompletedworksheetforroofstructureWKS1(No=heavymasonry,slate,etc).
2. Doestheroofhaveasingleroofcovering? Yes No
IfNo,submitcompletedworksheetforroofstructureWKS1.
3. Providemethodandtypeofweatherproofingroofpenetrations(e.g.flashing,caulk).__flashing_____
MountingSystemInformation:
1. ThemountingstructureisanengineeredproductdesignedtomountPVmodules? Yes NoIfNo,providedetailsofstructuralattachmentcertifiedbyadesignprofessional.
2. Formanufactured
mounting
systems,
fill
out
information
on
the
mounting
system
below:
a. MountingSystemManufacturer_UniRac_ProductNameandModel#__SolarMount___
b. TotalWeightofPVModulesandRails___1780________lbs
c. TotalNumberofAttachmentPoints____48___
d. WeightperAttachmentPoint(bc)____37___________lbs(ifgreaterthan40lbs,seeWKS1)
e. MaximumSpacingBetweenAttachmentPointsonaRail______48______inches(seeproduct
manualformaximumspacingallowedbasedonmaximumdesignwindspeed)
f. TotalSurfaceAreaofPVModules(squarefeet)_____674____________ft2
g. DistributedWeightofPVModuleonRoof(bf)______2.64______lbs/ft2
IfdistributedweightofthePVsystemisgreaterthan5lbs/ft2,seeWKS1.
Step2:ElectricalReviewofPVSystem(CalculationsforElectricalDiagram)InorderforaPVsystemtobeconsideredforanexpeditedpermitprocess,thefollowingmustapply:
1. PVmodules,utilityinteractiveinverters,andcombinerboxesareidentifiedforuseinPVsystems.
2. ThePVarrayiscomposedof4seriesstringsorless,and15kWSTCorless.
3. TheInverterhasacontinuouspoweroutput13,440Wattsorless
4. Theacinterconnectionpointisontheloadsideofservicedisconnectingmeans(690.64(B)).
5. Theelectricaldiagram(E1.1)canbeusedtoaccuratelyrepresentthePVsystem.
Filloutthestandardelectricaldiagramcompletely.Aguidetotheelectricaldiagramisprovidedtohelpthe
applicantunderstandeachblanktofillin.Iftheelectricalsystemismorecomplexthanthestandardelectrical
diagramcaneffectivelycommunicate,provideanalternativediagramwithappropriatedetail.
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ContractorName,
AddressandPhone:
Billa
ndTedsSolar
456IndustrialDrive
SanJose,CA
40
8-555-1212
Bill
Ted
SitePlan
forSmall-Scale,Single-PhasePVSystems
SiteName:JoeandJaneHomeowner
SiteAddress:123SunnysideSt.,SanJose,CA
SystemACS
ize:6.9kWSolarArray
SIZE
FSCMNO
DWGNO
REV
S1.1
0
SCALE
NTS
Date:
SHEET
DrawnBy:
CheckedBy:
INVERTERWITH
SUPPLIED
COMBINERAND
DCDISCONNECT
3'-0"
3'-0"
3'-0"
J
EXISTINGALL-IN-ONE
SERVICEEQUIPMENT
W
ITH40-AMPPV
B
REAKERASAC
DISCONNECT
24SOLARWORLDSW175
MODULESIN2SERIESSTRINGS
OF12MODULESEACHON
EXISTINGROOFSTRUCTURE
ROOFTOPJ-BOXTO
TRANSITIONEXPOSED
USE-2TOTHWN-2
CONDUCTORSIN"EMT
10'-8"
11'-3"
12'-7"
EXISTINGFENCE
24SOLARWORLDSW175
MODULESIN2SERIESSTRINGS
OF12MODULESEACHON
EXISTINGSHADESTRUCTURE
J
7/28/2019 Project Modul
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ContractorName,
AddressandPhone:
Billa
ndTedsSolar
456IndustrialDrive
SanJose,CA
40
8-555-1212
Bill
Ted
One-LineStandardElectricalDiagram
forSmall-Scale,Single-PhasePVSystems
SiteName:JoeandJaneHomeowner
SiteAddress:123SunnysideSt.,SanJose,CA
SystemACS
ize:6.9kWSolarArray
SIZE
FSCMNO
DWGNO
REV
E1.1
0
SCALE
NTS
Date:
SHEET
DrawnBy:
CheckedBy:
DESCRIPTIONORCO
NDUCTORTYPE
USE-2
orPVWIRE
BARECOPPEREQ.G
RD.COND.(EGC)
THWN-2
orXHHW
-2
orRHW-2
THWN-2
orXHHW
-2
orRHW-2
INSULATEDEGC
DCGROUNDINGELE
CTRODECOND.
THWN-2
orXHHW
-2
orRHW-2
INSULATEDEGC
TAG
12345
CONDUITANDCONDUCTORSCHEDULE
COND.
GAUGE
10AWG
10AWG
10AWG
N/A
N/A
6AWG
8AWG
10AWG
NUMBEROF
CONDUCTORS
8BLACK
1BARECU
4-R,4-W,1-G
N/A
N/A
1BARECU
1-R,1-B,1-W
1GREEN
CONDUIT
TYPE
N/A
N/A
EMT
N/A
N/A
EMT
CONDUIT
SIZE
N/A
N/A
"
N/A
N/A
"
DESCRIPTION
SOLARPVMODULE
PVARRAY
J-BOX(IFUSED)
COMBINER(IFUSED
)
DCDISCONNECT
DC/ACINVERTER
GENMETER(IFUSE
D)
ACDISCONNECT(IF
USED)
SERVICEPANEL
TAG
123456789
PARTNUMBER
SW175mono
N/A
SMA-supplied
SMA-supplied
SB7000US
FORM2S
D222NRB
SD200SL
NOTES
SOLARWOR
LD,QUANTITY-36(SEENOTESSHEETFORDETAILS)
ARRAYIS4
STRINGSWITH12MODULESPERSERIES
STRING
NEMA4,PVCJUNCTIONBOX
15-AMAXFUSEW/15-AFUSES,600VDC,4-STRINGMA
X
LISTEDWITHINVERTER,600VDC,60-AMP(SEEGUIDE
APPENDIXB)
SMA7000W
ATT,SINGLEPHASE(SEENOTESSHEETFORDETAILS)
GENERALE
LECTRIC4-JAW
SQUARED,
240VAC,60-AMPFUSED(SEEGUIDEAPPE
NDIXB)
240VAC,200
-AMAIN,200-ABUS,40-AINVERTEROCPD
(SEENOTE5FORINVERTEROCPDs,ALSOSEEGUIDESECTION9)
FORUNUSEDSERIESSTRINGS
PUT"N/AinBLANKABO
VE
SEEGUIDEAPPENDIXB
FOR
INFORMATIONONMODUL
EAND
ARRAYGROUNDING
___12___MODULES
IN
SERIESSOURCE-CIRC
UIT
___12___MODULES
IN
SERIESSOURCE-CIRC
UIT
___12___MODULESIN
SERIESSOURCE-CIRC
UIT
___12___MODULESIN
SERIESSOURCE-CIRC
UIT
DC
DISCO
INVERTER
A
C
DIS
CO
AC
DC
M
BUILDING
GROUNDING
ELECTRODE
G
Disrega
rdif
providedwith
inverter
COMBINER
MUTILITY
SERVICE
MAINSERVICE
PANEL
MAIN
OCPD
INVERTER
OCPD
J-BOX
1
1
3
4
5
6
7
9
2
3
4
5
8
2
EQUIPMENTSCH
EDULE
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APPENDIXB:STRUCTURAL
STRUCTUREWORKSHEETWKS1
Ifarrayisroofmounted:
Thissectionisforevaluatingroofstructuralmembersthataresitebuilt.Thisincludesrafter
systemsandsitebuilttrusses.Manufacturedtrussandroofjoistsystems,wheninstalledwith
properspacing,meettheroofstructurerequirementscoveredinitem2below.
1. Roofconstruction: Rafters Trusses Other:
___________________________________
2. Describesitebuiltrafterororsitebuilttrusssystem.
a. RafterSize:___x___inches
b. RafterSpacing:________inches
c. Maximumunsupportedspan:_____feet,_____inches
d. Aretheraftersoverspanned?(seetheIRCspantablesinB.2.) Yes No
e. IfYes,completetherestofthissection.
3. Iftheroofsystemhas:
a. overspannedraftersortrusses,
b. thearrayover5lbs/ft2onanyroofconstruction,or
c. theattachmentswithadeadloadexceeding40lbsperattachment;
itis
recommended
that
you
provide
one
of
the
following:
i. Aframingplanthatshowsdetailsforhowyouwillstrengthentherafters
usingthesuppliedspantablesinB.2.
ii. Confirmation certifiedbyadesignprofessionalthattheroofstructurewill
supportthearray.
Ifarrayisgroundmounted:
1. Showarraysupports,framingmembers,andfoundationpostsandfootings.
2. Provideinformationonmountingstructure(s)construction.Ifthemountingstructureis
unfamiliarto
the
local
jurisdiction
and
is
more
than
six
(6)
feet
above
grade,
it
may
requireengineeringcalculationscertifiedbyadesignprofessional.
3. Showdetailonmoduleattachmentmethodtomountingstructure.
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B.2 SPANTABLESAframingplanisrequiredonlyifthecombinedweightofthePVarrayexceeds5poundsper
squarefoot(PSForlbs/ft2)ortheexistingraftersareoverspanned.Thefollowingspantables
fromthe2003InternationalResidentialCode(IRC)canbeusedtodetermineiftheraftersare
overspanned.Forinstallationsinjurisdictionsusingdifferentspantables,followthelocal
tables.
SpanTableR802.5.1(1),
Usethistableforrafterspansthathaveconventionallightweightdeadloadsanddonothaveaceilingattached.
10 PSF Dead LoadRoof live load = 20 psf, ceiling not attached to rafters, L/=180
Rafter Size 2 x 4 2 x 6 2 x 8 2 x 10 2 x 12
Spacing(inches)
Species GradeThemeasurementsbelowareinfeetinches
(e.g.910=9feet,10inches).
16Douglas
Firlarch
#2or
better910 144 182 223 259
16 Hemfir#2or
better92 142 1711 2111 255
24Douglas
Firlarch
#2or
better710 119 1410 182 210
24 Hemfir#2or
better73 115 148 1710 209
Usethistableforrafterspansthathaveheavydeadloadsanddonothaveaceilingattached.
20 PSF Dead LoadRoof live load = 20 psf, ceiling not attached to rafters, L/=180
Rafter Size 2 x 4 2 x 6 2 x 8 2 x 10 2 x 12
Spacing(inches)
Species GradeThemeasurementsbelowareinfeetinches
(e.g.910=9feet,10inches).
16Douglas
Firlarch
#2or
better86 125 159 193 224
16 Hemfir#2or
better85 123 156 1811 220
24Douglas
Firlarch
#2or
better611 102 1210 158 183
24 Hemfir#2or
better610 100 128 156 1711
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SpanTableR802.5.1(2),
Usethistableforrafterspanswithaceilingattachedandconventionallightweightdeadloads.
10 PSF Dead LoadRoof live load = 20 psf, ceiling attached to rafters, L/=240
Rafter Size 2 x 4 2 x 6 2 x 8 2 x 10 2 x 12
Spacing(inches)
Species GradeThemeasurementsbelowareinfeetinches
(e.g.910=9feet,10inches).
16Douglas
Firlarch
#2or
better811 141 182 223 259
16 Hemfir#2or
better84 131 173 2111 255
24Douglas
Firlarch
#2or
better710 119 1410 182 210
24 Hemfir#2or
better73 115 148 1710 209
Usethistableforrafterspanswithaceilingattachedandwhereheavydeadloadsexist.
20 PSF Dead LoadRoof live load = 20 psf, ceiling attached to rafters, L/=240
Rafter Size 2 x 4 2 x 6 2 x 8 2 x 10 2 x 12
Spacing(inches)
Species GradeThemeasurementsbelowareinfeetinches
(e.g.910=9feet,10inches).
16Douglas
Firlarch
#2or
better86 125 159 193 224
16 Hemfir#2or
better84 123 156 1811 220
24
DouglasFirlarch
#2or
better611
10
2
1210
15
8
183
24 Hemfir#2or
better610 100 128 156 1711
Usetheconventionallightweightdeadloadtablewhentheexistingroofingmaterialsarewood
shake,woodshingle,compositionroofingorlightweighttileroofs.(Therationaleforallowing
thesetablestobeusedisthattheinstallationofaPVsystemshouldbeconsideredaspartof
theliveload,sinceadditionalloadingwillnotbeaddedtothesectionoftheroofwhereaPV
arrayisinstalled.)
Whereheavy
roofing
systems
exist
(e.g.
clay
tile
or
heavy
concrete
tile
roofs),
use
the
20
lbs/ft
2
deadloadtables.
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APPENDIXC:SPECIALELECTRICALTOPICS
ModuleFrameGrounding:
Theprimary
concern
raised
by
industry
experts,
including
the
Solar
ABCs,
has
been
the
fact
that
theanodizedaluminumframesincontactwithanodizedaluminumrailsmaynotcreatean
adequateandreliableelectricalconnection.Untilthisissuewasraised,mostinspectorsand
contractorsweresatisfiedwithgroundingthemetalsupportstructureratherthangrounding
individualmodules.Severalstandardandnewgroundingmethodscanaddresstheelectrical
bondofthemoduleframetoitssupportbypenetratingeachnonconductivesurfacewitha
sharp,metallurgicallycompatibledevice.Thisdevicemaybeasimpleasastainlesssteelstar
washer,orasuniqueasaspeciallydesignedgroundingclipwithsharppointstopiercethe
anodizing.
PVmodule
grounding
options
include
avariety
of
methods
including
grounding
screws
or
lugs
oneachmoduleconnectedtoagroundwire,ormethodsthatcreateanelectricalbond
betweenthemoduleframeanditssupportstructure.InstallationmanualsforPVmoduleshave
becomemoreexplicitaboutgroundingmethods,butitisnotnecessaryforthemanualtostate
everypossiblemethodofcompliance.TheUL1703teststandardforthesafetyofPVmodulesis
beingrevisedtoallowanymethodthatmeetstherequirementsofUL467,Groundingand
BondingEquipmentaslongasthemetalsarecompatibleandthematerialsareableto
withstandanoutdoorenvironmentandexpandstheoptionsforgroundingmodules.
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ACConnectiontoBuildingElectricalSystems
ACConnectiontoLoadSideofMainServicePanel
The
connection
of
PV
systems
inverter
output
circuit
to
the
load
side
of
the
Main
Service
panel
isthemostcommoninstallationmethod.Thistypeofconnectionisgovernedbythe
requirementsofNEC690.64(B). TheserequirementsdictatethatthemaximumsumofOCPDs
thatcanbefedintoaconductororbusbaris120%ofthebusbarorconductorrating(NEC
690.64(B)(1)).Forexample,ifabusbarhasacurrentratingof225amps,andamainbreaker
ratedat200amps,thenthemaximumbreakerratingforaPVinverteris70ampsasshown
below:
MaximumallowableOCPD:Busbar=225A;120%ofBusbar=225Ax1.2=270A
ExistingMainOCPD=200A
MaximumPVOCPD=MaximumallowableOCPDExistingMainOCPD
=270A200A=70A
Todeterminethemaximumsizeinverterthatcanbefedintoa70AOCPD,rememberthatmost
circuitbreakersandotherOCPDsarelimitedto80%oftheircurrentratingforcontinuous
operation. Thismeansthat70Acircuitbreakermustbesizedsothat56Acanpassthroughthe
breakeronacontinuousbasis(3hoursormore).SincePVinvertersareratedbasedontheir
maximumpowerat40Cforacontinuous3hourperiod,aninvertercapableofacontinuous
56Aiscapableof11,648Wattsat208Vac;13,440Wacat240Vac;and15,512Wacat277Vac.
Theonlywaytoputmorecurrentintotheloadsideoftheservicepanelinthisisexample,isto
reducethesizeofthemainOCPD.TotheextentthatthemainOCPDisreduced,thePVinverter
OCPDmaybeincreased.However,anytimeamainOCPDisreduced,aloadcalculation
followingtherequirementsofNECArticle220mustbecalculatedtoshowthattheloadonthe
mainOCPDwillnotseemorethanan80%continuousloadatthechosenOCPDrating.
Ifnootherpanelboardsexistonthisservice,theonlyotheropportunitytoinstallalargerPV
systemistomakeasupplysideserviceconnection(NEC690.64(A)).Thismethodisdiscussedin
theACSupplySideConnectionsectioninthisAppendix.
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ACConnectiontoSubpanel:
Whenasiteservicecontainsmorethanonepanelboard,thepanelsfedfromthemainservice
panelarereferredtoassubpanels.TheNEC,in690.64(B)(1),allowstheinverterOCPDtobe
connectedatanylocationinthepremiseswiringsystem,providedthatthe120%ofbusbarand
conductorampacity
limitation
is
observed.
Forexample,alargeresidencehasamainpanelwitha400ampratingwitha400ampmain
OCPD.Froma200ampbreakerinthis400amppanelisa200amppanelattheoppositeend
oftheresidence.Inthisexample,thePVarrayislocatedmuchclosertothe200amppanel,so
thepreferredinterconnectionpointisthe200amppanel.AslongastheinverterOCPD
complieswithlimitationsofthe200amppanel,theinvertercaninterconnectatthatpanel.
Witha200ampbusbaranda200ampmainbreaker,thelargestPVOCPDallowedinthatpanel
is40amps(seediscussiononACConnectiontoLoadSideofMainServicePanelinthis
Appendix).Assuming
a40
amp
PV
OCPC
is
sufficient
for
the
PV
inverter
(e.g.
7000
Watt
inverter),theissuesofconcerninthesubpanelareaddress.
Nowconsiderthecurrentflowatthemainservicepanel.The2008NECinstructstheinstallerto
calculatethesumofthesupplyOCPDsatthemainservicepanelbasedontheratingofinverter
OCPD,whichis40amps,notthe200ampfeederbreakerthatfeedsthesubpanel[NEC
690.64(B)(1)].Clearly,the40ampPVOCPDdoesnotexceedthe120%ofbusbarratinginthe
400amppanel,whereas,hadthe200ampfeederbreakervaluebeenusedinthecalculation,
theinstallationwouldhavebeeninviolation.
Takingthisexampleoneadditionalstep,shouldanotherPVinverterbedesired,duetothelarge
electricalconsumptionoftheresidence,thereisstillampacityallowanceinthe400ampmainpanelbusbar.TheallowableinverterOCPDsizewouldbecalculatedasfollows:
MaximumallowableOCPD:Busbar=400A;120%ofBusbar=400Ax1.2=480A
ExistingMainOCPD=400A;InverterOCPDin200Asubpanel=40A
MaximumPVOCPDin400Apanel=MaximumallowableOCPDExistingMainOCPD
InverterOCPDin200Asubpanel=480A400A=40A
Thereforean
additional
40A
inverter
OCPD
could
be
placed
in
the
main
panel
without
any
changestothepanel.
ShouldalargerPVsystembedesiredthancouldbehandledbythetwo40Abreakersinthis
example,refertothediscussionsinACConnectiontoLoadSideofMainServicePanelinthis
Appendix.
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ACSupplySideConnection:
WhenthesizeofPVsystemisrelativelylargerelativetothesizeofthesiteservice,itisfairly
commontoconsiderasupplysideconnectionfortheinverterOCPD.Wheneverthe120%
allowanceforOCPDsconnectedtobusbarsorconductorscannotbeobserved,duetosizeof
therequired
PV
OCPD
and
the
limited
size
of
the
service
panel,
the
supply
side
connection
may
betheonlyalternativeavailable.Asupplysideconnectionbydefinitionismadebetweenthe
servicemeterandtheservicedisconnect.
Notallservicescanbelegallyconnectedatthispoint.Forinstance,manyallinonemeter
panels,usedroutinelyinnewresidentialconstruction,havenomeansofmakingsucha
connectionwithoutviolatingthelistingoftheproduct.Ontheotherendofthesizespectrum,
manylarge3,000ampservicepanelshavenospaceforsuchaconnection.Tofurther
complicatethissituation,someutilitieshavebegunrequiringmeteringcurrenttransformersto
beinstalledontheloadsideofserviceOCPD,makingasupplysideconnectionimpossible.
Withthosecomplicationsaside,wewilldiscussthesituationswhereasupplysideconnectionis
possibleanddoesnotviolatetheequipmentlistingsoftheserviceequipment.TheNECcovers
supplysideconnectionsin230.82.ThesupplysideconnectionforthePVsystemmusthavea
disconnectandOCPDlocatedimmediatelyadjacenttothemainservicedisconnectasspecified
in230.91.Eventhoughthetaprule,discussedinArticle240.99doesnotapplytosupplyside
connections,thesizeoftheconductorsconnectingthesupplysideconnectiontothePVOCPD
aresizedaccordingtoratingoftheOCPD.Therefore,ifa60ampfuseddisconnectisusedas
thePVOCPD,theconductorsizebetweenthesupplysideconnectionandthePVOCPDneed
onlybe6AWG,regardlessofthesizeofserviceconductors.
ThemethodofterminationofPVconductorstothesupplyconductorsorbusbar,dependsontheserviceequipmentandconductors.Inanycase,theservicevoltagewillneedtobe
interruptedtotieintotheserviceconductorsorbusbarunlesstheveryrareexceptions
outlinedinNFPA70Eareinvolvedatfacilitieslikehospitalswherethecutinprocessmustbe
donewhileenergized.Typicalterminationmethodsincludeseveraloptions:
1. luggingtoanaccessibleperforatedbuswithinserviceequipment;
2. usingemptysetofdoublebarrellugswithinserviceequipment;
3. usingpiercinglugsonconductorsbetweenmeterandservicedisconnect;
4. anylugidentifiedformakingconnectionstoconductorsofthesizerangeinstalled.
Ofteninstallinglugsonserviceconductorswillrequireremovalofserviceconductorsand
conduitandreinstallingconductorswithajunctionboxtoaccommodatetheconnection.
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SourceCircuitOvercurrentProtection:
SourcecircuitovercurrentprotectionmustbesizedsothatboththePVmoduleandthe
conductorfromthemoduletotheovercurrentdeviceareproperlyprotected[690.9(A),240.20
(A)].PVmodulesmustbeprotectedsothatthemaximumseriesfuserating,printedonthe
listinglabel,
is
not
exceeded.
It
is
important
to
note
that
even
though
the
listing
label
states
fuserating,amoreaccuratetermwouldbethemaximumseriesovercurrentprotection
ratingsinceeitherafuseoracircuitbreakermaybeusedtosatisfythislistingrequirement.The
modulemaybeprotectedeitherbyinstallingfusesorcircuitbreakersinaseriesstringof
modulesorbythedesignofthePVsystem.
InverterslistedwithaMaximumutilitybackfeedcurrentthatiswellabove2amps(typically
equaltothemaximumallowableoutputovercurrentprotection)mustbeassumedtoprovide
backfeedcurrenttothePVarray.Eachsourcecircuitmusthaveovercurrentprotectionthatis
greaterthanorequaltotheminimumPVSourceCircuitcurrentratingandlessthanorequalto
the
maximum
series
fuse
rating.
Explanation:Foranarraywithamaximumsourcecircuitcurrentof6.8ampsandamaximum
seriesfuseratingof15amps,Theminimumfuseratingwouldbe9amps(nextlargerfuseratingabove
8.5amps;6.8Ax1.25=8.5A)andthemaximumwouldbe15amps.
Inverterslistedwithamaximumutilitybackfeedcurrentthatis2ampsorless(e.g.FroniusIG
5100),twosourcecircuitscanbeconnectedtotheinverterwithoutrequiringovercurrent
protectiononeithercircuit.
Explanation:Ifanarraycontainingtwostringsinparallelisconnectedtoaninverterthatisa
limitedbackfeedingsource(2ampsorless),themaximumcurrentinastringisequaltothecurrentfrom
theotherstringinparallelplusthemaximumbackfedcurrentfromtheinverter.Ifthemaximumcurrent
ofeachstringis6.8Amps,andtheinverterprovides2amps,thenthemaximumcurrentinafaultatanyPVmoduleis8.8Ampsandthemaximumseriesfuseratingofthemodulewillneverbeexceeded(i.e.a
modulewithanISCof5.4ampwillhaveamaximumseriesovercurrentdeviceratingofatleast10amps).
Forsmallerinverterslistedwithamaximumutilitybackfeedcurrentthatisnolargerthanthe
modulemaximumovercurrentdevicerating(e.g.EnphaseM200witha1.6amputility
backfeed),asinglesourcecircuitcanbeconnectedtotheinverterwithoutrequiring
overcurrentprotectiononthearraycircuit.
Explanation:Ifasinglestringarray(couldbeasinglemodulearray)isconnectedtoaninverter
thatprovideslessthantheratedmodulemaximumovercurrentdeviceratinginbackfeedcurrent,itis
equivalenttohavingthatsizeovercurrentdevicepreventcurrentflowfromtheutilityandthearrayis
protected.ThemaximumreversefaultcurrentatanyPVmoduleistheamountoftheinverterutilitybackfeedcurrentandthemaximumseriesfuseratingofthemodulewillneverbeexceeded.
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DisconnectingMeans:
TheNECdefinesdisconnectingmeansinthefollowway:
NECArticle100DisconnectingMeans.Adevice,orgroupofdevices,orothermeansbywhich
theconductors
of
acircuit
can
be
disconnected
from
their
source
of
supply.
Aprimarypurposeofadisconnectingmeansistoopenacircuitprovidingasourceofsupplyso
thattheequipmentfedbythatsourcecanbemaintainedwithoutexposingtheoperatorto
hazardousvoltages(NFPA70E).
DisconnectingMeansinInverters:
Variousinvertershaveprovidedavarietyofintegraldcandacdisconnects.Thesedisconnects
mayormaynotprovidethenecessaryisolationformaintenance.Thekeyindifferentiating
whetherthesupplieddisconnectsprovidetheappropriateisolationistoreviewtheprimary
method
of
maintenance
and
repair
of
the
device.
If
the
device
has
a
standard
means
of
removingthepartsneedingservice,withoutexposingthetechniciantohazardousvoltages
(anythingover50Volts),thesupplieddisconnectsmeettheintentofmaintenance
disconnectingmeans.Ifthetechnicianisexposedtovoltagesabove50Voltsduringservice,
evenwiththesupplieddisconnectingmeans,externaldisconnectingmeansmaybenecessary.
ItisimportanttopointoutthateverycurrentlyavailablePVinverter,thatdoesnotoperateon
abatterysystem,hasinputcapacitors.Thesecapacitorsmayremainenergizedforfiveormore
minutesafterallexternalsourcesareremovedfromaninverter.Internalbleedresistors
removethisvoltageoveraprescribedtimeperiod,andwarninglabelsareprovidedonthe
invertertoidentifythishazard.Thishazardistypicalofelectricalequipmentusingsignificant
capacitance.This
capacitive
source
is
controlled
by
warning
signage
and
bleed
resistors
and
not
generallybyinternalorexternaldisconnects.Disconnectsshouldnotberequiredtocontrolthe
capacitivesourceduringmaintenanceorserviceoftheinverter.
UtilityRequiredDisconnectingMeans:
UtilitiesmayrequiresomemethodtoisolatePVsystemsfromtheirgridduringmaintenance
procedures.Theisolationdeviceisusuallyrequiredtoprovideavisiblebreakinorderto
comply,andmoldedcasecircuitbreakersdonotmeetthatrequirement.Severalutilities,
includingtheutilitywiththemostPVinstallationsintheU.S.,PacificGas&Electric,have
adoptedapolicy
of
allowing
residential
PV
systems
with
self
contained
meters
(the
most
commonresidentialtypemeter)toprovidethenecessaryvisiblebreakviaremovalofthe
meter.Forinstallationswithcurrenttransformermeters,aseparatevisiblebreakswitchis
almostalwaysrequired.Whentheutilityrequiresavisiblebreakswitch,thisswitchmaybe
usedtoprovidetheNECrequiredacswitchformaintainingtheinverteriftheinverterislocated
intheimmediatevicinityoftheswitch.
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Provisionsforthephotovoltaicpowersourcedisconnectingmeans:
The2005NECstatesin690.14(C)(1),Location.Thephotovoltaicdisconnectingmeansshallbe
installedatareadilyaccessiblelocationeitheroutsideofabuildingorstructureorinside
nearestthepointofentranceofthesystemconductors.Thephotovoltaicsystemdisconnecting
meansshall
not
be
installed
in
bathrooms.
a) ReadilyaccessibleNECArticle100states,Accessible,Readily(ReadilyAccessible).
Capableofbeingreachedquicklyforoperation,renewal,orinspectionswithoutrequiring
thosetowhomreadyaccessisrequisitetoclimboverorremoveobstaclesortoresortto
portableladders,andsoforth.
b) Readilyaccessibleprovisionisprimarilyforemergencyoperation.Ifthedisconnectis
notmountedincloseproximityoftheserviceentrancedisconnect(usuallywithin10
feetofthemeterlocationorservicedisconnectswitch),thenadiagramordirectory
mustbeprovidedtoclearlyidentifywherethedisconnectingmeansislocated.
c) A
rooftop
disconnect
on
a
residential
roof
will
normally
not
qualify
as
a
readily
accessibledisconnect.
Anexceptiontothisrequirementwasaddedtothe2005NECtoprovideadditionalclarification
forresidentialandbuildingintegratedPVsystems.Thisexceptionreads:
Exception:Installationsthatcomplywith690.31(E)shallbepermittedtohavethe
disconnectingmeanslocatedremotefromthepointofentryofthesystemconductors.
NEC690.31(E)states:
(E)Direct
Current
Photovoltaic
Source
and
Output
Circuits
Inside
aBuilding.
Where
direct
currentphotovoltaicsourceoroutputcircuitsofautilityinteractiveinverterfromabuilding
integratedorotherphotovoltaicsystemareruninsideabuildingorstructure,theyshallbe
containedinmetallicracewaysorenclosuresfromthepointofpenetrationofthesurfaceofthe
buildingorstructuretothefirstreadilyaccessibledisconnectingmeans.Thedisconnecting
meansshallcomplywith690.14(A)through690.14(D).
Althoughmetalcladcableisnotspecificallycalledoutin690.31(E),manyjurisdictionsconsider
installationswithmetalcladcableasmeetingtheintentofthisnewprovision.Notethatthis
newsectionspecificallymentionsbuildingintegratedsystems.Thewaythe2002NECwas
written,aroof
integrated
PV
system
cannot
reasonably
comply
the
690.14(C)(1)
as
written.
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APPENDIXD:COSTSOFPERMITS
Eachjurisdictionmayhavedifferentinternalcostsstructuresandapproachestoworking
withsolarPVsystems.Thefollowingsectionisprovidedasasuggestionindevelopingthe
coststructureforalocaljurisdiction.
Explanation:Costsforpermitsareoftenbasedontheoverallprojectcost.Thisworkswellfor
manyconventionalprojectsbecausethisaccuratelyrepresentsthescaleoftheproject.However,
withaPVinstallation,theequipmentcostsaremuchhigherthanwithotherprojectsofsimilar
scope.ItisthereforerecommendedthatanalternativepermitfeescalebeusedforPVsystem
installations.ThescopeofaPVinstallationissimilartothatofinstallingaretrofittedresidential
HVACsystem.ThepermittingcostsforaPVsystemshouldbesimilartothoseforanHVAC
system.
Althoughinitialplanreviewandfieldinspectioncostsmaybeslightlyhigherforthefirstfew
systems,thosecostsshouldreduceasthelocaljurisdictionbecomesfamiliarwiththe
installations.Asubdivisionofmorethan10unitsshouldbeconsideredforanadditionalfee
reductionbasedontherepetitivenatureofthereviews.Asuggestedfeescheduleisasfollows:
SmallPVsystem(upto4kW):$75 $200
LargePVsystem(upto10kW):$150 $400
Forsystemsof1050kW,considerapermitcostof$15 $40perkW.
Forsystemsof50100kW,considerapermitcostof$1,500.
Forsystemsof100500kW,considerapermitcostof$3,000.
Forsystemsupto1000kW,considerapermitcostof$3,000$5,000.
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APPENDIXE:TEMPERATURETABLES
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High2%
DB 0"0.5" 0.5"3.5" 3.5"12" 12"36" Max Min
AK BARROW 4 14 47 36 31 28 19 43
AK DEADHORSE 23 19 52 41 36 33 24 45
AK BARTERISWSOAP 11 15 48 37 32 29 N/A N/A
AK KOTZEBUE 5 20 53 42 37 34 24 39
AK BETTLES 205 26 59 48 43 40 29 47
AK FORTYUKON 135 27 60 49 44 41 29 48
AK NOME 7 21 54 43 38 35 24 37
AK SAINTMARY`S(AWOS) 95 22 55 44 39 36 24 34
AK UNALAKLEETFIELD 4 21 54 43 38 35 N/A N/A
AK BETHEL 46 22 55 44 39 36 25 35
AK MCGRATH 103 25 58 47 42 39 2846
AK TALKEETNA 105 24 57 46 41 38 27 36
AK KENAIMUNICIPALAP 26 20 53 42 37 34 24 33
AK SOLDOTNA 33 21 54 43 38 35 24 34
AK NENANAMUNICIPALAP 109 27 60 49 44 41 30 46
AK FAIRBANKS 138 27 60 49 44 41 31 43
AK EIELSONAFB 167 27 60 49 44 41 31 44
AK BIGDELTA 388 25 58 47 42 39 28 47
AK FTRICHARDSON/BRYANTAPT 115 23 56 45 40 37 27 31
AK GULKANA 481 24 57 46 41 38 27 45
AK ELMENDORFAFB 65 23 56 45 40 37 25 29
AK ANCHORAGE 35 22 55 44 39 36 25 26
AK ANCHORAGEMERRILLFIELD 42 23 56 45 40 37 26 26
AK VALDEZWSO 7 21 54 43 38 35 25 17
AK WHITTIER 9 21 54 43 38 35 23 17
AK SEWARD 18 21 54 43 38 35 26 17
AK NORTHWAYAIRPORT 522 26 59 48 43 40 28 48
AK CORDOVA 12 21 54 43 38 35 26 23
AK STPAULIS. 7 12 45 34 29 26 15 19
AK COLDBAY 29 15 48 37 32 29 19 17
AK DILLINGHAM(AMOS) 29 21 54 43 38 35 24 34
AK KINGSALMON 15 22 55 44 39 36 25 35
AK PORTHEIDEN(AMOS) 29 18 51 40 35 32 N/A N/A
AK ILIAMNAARPT 56 21 54 43 38 35 N/A N/A
AK HOMERARPT 27 18 51 40 35 32 21 21
AK MIDDLETONISLANDAUT 36 17 50 39 34 31 19 10
AK KODIAK 34 20 53 42 37 34 24 17
AK YAKUTAT 9 20 53 42 37 34 2421
AK SITKAJAPONSKIAP 4 19 52 41 36 33 24 11
AK JUNEAUINT`LARPT 3 23 56 45 40 37 27 18
AK WRANGELL 13 21 54 43 38 35 25 13
AK KETCHIKANINTLAP 23 22 55 44 39 36 25 14
AK ANNETTE 34 23 56 45 40 37 27 12
AK SHEMYA 30 13 46 35 30 27 14 8
AK ADAKNAS 5 15 48 37 32 29 20 11
AK FIVEFINGERISLAND 7 18 51 40 35 32 22 9
AL MOBILE 67 34 67 56 51 48 36 7
AL MONTGOMERY 62 36 69 58 53 50 37 9
DesignTemperaturesForVariousU.S.CitiesThefollowingtableindicatesthe2%designtemperature(averagedforJuneAugust)forvariouscities;andthe
lowestexpectambienttemperature[690.7]foreachlocation(MinMeanExtremeAnnualDB).Thefirstcolumnis
elevationofthestationforcomparingclimateswithlocationsnotlisted.ColumntworepresentstheASHRAE2%
designtemperature(1).Thethirdthroughsixthcolumnistheresultantambienttemperatureinsidetheconduit
unloaded(2).Itisthetemperaturethewireissubjectedto.Thelastcolumnisthelowestexpectambient
temperatureforthatcity,basedon30yearsofweatherdata.Thisisthetemperaturetobeusedformaximum
voltagecalculationsinNEC690.7.AlltemperaturesinCelcius.
Distanceaboveroof.Temp.
in
Conduit
in
Sunlight
(C)Elev
(M)
ExtremeAnnual
DB
MeanState Station
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State Station Elev (M) 2% 0"-0.5" 0.5"-3.5" .3.5"-12" 12"-36" Max Min .
AL MAXWELLAFB 53 36 69 58 53 50 38 6
AL DOTHANMUNICIPALAP 97 35 68 57 52 49 37 8
AL CAIRNSFIELDFORTRUCKER 91 35 68 57 52 49 37 8
AL BIRMINGHAM 192 35 68 57 52 49 37 12
AL GADSENMUNI(AWOS) 173 34 67 56 51 48 N/A N/A
AL TUSCALOOSAMUNICIPALAP 51 36 69 58 53 50 37 12
AL ANNISTONMETROPOLITANAP 186 35 68 57 52 49 37 12
AL CENTREVILLEWSMO 140 34 67 56 51 48 36 11
AL HUNTSVILLE 190 35 68 57 52 49 36 13
AL MUSCLESHOALSREGIONALAP 164 35 68 57 52 49 37 13
AL DAUPHINISLAND 8 31 64 53 48 45 33
2
AR NORTHLITTLEROCK 170 35 68 57 52 49 37 12
AR LITTLEROCKADAMSFIELD 78 37 70 59 54 51 39 12
AR LITTLEROCKAFB 103 37 70 59 54 51 39 13
AR WALNUTRIDGE(AWOS) 83 35 68 57 52 49 38 13
AR JONESBOROMUNICIPAL 80 36 69 58 53 50 38 16
AR BLYTHEVILLEAFB 79 36 69 58 53 50 38 15
AR STUTTGART(AWOS) 68 36 69 58 53 50 38 9
AR PINEBLUFFFAAAP 63 36 69 58 53 50 38 9
AR TEXARKANAWEBBFIELD 110 37 70 59 54 51 39 10
AR ELDORADOGOODWINFIELD 76 37 70 59 54 51 39 9
AR FORTSMITH 141 37 70 59 54 51 39 14
AR BENTONVILLE(AWOS) 395 34 67 56 51 48 36 17
AR FAYETTEVILLE
DRAKE
FIELD 381 35 68 57 52 49 37
18AR HARRISONFAAAP 418 35 68 57 52 49 37 16
AR FLIPPIN(AWOS) 350 36 69 58 53 50 N/A N/A
AR BATESVILLE(AWOS) 141 37 70 59 54 51 38 13
AR ROGERS(AWOS) 415 34 67 56 51 48 37 16
AZ DOUGLASBISBEEDOUGLASIN 1249 37 70 59 54 51 40 9
AZ TUCSON 779 41 74 63 58 55 43 3
AZ DAVISMONTHANAFB 808 40 73 62 57 54 43 2
AZ SAFFORD(AMOS) 950 40 73 62 57 54 42 10
AZ PHOENIX 339 43 76 65 60 57 46 0
AZ LUKEAFB 331 44 77 66 61 58 47 1
AZ YUMAINTLARPT 62 44 77 66 61 58 47 2
AZ KINGMAN(AMOS) 1033 38 71 60 55 52 40 8
AZ PAGEMUNI(AMOS) 1304 37 70 59 54 51 40 9
AZ PRESCOTTLOVE
FIELD 1536 35 68 57 52 49 37
13
AZ WINSLOWMUNICIPALAP 1490 36 69 58 53 50 39 15
AZ FLAGSTAFF 2135 30 63 52 47 44 32 22
CA ELTOROMCAS 116 33 66 55 50 47 38 3
CA TUSTINMCAF 18 34 67 56 51 48 39 2
CA MARCHAFB 462 38 71 60 55 52 42 2
CA ONTARIO 303 38 71 60 55 52 42 1
CA NORTONAFB/SANBERN 353 39 72 61 56 53 43 2
CA BURBANKGLENDALEPASADENA 225 37 70 59 54 51 41 1
CA SANLUISOBISPO 64 31 64 53 48 45 37 2
CA SANDIEGO 9 29 62 51 46 43 34 5
CA SANDIEGONORTHISLANDNA 14 28 61 50 45 42 34 5
CA CAMPPENDLETONMCAS 22 34 67 56 51 48 39 3
CA SANDIEGOMIRAMARNAS 139 33 66 55 50 47 38 1
CA LOSANGELES 32 29 62 51 46 43 35 4
CA LONGBEACH 17 33 66 55 50 47 39 2
CA EDWARDSAFB 705 41 74 63 58 55 44 10
CA DAGGETT 588 42 75 64 59 56 45 5
CA LANCASTERGENWMFOXFIEL 712 39 72 61 56 53 42 9
CA GEORGEAFB 869 38 71 60 55 52 41 6
CA SANDBERG 1376 33 66 55 50 47 35 6
CA BAKERSFIELD 150 40 73 62 57 54 43 2
CA FRESNO 100 40 73 62 57 54 42 3
CA VISALIAMUNI(AWOS) 89 38 71 60 55 52 40 3
2
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State Station Elev (M) 2% 0"-0.5" 0.5"-3.5" .3.5"-12" 12"-36" Max Min .
CA PT.PIEDRASBLANCA 21 26 59 48 43 40 N/A N/A
CA POINTMUGUNF 3 28 61 50 45 42 34 2
CA SANTABARBARAMUNICIPALA 2 29 62 51 46 43 35 1
CA SANTAMARIA 72 29 62 51 46 43 35 3
CA PASOROBLESMUNICIPALARP 243 39 72 61 56 53 43 6
CA BISHOPAIRPORT 1250 38 71 60 55 52 41 14
CA CASTLEAFB 60 38 71 60 55 52 40 3
CA SACRAMENTO 8 38 71 60 55 52 41 3
CA MATHERFIELD 29 38 71 60 55 52 41 3
CA MCCLELLANAFB 25 39 72 61 56 53 42 3
CA BEALEAFB 38 38 71 60 55 52 41
3
CA SACRAMENTOMETROPOLITANA 7 38 71 60 55 52 41 3
CA SALINASMUNICIPALAP 21 28 61 50 45 42 35 1
CA STOCKTONMETROPOLITANARP 6 38 71 60 55 52 41 3
CA OAKLANDMETROPOLITANARPT 1 28 61 50 45 42 33 1
CA SANFRANCISCO 5 28 61 50 45 42 35 1
CA SANJOSEINTLAP 15 34 67 56 51 48 38 0
CA BLUECANYONAP 1609 29 62 51 46 43 31 9
CA UKIAHMUNICIPALAP 188 38 71 60 55 52 42 3
CA REDBLUFFMUNICIPALARPT 106 41 74 63 58 55 44 4
CA REDDINGMUNICIPALARPT 153 41 74 63 58 55 44 5
CA EUREKA 18 20 53 42 37 34 N/A N/A
CA ARCATA 69 21 54 43 38 35 28 3
CA MOUNT
SHASTA 1077 33 66 55 50 47 35
12CA ALAMEDANAS 4 29 62 51 46 43 34 3
CA MOUNTAINVIEWMOFFETTFLD 11 31 64 53 48 45 36 0
CA TRAVISFIELDAFB 18 37 70 59 54 51 41 3
CA LEMOOREREEVESNAS 73 40 73 62 57 54 42 3
CA IMPERIAL 17 44 77 66 61 58 47 1
CA PALMSPRINGSTHERMALAP 34 44 77 66 61 58 48 5
CA BLYTHERIVERSIDECOARPT 118 45 78 67 62 59 48 1
CA POINTARENA 12 17 50 39 34 31 21