All G20 units are A.G.A. (American Gas Association) and
C.G.A (Canadian Gas Association) certified.
In the US, installation of Lennox gas central furnaces
must conform with local building codes or, in the ab-
senceof local codes,with the currentNational FuelGas
Code (ANSI--Z223.1). The National Fuel Gas Code is
available from:
American National Standards Institute, Inc.
1430 Broadway
New York, NY 10018
NOTE--G20X series units (units equipped with flame
rods) are certified for use with natural gas only.
Air supply for combustion and ventilation must con-
form to the methods outlined in the current National
Fuel Gas Code.
WARNING
Product contains fiberglass wool.
Disturbing the insulation in this product duringinstallation, maintenance, or repair will exposeyou to fiberglass wool. Breathing this may causelung cancer. (Fiberglass wool is known to theState of California to cause cancer.)
Fiberglass wool may also cause respiratory, skin,and eye irritation.
To reduce exposure to this substanceor for furtherinformation, consult material safety data sheetsavailable from address shown below, or contactyour supervisor.
ance shall be made around air openings into the vesti-
bule area. Provisions shall be made for proper opera-
tion and for combustion air and ventilation air supply
according to the current CAN/CGA--B149 standards.
All electrical wiring and grounding for the unitmust be
in accordancewith the current regulations of the Cana-
dian Electrical Code Part I (C.S.A. Standard C22.1) and/
or local codes.
NOTE--G20 series units must not be used as a
�construction heater� at any timeduring any phase of
construction. Very low return air temperature, harm-
ful vapors andmisplacementof the filterswill damage
the unit and its efficiency.
GENERAL
These instructions are intended as a general guide
and do not supersede local codes in anyway. Authori-
ties having jurisdiction should be consulted before
installation.
A--Shipping and Packing List
1--Leveling bolt package (if ordered)
1--Thermostat (if ordered)
1--Rubber grommet (for electrical make--up)
B--Shipping Damage
Check unit for shipping damage. Receiving party
should contact last carrier immediately if any shipping
damage is found.
WARNING
Improper installation, adjustment, alteration, ser-vice or maintenance can cause property damage,personal injury or loss of life. Installation and ser-vice must be performed by a qualified installer,service agency or the gas supplier.
COMBUSTION, DILUTION & VENTILATION AIR
Until recently, therewas no problem in bringing in suf-
ficient amounts of outdoor air for combustion ---- in-
filtration provided all the air that was needed and then
some. In today�s homes built with energy conservation
inmind, tight construction practices make it necessary
to bring in air from outside for combustion. Consider-
ationmust also be given to the use of exhaust fans, ap-
pliance vents, chimneys and fireplaces because they
force additional air that could be used for combustion
out of the house. Unless outside air is brought into the
home for combustion, negative pressure (pressure
outside is greater than inside pressure)will build to the
point that a down draft can occur in the furnace vent
pipe or chimney. Combustion gases enter the living
space creating a potentially dangerous situation.
In the absence of local codes concerning air for com-
bustion and ventilation, this section outlines guide-
lines and recommends procedures for installing G20
furnaces in amanner that ensures efficient and safeop-
eration. Special consideration must be given to com-
bustion air needs as well as requirements for exhaust
vents and gas piping. A portion of this information has
been reprintedwith permission from the National Fuel
Gas Code (ANSI--Z223.1). This reprintedmaterial is not
the complete and official position of the ANSI on the
referenced subject, which is represented only by the
standard in its entirety.
In Canada, refer to the standard CAN/CGA--B149.1 and
5-- The entire length of single wallmetal vent connec-
tor shall be readily accessible for inspection, clean-
ing, and replacement.
6-- Single appliance venting configurations with zero
lateral lengths, see tables 2 and 3, are assumed to
have no elbows in the vent system. For all other
vent configurations, vent system is assumed to
have two 90E elbows. For each additional 90E el-
bow or equivalent (for example two 45E elbows
equal one 90E elbow) beyond two, the maximum
capacity listed in venting table should be reduced
by 10 percent (0.90 x maximum listed capacity).
7-- The common venting tables 4, 5, 6, and 7 were
generated using a maximum horizontal vent con-
nector length of 1--1/2 feet (18 inches) for each inch
of connector diameter as follows:
CONNECTOR
DIAMETER
(INCHES)
MAXIMUM HORIZONTALCONNECTOR LENGTH
(FEET)
3 4--1/2
4 6
5 7--1/2
6 9
7 10--1/2
3DJH ��
8-- If the commonvertical vent is offset, themaximum
common vent capacity listed in the common vent-
ing tables should be reduced by 20%, the equiva-
lent of two 90E elbows (0.80 x maximum common
vent capacity). The horizontal length of the offset
shall not exceed 1--1/2 feet for each inch of com-
mon vent diameter.
9-- The vent pipe shouldbe as short as possiblewith
the least number of elbows and angles to do the
job. The vent connector should be routed to the
vent utilizing the shortest possible route.
10-- A vent connector shall be supported without any
dips or sags and shall slope aminimumof 1/4� per
linear foot of connector, back towards the ap-
pliance.
11 Vent connectors shall be firmly attached to furnace
flue collars by sheet metal screws or other ap-
proved means, except vent connectors of listed
Type �B� vent material which shall be assembled
in accordance with the manufacturer�s instruc-
tions. Joints between sections of single wall con-
nector piping shall be fastened by sheet metal
screws or other approved means.
12-- When the vent connector used for Category I ap-
pliances must be located in or pass through a
crawl space or other areas whichmaybe cold, that
portion of the vent connector shall be listed
double--wall Type B vent material or material hav-
ing equivalent insulation qualities.
13-- All venting pipe passing through floors, walls, and
ceilingsmust be installed with the listed clearance
to combustible materials and be fire stopped ac-
cording to local codes. In absence of local codes,
refer to NFGC (Z223.1).
14-- No portion of the venting system can extend into, or
pass through any circulation air duct or plenum.
15-- Vent connectors serving Category I appliances
shall not be connected to any portion of mechani-
cal draft systems operation under positive pres-
sure such as Category III or IV venting systems.
16-- If vent connectors are combined prior to entering
the common vent, themaximum common vent ca-
pacity listed in the common venting tables must be
reduced by 10%, the equivalent of one 90E elbow
(0.90 x maximum common vent capacity).
17--Common vent diametermust always be at least as
large as the largest vent connector diameter.
18-- In no case, shall the vent connector be upsized
more than two consecutive table size diameters
over the size of the drafthood outlet or flue collar
outlet.
19-- A manual damper, barometric draft regulator or
flue restrictor must not be installed between fur-
nace and any chimney.
20-- When connecting this appliance to an existing dedi-
cated or common venting system, the venting sys-
tem, must be inspected for signs of corrosion, and
general condition. The sizing of the vent system
must be reviewed and conform to these instructions
and the provided venting tables in the U.S.A., and
the appropriate venting tables in the standards of
CAN/CGA--B149.1 and B149.2 of the National Gas
and Propane Installation Code in Canada. If the ex-
isting system is in conflict with these requirements,
the venting system must be resized.
TABLE 2
CAPACITY OF TYPE B DOUBLE--WALL VENTS WITH
TYPE B DOUBLE--WALL CONNECTORS
SERVING A SINGLE CATEGORY I APPLIANCE
Height Lateral
Vent and Connector Diameter -- D(inches)
HeightH
(f )
LateralL
(f )
4 Inch 5 Inch 6 InchH(feet)
L(feet) MAXIMUM Appliance Input Rating in
Thousands of Btu Per Hour
0 86 141 205
62 67 105 157
64 64 103 153
6 61 100 149
0 94 155 235
82 75 120 180
85 71 115 173
8 66 109 165
0 100 166 255
102 81 129 195
105 77 124 188
10 70 115 175
0 112 187 285
2 93 150 225
15 5 87 142 2175
10 82 135 208
15 76 128 198
0 119 202 307
2 100 166 249
205 96 160 241
2010 89 150 228
15 84 142 217
20 78 134 206
0 128 220 336
2 112 185 280
5 108 176 273
30 10 102 171 261
15 96 163 249
20 90 154 237
30 NR NR 219
NOTE: Single appliance venting configurations with zero lateral lengthsare assumed to have no elbows in the vent system. For all other vent con-figurations, the vent system is assumed to have two90E elbows. For eachadditional 90E elbow or equivalent (for example two 45E elbows equalone 90E elbow) beyond two, the maximum capacity listed in the ventingtable should be reduced by 10 percent (0.90 x maximum listed capacity).
3DJH ��
TABLE 3CAPACITY OF TYPE B DOUBLE--WALL VENTS WITH
SINGLE--WALL METAL CONNECTORSSERVING A SINGLE CATEGORY I APPLIANCE
Height Lateral
Vent and Connector Diameter -- D(inches)
HeightH
(f )
LateralL
(f )
4 Inch 5 Inch 6 InchH(feet)
L(feet) MAXIMUM Appliance Input Rating in
Thousands of Btu Per Hour
0 85 140 204
6
2 66 104 156
64 63 102 152
6 60 99 148
0 93 154 234
8
2 75 119 179
85 69 114 171
8 64 107 163
0 99 165 254
10
2 80 128 194
105 76 122 186
10 68 112 171
0 111 186 283
2 93 149 224
15 5 86 140 217
10 79 131 203
15 72 124 192
0 118 201 306
2 99 165 248
20
5 94 158 239
2010 86 146 224
15 80 136 210
20 NR 126 196
0 127 219 334
2 111 183 279
5 106 173 271
30 10 98 168 25730
15 NR 157 242
20 NR NR 228
30 NR NR NR
NOTE: Single appliance venting configurations with zero lateral lengthsare assumed to have no elbows in the vent system. For all other vent con-figurations, the vent system is assumed to have two 90E elbows. For eachadditional 90E elbow or equivalent (for example two 45E elbows equalone 90E elbow) beyond two, the maximum capacity listed in the ventingtable should be reduced by 10 percent (0.90 x maximum listed capacity).
TABLE 4CAPACITY OF TYPE B DOUBLE--WALL VENTS WITH
TYPE B DOUBLE--WALL CONNECTORSSERVING TWO OR MORE CATEGORY I APPLIANCES
VENT CONNECTOR CAPACITY
VentH i ht
ConnectorRi
Vent and Connector Diameter -- D(inches)
HeightH
RiseR
4 Inch 5 Inch 6 InchH
(feet)R
(feet) MAXIMUM Appliance Input Rating inThousands of Btu Per Hour
1 46 72 104
6 2 55 86 1246
3 62 96 139
1 48 76 109
8 2 57 90 129
3 64 101 145
1 50 78 113
10 2 59 93 134
3 67 104 150
1 53 83 120
15 2 63 99 1425
3 71 111 160
1 56 87 125
20 2 66 104 1490
3 74 116 168
1 59 93 134
30 2 70 110 15830
3 79 124 178
TABLE 5CAPACITY OF TYPE B DOUBLE--WALL VENTS WITH
TYPE B DOUBLE--WALL CONNECTORSSERVING TWO OR MORE CATEGORY I APPLIANCES
COMMON VENT CAPACITY
Common Vent Diameter -- D (inches)
VentHeig
4 Inch 5 Inch 6 Inch 7 InchHeight
Appliance Input Rating in Thousands of Btu Per HourhtH
(feet)
NAT+
NAT
FAN+
NAT
NAT+
NAT
FAN+
NAT
NAT+
NAT
FAN+
NAT
NAT+
NAT
FAN+
NAT
6 65 81 103 116 147 161 200 248
8 73 90 114 129 163 178 223 275
10 79 97 124 141 178 194 242 299
15 91 112 144 164 206 228 280 352
20 102 123 160 183 229 255 310 394
30 118 138 185 210 266 297 360 459
3DJH ��
TABLE 6CAPACITY OF TYPE B DOUBLE--WALL VENT WITH
SINGLE--WALL METAL CONNECTORSSERVING TWO OR MORE CATEGORY I APPLIANCES
VENT CONNECTOR CAPACITY
VentH i ht
ConnectorRi
Vent and Connector Diameter -- D(inches)
HeightH
RiseR
4 Inch 5 Inch 6 InchH
(feet)R
(feet) MAXIMUM Appliance Input Rating inThousands of Btu Per Hour
1 46 71 102
6 2 55 85 1236
3 62 95 138
1 52 81 116
15 2 62 97 138
3 70 109 157
1 57 89 129
30 2 67 106 152
3 76 120 172
TABLE 7CAPACITY OF TYPE B DOUBLE--WALL VENTS WITH
SINGLE--WALL METAL CONNECTORSSERVING TWO OR MORE CATEGORY I APPLIANCES
COMMON VENT CAPACITY
Common Vent Diameter -- D (inches)
VentHeig
4 Inch 5 Inch 6 Inch 7 InchHeight
Appliance Input Rating in Thousands of Btu Per HourhtH
(feet)
NAT+
NAT
FAN+
NAT
NAT+
NAT
FAN+
NAT
NAT+
NAT
FAN+
NAT
NAT+
NAT
FAN+
NAT
6 64 78 100 113 144 158 196 244
8 71 87 112 126 159 173 218 269
10 76 94 120 137 174 189 236 292
15 88 108 140 159 200 221 274 343
20 98 118 155 177 223 247 302 383
30 113 132 179 202 257 286 349 446
Removal of Unit from Common Venting System
In the event that an existing furnace is removed from a
venting system commonly run with separate gas ap-
pliances, the venting system is likely to be too large to
properly vent the remaining attached appliances. The
following test should be conducted while each ap-
pliance in operation and theother appliances not in op-
eration remain connected to the common venting sys-
tem. If the venting system has been installed
improperly, the system must be corrected as outlined
in the previous section.
1-- Seal any unused openings in the common venting
system.
2-- Visually inspect the venting system for proper size
and horizontal pitch and determine there is no
blockage or restriction, leakage, corrosion and
other deficiencies which could cause an unsafe
condition.
3-- Insofar as is practical, close all building doors and
windows andall doors between the space inwhich
the appliances remaining connected to the com-
mon venting system are located and other spaces
of the building. Turn on clothes dryers and any ap-
pliances not connected to the common venting
system. Turn on any exhaust fans, such as range
hoods and bathroom exhausts, so they will oper-
ate at maximum speed. Do not operate a summer
exhaust fan. Close fireplace dampers.
4-- Follow the lighting instruction. Place the appliance
being inspected in operation. Adjust thermostat
so appliance will operate continuously.
5-- Test for spillage at the draft hood relief opening af-
ter 5 minutes of main burner operation. Use the
flame of a match or candle, or smoke from a ciga-
rette, cigar or pipe.
6-- After it has been determined that each appliance
remaining connected to the common venting sys-
temproperly ventswhen testedas outlined above,
return doors, windows, exhaust fans, fireplace
dampers and any other gas--burning appliance to
their previous condition of use.
7-- If improper venting is observed during any of the
above tests, the common venting systemmust be
corrected. The common venting system should be
re--sized to approach the minimum size as deter-
mined by using the appropriate tables in appendix
G in the current standards of theNational FuelGas
Code ANSI Z223--1 in the U.S.A., and the appropri-
ate Category 1 Natural Gas and Propane ap-
pliances venting sizing tables in the current stan-
dards of theCAN/CGA--B149.1 and .2 in theNatural
Gas and Propane Installation Code in Canada.
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This furnace is design certified by the American Gas
Association for horizontal venting through an outside
wall only with the use of a Field Controls Company
Model #SWG--5L side wall venting kit available from
Lennox Dealer Service Center. No other Field brand
venting kit or any other manufacturer�s venting kit is
acceptable. Horizontal venting of this furnace without
the use of the above stated kit is prohibited. See figure
10 for field wiring of side wall horizontal venting kit.
When horizontally vented, minimum clearance for ter-
mination from electric meters, gas meters, regulators
and relief equipment is 4 ft. (1.2m).
At vent termination, care must be taken to maintain
protective coatings over buildingmaterials (prolonged
exposure to exhaust condensate can destroy protec-
tive coatings). It is recommended that the exhaust out-
let not be located within 6 ft. (1.8m) of a condensing
unit because the condensate can damage the painted
coating.
3DJH ��
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Gas Supply
1-- This unit is shipped standard for left side installa-
tion of gas piping. Simply connect gas supply to
piping assembly.
2-- A piping hole is also fabricated in the right side of
the unit for alternate piping arrangements.
3-- When connecting gas supply, factors such as
lengthof run, number of fittings and furnace rating
must be considered to avoid excessive pressure
drop. Table 8 lists recommendedpipe sizes for typ-
ical applications.
4-- Gas piping must not run in or through air ducts,
clothes chutes, chimneys or gas vents, dumbwait-
ers or elevator shafts.
5-- Piping should be sloped 1/4 inch per 15 feet (6mm
per 4.57m) upward toward the meter from the fur-
nace. The pipingmust be supported at proper inter-
vals, every 8 to 10 feet (2.44m to 3.05m), using suit-
able hangers or straps. A drip leg should be
installed in vertical pipe runs to the unit.
6-- In some localities, codes may require installation
of a manual main shut--off valve and union (fur-
nished by installer) external to the unit. Union
must be of the ground joint type.
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NOTE--In the case emergency shut--off is required, shut
offmainmanual gas valve and disconnectmain power
to unit. These devices should be properly labeled by
the installer.
NOTE--Installer must provide a 1/8� (3.2mm) N.P.T.
plugged tap in the field piping upstreamof the gas sup-
ply connection to the unit. Tap must be accessible for
test gauge connection. See figure 11.
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TABLE 8GAS PIPE CAPACITY -- FT3/HR (kL/HR)
Nominal Internal Length of Pipe--Feet(m)NominalIron Pipe Size--Inches(mm)
InternalDiameter
--Inches(mm)10
(3.048)20
(6.096)
30
(9.144)
40
(12.192)
50
(15.240)
60
(18.288)
70
(21.336)
80
(24.384)
90
(27.432)
100
(30.480)
1/4
(6.35)
.364
(9.246)
43
(1.13)
29
(.82)
24
(.68)
20
(.57)
18
(.51)
16
(.45)
15
(.42)
14
(.40)
13
(.37)
12
(.34)
3/8
(9.53)
.493
(12.522)
95
(2.69)
65
(1.84)
52
(1.47)
45
(1.27)
40
(1.13)
36
(1.02)
33
(.73)
31
(.88)
29
(.82)
27
(.76)
1/2
(12.7)
.622
(17.799)
175
(4.96)
120
(3.40)
97
(2.75)
82
(2.32)
73
(2.07)
66
(1.87)
61
(1.73)
57
(1.61)
53
(1.50)
50
(1.42)
3/4
(19.05)
.824
(20.930)
360
(10.19)
250
(7.08)
200
(5.66)
170
(4.81)
151
(4.28)
138
(3.91)
125
(3.54)
118
(3.34)
110
(3.11)
103
(2.92)
1
(25.4)
1.049
(26.645)
680
(919.25)
465
(13.17)
375
(10.62)
320
(9.06)
285
(8.07)
260
(7.36)
240
(6.80)
220
(6.23)
205
(5.80)
195
(5.52)
1--1/4
(31.75)
1.380
(35.052)
1400
(39.64)
950
(26.90)
770
(21.80)
660
(18.69)
580
(16.42)
530
(15.01)
490
(13.87)
460
(13.03)
430
(12.18)
400
(11.33)
1--1/2
(38.1)
1.610
(40.894)
2100
(59.46)
460
(41.34)
1180
(33.41)
990
(28.03)
900
(25.48)
810
(22.94)
750
(21.24)
690
(19.54)
650
(18.41)
620
(17.56)
2
(50.8)
2.067
(52.502)
3950
(111.85)
2750
(77.87)
2200
(62.30)
1900
(53.80)
1680
(47.57)
1520
(43.04)
1400
(39.64)
1300
(36.81)
1220
(34.55)
1150
(32.56)
2--1/2
(63.5)
2.469
(67.713)
6300
(178.39)
4350
(123.17)
3520
(99.67)
3000
(84.95
2650
(75.04)
2400
(67.96)
2250
(63.71)
2050
(58.05)
1950
(55.22)
1850
(52.38)
3
(76.2)
3.068
(77.927)
11000
(311.48)
7700
(218.03)
6250
(176.98)
5300
(150.07)
4750
(134.50)
4300
(121.76)
3900
(110.43)
3700
(104.77)
3450
(97.69)
3250
(92.03)
4
(101.6)
4.026
(102.260)
23000
(651.27)
15800
(447.39)
12800
(362.44)
10900
(308.64)
9700
(274.67)
8800
(249.18)
8100
(229.36)
7500
(212.37)
7200
(203.88)
6700
(189.72)
NOTE--Capacity given in cubic feet of gas per hour (kilo liters of gas per hour) and based on 0.60 specific gravity gas.
3DJH ��
Leak Check
After gas piping is completed, carefully check all piping
connections (factory and field) for gas leaks. Use a leak
BEFORE LIGHTING smell all around the appliance area
for gas. Be sure to smell next to the floor because some
gas is heavier than air and will settle on the floor.
Use only your hand to push in or turn the gas control
knob or lever. Never use tools. If the knob or lever will
not push in or turn by hand, do not try to repair it, call a
qualified service technician. Force or attempted repair
may result in a fire or explosion.
To place G20 furnace into operation:
All G20 units are equipped with an intermittent pilot igni-
tion system. Do not attempt to manually light pilots on
these furnaces. Each time thermostat calls forheat, thepi-
lot will automatically light. The pilot does not burn when
there is no call for heat on units with electronic ignitions.
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1-- STOP! Read the safety information at the begin-
ning of this section.
2-- Set thermostat to lowest setting. See figure 16.
3-- Turn off all electrical power to appliance.
4-- This appliance is equipped with an ignition device
which automatically lights the pilot. Do not try to
light the pilot by hand.
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5-- Remove control access panel.
6-- On Honeywell VR8204 gas valves, turn knob on
gas valve clockwise to OFF. Units with Robert-
shaw 7200 gas valve, depress lever and move to
OFF position. Do not force. See figure 18.
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7-- Wait five (5) minutes to clear out any gas. If you
then smell gas, STOP! Immediately call your gas
supplier from a neighbor�s phone. Follow the gas
supplier�s instructions. If you do not smell gas go
to next step.
8-- On Honeywell VR8204 gas valves, turn knob on
gas valve counterclockwise to ON. Units with
Robertshaw 7200 gas valve, depress lever and
move to ON position. Do not force.
9-- Replace control access panel.
10-- Turn on all electrical power to unit.
3DJH ��
11-- Set thermostat to desired setting.
NOTE--When unit is initially started, steps 1 through 11
may need to be repeated to purge air from pilot line.
12-- If the appliance still will not operate, follow the
instructions �To Turn Off Gas To Unit� and call
your service technician or gas supplier.
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1-- Set thermostat to lowest setting.
2-- Turnoff all electrical power tounit if service is to be
performed.
3-- Remove control access panel.
4-- On Honeywell VR8204 gas valves, turn knob on gas
valve clockwise to OFF. Units with Robertshaw
7200 gas valve, depress lever andmove toOFFposi-
tion. Do not force.
5-- Replace control access panel.
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G20 series units are certified for installations from 0 to
4000 feet (0 to 1219m) above sea level without modifi-
cation. For installations from 4000 feet to 7500 feet
(1219m to 2286m) above sea level, a high altitude kit
(44H56) must be installed. The kit contains special flue
baffles used to replace factory--installed baffles. No
derate is required.
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Gas Flow
To check for proper gas flow to combustion chamber, de-
termineBtu input from appliance rating plate. Divide this
input rating by theBtuper cubic foot of available gas. Re-
sult is the required number of cubic ft. (cubic meter) per
hour. Determine the flow of gas through gas meter for
twominutes andmultiply by 30 to get the hourly flow of
gas to burner.
Gas Pressure
1-- Check gas line pressure with unit firing at maxi-
mum rate. A minimum of 4.5� w.c. (1.12kPa) for
natural gas or 10.5� w.c. (2.61kPa) for LP/propane
gas should be maintained.
2-- After linepressurehasbeencheckedandadjusted,
check manifold pressure. Correct manifold pres-
sure for LP/propane gas is 9.5� w.c. (2.36kPa) No
adjustment is needed inhigh altitude applications.
A natural gas to LP/propane gas changeover kit is
required to convert unit. Refer to the installation
instructions supplied with changeover kit for con-
version procedure.
Correct manifold pressure for natural gas is 3.5�
w.c. (.87kPa). No adjustment is needed in high alti-
tude applications. See figures 19 and 20 for man-
ifold pressure adjustment screw location.
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Limit Control
Limit Control--Factory set: No adjustment necessary.
Fan Control
The fan on time of 45 seconds is not adjustable. Fan off
time (time that the blower operates after the heat de-
mand has been satisfied) can be adjusted by moving
the jumper on the BCC2blower control center. The unit
is shipped with a factory fan off setting of 90 seconds.
Fan off timewill affect comfort and is adjustable to sat-
isfy individual applications. See figure 21.
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Temperature Rise
Check temperature rise and, if necessary, adjust blow-
er speed to maintain temperature rise within range
shown on unit rating plate.
Thermostat Adjustment
Set thermostat heat anticipation setting for G20 units
at .10 ampsor at the lowest setting availablebutnot be-
low .10 amps. An isolation relay is built into the BCC2
blower control board to enhance the compatibility of
the thermostat to the gas control.
Electrical
1-- Check all wiring for loose connections.
2-- Check for correct voltage at unit (unit operating).
3-- Check amp--draw on blower motor.
Motor Nameplate__________Actual__________
Blower Speeds
Blower speed selection is accomplished by changing
the taps at the harness connector at the blower motor.
See figure 22.
Refer to speed selection chart on unit wiring diagram.
NOTE--CFM readings are taken external to unit with a
dry evaporator coil and without accessories.
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Flue and Chimney
1-- Check flue pipe, chimney and all connections for
tightness and to make sure there is no blockage.
2-- Check unit for proper draft.
Failure to Operate
If unit fails to operate check the following:
1-- Is thermostat calling for heat?
2-- Is main disconnect switch closed?
3-- Is there a blown fuse?
4-- Is filter dirty or plugged? Dirty or plugged filters
will cause unit to go off on limit control.
5-- Is gas turned on at meter?
6-- Is manual main shut--off valve open?
7-- Is internal manual shut--off valve open?
After items 1 through 7 have been checked and unit still
will not start, manually reset vent safety shut--off switch
located at the right sideof draft hood. If unit operation re-
sumes and then cuts out again, inspect furnace vent sys-
tem for proper sizing and installation. Also, check for
vent blockage and for proper draft. If unit still does not
start, reset roll--out switch on burner box. See figure 2. If
unit starts and cuts out, check heat section for blockage.
Pilot and Burner Flame
After the G20 unit has been installed and wired, the pi-
lot flame should be periodically checked and adjusted,
if necessary, to insure proper unit operation. Use the
following procedure to adjust the pilot flame.
Pilot Flame Adjustment
1-- Turn off power to the unit.
2-- Disconnect wire from MV terminal on the gasvalve.
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3-- On Honeywell VR8204 gas valves, turn knob ongas valve counterclockwise toON. Units with Rob-ertshaw7200gas valve, depress lever andmove toON position. Do not force.
4-- Restore power to unit.
5-- Set thermostat to call for heat.
At this point the pilot valve portion of the gas valve will
be energized after a call for heat is initiated. Pilotwill then
light. Examine the pilot flame to determine if it is a soft,
stable flame that surrounds the flame sensor. See figure
23. If this is not the case, the pilot needs adjustment.
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6-- Identify the gas valve being used and locate the pi-
lot adjustment screw. On some gas valves the ac-
tual adjustment screw is under a cap. See figures
24, and 25 for pilot adjustment screw locations.
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7-- Turn thepilot adjustment screwuntil the pilot flameis soft and stably surrounds the flame sensor.
8-- Take a microamp reading of the flame signal com-ing from the flame sensor. The normal range is0.80 to 1.20 microamps with a minimum of 0.70microamps.
9-- After correct pilot flame has been obtained, adjustthermostat to stop a call for heat.
10-- Turn off power to unit.
11-- Reconnect MV wire to MV terminal on gas valve.
12-- Restore power to unit and assure normal operation.
Burner Flame
Start burner and allow to operate for a few minutes to
establish normal burning conditions. Check burner
flame by observation. Flame should be predominantly
blue in color, strong in appearance and should rise di-
rectly from the burner ports in the heat exchanger.
Check to see that flame is burning from all continuous
ribbon ports and that flame does not impinge on the
