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MOBILE HOME TRAINING

Mobile Home Heating Systems

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Learning Objectives

By attending this session, participants will become aware of:

MOBILE HOME HEATING SYSTEMS

aware of:

• Mobile home heating system characteristics

• Mobile home heating system components

• Furnace testing protocols

• Furnace testing equipment

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• Improvements through cleaning and tuning

• Furnace replacement criteria

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Heating System Characteristics #1

FlueFlue

MOBILE HOME HEATING SYSTEMS

• Specifically designed for use in mobile homes

• Usually located in a closet

• Sealed combustion with dedicated combustion air inlets

• Short metal chimney design

• Compact interchangeable burners

• “Down-Flow” air distribution t

Heat ExchangerHeat Exchanger

BlowerBlower

Combustion AirCombustion Air

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system

• Ducts located in the belly cavity

• May mix outside air with conditioned air

Combustion AirCombustion Air

BurnerBurner

Photo courtesy of WV GOEO

Heating System Characteristics #2MOBILE HOME HEATING SYSTEMS

Furnace Main DuctRegisters

Return Air

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Combustion Air Intake

Exhaust

Heating System Characteristics #3MOBILE HOME HEATING SYSTEMS

Supply Air Fan

Return Air Intake

G Oil B

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Gas or Oil Burner

Supply Air Duct

Heating System Characteristics #4

Flue Vent Pipe for Exhaust Air and Gases (Hot)

Entry Pipe for Combustion Air (Cool)

MOBILE HOME HEATING SYSTEMS

Return Air Intake

Blower

Heat Exchanger

Combustion Chamber

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Chamber

Air Conditioner Coil CabinetTo Heating Ducts

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Chimney TerminationsMOBILE HOME HEATING SYSTEMS

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Photos courtesy of the US Department of Energy

Gas or Propane Oil

Oil HeatMOBILE HOME HEATING SYSTEMS

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Photos courtesy of PA WTC

Oil Burner and Combustion Air Inlet

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Make-Up AirMOBILE HOME HEATING SYSTEMS

Fresh Air InletFresh Air InletFresh Air InletFresh Air Inlet

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Photos courtesy of PA WTC

Furnace Testing Protocol

Furnaces must be tested to assess:• Safety (fuel leaks clearances etc )

MOBILE HOME HEATING SYSTEMS

• Safety (fuel leaks, clearances, etc.)

• Flue gas temperatures

• Oxygen (O2) or Carbon Dioxide (CO2)

• Carbon Monoxide (CO) levels

• Draft

Test HoleTest Hole

• Condition of the heat exchange

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• Temperature rise

• Operating fan temperaturesSingle wall flue for oil heat

Photo courtesy of PA WTC

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Testing Equipment - CriteriaMOBILE HOME HEATING SYSTEMS

Combustion analyzers should be able to read and calculate for:

• Flue gas oxygen content

• Flue gas temperature

• Ambient temperature

• Flue gas carbon monoxide

• Combustion efficiency

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Image Source: http://www.bacharach-inc.com/fyrite-tech.htm

Combustion efficiency

• Flue gas carbon dioxide content

• Flue gas carbon monoxide air-free content

Selected Testing EquipmentMOBILE HOME HEATING SYSTEMS

Draft Gauge Smoke Tester (for Oil)Image Source: www.bacharach-inc.comImage Source: www.bacharach-inc.com

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Inspection Mirror Digital Probe ThermometerImage Source: www.omnicontrols.com

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Di t d d b i

Furnace Testing Methods - VisualMOBILE HOME HEATING SYSTEMS

• Dirt and debriCheck for:

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• Burner alignment

• Soot, evidence of flame roll out

• Condition of the heat exchanger

• Vent pipe and roof termination

• Gas or oil leaks

• Condition of the wiring

• Condition of air filter

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Photo courtesy of PA WTC

Image Source: http://www.bacharach-inc.com/fyrite-tech.htm

Furnace Testing Methods - AnalyzerMOBILE HOME HEATING SYSTEMS

Test for:• Steady-state efficiency• Cracked heat exchanger• Carbon monoxide levels• Smoke (oil)• Temperature rise• Safety shut off features

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Test Procedure - Sealed Combustion Gas FurnacesMOBILE HOME HEATING SYSTEMS

• Drill a 3/8 inch hole through the outer and inner sleeves of the chimney flue assembly

• Extract a flue gas sample

• Record the stack temperature

• Test draft

• Enlarge the hole on the outer flue

• Apply plug with high temperature

Test HoleTest Hole

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sealant to the inner test hole

• Apply plug with high temperature sealant to outer hole

• OR use SS lag bolt with high temp sealant

Look for rust on the burner ports

MOBILE HOME HEATING SYSTEMS

Look for rust on the burner ports

Photo courtesy of PA WTC

Heat Exchanger Leakage Testing

Test Methods:•

• Measure the flue gas concentration before and after blower starts

– There should be no more than 1% oxygen change when the blower starts

• Observe change in draft, CO or flame when blower turns on

• Look for flame-damaged areas on the heat exchanger

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Temperature Rise TestMOBILE HOME HEATING SYSTEMS

• Place a thermometer probe into the return plenum and another one in the closest supply duct

• Record the temperatures• Calculate the difference to determine Temperature rise

the temperature rise test locations• The temperature rise should be

between 45˚ and 70˚, or no greater than the manufacturer’s specifications

• Excessive temperature rise indicates Temp ProbeTemp Probe

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Excessive temperature rise indicates insufficient airflow as a result of:– Dirty filter– Blockages– Insufficient return or supply duct

cross-sectional area– Low fan speed or dirty fan

Temp ProbeTemp Probe

Fan Operating Temperature Testing

• Verify fan operating temperatures

MOBILE HOME HEATING SYSTEMS

temperatures– High Limit – set at factory

(200˚) Fan-on/Fan-off test location– Fan-On (100˚ – 120˚)

– Fan-Off (90˚ – 100˚)

• Record the temperatures by placing one thermometer

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probe into the blower compartment and the other in the supply register closest to the furnace

Temp ProbeTemp Probe

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Blower MaintenanceMOBILE HOME HEATING SYSTEMS

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Photos courtesy of PA WTC

Remove and clean the blower

Filter ReplacementMOBILE HOME HEATING SYSTEMS

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Photos courtesy of PA WTC

Change out the furnace filter and educate the client

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Electrical ChecksMOBILE HOME HEATING SYSTEMS

Check for safety of electrical components

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Photos courtesy of PA WTC

Clearance To CombustiblesMOBILE HOME HEATING SYSTEMS

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Check clearance to combustibles

Photos courtesy of Tony Gill

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Clean & Tune – All Fuel Types

• Clean dirty burners

Cl d dj t bl

MOBILE HOME HEATING SYSTEMS

• Clean and adjust blower

• Replace furnace filter and educate clients how to replace

• Fix excessive temperature rise problems

• Check and adjust fan operating temperatures

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Furnace Replacement #1

A furnace should be replaced if any of the following

MOBILE HOME HEATING SYSTEMS

if any of the following conditions exist:

• The furnace has a cracked heat exchanger

• Repair and retrofit exceeds half the cost of replacement cost

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• The furnace is not operating or repairable

Photo courtesy of WV GOEO

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Furnace Replacement #2MOBILE HOME HEATING SYSTEMS

• Select a furnace specifically designed for use in a mobile home (UL-approved)

• Furnace should be sized to meet the heating load requirement of the home according to a Manual J heat loss calculation or MHEA assessment

• Note the differences between the old furnace and the new one

• Check to see how combustion air is

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Check to see how combustion air is supplied to the furnace

• Follow the manufacturer’s installation instructions exactly

Photo courtesy of WV GOEO

Summary

• Mobile home heating systems are specific to the housing type, and different from the heating systems in site built homes

MOBILE HOME HEATING SYSTEMS

site-built homes.

• Safety and efficiency tests must be performed using both visual and diagnostic tests.

• Mobile home furnaces sometimes need to be replaced due to poor maintenance and cracked heat exchangers.

Replace furnaces with models that are UL approved for

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• Replace furnaces with models that are UL-approved for use in mobile homes.

• Clean blowers, replace filters, and educate clients about the need for routine maintenance.