GAS HEATING Planned Maintenance Produced by Joe Marchese

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GAS HEATING Planned MaintenanceProduced
byJoe Marchese
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Personal Safety

• Good safety practices will prevent many injures
• Safety must be first on your mind at all times
• Always remove loose items when working around
  equipment with moving or rotating parts
• Be cautious of sharp objects

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Personal Safety

• Always lift with your legs and not with your back
• Wear a back support belt when lifting heavy
  objects
• When working with electrical equipment always
  verify that the power is off
• Do not rely on a shut-off switch or disconnect
  being off -- always check yourself

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Personal Safety

• Be cautious of hot surfaces or work areas
• Be cautious of any gas or oil leaks
• Always check for carbon monoxide
• Always follow proper safety practices when
  working with ladders
• Be cautious of confined spaces - provide proper
  ventilation when required

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Personal Safety Equipment
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Safety Shoes
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Safety Goggles
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Gloves
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Pocket Voltage Detector
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Back Support Belt
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Oil Absorbent
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Personal CO Detector
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Why Perform Planned Maintenance?

• To reduce equipment failures
• To keep equipment operating in a safe manner
• To keep equipment performing at peak efficiencies
  
• To maintain good indoor air quality

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What is the most important concern for a service
technician while performing a preventive
maintenance inspection?

• SAFETY

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Safety

• Carbon monoxide poisoning is a major concern
• Natural gas leaks can create a serious hazard
• Fire as a result of damaged or bypassed safety
  controls
• Lack of heat from improperly operating furnaces

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Keeping Equipment at Peak Efficiency

• Poor electrical connections can cause the system
  to work harder
• Improper gas combustion will decrease the
  efficiency of a gas-fired furnace
• Dirty filters will reduce the airflow through a
  system which will decrease the systems
  efficiencies

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Indoor Air Quality

• Humidifiers that are not operating properly can
  lead to poor indoor air quality
• Filters not maintained can lead to poor indoor
  air quality
• Carbon monoxide leaking into a structure is a
  serious indoor air quality issue

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How Long Should a PM Inspection Take?

• Depends on
• the type of equipment
• the detail in which the inspection is performed

SHORT INSPECTION vs. LONG INSPECTION
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What Are the Most Important Tools Used on a PM
Inspection?

• Your hands
• Your eyes
• Your ears
• Your nose

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First Steps

• Determine the type of furnace
• Barometric - standing pilot
• Barometric - direct spark Ignition
• Induced draft - DSI or hot surface ignition
• High efficiency - sealed combustion

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Maintenance Task Items

• Always following the equipment manufacturers
  guidelines
• Tasks can be grouped into four major categories
• Inspection
• Cleaning
• Lubrication
• Operation checks

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Maintenance Task Items

• Check availability of combustion air (80
  furnaces only)
• Clean and inspect air system accessories such as
  humidifiers and electronic air cleaners
• Check the condition of the electrical wiring and
  tightness of the terminals and connectors
• Clean or replace air filters

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Maintenance Task Items

• Clean and inspect fan compartment
• Clean and inspect the condensate drain system
  (90 furnaces only)
• Clean and inspect the vent system
• Clean and inspect burners and heat exchanger

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Maintenance Task Items

• Check thermostat and heat anticipator or cycle
  switch settings
• Check sequence of operation
• Check pilot/burner operation
• Perform combustion tests
• Check temperature rise
• Check safety controls

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Combustion Air

• Different furnace designs will have different
  styles to bring combustion air into a furnace.
• An 80 efficient furnace normally uses the air
  surrounding the furnace for its combustion air
• A 90 plus furnace normally uses outside air for
  its combustion air

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Combustion Air

• When performing an inspection the location of the
  furnace should be examined to make sure it has a
  sufficient volume to provide enough combustion
  air
• Make sure no other gas-fired appliances (such as
  a dryer or hot water heater) steal combustion air
  from the furnace

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Combustion Air

• Verify that the combustion air will not be
  contaminated by halogen compounds, such as
  fluoride, chloride, bromide and iodide vapor.
• If installed in a laundry room, make sure the
  exhausted products vented by the dryer do not
  enter the furnace and are used for combustion air

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Unconfined Space

• An unconfined spaced has a volume of at least 50
  cubic feet per 1000 Btus input total for all
  appliances located in the space
• If the unconfined space is constructed unusually
  tight, the combustion air must come from outside
  air or from spaces freely communicating with the
  outdoors

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Confined Spaces

• A confined space has a volume less than 50 cubic
  feet per foot per 1000 Btus of total input
  rating of all appliances installed in that space
• There must be provisions for supplying combustion
  air it can be ducted in from outdoors or from an
  unconfined space

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Confined Spaces

• The number of openings and the size of the
  openings will depend on whether the air comes
  from the outside or from adjoining unconfined
  space

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Combustion Air Requirements

• If combustion air is brought from within the
  structure there must be 2 openings
• Each opening must have a minimum free area of not
  less than 1 square inch per 1000 Btu of total
  input rating for all gas appliances in the space
  (should not be less than 100 square inches)
• If construction is unusually tight, outside air
  must be brought in

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Combustion Air Requirements

• If combustion air is brought from outside the
  structure there must also be 2 openings, however
• If two vertical ducts are used they must have at
  least 1 square inch of free area per 4000 Btus of
  total input for all gas appliances
• If two horizontal ducts are used they must have
  at least 1 square inch of free area per 2000 Btus
  of total input for all gas appliances

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Combustion Air Requirements

• A single opening can be used if it has a free
  area of 1 square inch per 3000 Btus of total
  input for all gas appliances
• Failure to comply with these guidelines may
  result in a furnace starved for combustion air
  which could lead to the formation of carbon
  monoxide

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Cleaning and Inspecting Air System Accessories
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Humidifiers
Maintenance required

• Replace media pad
• Clean mineral deposits from
• water reservoir or drain pan
• float, float valve orifice, and valve seat
• water solenoid valve orifice and strainer

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Humidifiers
Maintenance required

• Check for water overflow
• On wheel-type humidifiers, an approved water
  treatment solvent can be applied to water
  reservoir
• If a bypass humidifier is used, make sure the
  dampers are open for winter operation

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Recommended Indoor Humidity Levels at
Various Outdoor
Temperatures
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Electronic Air Cleaners
Maintenance required

• Turn voltage off to unit (9,000 to 11,000 VDC
  supplied by cleaners transformer)
• Remove the pre-filters and air cleaner cells
• Clean inside of cabinet
• Clean pre-filters with a mild soap solution

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Electronic Air Cleaners
Maintenance required

• Wash air cleaner cells with a solution of 3/4
  cup of dishwasher detergent and hot water
• Vinegar can also be used to clean cells
• Soak cells in solution for 15 to 20 minutes
• Rinse until all the solution is removed

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Electronic Air Cleaners
Maintenance required

• Inspect cells for any damage and reinstall with
  pre-filters
• Leave systems blower on for 30 minutes with
  power off to air cleaner to dry the cells
  thoroughly

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Heat Recovery Ventilators
Maintenance required

• Filters should be changed monthly and interior
  blower maintained on the same schedule as the
  furnace
• Drain pans and interior of unit
• Clean interior surface and wipe the drain pans
  with a soft cloth and a mild cleaning solution
• Check condensate drain

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Heat Recovery Ventilators
Maintenance required

• Heat Recovery Cores
• Remove from unit
• Use warm water and a mild soap
• Soak recovery core in solution for about three
  hours
• Allow to dry before reinstalling

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Electrical Connections

• Turn off voltage applied to the furnace
• Make a visual inspection of all wire terminals
  and wires
• Check for discoloration
• Check for frayed or damaged insulation
• Check for any loose connections and retighten all
  accessible screw terminals if needed
• Check fuse holders for tightness, if applicable

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Air Filters
Maintenance required

• Can be either cleaned or replaced, depending on
  type
• A clogged or dirty air filter will result in the
  system going off on its high temperature safety
  limit, resulting in poor heating of the
  conditioned space
• Make sure to install air filters in the correct
  direction of airflow

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Air Filters

• Some owners may choose to replace their own
  filters or have their in-house maintenance
  personnel install the filters
• There are many different types of filters
  available -- notify the customer of the various
  types so the best filter can be selected for the
  job

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Fan Compartment

• Check blower wheel for dirt build-up and clean
  when required
• An important maintenance task
• Dirt on blower wheel will reduce CFM delivered by
  fan
• This may be a time-consuming task
• May require removing entire drive assembly

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Fan Compartment (Direct Driven Blowers)

• Visually inspect fan motor for bearing wear by
  spinning fan wheel and notice how it slows down
  and stops
• Check fan motor for excess end play
• Some motors may have up to 1/8 end play
• Check motor bearing for oval shape
• There should be no vertical play with shaft
• Lubricate motor, if required

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Fan Compartment(Belt Driven Blowers)

• Check belt tension for proper adjustment
• 3/8 to 1/2 depression with a 10 lb. force
• If possible, use a belt tension gauge
• Visually inspect belt, bearing and pulley for
  signs of wear
• Visually inspect pulley and drive alignment
• use straight edge or string

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Fan Compartment (Belt Driven Blowers)

• Check pulley and drive set screws for tightness
• Record belt size
• When possible leave an extra belt on the job
• Mark belt size on unit
• Lubricate motor and fan bearings, when possible
• Some motors have sealed bearings and external
  lubrication is not needed

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Clean and Inspect Condensate Drain System

• Inspect condition of the condensate line
• Clear lines with compressed gas, if necessary
• Inspect condensate pump, remove and clean if
  required

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Condensate Pumps
Maintenance required

• Remove pump from system
• Remove reservoir from pump
• Clean reservoir of any dirt or grime and check
  float
• Reinstall
• Add water to system to check pumping operation

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Check Conditionof the Vent System

• Inspect pipes for any cracks or weak spots
• Clean out chimney base if access door is provided
• If no access door is provided, remove a section
  of pipe and examine for any clogs or restrictions
• Verify the vent system is pitched toward the
  furnace 1/4 per foot

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Draft Diverters
If the system has a draft diverter

• Check for obstructions
• Check for signs of corrosion
• Lightly tap area to see if walls are rusted

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Cleaning and Inspection of Gas Burners

• Remove and clean burners, mainly multi-port
  burners only
• Mono-port burners require little cleaning
• Use a mild brush and shop vacuum
• Do not damage or enlarge ports while cleaning
• Cleaning of burners may not be needed on every
  inspection, but must be checked

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Cleaning and Inspection of Gas Burners

• Check burner alignment to ensure no flame
  impingement is occurring on the heat exchanger
• Flame impingement will cause CO
• Make sure the burners are secure
• Check crossover tubes to ensure proper alignment

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Heat Exchangers

• Check for cracks
• Can be inspected for cracks in one of three ways
• Visual Method
• Requires removing burners
• The use of a good mirror and strong lamp
• Difficult to perform
• Air Flow Method
• Test Gas Method

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Standing Pilot Systems

• Remove and clean pilot assembly, where required
• Do not clean orifice with an object that may
  change the size of the orifice opening
• Check and adjust pilot flame, if necessary

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Pilot Assemblies

• Pilot flame should impinge a height of 3/8 to
  1/2 on the top of the thermocouple

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Thermocouples
Two dissimilar metals are welded together at one
end
When one of the junctions is heated and the other
end remains relatively cool, a low electric DC
voltage is produced
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Thermocouples
The voltage generated depends on the temperature
difference between the hot and cold junctions
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Output Voltages

• Normal output voltage of an unloaded thermocouple
  is 26 to 32 milli-volts DC
• The minimum acceptable output voltage is 18
  milli-volts DC
• Drop out time of the pilot solenoid should be
  within 2-1/2 minutes.

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Direct Ignition(Hot Surface Igniter)

• Hot surface igniter directly lights burners
• Made of ceramic
• Is very fragile

Uses flame rectification circuit
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Direct Ignition(Hot Surface Igniter)

• During preventive maintenance inspections,
  visually inspect for cracks or breaks
• At room temperature the resistance should equal
  45 to 90 ohms (if over 110 ohms, replace)

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Thermostats

• On mechanical thermostats check
• That the thermostat is level
• That the heating anticipator setting is properly
  set
• That the temperature gauge on the thermostat is
  within 2F of actual temperature of the living
  space

• Electronic thermostats only require checking the
  accuracy of the temperature gauge

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Heating Anticipators

• Wired in series with the controller contacts
• Set to match the amperage draw of the heating
  controls
• Too low of a setting will cause the on cycle to
  be too short
• Too high of a setting will cause the on cycle to
  be too long

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Sequence of Operation

• A major part of a preventive maintenance
  inspection is checking the sequence of operation
  of a furnace
• Necessary to verify the furnace is operating
  safely and efficiently
• Different furnace types will have varying
  sequences of operation

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Intermittent Pilot Furnaces
Sequence of operation

• Thermostat calls for heat
• Spark is generated to light pilot
• Once pilot flame is proven, the gas valve opens
  and flame is produced
• After a delay the indoor blower is turned on

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Standing Pilot Natural Draft
Sequence of operation

• Thermostat calls for heat
• Gas valve opens
• Burners are lit
• After a delay, based on air temperature the
  indoor blower motor will come on

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Standing Pilot Induced Draft
Sequence of operation

• Thermostat calls for heat
• Induced draft blower comes on
• Once draft has been proven, the gas valve opens
  and flame is produced and the flame is proved
• Indoor blower is turned on after a delay

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Direct IgnitionCondensing Furnace
Sequence of operation

• Thermostat calls for heat
• Induced draft blower comes on
• Once the induced draft blower builds a negative
  pressure in the blower housing, the differential
  pressure switch closes
• Hot surface igniter is energized

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Direct IgnitionCondensing Furnace
Sequence of operation (cont.)

• After a delay the gas valve opens and flame is
  produced
• Once the flame is proved, the gas valve will
  remain energized
• Indoor blower is turned on after a delay

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Check Record Manifold Gas Pressure

• Compare with manufacturers specifications
• Normally natural gas is 3.5 w.c. at the outlet
  of the gas valve
• Normally LP is 11 at the outlet of the gas valve

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Flame Color

• The flame should be a well-defined blue with
  slightly orange tips 
• If yellow tips are observed, it is a sign of
  incomplete combustion and the cause should be
  found and rectified 
• A yellow-tipped flame is producing CO which is
  not a desired result of combustion

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Flame Conditions
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Flame Conditions
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Flame Conditions
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Combustion Testing
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Combustion Efficiency

• Measuring the CO2 and flue gas temperature is a
  means of determining the combustion efficiency
• Steady state efficiency is the point at which
  combustion gas content reaches equilibrium and
  the stack temperatures stabilize

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Combustion Tests

• Measure ambient temperature and the stack
  temperature to obtain the net stack
  temperature
• Measure draft pressure
• Measure the carbon dioxide(CO2) level
• Measure the oxygen (O2)level
• Measure the carbon monoxide (CO) level

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Category I Appliance
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Fan Assisted Furnaces
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Category I Appliance Test Points
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Category IV Appliances
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Checking Airflow

• Tested by measuring the temperature rise across
  the heat exchanger
• Generally low-efficiency furnaces will have a
  temperature rise of 75F to 100F
• Generally high-efficiency furnaces will have a
  temperature rise of 40F to 70F
• Always look on the data plate of the furnace for
  the correct range

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Temperature Rise

• Always check the supply air temperature out of
  the line of sight of the heat exchanger, and the
  return air temperature as close as possible to
  the heat exchanger
• Before checking the temperature rise of a
  furnace, make sure the filter is clean and the
  airflow is not being restricted

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Temperature Rise

• All registers and dampers must be open
• The system should be operating for at least 15
  minutes
• Use the same type thermometer for measuring the
  supply and return temperatures
• Before checking the temperature rise, compare the
  accuracy of thermometers

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Temperature Rise

• A temperature rise that is higher than the range
  stated on the furnace indicates a shortage of
  airflow across the heat exchanger
• A temperature rise that is lower than the range
  stated on the furnace indicates too much airflow
  across the heat exchanger

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Adjusting the Fan Speed

• A direct drive blowers fan speeds can usually be
  changed by selecting the appropriate speed tap

• Common Color Coding
• White common
• Black high speed
• Yellow medium high speed
• Blue medium low speed
• Red low speed

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Adjusting the Fan Speed

• Belt-driven blowers can usually be adjusted by
  changing the flange on the motor pulley
• Adjusting the pulley flange towards the fixed
  flange will increase the speed of the blower
• Sometimes the pulley will need to be changed,
  using the formula

Diameter(drive) Diameter(driven) X
(rpm(fan)/rpm(motor))
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On belt driven fans always check the amperage
draw of the motor after making any adjust to the
fan speed
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Safety Controls Checks

• Verify the operation of the high temperature
  switch
• Block return airflow completely and observe the
  gas valve shutting down
• On induced draft furnaces, remove one end of the
  rubber hose from the air pressure switch and
  observe the gas valve shutting down

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THE END