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035-19671-001 Rev. A (0404)

4

Unitary Products Group

FURNACE USER MAINTENANCE

Every time the filters are changed the following items should be visually
inspected:

Check vent pipe for blockage or leakage.

Check all components to be sure they are in good condition and
that there are no obvious signs of deterioration.

Check for dirt or lint on any surfaces or on components. Do not try
to clean any of the surfaces or components. Cleaning of the fur-
nace and its components must be done by a qualified service pro-
fessional.

If, during the inspection of your furnace, you find any of the following
conditions:

Excessive amounts of dust and lint on components.

Damaged or deteriorated components or surfaces.

Leaks or blockage in the vent pipe passages.

Water on any surface inside or outside of the furnace.

Do not operate the furnace, call a certified dealer / servicing contractor
to check and / or clean your furnace, or for more information if you have
questions about the operation of your furnace.

If all components appear to be in good operating condition, replace the
front panels. Turn ON the gas and electrical power supplies to the fur-
nace, and set thermostat to the desired temperature.

Air Filters

Dirty filters greatly restrict the flow of air and may cause damage to the
moving parts of the furnace. If the filters become clogged the heat
exchangers and blower motor could overheat resulting in a potentially
dangerous situation.The filters should be checked every 3 months. On
new construction, check the filters every week for the first four weeks
and every three weeks after that, especially if the indoor fan is running
continuously. When replacing the filter(s) you must use filters that are
the same size as those recommended in Table 1. use the following pro-
cedure to determine the filter size. Never operate your furnace without a
suitable air filter.

1.

Measure the furnace width and use that measurement to deter-
mine the cabinet width.

A 14-1/2” wide cabinet is a “A” cabinet.

A 17-1/2” wide cabinet is a “B” cabinet.

A 21” wide cabinet is a “C” cabinet.

A 24-1/2” wide cabinet is a “D” cabinet.

2.

Locate the cabinet size on Table 1 then determine whether you
have a bottom or side return air duct using the following method.

a.

If the return air filter is on the left or right side of the furnace it
is a side return

b.

If the air filter is on the bottom of the furnace then you have a
bottom return.

C.

If the air filters are on the bottom and the side of the furnace
then you have a bottom and side return. You must replace
both air filters. Table 1 will indicates 2 filters by using brackets
with the number two (2).

D.

If the air filters are on both sides of the furnace then you have
a two sided return. You must replace both air filters. Table 1
will indicate 2 filters by using brackets with the number two
(2).

3.

After you determine the cabinet size and what return configuration
you have, look up the recommended filter size from Table 1.

Removing Filters

Internally Mounted Air Filters

Most upflow furnaces have their filters located on the side or bottom of
the furnace in a filter wire retainer located inside the blower compart-
ment. To check filters located in the blower compartment:

1.

Remove the upper furnace door by lifting up. Pull out bottom of
door and lower from furnace.

2.

Remove the blower compartment panel by lifting up.

3.

The filters will be located on the bottom or on one of the sides. To
remove bottom-mounted or side mounted filter (s) on all furnaces,
push the looped end of the filter retainer rod in, and then move the
retainer rod away from the filter.

4.

Reverse the procedure to reinstall filters.

Externally Mounted Air Filters

Some installations may have the air filter in a rack attached to the cas-
ing of the furnace or placed in the return air duct. You can gain access
to the filter by pulling on the door or unscrewing the retaining screw,
then slide the filter(s) out of its channel. Replace throw away filter(s)
with the same size new filter(s). Throw away filter(s) may be replaced
with cleanable filter(s) at this time. Cleanable filter(s) may be cleaned as
described in the manufacturer instructions or as described below and
then re-installed.

To replace the filter after cleaning you must do the following:

1.

Slide filter into place.

2.

Snap the door on or place the door in position and tighten the
retaining screws, if provided.

3.

Make sure the door is secure to the end of the filter rack.

How to Clean your Filter

High-velocity filters may be cleaned with a vacuum cleaner or washed
with a garden hose. Be sure to shake off excess water and allow filter to
completely dry before re-installing the filter.

Before proceeding, be sure the area is well ventilated. Turn
the thermostat OFF. If the blower is running, wait until it
stops automatically. Turn OFF the gas and electrical power
supplies to the furnace. Check all metal parts and surfaces
to be sure they have cooled to room temperature before
you begin.

 FIGURE 6: 

Upflow Internal Filter Retainer

TABLE 1: 

Filter Sizes

Cabinet Size

Side (in)

Side (mm)

Bottom (in)

Bottom (mm)

A

16 x 25

40.6 x 63.5

14 x 25

35.6 x 63.5

B

16 x 25

40.6 x 63.5

16 x 25

40.6 x 63.5

C

(2) 16 x 25

(2) 40.6 x 63.5

20 x 25

50.8 x 63.5

D

(2) 16 x 25

(2) 40.6 x 63.5

22 x 25

55.9 x 63.5

FILTER

PROVIDED

POSITION WIRE RETAINER
PROVIDED UNDER FLANGE

RIGHT SIDE
INSTALLATION
SHOWN

FURNACE
FRONT

CLIPS

Summary of Contents for G8D-UH

Page 1: ...electrical parts that have been wet or the furnace if deemed necessary FIRE OR EXPLOSION HAZARD Failure to follow safety warnings exactly could result in serious injury death or prop erty damage Do not store or use gasoline or other flammable vapors and liquids in the vicinity of this or any other appliance WHAT TO DO IF YOU SMELL GAS Do not try to light any appliance Do not touch any electrical s...

Page 2: ...space containing the furnace 4 Examine the furnace casing making sure the physical support is sound without sagging cracks or gaps Examine the furnace base making sure it is physically sound without cracks gaps or sagging and has a good seal 5 Examine the furnace casing for obvious signs of deterioration 6 Examine the burner flames to make sure they are in good adjust ment Refer to the pictorial s...

Page 3: ...part of the control system and any gas control which has been under water Operating Instructions 1 STOP Read the safety information above 2 Set the thermostat to the lowest setting 3 Turn off all electric power to the appliance 4 Remove burner door 5 Move gas control switch to the OFF position Do not force See Figure 4 6 Wait five 5 minutes to clear out any gas If you then smell gas STOP Follow B ...

Page 4: ...ters by using brackets with the number two 2 D If the air filters are on both sides of the furnace then you have a two sided return You must replace both air filters Table 1 will indicate 2 filters by using brackets with the number two 2 3 After you determine the cabinet size and what return configuration you have look up the recommended filter size from Table 1 Removing Filters Internally Mounted...

Page 5: ...en using a 2 Stage thermostat the Timer should be discon nected The Inducer Motor is shifted to high speed by the control closing the contacts of 2LP The High Fire Pressure Switch The Control checks that 2LP is closed The Gas Valve is energized on 2nd Stage High Fire The Control simultaneously de energizes the Heat Low relay and energizes the Heat High relay providing 120 Volts AC to a different s...

Page 6: ...ess doors 2 Remove blower assembly mounting screws and slide the blower assembly out of the slots in the deck If the two shipping screws were not previously removed also remove and discard these two screws located on each front corner of the blower assembly 3 Loosen the blower wheel set screw that secures the blower wheel to the blower motor shaft 4 Remove the motor mount bolts 5 Slide the variabl...

Page 7: ...placement gaskets be avail able before removing vent motor 1 Remove six mounting screws that hold the vent motor to the restrictor plate The surface is gasketed and gasket can be reused if it is carefully removed It is necessary to remove this assembly to gain access to the restrictor plate mounting holes The assembly may be vacuumed if cleaning is necessary If any vent assembly parts are damaged ...

Page 8: ...Dirty Filter Improperly sized duct system Incorrect blower speed selection Incorrect firing rate Faulty blower motor Faulty Control 6 Flash Reason 1LP has opened five times during one call for heat Effect Control enters Soft Lockout It will automatically reset and try again after 1 hour Causes Restricted vent system Vent system that exceeds specifications High wind 7 Flash Reason Flame rectificati...

Page 9: ...OW INDUCER LOW STAGE PRESSURE SWITCH HSI 1ST STAGE MAIN VALVE FLAME SENSE LOW CIRCULATOR HEAT SPEED 1ST STAGE LOW PRESSURE SWITCH CLOSE RECOGNITION HSI WARM UP 17 SEC IGNITION ACTIVATION PERIOD 4 SEC TRIAL FOR IGNITION 7 SEC INTER PURGE 60 SEC HSI WARM UP 27 SEC IGNITION DEACTIVATION PERIOD 3 SEC HEAT FAN DELAY ON 30 SEC BURN TIME POST PURGE 15 SEC HEAT FAN DELAY OFF SELECTABLE 60 90 120 180 SEC O...

Page 10: ...035 19671 001 Rev A 0404 10 Unitary Products Group SECTION III REPLACEMENT PARTS LIST 28 38 39 32 27 3 30 26 5 10 9 22 24 6 20 11 2 37 29 8 23 12 7 35 17 19 21 13 1 16 15 25 4 41 12A 7 35 24 36 12 19 11 ...

Page 11: ...N GAS 20 BRACKET IGNITER 21 DECK BLOWER Rear 22 DECK FRONT 23 HEAT EXCHANGER ASS Y 24 MANIFOLD GAS 25 PANEL ACCESS BURNERS 26 PAN BASE 27 PANEL FRONT Blower 28 PANEL TOP 29 WRAPPER INSULATED 30 CHANNEL TOE PLATE 31 FILTER 32 PLUG WINDOW CLEAR 875 33 RETAINER FILTER 34 CLIP SPRING FILTER RETAINER 35 BRACKET ROLL OUT SWITCH MISCELLANEOUS 36 ORIFICE BURNER Natural 45 37 PLATE RESTRICTOR N Model PLATE...

Page 12: ...stage Heat One Stage Cool ALL MODELS 2TB17700424 THERMOSTAT Subbase for 2TH13700424 ALL MODELS 2ET07700324 THERMOSTAT Programmable ALL MODELS 2ET07700224 THERMOSTAT Deluxe Programmable One stage Heat One stage Cool with subbase ALL MODELS REPLACEMENT PART CONTACT INFORMATION This is a generic parts list To request a complete parts list refer to the contact information below Visit our website at ww...

Page 13: ...035 19671 001 Rev A 0404 Unitary Products Group 13 SECTION IV WIRING DIAGRAM FIGURE 9 Wiring Diagram ...

Page 14: ...035 19671 001 Rev A 0404 14 Unitary Products Group NOTES ...

Page 15: ...035 19671 001 Rev A 0404 Unitary Products Group 15 ...

Page 16: ...applies only to products installed in the United States and Canada EXCLUSIONS This warranty does not cover any 1 Shipping labor or material charges 2 Damages resulting from transportation installation or servicing 3 Damages resulting from accident abuse fire flood alteration or acts of God tampering altering defacing or removing the product serial number will serve to void this warranty 4 Damages ...

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