43
FURNACE DAMAGE HAZARD
Failure to follow this caution may result in shorten furnace
life.
Set air temperature rise within limits specified on the rating
plate to prevent reduced life of furnace components.
Operation is within a few degrees of the mid--point of rise
rangewhensetupswitchSW1--4isOFF.
CAUTION
!
When setup switch SW1--4 is ON, operation will be near the high
end of the rise range for improved comfort.
This furnace is capable of automatically providing proper airflow
to maintain the temperature rise within the range specified on unit
rating plate.
NOTE: If the temperature rise is outside this range, first check:
(1.) Gas input for low heat operation.
(2.) Derate for a ltitude if applicable.
(3.) Return and supply ducts for excessive restrictions
causing static pressures greater than 0.50--in. wc.
(4.) Ensure low--heat rise adjust switch SW1--3 is in
ON position when bypass humidifier is used.
Refer to Table 8 and Fig. 27 and 59.
(5.) Make sure proper model plug is installed.
5. Adjust Manifold Pressure to Obtain High Heat Rate
a. Remove high heat regulator adjustment cap from gas
valve pressure regulator.
b. Jumper R, W/W1 and W2 thermostat connections on
control to run furnace in high heat. (See Fig. 27 and
59.)
c. Turn high--heat adjusting screw (3/16 or smaller
flat--tipped screwdriver)) counterclockwise (out) to
decrease input rate or clockwise (in) to increase rate.
d. Re--install high--heat adjustment caps.
NOTE: DO NOT set high--heat manifold pressure less than
3.2--in. wc or more than 3.8--in. wc for natural gas. If manifold
pressure is outside this range, change main burner orifices.
6. Verify natural gas high heat input rate by clocking meter.
NOTE: Gas valve regulator adjustment caps must be in place for
proper input to be clocked.
a. Turn off all other gas appliances and pilots served by
the meter.
b. Run for 3 minutes in high --heat operation.
c. Measure time (in sec) for gas meter to complete 1
revolution and note reading.
d. Refer to Table 11 for cubic ft. of gas per hr.
e. Multiply gas rate cu ft./hr by heating value (Btu/cu ft.)
to obtain input.
NOTE: Using the 2 cu. ft.. or 5 cu. ft.. gas meter dial provides
greater accuracy in verifying gas input rate.
If clocked rate does not match required input from Step 1,
increase manifold pressure to increase input or decrease manifold
pressure to decrease input. Repeat steps b through e until correct
high heat input is achieved. Re--install high--heat regulator seal
cap on gas valve.
7. Set high heat temperature rise.
Jumper R to W/W1 and W2 to check high--gas--heat
temperature rise. Do not exceed temperature rise ranges
specified on furnace rating plate for high heat. The furnace
must operate within the temperature rise ranges specified
on the furnace rating plate.
Determine the air temperature rise as follows:
NOTE: Blower access door must be installed when taking
temperature rise reading. Leaving blower access door off will
result in incorrect temperature measurements.
a. Verify the unit is operating in high heat per Step 6.
Place thermometers in return and supply ducts as close
to furnace as possible. Be sure thermometers do not
see radiant heat from heat exchangers. Radiant heat
affects temperature rise readings. This practice is
particularly important with straight--run ducts.
b. When thermometer readings stabilize, subtract
return--air temperature from supply --air temperature to
determine air temperature rise.
FURNACE DAMAGE HAZARD
Failure to follow this caution may result in shorten furnace
life.
Set air temperature rise within limits specified on the rating
plate to prevent reduced life of furnace components.
Operation is within a few degrees of the mid--point of rise
rangewhensetupswitchSW1--4isOFF.
CAUTION
!
When setup switch SW1--4 is ON, operation will be near the high
end of the rise range for improved comfort.
This furnace is capable of automatically providing proper airflow
to maintain the temperature rise within the range specified on unit
rating plate.
NOTE: If the temperature rise is outside this range, first check:
(1.) Gas input for low--and high-- heat operation.
(2.) Derate for altitude if applicable.
(3.) Return and supply ducts for excessive restrictions
causing static pressures greater than 0.50--in. wc.
(4.) Make sure proper model plug is installed.
c. Remove thermostat jumpers and release blower access
door switch.
d. Repeat Steps a through c as required to adjust for
proper rise.
e. When correct high heat input rate and temperature rise
is achieved, turn gas valve ON/OFF switch to OFF.
f. Release blower access door switch.
g. Remove manometer or similar device from gas valve.
h. Re--install manifold pressure tap plug in gas valve.
(See Fig. 55.)
FIRE HAZARD
Failure to follow this warning could result in personal
injury, death, and/or property damage.
Reinstall manifold pressure tap plug in gas valve to prevent
gas leak.
!
WARNING
i. Remove thermostat jumper wire from furnace control
board.
j. Turn gas valve ON/OFF switch to ON.
315A
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