69
12. Remove water column manometer or similar device from
manifold pressure tap.
FIRE HAZARD
Failure to follow this warning could result in personal
injury, death, and/or property damage.
Manifold pressure tap set screw must be tightened or
⅛
--in.
NPT pipe plug must be installed to prevent gas leaks.
!
WARNING
13. Tighten set screw on manifold tower pressure tap with
3/32--in hex wrench, or if 1/8--in. NPT plug was removed,
apply pipe dope sparingly to end of plug and reinstall in the
gas valve.
14. Turn gas valve ON/OFF switch to ON.
15. Move setup SW1--2 on furnace control to position required
for attached thermostat (OFF for single-stage thermostats,
ON for two-stage thermostats).
16. Check for gas leaks and verify furnace operation.
Adjust Temperature Rise
NOTE
: Blower door must be installed when taking temperature
rise reading. Leaving blower door off will result in incorrect
temperature measurements, due to possible changes in duct static
pressure and airflow.
FURNACE DAMAGE HAZARD
Failure to follow this caution may result in:
S
Overheating the heat exchangers or condensing flue gases
in heat exchanger areas not designed for condensate.
S
Shortened furnace life
S
Component damage.
Temperature rise must be within limits specified on furnace
rating plate. Recommended operation is at midpoint of rise
range or slightly above.
CAUTION
!
When setup switch SW1--4 is ON, operation will be near the high
end of the rise range for improved comfort.
Furnace must operate within ranges of temperature rise specified
on the furnace rating plate. Determine air temperature rise as
follows:
1. Place thermometers in return and supply ducts as near
furnace as possible. Be sure thermometers do not see heat
exchanger so that radiant heat does not affect readings. This
practice is particularly important with straight-run ducts.
2. When thermometer readings stabilize, subtract return-air
temperature from supply-air temperature to determine air
temperature rise.
NOTE
: Temperature rise can be determined for Minimum Heat,
Intermediate Heat and Maximum Heat operation by locking the
furnace in each mode of operation. The mode of operation is based
on the position of Set-up switch SW1--2 and SW4--2 on the
furnace control board.
The furnace is capable of automatically providing proper airflow
to maintain the temperature rise within the range specified on
furnace rating plate. If temperature rise is outside this range,
proceed as follows:
a. Check gas input for minimum, intermediate and maximum
heat operation.
b. Check derate for altitude if applicable.
c. Check all return and supply ducts for excessive restrictions
causing static pressure greater than 0.5--in. w.c.
d. Ensure Min/Int Heat Rise Adjust switch SW1--3 on furnace
control is in ON position when a bypass humidifier is used.
See Fig. 65 for switch location.
e. Check Troubleshooting Guide for Variable--Speed Step
Modulating Condensing Furnaces.
f. Verify correct model plug is installed.
To lock the furnace in Minimum Heat:
1. Turn SW1--2 ON at the furnace control. Setup switch
SW4--2 must be OFF.
2. Connect a jumper across R and W/W1 at the thermostat
terminals at the furnace control.
3. Allow the burners to ignite and the blower to turn on.
4. Allow the supply temperature to stabilize and verify the
proper rise range.
If the temperature rise is too high or too low in Minimum
Heat:
1. Remove jumpers from R and W/W1.
2. Wait until the blower off delay is completed.
3. Turn 115 VAC power off.
4. Check the position of setup switch SW1--3. When set to
ON, airflow is raised 18% for Minimum Heat and for
Intermediate Heat. Factory default position is OFF.
5. Turn 115 VAC power on.
6. Re--check Minimum Heat Temperature Rise
To lock the furnace in Intermediate Heat:
1. Turn SW1--2 OFF and SW4--2 ON at the furnace control.
2. Connect a jumper across R and W/W1 at the thermostat
terminals at the furnace control.
3. Allow the burners to ignite and the blower to turn on.
4. Allow the supply temperature to stabilize and verify the
proper rise range.
If the temperature rise is too high or too low in Intermediate
Heat:
1. Remove jumpers from R and W/W1.
2. Wait until the blower off delay is completed.
3. Turn 115 VAC power off.
4. Check the position of setup switch SW1--3. When set to
ON, airflow is raised 18% for Minimum Heat and for
Intermediate Heat. Factory default position is OFF.
5. Turn 115 VAC power on.
6. Re--check Minimum Heat Temperature Rise.
To lock the furnace in Maximum Heat:
1. Connect a jumper across R and W/W1 and W2 at the
thermostat terminals at the furnace control.
2. Allow the burners to ignite and the blower to turn on.
3. Allow the supply temperature to stabilize and verify the
proper rise range.
If the temperature rise is too high or too low in Maximum
Heat:
1. Remove jumpers from R and W/W1 and W2.
2. Wait until the blower off delay is completed.
3. Turn 115 VAC power off.
4. Check the position of setup switch SW1--4. When set to
OFF and SW1--3 is set to OFF, airflow is raised 10% for
Minimum Heat, 7.5% for Intermediate Heat and 17.5% for
Maximum Heat. Factory default position is ON. If SW1--3
is ON and SW1--4 is OFF, airflow is raised 18% for Mini-
mum and Intermediate heat and 10% for Maximum Heat.
