59MN7C: Installation, Start-up, Operating and Service and Maintenance Instructions
Manufacturer reserves the right to change, at any time, specifications and designs without notice and without obligations.
56
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 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: The temperatures read by the RAT and SAT sensors connected
to the control board can be displayed during heating and cooling
operation by enabling this feature in the (t°) menu item. See Fig. 59.
Select F for Fahrenheit or C for Celsius. When enabled, the display will
cycle through the current operating mode, SAT, RAT, and temperature
differential. If displayed SAT value does not agree with measured
values, relocate SAT sensor farther away from furnace or after a bend in
the ductwork.
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 (Htt)
setting 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:
1. Check gas input for minimum, intermediate and maximum heat
operation.
2. Check derate for altitude if applicable.
3. Check all return and supply ducts for excessive restrictions causing
static pressure greater than 0.5-in. w.c.
4. Check Troubleshooting Guide for Variable-Speed Step Modulating
Condensing Furnaces.
To lock the furnace in Minimum Heat:
1. On the 3 digit display, navigate to (Htt) and select (2St-LHt) to lock
the furnace in low-heat operation. See Fig. 59 and Fig. 60.
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. Refer to the FURNACE CONTROL PROGRAMMING AND
NAVIGATION section of this manual for instructions on adjusting
the blower speed.
5. Turn 115 VAC power on.
6. Re-check Minimum Heat Temperature Rise
To lock the furnace in Intermediate Heat:
1. On the 3 digit display, navigate to (Htt) and select (2St-iHt) to lock
the furnace in intermediate-heat operation. See Fig. 59 and Fig. 60.
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. Refer to the FURNACE CONTROL PROGRAMMING AND
NAVIGATION section of this manual for instructions on adjusting
the blower speed.
5. Turn 115 VAC power on.
6. Re-check Intermediate 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. Refer to the FURNACE CONTROL PROGRAMMING AND
NAVIGATION section of this manual for instructions on adjusting
the blower speed.
5. Turn 115 VAC power on.
6. Re-check Maximum Heat Temperature Rise.
After the temperature rise has been verified:
1. Remove jumpers from thermostat terminals.
2. Allow the blower off delay to complete.
3. On the 3 digit display, navigate to (Htt) and select (1St), (2St-LHT)
or (2St-iHt) to depending on thermostat type and desired operating
mode. See Fig. 58.
4. Proceed to “Adjust Blower OFF Delay” or install blower door if
complete.
CAUTION
!
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.
WARNING
!
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.
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