68
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. 56 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 Minim-
um and Intermediate heat and 10% for Maximum Heat.
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. Turn set--up switches SW1--2 and SW4--2 to the OFF
position unless two--stage thermostat operation is desired.
See Fig. 56.
4. Proceed to “Adjust Blower Off Delay” or install blower
door if complete.
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
FURNACE OVERHEATING HAZARD
Failure to follow this caution may result in reduced furnace
life.
Recheck temperature rise. It must be within limits specified
on the rating plate. Recommended operation is at the
mid--point of rise range or slightly above.
CAUTION
!
Adjust Blower Off Delay (Heat Mode)
a. Remove blower door if installed.
b. Turn Dip switch SW--7 or SW--8 ON or OFF for desired
blower off delay. See Table 19 and Fig. 34, 56 and 65.)
Adjust Cooling Airflow – High-Speed and
Low-Speed Cooling
The ECM blower can be adjusted for a range of airflows for
low-speed or high-speed cooling. See Table 9 – Air Delivery –
CFM (With Filter ) and Fig. 56 – Furnace Setup Switches and
59MN
7A