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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.
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.
Place SW- -1 (LHT) in ON position. Jumper R to W/W1 and W2 to
check high- -gas- -heat temperature rise. To check low- -gas- -heat
temperature rise, remove jumper to W2. Determine air temperature
rise for both high and low gas heat. Do not exceed temperature rise
ranges specified on unit rating plate for high and low gas heat.
This furnace must operate within the temperature rise ranges
specified on the furnace rating plate. Determine the air temperature
as
follows:
1. Place duct thermometers in return and supply ducts as close
to furnace as possible. Be sure thermometers do not "see"
heat exchangers so that radiant heat does not affect
thermometer readings. This is particularly important with
straight run ducts.
2. When thermometer readings stabilize, subtract return- -air
temperature from supply- -air temperature to determine
temperature rise.
If the temperature rise is outside this range, check the following:
1. Gas input for low- -and high gas heat operation.
2. Derate for altitude if applicable.
3. Return and supply ducts for excessive restrictions causing
static pressures greater than 0.50- -in. w.c. (125 Pa).
4. Adjust temperature rise by adjusting blower speed.
S Increase blower speed to reduce temperature rise.
S Decrease blower speed to increase temperature rise.
WARNING
!
ELECTRICAL OPERATION HAZARD
Failure to follow this warning could result in personal injury
or death.
Disconnect 115vac electrical power before changing speed tap.
For low- -heat, the following connections can be made at LO HT on
control:
a. Orange blower motor lead
b. Red blower motor lead - - Factory Setting
(Read following caution before changing taps).
CAUTION
!
UNIT DAMAGE HAZARD
To avoid operating outside the rise range and avoid
component damage:
Refer to the Air Delivery Tables to determine which airflows
and settings are allowed for proper heating airflow. DO NOT
use the highlighted settings for High- -Stage Heating airflow.
The highlighted settings are to be used for Low- -Stage Heating
and Cooling ONLY.
Change the blower speed taps as required to maintain proper
temperature rise for Heating and Cooling as described above. To
change blower motor speed selections for heating mode, remove
blower motor lead from control HEAT terminal(s). See Fig. 38.
Select desired blower motor speed lead(s) from the other motor
leads and relocate it/them to LO HT (low stage heat, low stage cool
blower tap) or HI HT (high stage heat blower tap) terminal(s).
Reconnect original lead on SPARE terminal.
Adjust Blower Off Delay (Heat Mode)
If desired, the main blower off time delay period may be
lengthened or shortened when operating in the heating mode to
provide greater comfort. For position and location of switches on
control center. See Fig. 38 and 71.
1. Remove blower door if installed.
2. Turn Setup switch SW- -2
desired blower off delay. See Table 19 and Fig. 38 and 71.
3. Proceed to "Set Blower Off Delay" before installing blower
door.
Adjust Cooling Airflow
The cooling airflow can be set from the remaining blower speed
taps. Refer to the Air Delivery Tables in these instructions.
If a two- -stage air conditioning or heat pump is installed, the Low
Cooling Speed is the same speed tap as the Low Heat speed (LO
HT).
Adjust Continuous Fan Airflow
The Continuous Fan airflow can be set from the remaining blower
speed taps. Refer to the Air Delivery Tables in these instructions.
The Continuous Fan speed can be changed to any other speed tap
by toggling the Fan switch at the thermostat. See the Sequence of
Operation for details.
CAUTION
!
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.
Adjust Thermostat Heat Anticipator
Mechanical thermostat. Set thermostat heat anticipator to match
the amp. draw of the electrical components in the R- -W/W1 circuit.
Accurate amp. draw readings can be obtained at the wires normally
connected to thermostat subbase terminals, R and W. The
thermostat anticipator should NOT be in the circuit while
measuring current.
1. Set SW- -1 (LHT) switch on furnace control board to ON.
2. Remove thermostat from subbase or from wall.
66
and SW- -3 ON or OFF for
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