39
c. This furnace is capable of automatically providing
proper airflow to maintain the temperature rise within
the range specified on furnace rating plate. If temperat-
ure rise is outside this range, proceed as follows:
(1.) Check gas input for low-- and high--heat opera-
tion.
(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.) Ensure Comfort/Efficiency SW 1--4 on furnace
control is in OFF=Efficiency position when a
bypass humidifier is used. (See Fig. 26 for switch
location.)
(5.) Make sure proper model plug is installed.
d. Remove thermostat jumpers and release blower access
door switch.
e. Repeat Steps a through c as required to adjust for high
heat temperature rise.
f. When correct high heat input rate and temperature rise
is achieved, turn gas valve ON/OFF switch to OFF.
g. Release blower access door switch.
h. Remove manometer or similar device from gas valve.
i. Re--install manifold pressure tap plug in gas valve.
(See Fig. 49.)
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
j. Remove thermostat jumper wire from furnace control
board.
k. Turn gas valve ON/OFF switch to ON.
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
!
l. Proceed to Step 6, “Set Blower Off Delay” before in-
stalling blower access door.
7. Set Blower Off Delay
a. Remove blower access door if installed.
b. TurnDipswitchSW--7orSW--8ONorOFFforde-
sired blower off delay. (See Table 52 and Fig. 26 and
55.)
8. Set thermostat heat anticipator.
a. 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 ther-
mostat subbase terminals, R and W. The thermostat
anticipator should NOT be in the circuit while measur-
ing current.
(1.) Set SW1-- 2 switch on furnace control board to
ON.
(2.) Remove thermostat from subbase or from wall.
(3.) Connect an amp. meter as shown in Fig. 51.
across the R and W subbase terminals or R and
W wires at wall.
(4.) Record amp. draw across terminals when furnace
is in low heat and after blower starts.
(5.) Set heat anticipator on thermostat per thermostat
instructions and install on subbase or wall.
(6.) Turn SW1--2 switch OFF.
(7.) Install blower access door.
b. Electronic thermostat: Set cycle rate for 3 cycles per
hr.
9. Set Airflow for Air Conditioning -- Single Stage and High
Stage Cooling
The ECM blower can be adjusted for a range of airflow
for Low Speed or High Speed cooling. See Table 4 --Air
Delivery -- CFM (With Filter ).
The cooling airflow is adjusted by turning Setup switches
SW2--6, SW2-- 7 and SW2--8 either ON or OFF. Select the
required airflow from Fig. 53.
NOTE: 5.5 ton airflow will truncate at 2200 cfm on applicable
models. For a complete explanation of cooling airflow, refer to
the section titled “Sequence of Operation.”
10. The Continuous Fan airflow selection via Setup switches
SW2--3, SW2--4, SW2--5 is also the switch setting for
low--speed cooling when the furnace is used with a
two--speed cooling or heat pump unit. Refer to Fig. 52 and
53 and the Adjustments section for setup switch
configurations. This setup feature allows continuous fan
airflow or low-- cooling airflow to be adjusted.
The continuous fan speed can be further adjusted at the
thermostat using the Continuous Blower Speed Selection
from Thermostat function. Changing the continuous fan
speed at the thermostat DOES NOT change the low speed
cooling airflow selected at the control board. See the
section titled Continuous Blower Speed Selection from
Thermostat in the Sequence of Operation section of this
document.
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