44
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
!
k. Proceed to Step 9, “Set Blower Off Delay” before
installing blower access door.
8. Set Blower Off Delay
a. Remove blower access door if installed.
b. TurnDipswitchSW--7orSW--8ONorOFFfor
desired blower off delay. (See Table 8 and Fig. 27 and
59.)
9. 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
thermostat subbase terminals, R and W. The thermostat
anticipator should NOT be in the circuit while
measuring 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. 57
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.
10. Set Airflow for Air Conditioning --Single Stage and High
Stage Cooling
The ECM blower can be adjusted for a range of airflows
for Low Speed or High Speed cooling. See Table 5 --Air
Delivery -- CFM (With Filter ). Depending on the model
size, the cooling airflow can be adjusted from 1. tons
nominal cooling to 3 ., to 4 or to 6 tons of nominal
cooling based on 350 cfm ton.
The cooling airflow is adjusted by turning Setup switches
SW2--1, SW2--2 and SW2-- 3 either ON or OFF. Select the
required airflow from Fig. 63. Fig. 63 is based on 350
CFM per ton. For airflow at 400 CFM per ton, turn Setup
SW1--5 ON (See Table 8 and Fig. 27 and 59.)
NOTE: 6 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.”
11. Set Airflow For Continuous Fan/Low Speed Cooling
Airflow The ECM blower motor can be adjusted for
continuous fan speeds different than heating or cooling fan
speed. See Table 5 -- Air Delivery -- CFM (With Filter).
Select the required continuous fan airflow from Fig. 63.
The continuous fan speed is also the fan speed for low
speed cooling when furnace is used with a 2--speed
cooling unit. Adjust the Continuous Fan CFM to match
the airflow required for low speed cooling. Select the
required airflow from Fig. 61. For airflow at 400 CFM per
ton, turn Setup SW1--5 ON (See Fig. 63.) The airflow
selected for low speed cooling will also be the airflow
used for continuous fan.
The continuous fan speed can be further adjusted at the
thermostat using the “Comfort Fan” select function.
Changing the continuous fan speed at the thermostat
DOES NOT change the low speed cooling airflow
selected at the control board.
315A
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