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 sub-base or from wall.
(3.) Connect an amp meter as shown in Fig. 49 across the
R and W terminals or R and W wires.
(4.) Record amp draw across terminals when furnace is in
low heat and after blower starts.
(5.) Set heat anticapator 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.
11. 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. Depending on the model
size, the cooling airflow can be adjusted from 1½ tons nominal
cooling to 3 ½, 4 or 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 55. Fig. 55 is based on 350 CFM per
ton. For airflow at 400 CFM per ton, turn Setup SW1-5 ON
(See Table 6 and Fig. 32 and 51.)
NOTE:
6 ton airflow will truncate at 2200 cfm on applicable
models. For complete explanation of cooling airflow, refer to the
section titled
″
Sequence of Operation
″
12. 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. Select the
required continuous fan airflow from Fig. 55.
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.
55. For airflow at 400 CFM per ton, turn Setup SW1-5 ON
(See Fig. 55.) 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.
Step 4—Check Safety Controls
The flame sensor, gas valve, and pressure switch were all checked
in the Start-up procedure section as part of normal operation.
1. Check Main Limit Switches
This control shuts off combustion control system and ener-
gizes air-circulating blower motor, if furnace overheats. By
using this method to check limit control, it can be established
that limit is functioning properly and will operate if there is a
restricted return-air supply or motor failure. If limit control
does not function during this test, cause must be determined
and corrected.
a. Run furnace for at least 5 minutes.
b. Gradually block off return air with a piece of cardboard or
sheet metal until the limit trips.
c. Unblock return air to permit normal circulation.
d. Burners will re-light when furnace cools down.
2. Check draft safeguard switch.
The purpose of this control is to permit the safe shutdown of
the furnace during certain blocked vent conditions.
a. Verify vent pipe is cool to the touch.
b. Disconnect power to furnace and remove vent connector
from furnace vent elbow.
c. Restore power to furnace and set room thermostat above
room temperature.
d. After normal start-up, allow furnace to operate for 2
minutes, then block vent elbow in furnace 80 percent of
vent area with a piece of flat sheet metal.
e. Furnace should cycle off within 2 minutes.
f. Remove blockage and reconnect vent pipe to furnace vent
elbow.
g. Switch will auto-reset when it cools.
h. Re-install vent pipe.
NOTE:
Switch should remain open longer than 3 minutes,
furnace control board will lockout the furnace for 3 hours. To reset
furnace control board, turn thermostat above room temperature or
from HEAT to OFF and turn 115 v power OFF, then back ON.
3. Check Pressure Switch(es)
This control proves operation of the draft inducer blower.
a. Turn off 115-v power to furnace.
b. Disconnect inducer motor lead wires from wire harness.
TABLE 10–(Tabulated Data Based On 22,000 Btuh High-Heat/14,500 Btuh for Low-Heat Per Burner,
Derated 4 Percent For Each 1000 Ft Above Sea Level)
ALTITUDE
RANGE
(FT)
AVG GAS
HEAT VALUE
AT ALTITUDE
(BTU/CU FT)
SPECIFIC GRAVITY OF NATURAL GAS
0.58
0.60
0.62
0.64
Orifice
No.
Manifold
Pressure
Orifice
No.
Manifold
Pressure
Orifice
No.
Manifold
Pressure
Orifice
No.
Manifold
Pressure
U.S.A.
Only
9001
to
10,000
600
45
3.7/1.6
45
3.8/1.7
44
3.3/1.4
44
3.4/1.5
625
46
3.6/1.6
46
3.7/1.6
46
3.8/1.7
45
3.8/1.6
650
47
3.8/1.6
46
3.4/1.5
46
3.6/1.5
46
3.7/1.6
675
47
3.5/1.5
47
3.6/1.6
47
3.7/1.6
46
3.4/1.5
700
48
3.7/1.6
48
3.8/1.7
47
3.5/1.5
47
3.6/1.6
725
48
3.5/1.5
48
3.6/1.6
48
3.7/1.6
48
3.8/1.7
* Orifice numbers 43 are factory installed
34