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If the suction pressure does not drop and the discharge pres-
sure does not rise to normal levels:
1. Note that the evaporator fan is probably also rotating
in the wrong direction.
2. Turn off power to the unit and install lockout tag.
3. Reverse any two of the unit power leads.
4. Reapply power to unit. Reenergize compressor.
The suction and discharge pressure levels should now move
to their normal start-up levels.
NOTE: When the compressor is rotating in the wrong direc-
tion, the unit will make an elevated level of noise and will
not provide cooling.
X. COOLING
To start unit, turn on main power supply. Set system selector
switch at COOL position and fan switch at AUTO. position.
Adjust thermostat to a setting below room temperature.
Compressor, indoor and outdoor fans start on closure of
contactors.
Check unit charge. Refer to Checking and Adjusting
Refrigerant Charge section, page 62. Unit must operate a
minimum of 10 minutes before adjusting charge.
Reset thermostat at a position above room temperature.
Compressor and outdoor fans will shut off. Evaporator fan
will shut off after 30-second delay.
A. To Shut Off Unit
Set system selector switch at OFF position. Resetting ther-
mostat at a position above room temperature shuts unit off
temporarily until space temperature exceeds thermostat
setting.
XI. MAIN BURNERS
Main burners are factory set and should require no
adjustment.
TO CHECK ignition of main burners and heating controls,
move thermostat set point above room temperature and ver-
ify that the burners light and evaporator fan is energized.
After ensuring that the unit continues to heat the building,
lower the thermostat setting below the room temperature
and verify that the burners and evaporator fan turn off (fan
will turn off only if fan selector switch is in the AUTO. posi-
tion). Refer to Table 31 for the correct orifice to use at high
altitudes.
NOTE: Upon a call for heat, the main burners will remain on
for a minimum of 60 seconds.
A. Adjust Gas Input
The gas input to the unit is determined by measuring the
gas flow at the meter or by measuring the manifold pressure.
Manifold pressure should be 3.5 in. wg. in high-fire
operation.
NOTE: Unit uses a 2-stage gas valve. There is no need to
adjust the “Low Fire” manifold pressure.
Measure Gas Flow (Natural Gas Units)
Minor adjustment to the gas flow can be made by changing
the manifold pressure. The manifold pressure must be
3.5 in. wg. Normal manifold pressure is 3.5 in. wg in high
fire (W1 and W2 inputs to gas valve).
Proceed as follows:
1. Turn off gas supply to unit.
2. Remove pipe plug on manifold then connect manome-
ter at this point. Turn on gas to unit. Ensure gas
valve is in high fire operation.
Observe manifold pressure in high fire (W1 and W2 ener-
gized) and proceed as follows to adjust gas input:
1. Remove cover screw over regulator adjustment screw
on gas valve. Ensure gas valve is operating in high
fire mode.
2. Turn regulator adjustment screw clockwise to
increase gas input, or turn regulator adjustment
screw counterclockwise to decrease input. High fire
manifold pressure must be 3.5 in. wg.
3. Replace cover screw cap on gas valve.
4. Turn off gas supply to unit. Remove manometer from
pressure tap and replace pipe plug on gas valve. Turn
on gas to unit and check for leaks.
Table 31 — Altitude Compensation*
*As the height above sea level increases, there is less oxygen per cubic foot
of air. Therefore, heat input rate should be reduced at higher altitudes.
†Orifice available through your local distributor.
XII. HEATING
1. Purge gas supply line of air by opening union ahead
of gas valve. When gas odor is detected, tighten union
and wait 5 minutes before proceeding.
2. Turn on electrical supply and open manual gas valve.
3. Set system switch selector at HEAT position and fan
switch at AUTO. or ON position. Set heating temper-
ature lever above room temperature.
4. The induced-draft motor will start, purging heat
exchangers.
5. After a call for heating, the main burners should light
within 5 seconds. If the burners do not light, then
there is a 22-second delay before another 5-second
ignition try. If the burners still do not light, the time
delay is repeated. If the burners do not light within
15 minutes, there is a lockout. To reset the control,
break the 24 v power to W1.
6. The evaporator-fan motor will turn on 45 seconds
after the burners are ignited.
7. The evaporator-fan motor will turn off 45 seconds
after the thermostat temperature is satisfied.
8. Adjust airflow to obtain a temperature rise within
the range specified on the unit nameplate and in
Tables 1A and 1B.
WARNING: Unsafe operation of the unit may
result if manifold pressure is outside 3.4 to 3.6 in. wg
range. Personal injury or unit damage may result.
ELEVATION
(Ft)
125,000, 180,000, AND
220,000 BTUH
NOMINAL INPUT
250,000 BTUH
NOMINAL INPUT
Natural
Gas
Orifice
Size†
Liquid
Propane
Orifice
Size†
Natural
Gas
Orifice
Size†
Liquid
Propane
Orifice
Size†
0-2,000 31 41 30 38
2,000 32 42 30 39
3,000 32 42 31 40
4,000 32 42 32 41
5,000 33 43 33 42
6,000 34 43 34 43
7,000 35 44 35 43
8,000 36 44 36 44
9,000 37 45 37 44
10,000 38 46 38 45
11,000 39 47 39 45
12,000 40 47 40 46
13,000 41 48 41 47
14,000 42 48 42 47