START-UP
Unit Preparation —
Make sure that unit has been in-
stalled in accordance with these installation instructions and
applicable codes.
Return-Air Filters — Make sure correct filters are in-
stalled in filter tracks. See Table 1. Do not operate unit with-
out return-air filters.
Compressor Mounting — Compressors are inter-
nally spring mounted. Do not loosen or remove compressor
holddown bolts.
Internal Wiring — Check all electrical connections in
unit control boxes. Tighten as required.
Refrigerant Service Ports — To service refrigerant
service ports, remove refrigerant service port access panel.
See Fig. 35. Each unit system has 4 Schrader-type service
gage ports: one on the suction line, one on the liquid line,
and two on the compressor discharge line. Be sure that caps
on the ports are tight. When a controls upgrade package is
used, one Schrader-type valve is located under both the high-
pressure switch and the low-pressure switch.
Cooling — Set space thermostat to OFF position. 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. Compres-
sor starts on closure of contactor.
Check unit charge. Refer to Service, Refrigerant Charge
section, page 30.
Reset thermostat at a position above room temperature.
Compressor will shut off. Evaporator fan will shut off after
30-second delay.
TO SHUT OFF UNIT — Set system selector switch at OFF
position. Resetting thermostat at a position above room tem-
perature shuts unit off temporarily until space temperature
exceeds thermostat setting.
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 verify
that the burners light and evaporator fan is energized. After
ensuring that the unit continues to heat the building, lower
the thermostat setting below 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. position.)
Refer to Table 19 for the correct orifice to use at high
altitudes.
Table 19 — Altitude Compensation*
ELEVATION
(ft)
74,000 AND 115,000 BTUH
NOMINAL INPUT
150,000 BTUH
NOMINAL INPUT
Natural
Gas
Orifice
Size†
Liquid
Propane
Orifice
Size†
Natural
Gas
Orifice
Size†
Liquid
Propane
Orifice
Size†
0-2,000 33 45 30 38
2,000 34 46 30 39
3,000 35 47 31 40
4,000 36 47 32 41
5,000 36 47 33 42
6,000 37 48 34 43
7,000 37 48 35 43
8,000 38 49 36 44
9,000 39 49 37 44
10,000 41 50 38 45
11,000 43 50 39 45
12,000 44 51 40 46
13,000 44 51 41 47
14,000 45 52 42 47
*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.
†Orifices available through your Carrier distributor.
Heating
1. Purge gas supply line of air by opening union ahead of
gas valve. If gas odor is detected, tighten union and wait
5 minutes before proceeding.
2. Turn on electrical supply and manual gas valve.
3. Set system switch selector at HEAT position and fan switch
at AUTO. or ON position. Set heating temperature lever
above room temperature.
4. The induced draft motor will start.
5. After a call for heating, the main burners should light within
5 seconds. If the burner does not light, then there is a
22-second delay before another 5-second try. If the burner
still does not light, the time delay is repeated. If the burner
does 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
thermostat temperature is satisfied.
8. Adjust airflow to obtain a temperature rise within the range
specified on the unit nameplate.
NOTE: The default value for the evaporator-fan motor
ON/OFF delay is 45 seconds. The Integrated Gas Unit
Controller (IGC) modifies this value when abnormal limit
switch cycles occur. Based upon unit operating conditions,
the ON delay can be reduced to 0 seconds and the OFF de-
lay can be extended to 180 seconds. When one flash of the
LED is observed, the evaporator-fan ON/OFF delay has been
modified.
If the limit switch trips at the start of the heating cycle
during the evaporator ON delay, the time period of the ON
delay for the next cycle will be 5 seconds less than the time
at which the switch tripped. (Example: If the limit switch
trips at 30 seconds, the evaporator-fan ON delay for the next
cycle will occur at 25 seconds.) To prevent short-cycling, a
5-second reduction will only occur if a minimum of 10 min-
utes has elapsed since the last call for heating.
Fig. 35 — Cleaning Condenser Coil
27
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