Carrier 48LJD - Manual (Page 20)

START-UP
IMPORTANT: Energize crankcase heater 24 hours prior
to base unit start-up to remove absorbed refrigerant
from oil to prevent damage to compressor. Heater is
energized as long as there is power to the unit.
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
without 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 — Each unit system has
3 Schrader-type service gage ports: one on the suction line,
one on the liquid line, and one on the compressor discharge
line. Be sure that caps on the ports are tight. 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. Ad­
just thermostat to a setting below room temperature. Com­
pressor starts on closure of contactor.
Check unit charge. Refer to Service, Refrigerant Charge
section, page 22.
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 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 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 16 for the correct orifice to use at high
altitudes.
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 tempera­
ture 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
W l .
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
and OFF delay is 45 seconds. The Integrated Gas Unit Con­
troller (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 delay can
be extended to 180 seconds.
Table 16 — Altitude Compensation*
ELEVATION
(ft)
74,000 AND 115,000
BTUH NOMINAL
INPUT
150,000 BTUH
NOMINAL INPUT
Natural
Gas
Orifice
Sizet
Liquid
Propane
Orifice
Sizet
Natural
Gas
Orifice
Sizet
Liquid
Propane
Orifice
Sizet
0-2,000 33 43 30 38
2,000 34 43 30 39
3,000 35 44 31 40
4,000 36 44 32 41
5,000 36 44 33 42
6,000 37 45 34 43
7,000 37 45 35 43
8,000 38 46 36 44
9,000 39 47 37 44
10,000 41 48 38 45
11,000 43 48 39 45
12,000 44 49 40 46
13,000 44 49 41 47
14,000 45 50 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.
fOrifices available through your Carrier distributor
TO SHUT OFF UNIT — Set system selector switch at OFF
position. Resetting heating selector lever below room tem­
perature will temporarily shut unit off until space tempera­
ture falls below thermostat setting.
Safety Relief — A soft solder joint at the suction ser­
vice Schrader port provides pressure relief under abnormal
temperature and pressure conditions (i.e., fire in building).
Ventilation (Continuous Fan) — Set fan and sys­
tem selector switches at ON and OFF positions, respec­
tively. Evaporator fan operates continuously to provide constant
air circulation. When the evaporator-fan selector switch is
turned to the OFF position, there is a 30 second delay be­
fore the fan turns off.
Operating Sequence
COOLING, UNITS WITHOUT ECONOMIZER - When
thermostat calls for cooling, terminals G and Y1 are ener­
gized, and the indoor (evaporator) fan motor (IFM), com­
pressor, and outdoor (condenser) fan motor (OFM) start.
The OFM runs continuously while the unit is in cooling.
When the thermostat is satisfied, C is deenergized and the
compressor and OFM shut off. After a 30 second delay, the
IFM shuts off. If the thermostat fan selector switch is in the
ON position, the evaporator motor will run continuously.
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