43
START-UP
Unit Preparation —
Make sure that unit has been
installed in accordance with these installation instructions and
applicable codes.
Return-Air Filters —
Make sure correct filters are
installed in filter tracks. See Tables 1A and 1B. Do not operate
unit without return-air filters.
Compressor Mounting —
Compressors are internally
spring mounted. Do not loosen or remove compressor hold-
down bolts.
Internal Wiring —
Check all electrical connections in
unit control boxes. Tighten as required.
Gas Piping —
Check gas piping for leaks.
Refrigerant Service Ports —
To service refrigerant
service ports, remove compressor access panel. Each unit sys-
tem has 3 Schrader-type service gage ports: one on the suction
line, one on the liquid line, and one on the compressor dis-
charge line. Be sure that caps on the ports are tight. The
Schrader-type valve on the discharge line is located under the
low-pressure switch. Another valve is located on the discharge
line underneath the high-pressure switch. It is screwed on a
Schrader fitting but there is no Schrader core.
High Flow Valves —
Located on the compressor hot gas
and suction tubes are High Flow Valves. Large black plastic
caps distinguish these valves with O-rings located inside the
caps. These valves cannot be accessed for service in the field.
Ensure the plastic caps are in place and tight or the possibility
of refrigerant leakage could occur.
Compressor Rotation —
On 3-phase units with scroll
compressors, it is important to be certain compressor is rotating
in the proper direction. To determine whether or not compres-
sor is rotating in the proper direction:
1. Connect service gages to suction and discharge pressure
fittings.
2. Energize the compressor.
3. The suction pressure should drop and the discharge pres-
sure should rise, as is normal on any start-up.
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.
3. Reverse any two of the unit power leads.
4. Reapply power to the 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 makes an elevated level of noise and does not
provide cooling.
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 ther-
mostat to a setting below room temperature. Compressor starts
on closure of contactor.
Check unit charge. Refer to Service, Refrigerant Charge
section, page 46.
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 ex-
ceeds 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 Tables 30A and 30B for the correct orifice to use at
high altitudes.
Table 30A — Altitude Compensation* —
Standard and No NOx Units
*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.
Disconnect gas piping from unit when leak
testing at pressure greater than
1
/
2
psig. Pres-
sures greater than
1
/
2
psig will cause gas
valve damage resulting in hazardous condi-
tion. If gas valve is subjected to pressure
greater than
1
/
2
psig, it must be replaced
before use. When pressure testing field-
supplied gas piping at pressures of
1
/
2
psig
or less, a unit connected to such piping must
be isolated by manually closing the gas
valve.
ELEVATION
(ft)
72,000, 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 43 30 37
2,000
36 44 31 39
3,000
36 45 31 40
4,000
37 45 32 41
5,000
38 46 32 42
6,000
40 47 34 43
7,000
41 48 35 43
8,000
42 49 36 44
9,000
43 50 37 45
10,000
44 50 39 46
11,000
45 51 41 47
12,000
46 52 42 48
13,000
47 52 43 49
14,000
48 53 44 50
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