Form I-MAPSIII&IV, Page 66
Power Supply Voltage Phasing
Blower Rotation - If blower rotation is not correct, reverse by interchanging two wires
on the 3-phase supply connection to the blower motor.
Compressors
□ Connect refrigerant pressure gauges to the suction and discharge lines of the
compressors and an electric meter to the power supply.
CAUTION: Be sure to connect pressure gauges to the suction
and discharge lines before system startup so that compressor
rotation can be checked immediately. Scroll compressors
will be destroyed if allowed to operate in the wrong direction.
□ Record the ambient temperature. Adjust the system controller so that a call for
cooling exists.
NOTE: Outdoor ambient lockouts may prevent mechanical cooling. Temporarily
override lockouts by lowering the cooling setpoint. When testing is complete, reset
the controller.
□ Because it is possible to unknowingly connect 3-phase power in such a way
as to cause the scroll compressor or blower to rotate in reverse, it is very
important to check this on startup. See below and Paragraph 7.2.3.
Check Compressors - Immediately at startup, observe the gauges. If the
suction pressure rises and discharge pressure drops, the compressor is
operating in reverse and must be shut down. Turn off the power and switch
the 3-phase line voltage wiring connections before restarting the unit.
(Important NOTE: If allowed to operate for several minutes in reverse, the
compressor’s internal protector will trip. If a compressor is repeatedly allowed to
restart and run in reverse, the compressor will be permanently damaged.)
10.0 Commissioning and Startup (cont'd)
10.3 Checklist Prior
to Startup
(cont'd)
10.3.1 Gas Heat
Checklist Prior to
Startup (cont'd)
Check the subcooling and superheat.
Subcooling is the measurement of liquid refrigerant stored in the condenser coil.
Too much subcooling indicates a system overcharge. Too little indicates a system
undercharge and may not provide the thermal expansion valve with a full column
of liquid refrigerant for proper operation.
Superheat is the verication that the evaporator coil is properly using the
refrigerant supplied. Too much superheat indicates that the coil is undercharged.
Too little superheat indicates that the coil is overcharged and potentially ooding
liquid refrigerant to the compressor.
Two important requirements before checking subcooling & superheat:
1) Each circuit MUST be isolated before measuring its temperature. Another
active circuit will inuence the reading and make it impossible to determine
accurate superheat and subcooling.
2) If the circuit is equipped with an optional hot gas bypass valve, the valve must
be disabled before measuring subcooling and superheat. Disable the hot gas
bypass valve by removing the cover and adjusting the spring tension. Count and
record the number of counterclockwise turns until the spring tension is relieved.
(When you can return the bypass valve to its original setting, turn the spring the
same number of turns clockwise.) To check setting, see Paragraph 7.7.
Instructions for Checking and Adjusting the Subcooling of an Isolated
Circuit:
□ Measure and record temperature and pressure of the liquid line at the condenser
coil outlet. At initial startup, ll out the "Startup Form" (See page 70.)
STEP 1) Record Measurements: Temperature =
________°F (°C) and Pressure = ________ psig
IMPORTANT:
All refrigeration
checks must
be made by a
qualied R-410A
refrigeration
technician.
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