036-21540-001-A-0503
Unitary Products Group
19
START-UP AND OPERATION
Start unit and check rotation of fans and compressors.
Scroll compressors will only compress in one rotational
direction. Three phase compressors will rotate in either
direction depending upon phasing of the power. Since
there is a 50-50 chance of connecting power in such a
way as to cause rotation in the reverse direction,
it is
important to ensure proper rotation direction is
achieved when the system is installed and oper-
ated.
Verification of proper direction is made by observing
that suction pressure drops and discharge pressure
rises when the compressor is energized. Reverse rota-
tion also results in an elevated sound level as well as
substantially reduced current draw.
There is no negative impacts on durability caused by
operating three phase Scroll compressors in the
reversed direction for a short period of time (less than
one hour). However, after several minutes of operation
the compressors internal protector will trip.
If opposite rotation is needed, disconnect and reverse
any two leads of the three-phase supply. Reconnect
power and observe for correct rotation.
Observe unit operation and check for unusual noise or
vibration.
Prior to starting unit for the first time, turn the ther-
mostat system switch to OFF - or raise the cooling
set point to the highest temperature, to prevent the
unit from starting. Close the electrical disconnect
switch. This will energize the compressor crank-
case heater(s). WAIT A MINIMUM OF FOUR
HOURS BEFORE STARTING THE SYSTEM. This
period will allow the crankcase heater to vaporize
any liquid refrigerant in the compressor crankcase.
TABLE 5: REFRIGERANT CHARGE
TABLE 6: PRESSURE SWITCH SETTINGS
