035-18518-001-B-0703
16
Unitary Products Group
INITIAL START-UP
1.
Supply power to the unit through the disconnect
switch at least 8 hours prior to starting the com-
pressor.
2.
Move the system switch on the thermostat to the
AUTO or COOL position.
3.
Reduce the setting of the room thermostat to ener-
gize the compressor.
4.
Check the operation of the evaporator unit per the
manufacturer's recommendations.
5.
With an ammeter, check the compressor amps
against the unit data plate.
6.
Check for refrigerant leaks.
7.
Check for any abnormal noises and/or vibrations,
and make the necessary adjustments to correct
(e.g. fan blade(s) touching shroud, refrigerant lines
hitting on sheet metal, etc.)
8.
After the unit has been operating for several min-
utes, shut off the main power supply at the discon-
nect switch and inspect all factory wiring
connections and bolted surfaces for tightness.
PHASING
Scroll compressors operate in one direction only, if a
three phase scroll compressor is experiencing:
• Low amperage draw
• Similar discharge and suction pressures
• Increased noise level
then the compressor is operating in reverse. To correct
this condition, switch any two (2) line voltage leads at
the contactor. Please note, single phase scroll com-
pressors will start and run in one direction only. The
reverse operation is not a concern.
OPERATION
UNIT OPERATION - 7-1/2
When the external control calls for cooling at terminal:
1.
The system controller (SC) is energized. The sys-
tem controller starts the compressor and enables
the condenser fans by energizing contactor 1M
(and 2M on the 208/230 volt models).
Condenser fan motor #1 is energized with the
compressor. Fan motor #2 operation is controlled
through the Pressure Switch (PS) which will de-
energize the motor when the discharge pressure
falls below 180 PSI. The motor will be energized
when the discharge pressure reaches 270 PSI.
2.
Safety Lockout: The system controller (SC) has a
lockout circuit to prevent compressor short-cycling
on a safety control with automatic reset. If the high
or low refrigerant pressure switches (HP or LP)
open, the SC will enter lockout mode.
SC provides a 90 second bypass of the low pres-
sure switch LP to prevent nuisance lockouts during
unit start-up.
A malfunction light (24V, 2 A max. resistive load)
can be energized through SC, by connecting the
light between terminals X and B on TB1. Terminal
X will energize when SC locks out.
3.
Unit is equipped with an anti-short cycle timer to
prevent two successive compressor starts within 5
minutes. If the compressor fails to start with a call
for cooling and SC is not locked out, wail at least 6
minutes for the anti-cycle timer to reset.
NOTE:
To reset the unit after a lockout:
A.
Turn the system switch on the thermostat to the
“OFF” position and back to the “COOL” position.
OR
B.
Increase the set point of the room thermostat above
the temperature in the conditioned space and return
it to its original setting.
If the unit continues to be shut down by one of its safety
controls, service should be called to determine the
Do not attempt to start the compressor without
at least 8 hours of crankcase heat or compres-
sor damage will occur.
Units equipped with scroll compressors oper-
ate in one direction only.
Incorrect scroll compressor rotation can dam-
age or fail the compressor(s).
