Reznor MASA Unit Installation Manual - Manual (Page 24)

Form I-COND, P/N 220746R6, Page 24
9.2 Start-up
9.0 Final Checks
and Start-Up
(cont’d)
□
Record the ambient temperature. Adjust the system controller so that
a call for cooling exists.
NOTE: If the system has digital controls, outdoor ambient lockouts
may prevent mechanical cooling. Temporarily override lockouts by
lowering the cooling setpoint. (If installing a PreevA ® air handler, refer
to the digital programmable control section in the instruction manual.)
When testing is complete, reset the controller.
□
Because it is a possible to unknowingly connect 3-phase power
in such a way as to cause the scroll compressor to rotate in
reverse, it is very important to check this on startup.
Immediately at startup, observe the gauges. If the suction pres-
sure 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.)
9.2.2 Operating Sequence
•
For a two-stage cooling sequence, jumper Terminal Y2 to Y3. The
operating sequence is #1 (Circuit A Compressor); then #1 and #2
(both Circuit A and Circuit B Compressors).
• For a three-stage cooling sequence, the operating sequence is #1
(Circuit A Compressor); then #2 (Circuit B Compressor); and then #1
and #2 (both Circuit A and Circuit B Compressors).
NOTE: Redo startup procedures when the cooling season begins.
CAUTION
Crankcase heaters must be allowed to warm up for at least
24 hours prior to startup. Disable cooling controls before
turning on power to warmup crankcase heaters. See Hazard
Levels, page 3.
Assumptions: All pre-startup checks have been made and crankcase heaters
have been allowed to warmup for at least 24 hours.
9.2.1 Power Supply Voltage Phasing
□
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 start-up so that compressor
rotation can be checked immediately. Scroll compressors
will be destroyed if allowed to operate in the wrong direction.
See Hazard Levels, page 3.