Reznor MASA Unit Installation Manual - Manual (Page 19)

Form I-COND, P/N 220746R6, Page 19
Key: V1, V2, V3 = line voltages as measured
VA (average) =
(V1 + V2 + V3)
3
VD = line voltage (V1, V2, or V3) that deviates farthest from average (VA)
Formula:
% Line Voltage Imbalance =
[100 x (VA - VD)]
VA
If the power supply is not within these tolerances, contact the power company
prior to operating the system.
Check Voltage Supply - See voltage use range on the rating plate. Measure
(and record) each supply leg voltage at all line disconnect switches. Readings
must fall within the allowable range.
Check Voltage Imbalance - In a 3-phase system, excessive voltage imbal-
ance between phases will cause compressor motors to overheat and eventu-
ally fail. Maximum allowable imbalance is 2%. To determine voltage imbalance,
use recorded voltage measurements taken above in the following formula.
NOTE: If the unit is equipped with Option BF14, an over/under voltage protec-
tion device, the unit will shut down on an over or under voltage supply condi-
tion and also if there is a phase loss. This is an auto reset device and will reset
when the power condition is corrected.
Compressor Wiring - A 3-phase scroll compressor must be phased correctly
or compressor will operate in reverse. Since there is a chance of unknow-
ingly connecting the power in such a way as to cause rotation in reverse,
it is important to check this on startup.
CAUTION
Be sure to connect pressure gauges to the suction and
discharge lines before startup so that compressor rotation
can be checked immediately. Scroll compressors will be
destroyed if operated in the wrong direction. See Hazard
Levels, page 3.
Before initial startup, connect refrigerant pressure gauges to the compres-
sor suction and discharge lines. At startup, observe the gauges. If the suction
pressure rises and discharge pressure drops, the compressor is operat-
ing in reverse and should be shut down. (After several minutes of opera-
tion 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 perma-
nently damaged.) Turn off the power and switch the 3-phase line voltage
wiring connections before restarting the unit.
7.3 Unit Wiring
Requirements
CAUTION
If any of the original wire as supplied with the appliance must
be replaced, it must be replaced with wiring material having
a temperature rating of at least 105°C. See Hazard Levels,
page 3.