Start-Up; General; Crankcase Heaters; Confirm The Input Power Phase Sequence - Carrier Omnizone 50BV020-064 Installation, Start-Up, Service And Controls Operation And Troubleshooting

START-UP

General

Complete "START-UP CHECKLIST" on page CL-1 before at-
tempting system start-up. Refer to Tables 15-19 on pages 45-49
for performance data of all units.

CRANKCASE HEATERS

The 50BVT,V,W, 034-064 units include crankcase heaters. Crank-
case heaters are energized as long as there is power to the unit.
Wait 24 hours before starting the compressors to permit warming
by the crankcase heaters.
AFTER 24 hours, continue with the procedures below.

CONFIRM THE INPUT POWER PHASE SEQUENCE

The input power phase rotation sequence must be L1-L2-L3=
ABC (or forward or clockwise) as indicated with a phase rotation
meter. Incorrect input phase rotation will cause the compressors to
rotate in reverse, which results in no cooling capacity.
IMPORTANT: On VAV units, fan rotation direction CANNOT
be used for the phase sequence check; fan rotation for VAV units
with a variable speed drive is independent of the unit input
wiring sequence.
If the compressor is rotating in the wrong direction, it may: emit
increased noise; shut down due to internal overload protection;
have only a small decrease in suction pressure when it starts; or
have only a small increase in discharge pressure when it starts.
Also, no cooling will be produced at the evaporator. If any of these
conditions occurs, refer to the Service section to correct the com-
pressor rotation before continuing.

INTERNAL WIRING

Check all electrical connections in unit control boxes; tighten as
required.

RETURN-AIR FILTERS

Check that correct filters are installed in filter racks (see Tables 2
and 3). Do not operate unit without return-air filters.

COMPRESSOR MOUNTING

Compressors are internally mounted on resilient rubber supports.
Do not loosen or remove compressor hold down bolts.

REFRIGERANT SERVICE PORTS

Each refrigerant system has a total of 2 Schrader-type service
gauge ports per circuit. One port is located on the suction line, and
one on the compressor discharge line. Be sure that caps on the
ports are tight.

WATER PIPING

Verify water piping is properly installed and water flow is pres-
ent prior to operating unit. Check for water leaks and correct as
needed.

CV Unit Start-Up

EVAPORATOR FAN

Fan belt and variable pitch motor pulleys are factory-installed. Be
sure that fans rotate in the proper direction.

COOLING

Set the space thermostat to OFF position. Turn on unit power. Set
space thermostat to COOL and the fan to AUTO. Adjust the ther-
mostat temperature
Compressor 1 starts on closure of contactor (compressors 1 and 2
on 4-circuit units with 2-stage thermostat).
Adjust the thermostat to an even lower setting until the thermostat
energizes Y2 (the second cooling stage). Compressor 2 starts on
closure of contactor (compressors 3 and 4 on 4-circuit units with
2-stage thermostat).
Adjust the thermostat temperature to a setting just below room
temperature. The second stage of cooling should turn off.
Set the thermostat temperature above room temperature. All com-
pressors and the unit fan should now be off.
Set the thermostat below room temperature and confirm that the
compressors and fan turn off.
44
setting below room temperature.