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Start Up Procedure
WARNING
When the disconnect switch is closed, high voltage is present
in some areas of the electrical panel. Exercise caution when
working with the energized equipment. Failure to heed this
warning could lead to personal injury.
1.
Restore power to system.
2.
Turn thermostat blower position to ON or use the DDC
(direct digital control) interface to enable the unit blower. The
blower should start.
3.
Balance airflow at diffusers/dampers.
4.
Adjust all water valves to the full open position.
5.
Use the thermostat or DDC control to enable the compressor
by placing the unit in cooling mode.
6.
Verify compressor operation. If scroll compressor, verify
compressor rotation direction.
SCROLL COMPRESSOR ROTATION
It is important to be certain compressor is rotating in the proper di-
rection. To determine whether or not compressor is rotating in the
proper direction:
1.
Connect service gauges to suction and discharge pressure
fittings.
2.
Energize the compressor by using the thermostat or DDC
control to put the unit in cooling mode.
3.
The suction pressure should drop and the discharge pressure
should rise, as is normal on any start-up.
If the suction pressure does not drop and the discharge pressure
does not rise to normal levels:
1.
Turn off power to the unit. Install disconnect tag.
2.
Reverse any two of the unit power leads.
3.
Reapply power to the unit and verify pressures are correct.
The suction and discharge pressure levels should now move
to their normal start-up levels.
When the compressor is rotating in the wrong direction, the unit
makes more noise and does not provide cooling.
After a few minutes of reverse operation, the scroll compressor in-
ternal overload protection will open, thus activating the unit lock-
out. This requires a manual reset. To reset the lockout, turn the
thermostat on and then off or power cycle the unit power feed.
NOTE: There is a 5-minute time delay before the compressor will
re-start.
Refer to Table 13 for 50HQP,VQP typical unit operating pres-
sures and temperatures.
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