START-UP PROCEDURES CONTINUED
CAUTION
If blower rotation is incorrect, shut electric power
OFF at unit disconnect and reverse any two supply
wires at field connections ONLY. Do NOT reverse
the blower and/or compressor leads or rewire any
internal wiring. After rewiring is done, repeat
blower rotation check to ensure that blower
rotation is now correct.
9. Turn electric power ON at unit disconnect.
Cooling Checks
The compressors have a five minute anti-cycle delay
that is activated whenever the compressors turn off. For
instance, if the unit is manually shut off when the
compressors are running and the unit is turned back on
two minutes later, it will be an additional three minutes
before the compressors will restart.
CAUTION
Do NOT operate the unit with the compressor(s) running
until proper blower rotation has been confirmed during
the Blower and Phasing Check in the previous section. If
the phasing is incorrect, the scroll compressor(s) (if
equipped) will run backwards and they will be damaged.
PREPARING EQUIPMENT FOR OPERATION
PRE-START CHECKLIST
Is the unit properly located and level with proper
clearance?
Is the ductwork correctly installed?
Is the condensate line properly sized, run, trapped,
pitched and primed?
Is the air filter of the correct size and number, clean and
in place?
Is the wiring properly sized and connected according to
the unit wiring diagram?
Are all wiring connections tight including those in the unit
and compressor electrical boxes?
Has the unit been properly grounded and fused with the
recommended fuse size? See wiring data.
Has the unit been leak tested?
Do the condenser fans and indoor blower turn free
without rubbing and are they tight on the shafts?
Have all of the setscrews been tightened on the blower
motor and fan?
Has the belt tension in the blower been checked and
pulley aligned?
Has all work been done in accordance with applicable
local and national codes?
Are all covers and access panels in place to prevent air
loss and safety hazards?
Has the voltage been checked?
Has the crankcase heater been energized for 8 hours?
Be sure the system switch is “OFF”.
START-UP AND REQUIRED FIELD ADJUSTMENTS
Do not attempt to start-up system below 50°F. ambient
temperature.
Be sure the crankcase heater has been energized for a
minimum of 8 hours.
Break the vacuum with liquid R10A. Add to the liquid line
at the condenser until pressures are equalized.
Turn system switch on and operate unit. Now add
refrigerant vapor in the suction side until the liquid sight
glass is clear of bubbles. It is recommended the system
be charged initially by clearing the sightglass. Do not
overcharge, verify subcooling.
On systems with optional hot gas reheat it may be
necessary to adjust the reheat thermostat to 50 degrees
F. This setting will de-energize the reheat circuit. If not
disconnect the reheat thermostat.
On semi-hermetic compressors the cylinder unloading
coil will also be energized. It is energized by the
unloader pressure switch (senses suction pressure). The
unloader pressure switch MUST be field adjusted. It
should be set to close (unload) at 64 PSIG and open at
78 PSIG. This will maintain a refrigerant temperature in
the evaporator of approximately 40 degrees F.
The hot gas bypass valve should be energized and this
should be the maximum charge required for these units.
Units with reheat will require additional charge for the
reheat circuit.
Adjusting the hot gas bypass valve. This bypass valve
Must be field adjusted. The valve must open at 112 PSIG.
It may be necessary to simulate a light load if the
outdoor temperature is above 70-75 degrees F. Reduce
the evaporator load (lower entering airflow) until the
suction pressure lowers to the point at which bypass is
desired (112 PSIG). If the hot gas bypass was de-
energized to stop hot gas flow, make sure it is now
energized. Turn the power assembly adjusting stem on
top of the regulator in a clockwise direction until bypass
occurs (you will hear the gas flowing or feel the hot gas
line, it will be warm when the unit starts to bypass).
Check or ensure suction pressure does not fall
below the predetermined set point (102 PSIG). A
clockwise turn of the adjusting stem will increase
the pressure setting; a counterclockwise turn will
decrease it. Adjustments should be made in small
increments, allowing the system to stabilize after
each turn. Vary the evaporator load to test at various
conditions to ensure the suction pressure does not
drop below the predetermined setpoint. Replace the
seal cap on the adjusting stem.
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