Control Sequence/Variable Air Volume (Optional); Pre Start-Up; Pre Start-Up Checklist; Special Tools Required - Greenheck DGX Installation, Operation And Maintenance Manual

Control Sequence - Variable Air Volume
(optional)
1. Heating/Cooling switch (S4) is closed between
terminal R and Y1.
2. N.O. contact on fan relay (RF) is energized and
closed.
3. When the outdoor air temperature is above the
set point plus the differential power passes
through N.O. contacts on outdoor air thermostat
(TS5) and energizes the cooling relay (RC1).
4. When the pressure switches LPS (refrigerant
low pressure switch) and HPS (refrigerant
high pressure switch) are in their normal state
relay R10 will energize. Starting the first stage
compressor contactor.
5. When the outdoor air temperature is above the
second stage offset plus the differential power
passes through N.O. contacts on outdoor air
thermostat (TS5) and energizes the cooling relay
(RC2).
6. When the pressure switches LPS and HPS
(refrigerant high pressure switch) are in their
normal state relay R11 will energize, starting the
second stage compressor contactor.
7. When the discharge air temperature drops below
the low temperature set point (TS9) factory set
at 55°F, the second stage compressor contactor
will de-energize, turning off the second stage
compressor.
8. The second stage compressor will re-energize
when the discharge air temeprature rises above
75°F.
®

Pre Start-Up

Pre Start-Up Checklist

(Complete prior to application of power)
 Verify proper drain trap installation. Refer to
Condensate Drain in Installation Concerns section.
Fill drain with water.
 Look over the piping system. Inspect for oil at
all tubing connections. Oil typically highlights a
leak in the system. If a leak is present, refer to the
maintenance section in this manual.
 Inspect all coils within the unit. Fins may get
damaged in transit or during construction. Carefully
straighten fins with a fin comb.
 Check condensing fans for any damage or
misalignment. Spin the blades and make sure they
are free turning without any resistance.
 Each compressor has a crankcase heater which
must have power supplied to it at least 24 hours
prior to start-up. If start-up is scheduled in
24 hours, unlock the power disconnect and
energize the unit without applying power to
terminal Y1.

SPECIAL TOOLS REQUIRED

• Voltage Meter (with wire probes)
• Amperage Meter
• Pressure Gauges (refrigerant)
• Thermometer
• Tachometer
• Incline Manometer or equivalent
Start-Up Checklist
The unit will be in operational mode during start-up.
Use necessary precautions to avoid injury. All data
must be collected while the unit is running. In order to
measure volts and amps, the control center door must
be open and the unit energized, using an adjustable
wrench to turn the disconnect handle.
After power has been applied
for 24 hours, verify that all
crankcase heaters are heating
properly. Either check the amp
draw on each heater or touch the
compressor near the top to verify
that the heater is warming the
compressor.
Crankcase Heater
(silver colored band)
WARNING
Do not touch the heater. It will cause severe burns!
See image of crackcase heater.
Packaged DX Module for Make-Up Air Unit
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