RT-SVX069A-EN
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cooling demand, the second compressor will be staged
back and the supply fan will switch to Low Speed until
the unit stages all cooling off or receives a call for Cool
2 again. Once the Supply Fan is no longer requested
ON after a Cooling call is cleared, the Supply Fan will
remain energized at Low Speed for 60 seconds as on
traditional units.
If the economizer is enabled and is being utilized as the
first stage of cooling (Y1 active), if the unit receives a
Y2 request, the unit will energize the first compressor
and will switch the supply fan to high speed until the
Y2 request is cleared.
Low Pressure Cutout
The low pressure cutouts are wired in series with the
high pressure cutouts and the temperature discharge
limits. If this circuit is open before a compressor is
started, the compressor in that circuit will not be
allowed to operate.
Anytime this circuit is opened, the compressor in that
circuit is turned off immediately.
High Pressure Cutout and Temperature
Discharge Limit
The high pressure controls and temperature discharge
limit are wired in series between the compressor
outputs on the LTB and the compressor contactors. If
the high pressure safety or temperature discharge limit
opens, the compressor on the affected circuit is turned
off.
Heating Operation
Standard unit operation for heating will continue on
units equipped with a two-speed indoor fan. During
heat mode, all units configured with staged electric or
gas heat will heat the supply air and space as normal
utilizing full speed indoor fan.
Emergency Stop
This input de-energizes the 24 Vac output from the
phase monitor and can be activated by opening a field
supplied device.
Compressor Start-Up
1. Attach a set of service gauges onto the suction and
discharge gauge ports for each circuit.
See,
for startup
instructions.
S
Sccrro
ollll C
Co
om
mp
prre
esssso
orrss
a. Once each compressor has started, verify that
the rotation is correct. If wired correctly the
suction pressure should drop and the discharge
pressure should rise. If a scroll compressor is
rotating backwards, it will not pump and a loud
rattling sound can be observed.
b. If the electrical phasing is correct, before
condemning a compressor, interchange any two
leads (at the compressor Terminal block) to
check the internal phasing. Refer to the
following illustration for the compressor
terminal/phase identification. Do not allow the
compressor to operate backwards for more than
5 seconds. Operation for a period of time longer
than this will result in compressor damage.
Figure 17.
Compressor terminal box
Compressor ZP**
3
2
1
Compressor HRH051
3
2
1
IP22
1. Spade connectors 1/4–in.
2. Earth connection
3. Power cable passage
Table 9. Compressor types
Tonnage
Compressor 1
Compressor 2
GB*090
ZP42
ZP31
GB*102
ZP42
ZP42
GB*120
ZP57
HRH051
GB*150
ZP72
HRH051
Table 10.
POE Oil recharge amount (fl. oz.)
Tonnage
Compressor 1
Compressor 2
GB*090
42
25
GB*102
42
42
GB*120
56
53
GB*150
60
53