Hot Gas Reheat Control (Optional); Energy Management Switch (Optional); Alarm Output (All Units) - Carrier Omnizone 50BV020-064 Installation, Start-Up, Service And Controls Operation And Troubleshooting

Select an appropriate commercial thermostat that has 2 stages of
cooling control. If the unit is a heat pump, make sure the thermo-
stat is capable of heat pump control.
Install the thermostat in the space where the temperature is being
controlled, according to the instructions provided with the
thermostat.
WARNING
Before wiring the thermostat to the unit, make sure that main
power to the unit has been disconnected. Failure to heed this
warning could result in personal injury.
To wire the thermostat:
1. Connect the 'C' terminal from the 50BV unit to the 'C'
terminal on the thermostat.
2. Wire the 'Y1' and 'Y2' terminals from the 50BV unit to the
'Y1' and 'Y2' terminals, respectively, at the thermostat.
3. Make a connection between the 'G' terminal on the unit and
the 'G' terminal on the thermostat.
4. Attach a wire from the 'R' terminal at the unit to the 'R'
terminal at the thermostat.
5. 50BVV ONLY: If the unit is a heat pump, connect a final wire
from terminal 'O' on the heat pump unit to the 'W1/O/B' ter-
minal at the thermostat. Configure the thermostat for heat
pump operation using the installation instructions provided
with the thermostat. Set the reversing valve polarity of the
thermostat to 'O'.
6. For units with cycling (on/off) HGRH, connect the thermostat
H output to the H terminal on the 50BV. Set up the thermostat
to provide an H output only, as the unit will automatically
enable the Y1 and O terminals when there is a call for H
(dehumidification).
See Fig. 29 for typical thermostat wiring.
50BVT,V044-064 Only
Unit sizes 044-064 have four independent refrigerant circuits.
These units can be controlled using a standard commercial, 2-
stage thermostat. In this case, the first stage of cooling will turn on
compressors 1 and 2, and the second stage will turn on compres-
sors 3 and 4. It is also possible to have 4 stages of cooling, using a
suitable field-supplied control method.
For 2-stage thermostat wiring, refer to Fig. 29. Jumpers must be
installed between the G and O terminals in Modules A and B. A
field-supplied, 24-v pilot relay should be used to energize Y2 on
Module B whenever Y1 is energized on Module A. Similarly, a
field-supplied 24-v pilot relay should be installed to energize Y4
on Module B whenever Y3 on Module A is energized (Y2 stage of
thermostat calls for cooling).
Finally, verify that transformer phasing is consistent between
Modules A and B.

HOT GAS REHEAT CONTROL (OPTIONAL)

On/Off HGRH
Units with on/off hot gas reheat (HGRH) will include an addition-
al H terminal on the input terminal board for dehumidification
control. To enable a call for dehumidification, a 24-v signal must
be sent to the H terminal with no voltage applied to the Y1 or O
terminals. Any call for cooling (Y1 and O) will override the dehu-
midification call.
Modulating HGRH
Units with modulating HGRH will require a field supplied con-
troller capable of controlling the MHGRH valve via a 0-10vdc
signal.

ENERGY MANAGEMENT SWITCH (OPTIONAL)

Units with the energy management switch (EMS) relay can be
field wired to disable unit operation when a 24-v signal is removed
from a factory-installed normally open relay. Removing the 24-v
signal causes the relay to open, which cuts 24-v power to the unit
control circuit. All unit components will be disabled when the
EMS is deactivated.

ALARM OUTPUT (ALL UNITS)

If the unit is being connected to a thermostat or DDC control with
an alarm indicator, this connection is made at the unit malfunction
output on the Unit Protection Module (UPM). See the Unit Protec-
tion Module heading in the Set Up Unit Controls section for fur-
ther details.
Thermostat
B
O
Y2 R W1 Y1 G C
2nd Stage Compressor Relay
Fig. 28 — Typical Wiring Unit Sizes 034
(Two-Stage Cooling Unit)
32
Typical
Uni t
24 vac Common
Fan Relay
Compressor Relay
Heat Pump
24 vac Return
C
O
Y1
Y2
R
G