Carrier Omnizone 50BVC Installation, Start-Up, Service And Controls Operation And Troubleshooting page 25

N.O.
AQUASTAT
FLUID IN
"BULB STRAPPED
TO FLUID" IN LINE
(FIELD INSTALLED)
Step 5 — Complete Electrical Connections
Verify that electrical requirements listed on the unit nameplate
match available power supply. The unit voltage must be within the
range shown in Tables 11-13 and phases must be balanced within
2%. Contact the local power company for line voltage corrections.
Never operate a motor where a phase imbalance in supply voltage
is greater than 2%.
For an unbalanced 3-phase supply voltage, use the following for-
mula to determine the percent of voltage imbalance:
Percent Voltage Imbalance
max voltage deviation from average voltage
= 100 x
average voltage
Example: Supply voltage is 460-3-60.
AB = 452 V
BC = 464 V
AC = 455 V
Average Voltage =
Determine maximum deviation from average voltage:
(AB) 457 – 452 = 5 V
(BC) 464 – 457 = 7 V
(AC) 457 – 455 = 2 V
Maximum deviation is 7 V.
Determine percent of voltage imbalance:
% Voltage Imbalance = 100 x
= 1.53%
This amount of phase imbalance is satisfactory as it is below the
maximum allowable 2%.
IMPORTANT: If supply voltage phase imbalance is more than
2%, contact the local electric utility company immediately.
POWER WIRING
Properly sized fuses or HACR (Heating, Air-Conditioning and
Refrigeration) circuit breakers must be installed for branch circuit
protection, according to the national and applicable local codes.
See unit nameplate and Tables 11-13 for maximum overcurrent
protection size.
These units are provided with single point, main power supply ter-
minal blocks. Refer to Fig. 7-15 for conduit connection locations.
Connect the power leads as indicated on the unit wiring diagrams
3-WAY MOTORIZED
BALL VALVE
N.C.
MBV
N.O.
Fig. 19 — Optional Water Economizer
452 + 464 + 455
3
1371
=
3
= 457
7
457
WATERSIDE
ECONOMIZER
COIL
(found in the Troubleshooting section) and be certain to connect
the ground lead to the ground lug in the unit high voltage electrical
box. Refer to Tables 11-13 for unit electrical data.
Modular Units
For units with multiple main air-conditioning sections, connect the
high voltage compressor power wiring to the line side of the high
voltage terminal block in the second section's high voltage electri-
cal box. This wiring is located in the upper portion of the compres-
sor compartment.
Connect the low voltage wiring, located in the compressor com-
partment, between the two air-conditioning sections using the
quick connects provided.
For the supply fan motor, connect the 3-phase high voltage wir-
ing, coiled behind the high voltage panel, to the line side of the
supply fan motor terminal block located in the fan compartment.
For VAV units, connect the 3-phase high voltage wiring to the line
side of VFD.
For units with multiple fans, connect the control power wiring
with the quick connects provided at the fan compartment junction.
CONTROL WIRING (CV ONLY)
A standard commercial thermostat controls constant volume units.
These units turn compressors on or off in response to zone tem-
perature. The 50BV units provide 2 stages of cooling. See Fig. 20
for typical thermostat wiring.
50BVC,Q020-034 and 50BVT,V034 Only
These models have 2 independent refrigerant circuits, each capa-
ble of being staged independently. Thermostat wiring is connected
to the 6-position low voltage terminal block located in the unit
electrical box. The 50BV units have a 24-vac control transformer,
which provides power to the control circuit and to the thermostat.
The thermostat connections and their functions are as follows:
C Transformer 24-vac Common
O Reversing Valve (heat pumps only)
Y1 1st Stage Compressor Contactor
Y2 2nd Stage Compressor Contactor
R Transformer 24-vac Hot
G Indoor Fan Contactor
H Dehumidification (on/off HGRH only)
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.
25
FLUID TO REFRIGERANT
HEAT EXCHANGER
POSITIVE SHUT-OFF SOLENOID
VALVE FOR VARIABLE SPEED
PUMPING SYSTEM
(FIELD INSTALLED)