23
Voltage to compressor terminals during compressor operation
must be within the voltage range indicated on the unit nameplate.
Phases must be balanced within 2%.
Use the following formula to determine the percent of voltage
imbalance.
% Voltage Imbalance:
Example: Supply voltage is 230-3-60
Determine maximum deviation from average voltage.
(AB) 227-224 = 3 v
(BC) 231-227 = 4 v
(AC) 227-226 = 1 v
Maximum deviation is 4 v.
Determine percent of voltage imbalance.
This amount of phase imbalance is satisfactory as it is below the maxi-
mum allowable 2%.
NOTE: Check all factory and field electrical connections for tightness.
Unit failure as a result of operation on improper line voltage or
excessive phase imbalance constitutes abuse and may cause dam-
age to electrical components.
For transformer 1 move the black wire connected to terminal
H2 and connect it to terminal H3.
For transformers 2 to 4, used for the 24 volt control circuits,
connect as follows:
1. Remove cap from red (208 v) wire.
2. Remove cap from spliced orange (230 v) wire. Disconnect
orange wire from black unit power wire.
3. Cap orange wire.
4. Splice red wire and black unit power wire. Cap wires.
If the unit is equipped with the optional convenience outlet,
connect the yellow wire to H2 on transformer 5.
FIELD CONTROL WIRING — The 50A Series units support a
large number of control options that can impact the field control
wiring. Refer to Fig. 21 and 22.
The control options that the unit can provide relate to the fol-
lowing parameters:
• CV (constant volume), VAV (variable air volume), SAV
(staged air volume), or VVT
®
(variable volume and variable
temperature) control operation
• Standalone with a thermostat (CV) or with a space sensor
(CV and VAV)
• Network application with CCN (Carrier Comfort Net-
work
®
) or other networks
• Demand controlled ventilation with CO
2
sensor
• Economizer and economizer with changeover control
• Building and duct static pressure control
• Fire shutdown and smoke control
• Diagnostics and monitoring
• For constant volume applications a thermostat (T-Stat) or
space temperature sensor (SPT) will be required.
T-STAT (Conventional Thermostat) — Unit can be controlled
with a Carrier-approved accessory electro-mechanical or electron-
ic thermostat that has two stages of cooling, two stages of heating
control, and an output for indoor fan control. It may also include
time of day scheduling or use the scheduling routines built into the
Comfort
Link controls.
Install thermostat according to the installation instructions in-
cluded with accessory thermostat. Locate thermostat assembly on
a solid interior wall in the conditioned space to sense average tem-
perature.
Route thermostat cable or equivalent single leads of colored
wire from subbase terminals through conduit into unit to low volt-
age connection in the main control box, as shown in Fig. 21 and
22. For thermostat TB4 connections see Fig. 21.
NOTE: For wire runs up to 50 ft, use no. 18 AWG (American
Wire Gage) insulated wire (35 C minimum). For 50 to 75 ft, use
no. 16 AWG insulated wire (35 C minimum). For over 75 ft, use
no. 14 AWG insulated wire (35 C minimum). All wire larger than
no. 18 AWG cannot be directly connected at the thermostat and
will require a junction box and splice at the thermostat. Set heat
anticipator settings as follows:
Settings may be changed slightly to provide a greater degree of
comfort for a particular installation.
SPT (Space Temperature Sensor) — For constant volume appli-
cations the
Comfort
Link controls can also be used with T55 and
T56 space temperature sensors that use a 10K thermistor. The T56
sensor also has the capability for a configurable temperature set
point offset at the thermostat. For variable air volume applications
only the T55 sensor can be used.
Install sensor according to the installation instructions included
with accessory sensor. Locate sensor assembly on a solid interior
wall in the conditioned space to sense average temperature.
= 100 x
max voltage deviation from average voltage
average voltage
AB = 224 v
BC = 231 v
AC = 226 v
Average Voltage
=
(224 + 231 + 226)
=
681
=
227
3
3
% Voltage Imbalance= 100x
4
= 1.78%
227
IMPORTANT: If the supply voltage phase imbalance is more than 2%,
contact your local electric utility company immediately.
IMPORTANT: On 208/230-v units, transformers 1 to 5 are
wired for 230-v. If 208/230-v unit is to be run with 208-v
power supply, the transformers must be rewired as follows:
IMPORTANT: BE CERTAIN UNUSED WIRES ARE
CAPPED. Failure to do so may damage the transformers.
A
B
C
MOTOR
UNIT SIZE
50A
STAGE 1
(W1) ON
STAGE 2
(W1 AND W2) ON
020-050
0.24
0.13
060
0.36
0.13
TB4
Fig. 21 — Field Control Thermostat Wiring
a48-8243
R
Y1
Y2
W1
W2
G
C
X
R
Y1
Y2
W1
W2
G
C
X
FIELD-
S
UPPLIED THERMO
S
TAT
LIGHT
RC
1
2
3
4
5
6
7
8
Fig. 22 — Space Temperature Sensor Wiring
a48-6854
T1
T2
1
2
4
3
5
6
7
8
9
10
11
12
1
3
14
15
16
TH
C
S
N
T56
S
PT
T55
S
PT
UNIT
TB5
