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POWER
SUPPLY

FIELD-SUPPLIED
FUSED DISCONNECT

HIGH VOLTAGE
POWER LEADS
(SEE UNIT WIRING
LABEL)

EQUIP GR

CONTROL BOX

LOW-VOLTAGE
POWER LEADS
(SEE UNIT
WIRING LABEL

)

WHT(W1)

YEL(Y)

GRN(G)

RED(R)

BRN(C)

THERMOSTAT
(TYPICAL)

ORN(O)

3-PHASE SHOWN
1-PHASE USES
TWO POWER
LEADS

VIO (W2)

SPLICE BOX

BLU(DH)

3-Phase
Only

GRA(Y2)

A09071

Fig. 10 -- High-- and Control--Voltage Connections

Single phase units:

1. Run the high--voltage (L1, L2) and ground lead into the

control box.

2. Connect ground lead to chassis ground connection.
3. Locate the black and yellow wires connected to the line side

of the contactor.

4. Connect field L1 to black wire on connection 11 of the

compressor contactor.

5. Connect field wire L2 to yellow wire on connection 23 of

the compressor contactor.

Three--phase units:

1. Run the high--voltage (L1, L2, L3) and ground lead into the

control box.

2. Connect ground lead to chassis ground connection.
3. Locate the black and yellow wires connected to the line side

of the contactor.

4. Connect field L1 to black wire on connection 11 of the

compressor contactor.

5. Connect field wire L3 to yellow wire on connection 13 of

the compressor contactor.

6. Connect field wire L2 to blue wire from compressor.

Special Procedures for 208--V Operation

ELECTRICAL SHOCK HAZARD

Failure to follow this warning could result in personal

injury or death.
Before installing or servicing system, always turn off main

power to system. Tag the disconnect switch with a suitable

warning label. With disconnect switch open, move black

wire from transformer (3/16 in.) terminal marked 230 to

terminal marked 208. This retaps transformer to primary

voltage of 208 vac.

WARNING

Control Voltage Connections

NOTE

: Do not use any type of power--stealing thermostat. Unit

control problems may result.
Use no. 18 American Wire Gage (AWG) color--coded, insulated
(35

C minimum) wires to make the control voltage connections

between the thermostat and the unit. If the thermostat is located

more than 100 ft (30.5 m) from the unit (as measured along the

control voltage wires), use no. 16 AWG color--coded, insulated
(35

C minimum) wires.

Standard Connections

Locate the eight (nine on 3--phase) low voltage thermostat leads in

24 volt splice box. See Fig. 10 for connection diagram. Run the
low--voltage leads from the thermostat, through the control wiring

inlet hole grommet (Fig. 2 and 3), and into the low--voltage splice
box. Provide a drip loop before running wires through panel.

Secure and strain relief all wires so that they do not interfere with

operation of unit. A gray wire is standard on 3--phase units for
connection to an economizer.
If an accessory electric heater is installed, low voltage leads from
heater must be connected to factory supplied control leads from

Indoor Fan Board P4 connector.

NOTE

: If the unit 24V wires do not have a matching receptacle,

cut the 24V wires from the electric heater plug, strip the ends, and
wire nut together to match the schematic connections. If the electric
heater 24V wires do not have a matching plug, cut the 24V wires
from the unit receptacle, strip the ends, and wire nut together to
match the schematic connections.
Factory wires are provided for electric heat staging W1 and W2
(W2 and W3 on IFB). If room thermostat has only one stage of

supplemental heat, connect white and violet wires shown in Fig. 10
to second stage heat field wire.
Some electric heaters have four control wires (plus common wire).

Consult unit wiring diagram and electric heater wiring diagram for
additional details.

Transformer Protection

The transformer is of the energy--limiting type. It is set to withstand
a 30--second overload or shorted secondary condition. If an

overload or short is present, correct overload condition and check

for blown fuse on Interface Fan Board. Replace fuse as required
with correct size and rating.

Accessory Electric Heaters Installation

Electric heaters may be installed with the 50VT--A units per

instructions supplied with electric heater package. See unit rating
plate for factory--approved electric heater kits.

Sequence of Operation

a. CONTINUOUS FAN

(1.) Thermostat closes circuit R to G energizing the

blower motor for continuous fan.

b. COOLING MODE

(1.) If indoor temperature is above temperature set

point, thermostat closes circuits R to G, R to Y and
R to O--The unit delivers cooling airflow.

c. ELECTRIC HEATING MODE

(1.) Thermostat closes circuit R to W/W1, or W2 and R
to G. There are no on or off delays.

d. HEAT PUMP HEATING MODE

(1.) Thermostat closes circuits R to G and R to Y. The

compressor, indoor and outdoor fans are energized.

e. HEAT PUMP HEATING WITH AUXILIARY

ELECTRIC HEAT

(1.) Thermostat closes circuits R to G, R to Y and R to

W/W1 or W2. The compressor, indoor and outdoor
fans are energized, as well as the electric heat

relays.

f. DEFROST MODE

The defrost mode is automatically energized by the
defrost board during heating mode. The defrost board

energizes “O” (reversing valve) and “W2” (electric
heat). It also de--energizes the outdoor fan. When defrost
is complete, unit will return to heating mode. If room

thermostat is satisfied during defrost, unit will shut
down and restart in defrost on next call for heat.

50V