Carrier 50VT-A Standard Connections, Special Procedures for 208-VOperation, Sequence of Operation

HIGH VOLTAGE POWER LEADS (SEE UNIT WIRING LABEL)

3-PHASE SHOWN

1-PHASE USES

TWO POWER	EQUIP GR
LEADS

CONTROL BOX

POWER

SUPPLY

FIELD-SUPPLIED FUSED DISCONNECT

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

LOW-VOLTAGE POWER LEADS (SEE UNIT)

WIRING LABEL

SPLICE BOX

WHT(W1)	W1
VIO (W2)	W2
YEL(Y)	Y
GRN(G)	G
RED(R)	R
BRN(C)	C
ORN(O)	O
BLU(DH)	DH
GRA(Y2)	3-Phase
	Only

THERMOSTAT (TYPICAL)

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.

50VT-- A

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

!WARNING

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.

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

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

Rto 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.

9