Carrier 25HCS installation instructions Install Electrical Accessories, Start-Up

Install Electrical Accessories

Refer to the individual instructions packaged with kits or accessories when installing.

Start-Up

!CAUTION

PERSONAL INJURY HAZARD

Failure to follow this caution may result in personal injury.

Wear safety glasses, protective clothing, and gloves when handling refrigerant and observe the following:

S Front seating service valves are equipped with Schrader valves.

!CAUTION

ENVIRONMENTAL HAZARD

Failure to follow this caution may result in environmental damage.

Federal regulations require that you do not vent refrigerant to the atmosphere. Recover during system repair or final unit disposal.

!CAUTION

UNIT OPERATION AND SAFETY HAZARD

Failure to follow this caution may result in personal injury, equipment damage or improper operation.

S Do not overcharge system with refrigerant.

S Do not operate unit in a vacuum or at negative pressure. S Do not disable low pressure switch in scroll compressor

applications.

S Compressor dome temperatures may be hot.

Follow these steps to properly start up system:

1.After system is evacuated, fully open liquid and vapor service valves.

2.Unit is shipped with valve stem(s) front seated (closed) and caps installed. Replace stem caps after system is opened to refrigerant flow (back seated). Replace caps finger-tight and tighten with wrench an additional 1/12 turn.

3.Close electrical disconnects to energize system.

4.Set room thermostat at desired temperature. Be sure set point is below indoor ambient temperature.

5.Set room thermostat to HEAT or COOL and fan control to ON or AUTO mode, as desired. Operate unit for 15 minutes. Check system refrigerant charge.

		TYPICAL		HEAT
HP THERMOSTAT		FAN COIL		PUMP
24 VAC HOT	R	R		R
24 VAC COM	C	C		C
HEAT STAGE 2	W2	W2	*	W2
		E *
COOL/HEAT	Y
STAGE 1		W3 *		Y
INDOOR FAN	G	G
RVS COOLING	O			O
EMERGENCY	E	* IF AVAILABLE
HEAT

LEGEND

24-V FACTORY WIRING

24-V FIELD WIRING

FIELD SPLICE CONNECTION

ODT

OUTDOOR THERMOSTAT

EHR EMERGENCY HEAT RELAY

SHR SUPPLEMENTAL HEAT RELAY

A02325 / A97413

Fig. 8 - Generic Wiring Diagrams

(See Thermostat Installation Instructions

for specific unit combinations)

Sequence of Operation

NOTE: Defrost control board is equipped with 5 minute lockout timer that is initiated upon any interruption of power.

Turn on power to indoor and outdoor units. Transformer is energized.

Cooling

On a call for cooling, thermostat makes circuits R-O, R-Y, and R-G. Circuit R-O energizes reversing valve, switching it to cooling position. Circuit R-Y sends low voltage through the safeties and energizes the T1 terminal on the circuit board. If the compressor has been off for 5 minutes, or power has not been cycled for 5 minutes, the OF2 relay and T2 terminal will energize. This will close the contactor, and start the outdoor fan motor and compressor.

When the cycle is complete, R-Y is turned off, stopping the compressor and outdoor fan. The 5 minute time guard begins counting. Compressor will not come on again until this delay expires. In the event of a power interruption, the time guard will not allow another cycle for 5 minutes.

NOTE: If the indoor blower off delay is enabled, it will run up to an additional 90 seconds to increase system efficiency.

Heating

On a call for heating, thermostat makes circuits R-Y and R-G. Circuit R-Y sends low voltage through the safeties and energizes the T1 terminal on the circuit board. T1 energizes the defrost logic circuit. If the compressor has been off for 5 minutes, or power has not been cycled for 5 minutes, the OF2 relay and T2 terminal will energize. This will close the contactor, start the outdoor fan motor and compressor.

When the cycle is complete, R-Y is turned off , stopping the compressor and outdoor fan. The 5 minute time guard begins counting. Compressor will not come on again until this time delay expires. In the event of a power interruption, the time guard will not allow another cycle for 5 minutes.

25HCS

5