Carrier 25HBB Install Electrical Accessories, Start-Up, Sequence of Operation, Heating, Defrost

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 com-

binations)

Sequence of Operation

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

Cooling

On a call for cooling, thermostat makes circuits R-O and R-Y, and R-G. Circuit R-O energizes reversing valve, switching it to cooling position. Circuit R-Y energizes contactor, starting outdoor fan motor and compressor circuit. R-G energizes indoor unit blower relay, starting indoor blower motor on high speed.

When thermostat is satisfied, its contacts open, de-energizing contactor and blower relay. Compressor and motors should stop.

NOTE: If indoor unit is equipped with a time-delay relay circuit, the indoor blower will run 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 energizes contactor, starting outdoor fan motor and compressor. Circuit R-G energizes indoor blower relay, starting blower motor on high speed.

Should temperature continue to fall, R-W2 is made through second-stage room thermostat. Circuit R-W2 energizes a relay, bringing on first bank of supplemental electric heat and providing electrical potential to second heater relay (if used). If outdoor temperature falls below setting of outdoor thermostat (field installed option), contacts close to complete circuit and bring on second bank of supplemental electric heat.

When thermostat is satisfied, its contacts open, de-energizing contactor and relay. All heaters and motors should stop.

Defrost

The defrost control is a time/temperature control which includes a field selectable (quick-connects located at board edge) time period between defrost cycles (30, 60, or 90 minutes), factory set to 90 minutes.

25HBB

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