Carrier 38AU Install Liquid Line Solenoid Valve, Capacity Control Liquid Line Solenoid Valve

38AU

	TXV			EQUALIZER LINE
INDOOR
	SENSING			SIGHT GLASS
COIL CKT	BULB
				A LOCATION
				FILTER DRIER
				A LOCATION
AIRFLOW	15 DIAMS			TXV
		10
	MIN
		DIAMS
		8 DIAMS		FLOW
		MIN
				LIQUID LINE
				SOLENOID
				VALVE
		Single Circuit Coil Piping Configuration
	For single compressor condensing units
	TXV			EQUALIZER LINE
INDOOR
	SENSING
COIL CKT 2	BULB
				SIGHT GLASS
				A LOCATION	FILTER DRIER
AIRFLOW	15 DIAMS			TXV
		10	CKT 2		A LOCATION
	MIN
		DIAMS
		8 DIAMS		SIGHT
		MIN
				GLASSES	FLOW
	TXV			B LOCATION
				FILTER
INDOOR	SENSING				LIQUID LINE
COIL CKT 1	BULB			DRIERS	SOLENOID
				B LOCATION	VALVE
AIRFLOW	15 DIAMS			TXV
		10	CKT 1
	MIN
		DIAMS

8DIAMS

MIN

Dual Circuit Coil Piping Configuration

For single compressor condensing units

C10202

Fig. 8 - Location of Sight Glass(es) and Filter Driers

Typical 38AUZ Systems

	TXV		EQUALIZER LINE
	SENSING
	BULB
AIRFLOW
	15 DIAMS		TXV
		10	CKT 2
	MIN
		DIAMS	8 DIAMS
			MIN	FLOW
			SIGHT
	TXV		GLASSES	LIQUID LINE
	SENSING		FILTER	SOLENOID VALVE
	BULB		DRIERS	CIRCUIT 2
AIRFLOW	15 DIAMS		TXV
		10	CKT 1
	MIN
		DIAMS
			8 DIAMS	FLOW
			MIN
				LIQUID LINE
	SUCTION			SOLENOID VALVE
	CIRCUIT 1			CIRCUIT 1

SUCTION

CIRCUIT 2

Dual Circuit Coil Piping Configuration

For two circuit condensing units

C10072

Fig. 9 - Location of Sight Glasses and Filter Driers

Typical 38AUD Systems

In some applications, depending on space and convenience requirements, it may be desirable to install 2 filter driers and sight glasses in a single circuit application. One filter drier and sight glass may be installed at A locations (see Fig. 8) or 2 filter driers and sight glasses may be installed at B locations (see Figs. 8 and 9).

Select the filter drier for maximum unit capacity and minimum pressure drop. Complete the refrigerant piping

from the indoor unit to the outdoor unit before opening the liquid and suction lines at the outdoor unit.

Install Liquid Line Solenoid Valve —

It is recommended that a solenoid valve be placed in the main liquid line (see Figs. 8 & 9) between the condensing unit and the evaporator coil. Locate the solenoid valve at the outlet end of the liquid line, near the evaporator coil connections, with flow direction arrow pointed at the evaporator coil. Refer to Table 9. (A liquid line solenoid valve is required when the liquid line length exceeds 75 ft [23 m].) This valve prevents refrigerant migration (which causes oil dilution) to the compressor during the off cycle, at low outdoor ambient temperatures. Wire the solenoid in parallel with the compressor contactor coil (see Figs. 8 & 9). This means of electrical control is referred to as solenoid drop control.

Solenoid drop control wiring: Control the power to the liquid line solenoid through a Solenoid Valve Relay (SVR) in all units. Use part number HN61PC005 (field-supplied, installed). 38AUZ unit requires one SVR; 38AUD unit requires two relays.

38AUD unit also requires a separate control power transformer for the liquid solenoid valve loads. Select transformer part number according to unit power supply.

Unit Power	Transformer Part #
208/230	HT01BD202

460HT01BD702

575HT01BD902

Mount the SVR (and transformer TRAN3 when used) in unit control box. Connect per wiring schematic label on unit or per Fig. 29 (38AUZ) or Fig. 30 (38AUD).

Capacity Control Liquid Line Solenoid Valve:

Evaporator capacity staging control via direct thermostat control of a liquid solenoid valve on the evaporator’s second stage circuit is not possible with 38AU models. If this installation is a retrofit for a unit that included automatic pressure-operated unloading, check the existing thermostat and liquid solenoid valve wiring for possible direct thermostat control of a solenoid valve; re-wire per Figs. 17 or 18 and 29 or 30.

Selecting an Accumulator –

Because all 38AU models use scroll compressors, an accumulator is not required. If an accumulator is to be added, check the accumulator manufacturer’s literature carefully for indication of its suitability for use with R-410A; look for minimum working pressure of 200 psig (1380 kPa). Select the accumulator first on the basis of its cataloged minimum capacity (tons) to ensure oil return from the accumulator, then on tube size or holding capacity.

Make Piping Connections —

Piping connections at the 38AU unit are ball valves with stub tube extensions. Do not open the unit service valves until all interconnecting tube brazing has been completed.

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