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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Image 16
Carrier 38AU Install Liquid Line Solenoid Valve, Capacity Control Liquid Line Solenoid Valve, Selecting an Accumulator