Trane 4TWA3 Electrical Connections, Defrost Control, Compressor Start UP, PIN Identification

Installer’s Guide

10.The gas valve can now be opened. For a ball type gas valve, open the gas valve by removing the shut-off valve cap and turning the valve stem 1/4 turn counterclock- wise, using 1/4" Open End or Adjustable wrench. See Figure 4. For brass gas line service valve opening, follow 8 and 9 on page 3. See Figure 5.

11.The gas valve is now open for refrigerant flow. Replace valve stem cap to prevent leaks. Again, these caps MUST BE REPLACED to prevent leaks. Replace valve stem and pressure tap cap finger tight, then tighten an additional 1/6 turn. See Figure 3.

If refrigerant lines are longer than 15 feet and/or a different size than recommended, it will be necessary to adjust system refrigerant charge upon completion of installation. See page 6 or the unit Service Facts.

E. ELECTRICAL CONNECTIONS

!WARNING

When installing or servicing this equipment, ALWAYS exercise basic safety precautions to avoid the possibility of electric shock.

1.Power wiring and grounding of equipment must comply with local codes.

2.Power supply must agree with equipment nameplate.

3.Install a separate disconnect switch at the outdoor unit.

4.Ground the outdoor unit per local code requirements.

5.Provide flexible electrical conduit whenever vibration transmission may create a noise problem within the structure.

6.The use of color coded low voltage wire is recommended to simplify connections between the outdoor unit, the thermostat and the indoor unit.

Table 1 — NEC Class II Control Wiring

	24 VOLTS
WIRE SIZE		MAX. WIRE LENGTH
18 AWG		150 FT
16 AWG		225 FT.
14 AWG		300 FT.

7.Table 1 defines maximum total length of low voltage wiring from outdoor unit, to indoor unit, and to thermostat.

8.Mount the indoor thermostat in accordance with instruc- tion included with the thermostat. Wire per appropriate hook-up diagram (included in these instructions).

F. DEFROST CONTROL

The demand defrost control measures heat pump outdoor ambient temperature with a sensor located outside the outdoor coil. A second sensor located on the outdoor coil is used to measure the coil temperature. The difference between the ambient and the colder coil temperature is the difference or delta-T measurement. This delta-T measure- ment is representative of the operating state and relative capacity of the heat pump system. By measuring the change in delta-T, we can determine the need for defrost. The coil sensor also serves to sense outdoor coil temperature for termination of the defrost cycle.

FAULT IDENTIFICATION

A fault condition is indicated by the flashing light on the defrost control inside the heat pump control box.

In normal operation, the defrost control light will flash once each second. If the light is flashing more than once per second or not at all, refer to the service manual for that unit.

PIN IDENTIFICATION (See Figure 6.)

1.TEST_COMMON (Shorting any of the other pins to this pin causes the function of the other pin to be executed. Leaving this pin open results in the normal mode of operation.)

2.TST = Test (Shorting TEST_COMMON to this pin speeds up all defrost board timings.)

3.FRC_DFT = Forced Defrost (Short TEST_COMMON to this pin for two [2] seconds to initiate a forced defrost. Remove the short after defrost initiates.)

6PIN IDENTIFICATION

	TEST COMMON
FRC DFT	TST

DEFROST CONTROL CHECKOUT

Normal operation requires:

a.LED on board flashing 1 time/second.

b.24V AC between R & B.

c.24V AC between Y & B with unit operating.

d.Defrost initiation when FRC_DFT pin is shorted to TEST_COMMON pin.

If a defrost control problem is suspected, refer to the service information in control box.

!WARNING

Do NOT connect 24 VAC to T1 (ODS-A) terminal. ODS-A thermistor WILL BE BLOWN.

G. COMPRESSOR START UP

After all electrical wiring is complete, SET THE THERMO-

STAT SYSTEM SWITCH IN THE OFF POSITION SO COMPRESSOR WILL NOT RUN, and apply power by closing the system main disconnect switch. This will activate the compressor sump heat (where used). Do not change the Thermostat System Switch until power has been applied for one (1) hour. Following this procedure will prevent potential compressor overload trip at the initial start-up.

H. OPERATIONAL AND

CHECKOUT PROCEDURES

Final phases of this installation are the unit Operational and Checkout Procedures which are found in this instruction on page 8. To obtain proper performance, all units must be operated and charge adjustments made in accordance with procedures found in the Service Facts and on page 6.

IMPORTANT:

Perform a final unit inspection to be sure that factory tubing has not shifted during shipment. Adjust tubing if necessary so tubes do not rub against each other when the unit runs. Also be sure that wiring connections are tight and wire routing is secure.

4 18-BC62D1-1