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d. Phase Sequence Relay. To remove the phase
sequence relay from three phase units, refer to
figure 4-20 and remove relay as follows:
(1) Remove four screws (13), nuts (14), and
washers (15).
(2) Remove relay (17) and two each of
washers (15 and 16).
e. Time Delay Relay. To remove the time delay
relay, refer to figure 4-20 and remove relay as
follows:
(1) TO remove time delay (18) from three
phase units, remove the phase sequence relay then
remove two remaining screws (13), nuts (14), and
flat washers (15).
(2) TO remove time delay relay (18) from
single phase units, remove four screws (13), nuts
(14), and flat washers (15).
f. Control Circuit Breaker. To remove the control
circuit breaker (19, fig. 4-20), remove circuit
breaker nut from front of junction box and pull
breaker to the rear of the junction box.
4-53. Assembly
a. General. Refer to figure 4-20 and install any
components that were removed. After installation
of components, make all the necessary electrical
connections.
b. Control Circuit Breaker. Install control circuit
breaker (19) through opening in junction box with
locating projection in opening provided. Install
breaker nut.
c. Time Delay Relay. Install time delay relay
(18) on junction box. Secure relay to single phase
junction box with four screws (13), nuts (14), and
washers (15). For three phase junction boxes, omit
the two inner sets of hardware.
d. Phase Sequence Relay. To install the phase
sequence relay on three phase junction box proceed
as follows:
(1) Place a flat washer (15) and flat washer
(16) over inner mounting holes of phase sequence
relay.
(2) Install phase sequence relay (17) on
washers and mounting flange of time delay relay.
Install four screws (13), flat washers (15), and nuts
(14).
e. Condenser Fan Relay. Install condenser fan
relay (12) on bracket (11) a nd secure relay with
three nuts (9) a nd flat washers (10). Install bracket
on junction box and install two screws (6), nut. (7),
a nd washers (8).
f. Heater and Compressor Motor Relays. Install
heater relay (5) or compressor motor relay (4) and
secure relay with four screws (1), nuts (2) and flat
washers (3).
4-54. Installation
a. Make any electrical connections that were
disconnected during removal.
b. Carefully install junction box into housing and
install seven screws and lock washers.
c. Refer to paragraph 4-48 and install control
module.
d. Refer to paragraph 4-21 and install top front
cover.
Section XVI. MAINTENANCE OF TRANSFORMER, RECTIFIER,
AND PRESSURE SWITCHES
4-55. General
The power transformer and rectifier reduces the
power voltage and converts the alternating current
to 24 volt direct current to operate the coils and
switches in the control circuit. The transformer is
rated at a secondary voltage of 30 vac with a
primary voltage of 115 vac. The transformer and
rectifier are located below the junction box. The
high and low pressure cutout switches are also
located below the junction box with the reset
buttons extending through the front of the housing.
The pressure cutout switches are connected in the
refrigeration system and are electrically connected
in the control system to the compressor motor relay
coil. Extreme high or low pressure opens the circuit
causing the compressor to stop.
4-56. Transformer
a. Testing. Test transformer as follows:
(1) Refer to paragraph 4-21 and remove top
cover. Refer to paragraph 4-50 and partially
remove junction box.
(2) Disconnect leads and check for continuity
across the primary winding and then across the
secondary winding.
If either winding is open,
replace the transformer.
(3) Check for shorts between one terminal a nd
transformer case and also between one primary
terminal and one secondary terminal using an
insulation tester, megger or multimeter on high
ohms setting. Replace transformer if a short is
indicated.
b. Removal. With junction box removed, refer to
figure 4-21 and remove four screws and lock
washers. Disconnect and remove transformer.
c. Installation. Refer to figure 4-21 and install
transformer, four screws, and four lock washers.
Connect leads. Refer to paragraph 4-54 and install
junction box.
4-31
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