Carrier 69NT40-541-505, Operation And Service Manual, Page: 106 / 143

T-368 7–14
7.13.1 Evaporator Coil Replacement
a. Pump unit down. (Refer to Section 7.4 ).
WARNING
!
Always turn OFF the unit circuit breakers
(CB-1 & CB-2) and disconnect main power
supply before working on moving parts.
b. With power OFF and power plug removed,
remove the screws securing the panel covering
the evaporator section (upper panel).
c. Disconnect the defrost heater wiring.
d. Remove the mounting hardware from the coil.
e. Unsolder the two coil connections, one at the
distributor and the other at the coil header.
f. Disconnect the defrost temperature sensor
(refer to Section 7.21 ) from the coil.
g. Remove middle coil support.
h. After defective coil is removed from unit, remove
defrost heaters and install on replacement coil.
i. Install coil assembly by reversing above steps.
j. Leak check connections. Evacuate and add
refrigerant charge.
7.13.2 Evaporator Heater Replacement
The heaters are wired directly back to the contactor and if
a heater failure occurs during a trip, the heater set con-
taining that heater may be disconnected at the contactor.
The next Pre-trip (P1) will detect that a heater set has
been disconnected and indicate that the failed heater
should be replaced. To remove a heater, do the following:
WARNING
!
Always turn OFF the unit circuit breakers
(CB-1 & CB-2) and disconnect main power
supply before working on moving parts.
a. Before servicing unit, make sure the circuit
breakers (CB-1 and CB-2) and start-stop switch
(ST) are in the OFF position, and the power plug
is disconnected.
b. Remove the upper back panel.
c. Determine which heater(s) need replacing by
checking resistance of each heater set. Refer to
Section 3.3 for heater resistance values. Once
the set containing the failed heater is deter-
mined, cut the splice connection and retest to
determine the actual failed heater(s).
d. Remove hold-down clamp securing heater(s) to
coil.
e. Lift the bent end of the heater (with the opposite
end down and away from coil). Move heater to
the side enough to clear the heater end support
and remove.
f. To replace a heater, do steps a through e in
reverse.
Figure 7.17 Heater Arrangement
Heater Element
Bracket
Retainer
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