Electrical Maintenance
129
Electric Heaters
Six electric heater elements are located
underneath the evaporator coil. If a heater element
is suspected of malfunctioning, check the
resistance of each individual heater element:
1. Turn unit power supply off.
2. Remove unit power plug from power supply
receptacle.
3. Open the control box door.
4. Test the insulation of each individual heater
element.
a. Test all 3 legs of the heater circuit to a
good ground connection. Connect a
calibrated 500 Vdc insulation tester
between each outgoing heater contactor
terminal and ground.
b. b. If the resistance between any contactor
terminal and ground is below 0.8 meg
ohms, isolate and check the resistance of
each individual heater element.
5. Check the resistance of each individual heater
element.
a. Disconnect and isolate each heater from
the circuit in the control box.
b. Check resistance of each heater with an
insulation tester between each heater and
ground. If the resistance between each
heater and ground is below 0.8 meg ohms,
the heater element is defective. On a
loaded container, remove the defective
heater from service by disconnecting at the
control box. If the container is empty,
remove the evaporator cover from the rear
of the unit and replace the heater or correct
any defective wiring. Repeat step 5a.
NOTE: When repairing heater connections,
protect the new connections from the ingress
of moisture with heat shrink tubing. All
heaters should be secured to prevent contact
with sharp metal edges.
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