Electrical Maintenance
162
Extended Capacity Heaters
If a unit is equipped with the Extended Capacity heaters (2000 Watts) the main CB (42-0352) is
adjustable and set to 27 amps. When changing out a MP4000 controller the HEATER ELEMENT TYPE
needs to be changed in the configuration menu from NORMAL CAPACITY to EXTENDED
CAPACITY. If the heater type is not change the unit will alarm during a PTI on heater capacity low. The
only difference between the 1360 Watt (18 GA) and 2000 Watt (16 GA) heater is the wire gauge size. So
care should be taken to confirm correct heater element is used when replacement is required.
Electric Heaters Malfunction
Three or 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 by performing the
following procedure:
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. 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.
Figure 139: Unit Configuration Menu
Figure 140: Heater Type
Summary of Contents for 098203
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Page 257: ...255 Schematic Diagram RELEASED 19 Sep 2013...
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