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FIELD WIRING DIAGRAMS — TYPICAL
ELECTRIC DEFROST — 208/230/1/60 — (2) UNIT COOLERS / (2) HEATER CONTACTORS
IMPORTANT WIRING NOTES - INSTALLER PLEASE READ CAREFULLY!
Sub-circuit fusing or service disconnect switches are not shown but may be required as per the NEC and / or local codes. It is
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the responsibility of the installing contractor to interpret and comply with all applicable electrical codes.
The defrost time clock, block out relay / auxiliary switch and contactors are typically located in the system condensing unit. All
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unit cooler power should feed from this unit. Make sure the total heater amp draw does not exceed the resistive amp rating o f
the contactors supplied. Also be sure the wire gauge size is adequate to carry the total amp load required.
When connecting (2) electric defrost unit coolers to (1) defrost timer remove the black wire from the defrost termination / fan
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delay control which is factory wired to terminal 2 - TB2 on unit cooler #2 and cap the wire. This will allow the fan delay on unit
cooler #1 to control the fans on both unit coolers.
When connecting (2) electric defrost unit coolers to (1) defrost timer remove the red wire from the defrost termination / fan
delay control which is factory wired to terminal 4 - TB1 on unit cooler #2 and hard wire to a field wire connected to terminal 1 -
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TB2 on unit cooler #1. This will place the (2) defrost termination controls in series so that both units must reach temperature
in order to terminate the defrost cycle.
The room thermostat and liquid line solenoid valve are shown as field installed but may be factory mounted in the unit cooler.
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Make sure the solenoid holding coil is wired for the correct control voltage (115 or 230).
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