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ELECTRIC DEFROST — 208/230/1/60 — (2) UNIT COOLERS / TIMER ONLY
Sub-circuit fusing or service disconnect switches are not shown but may be required as per the NEC and / or local codes.
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It is the responsibility of the installing contractor to interpret and comply with all applicable electrical codes.
The defrost time clock and block out relay are typically located in the system condensing unit. All unit cooler power should
feed from this unit. When connecting multiple unit cooler defrost heaters to (1) defrost time clock make sure the total heater
amp draw does not exceed the defrost timer contact rating (typically 40 resistive amps for an 8145-20 or equivalent timer),
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Also be sure the wire gauge size is adequate to carry the total amp load required. If the combined heater amp draw exceeds
the defrost timer rating a heater contactor must be installed (see alternate wiring diagram for 1 or 2 heater contactor wiring
arrangement).
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
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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 -
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.
When using a heater contactor with unit cooler defrost heaters factory wired for single phase remove factory installed jumper
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between terminals 2 & 3 on TB1 and wire directly to heater contactor.
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).
FIELD WIRING DIAGRAMS — TYPICAL
IMPORTANT WIRING NOTES - INSTALLER PLEASE READ CAREFULLY!
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