Electrical Information

The unit must be electrically grounded in accordance with the current National Electrical Code, ANSI/NFPA No. 70. In Canada, use current C.S.A. Standard C22.1, Canadian Electrical Code, Part 1. In addition, the installer should be aware of any local ordinances or electrical company requirements that might apply.. System power wiring must be properly fused and conform to the local and national electrical codes.. System power wiring is to the unit main disconnect (door interlocking disconnect switch standard on most units) or distribution block and must be compatible with the ratings on the nameplate: supply power voltage, phase, and amperage (Minimum Circuit Amps - MCA, Maximum Overcurrent Protection - MOP).. All wiring beyond this point has been done by the manufacturer and cannot be modified without affecting the unit’s agency / safety certification..

If field installing an additional disconnect switch, it is recommended that there is at least four feet of service room between the switch and system access panels.. When providing or replacing fuses in a fusible disconnect, use dual element time delay fuses and size according to the rating plate..

If power supply is desired thru bottom of unit, run the wiring through the curb, cut a hole in the cabinet bottom, and wire to the disconnect switch..

The electric supply to the unit must meet stringent requirements for the system to operate properly.. Voltage supply and voltage imbalance between phases should be within the following tolerances.. If the power is not within these voltage tolerances, contact the power company prior to operating the system..

Voltage Supply - See voltage use range on the rating plate.. Measure and record each supply leg voltage at all line disconnect switches.. Readings must fall within the allowable range on the rating plate..

Voltage Imbalance - In a 3-phase system, excessive voltage imbalance between phases will cause motors to overheat and eventually fail.. Maximum allowable imbalance is 2%.. To determine voltage imbalance, use recorded voltage measurements in this formula..

Key:	V1, V2, V3 = line voltages as measured
	VA (average) = (V1 + V2 + V3) / 3
	VD = Line voltage (V1, V2 or V3) that deviates farthest from average (VA)
Formula:	% Voltage Imbalance = [100 x (VA-VD)] / VA

CAUTION

If any of the original wire as supplied with the appliance must be replaced, it must be

replaced with wiring material having a temperature rating of at least 105ºC.

WARNING

To prevent injury or death due to electrocution or contact with moving parts, lock disconnect switch open.

WARNING

For units with a gas furnace, if you turn off the

power supply, turn off the gas.

Most factory supplied electrical components are pre-wired.. To determine what electrical accessories require additional field wiring, refer to the unit specific wiring diagram located on the inside of the unit control center access door.. The low voltage control circuit is 24 Vac and control wiring should not exceed 0..75 ohms.. Refer to Field Control Wiring Length/Gauge table for wire length maximums for a given wire gauge.. Control wires should not be run inside the same conduit as that carrying the supply power.. Make sure that field supplied conduit does not interfere with access panel operation..

Field Control Wiring Length/Gauge

Total Wire Length	Minimum Wire Gauge
125 ft..	18

200 ft..	16

300 ft..	14

450 ft..	12

If wire resistance exceeds 0..75 ohms, an industrial-style, plug-in relay should be added to the unit control center and wired in place of the remote switch (typically between terminal blocks R and G on the terminal strip (refer to Typical Control Center Components).. The relay must be rated for at least 5 amps and have a 24 Vac coil.. Failure to comply with these guidelines may cause motor starters to “chatter” or not pull in which can cause contactor failures and/or motor failures..

Note: Standard factory installed electric post-heaters have their own disconnect separate from the unit disconnect. Thus, each electric post-heater requires its own separate power connection.

45, 55, 90, HRE-20 specifications

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