Electrical Information - Greenheck HRE-20 Installation, operationand Maintenance Manual

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
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
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 .
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.
6
open.
Field Control Wiring Length/Gauge
Total Wire Length
125 ft .
200 ft .
300 ft .
450 ft .
CAUTION
For units with a gas furnace, if you turn off the
power supply, turn off the gas.
Minimum Wire Gauge
18
16
14
12
WARNING