Greenheck Fan 470658 MSX Installation of Electric Heater optional, Sizing of Supply Conductors

Installation of Electric Heater (optional)

Warning

Electrical Shock Hazard! Disconnect all power sources before doing any work on the unit.

General:

The requirements and practices described below are based on the National Electric Code (NEC) and The Space Heating Standard of the Underwriters Laboratories Inc. (UL). Although UL requirements are uniform throughout the country, local electrical codes may deviate from the National Electrical Code. Therefore, local inspection authorities should be consulted regarding local requirements.

Electrical Wiring Instructions:

1.Use the wiring diagram supplied with the heater as a guide in correlating field wiring with the heater internal wiring.

2.All field wiring to the heater must meet the requirements of the National Electric Code and any other applicable local or state codes.

3.Wiring to the heater must be rated for 75°C (167°F) minimum.

4.The fan is interlocked by the factory to the control circuit so the electric heater will not operate unless the fan is on.

5.If heater does not have a built-in disconnect switch or main circuit breaker, install a remote disconnect (furnished by others) in accordance with the National Electric Code, Article 424-65.

Calculation of Line Currents (amps):

Single Phase Current = wattsvolts

EXAMPLE: 5 kW, 208 volt
5000 watts	= 24 amps
208 volts
Three Phase Current		=		watts
			volts x 1.73
EXAMPLE: 14.4 kW, 208 volt
14400 watts		14400
208 volts x 1.73 =		360		= 40 amps

Sizing of Supply Conductors

The required minimum size of supply conductors is marked at the field wiring terminals within the heater control box or reference the Supply Wire Size table included in this section. The wire gauges are calculated for 125% of the heater line current as required by the National Electric Code, Article 424-3(b) based on conductor insulation rated for 75°C (167°F).

Supply Wire Size

(Not more than six conductors in Single Conduit 1)

AWG or	Max. Heater	AWG or	Max. Heater
	Line Current 2		Line Current 2
MCM		MCM
	Copper 3		Copper 3
14	12	0000	184
12	16	250	204
10	24	300	228
8	36	350	248
6	52	400	268
4	68	500	304
3	80	600	336
2	92	700	368
1	104	750	380
0	120	800	392
00	140	900	416
000	160	1000	436

1For 7-24 conductors in raceway or cable, reduce allowable heater line currents to 871% of those shown above.

2Based on 30°C. (86°F.) ambient temperature, for higher ambient temperature see National Electric Code table 310‑16 and 310-18 Note 13.

3Based on 80% of ratings in the National Electric Code table 310-16 for 75°C insulation.

Effect of Low Voltage on Wattage and British Thermal Unit (BTU)

The heating elements may be used on voltages lower than the design voltage of the heater, however, the wattage and BTU output will be reduced to the percentages listed in the table below.

De-rated Wattage For Low Voltage

		% of			% of
Heater	Line	Heater	Heater	Line	Heater
Voltage	Voltage	Wattage	Voltage	Voltage	Wattage
		and BTU			and BTU
480	460	92	208	200	92
	440	84		190	83
277	265	92	120	115	92
	254	84		110	84
240	230	92
	220	84
	208	75
	200	69

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