I Have a 36 KW Infrared Heater 240 Volts Has 3 Hot Lines,What Size the Portable Generator I Need and Amps Also?

I have a 36 KW infrared heater 240 Volts has 3 hot lines,what size the portable generator I need and amps also?

Our answers

Answer by Frank
That sounds like a GIANT heater. it would take 15 amps of 240v if 36kw is the electrical wattage. You would probably want a 5000w generator.

Answer by billrussell42
You need a 40 kW or 50 kW generator.

this is 150 amps. You will need a plug and socket rated at that current (and I don’t know of any) and wire rated at 150 amps, such as #3 AWG.


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{ 3 comments… read them below or add one }

Violet W

Hard to believe there are so many different answers given. I’ll base mine on US practice.

If you truly have a 240V 3-phase load (3 hots, no neutral), then the load amperage is calculated as follows:
I = 36kW/0.24kV/sqrt(3)=86.6A=87A

For resistance heat, minimum conductor size (ampacity) is 125%, or 125% x 87A = 109A. Select wire with 90degC insulation but apply it at its 75degC ampacity. Select 2 AWG, type THWN-2 or THW-2 (for wet or dry locations) or optionally THHN (for dry locations only).

Your circuit breaker should be loaded to 80% maximum (=109A). The next standard size up is 110A. Select 110A breaker (or fuses).

Resistive loads do not have a significant starting kVA, unlike motors. But it is a good idea not to load generators up to 100%. Limit it to 80%. Then the minimum generator size is:
36kW/80% = 45kW

Be careful when selecting a generator. Generators are rated in both kW and kVA, using an 80% power factor, where the kVA = kW/PF = 45kW/.80 = 56.25 kVA. So the minimum size generator should be rated:
56kVA/45kW (or larger).

If you are running the generator in stand-alone mode, then you will need to ground either the common point of a wye output (240/138V generator), or the midpoint of one winding of a delta output (240/120V generator).

Note: Since this is a purely resistive device, you can choose to power it from a 208V generator. The power will decrease with the square of the voltage, to a new value of:
P=36kW x (208/240)^2 = 27kW

This would require a 208V generator (probably configured 208/120V) with a minimum power rating of:

Load is 27kw/.208kV/sqrt(3)=75A
Wire ampacity = 75Ax125%=94A
select 3 AWG, same types as above
Breaker or fuses: 94A minimum, select next size up: 100A



You will need a 45 kVa 230 volt 3-phase generator. Amperes = 46000/230(0.8)(1.732}


Irv S

If you really need 36KW in three phase load, you’re out of the ‘portable’ class.
You’d need a pick-up or trailer to move it around.
You’re looking for about 90A. at 240 three phase delta.
That’s a pretty rare configuration though, (rural, industrial).
Are you sure you’re reading the nameplate right?
You’d have a 100A. load at the more noraml 208V. 3 Phase.
Unless the unit ‘comes on’ in stages, you’d need at least a 50KVA
M/G set to handle the ‘start’ surge.
Careful. An infra-red heater that big requires a lot of clearance
from ‘combustibles’ and personnel for safe operation.


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