600HP Motor Space Heater Voltage

[PEMBAVP]

The subject motor has space heaters rated at 1125 watts, 120 volts. My project – to install the motor – requires supply cables to the motor and space heaters that are 1750 feet long. My issue is I need to know the lowest acceptable voltage that can be delivered to the space heaters and still have them keep the motor dry when idle. The site is in Norco, LA and climate ranges from 25 – 95 degrees F.

 

[jraef]

The motor mfr are the ones that can answer that. The amount of heat put out by the heater will be directly affected by the lower voltage at the heater elements, so the relevant question is, how much "fudge factor" was there in the selection of 1125W heaters. Would 900W have done the job but the next size down was 750W so they went with 1125? Only the designer can answer that question.

"Dear future generations: Please accept our apologies. We were rolling drunk on petroleum."
— Kilgore Trout (via Kurt Vonnegut)
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[waross]

I generators of about that size I usually see heaters of about 1000 Watts connected at half voltage for long life. But a lot depends on the placement of the heaters and the conduction of the heat to the core. The core must be supplied with enough heat to keep it above the dew point when the temperature is rising.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[Compositepro]

waross correctly points out that the purpose of the heater is to keep the motor above the ambient dew point. This is the major unknown factor. I recently experienced the lathe in my shop being covered with condensation when the weather changed suddenly from near freezing night-time conditions to a warm and humid day.

 

[PEMBAVP]

Thanks for the replies. The mfgr stated that 90 percent voltage is acceptable.