Electrical equipment and Anti-Condensation Heaters

Why are anti-condensation heaters used with electrical equipment.
Condensation in a generator, motor or transformer typically forms when the temperature of moist ambient air is rising.
As the temperature of the moist air rises, the dew point of the air also rises.
The iron and copper is a thermal mass that is slow to change temperature.
When the dew point of the air rises past the much slower rising temperature of the iron and copper, you have condensation, often deep within the machine where you least want it.
The anti condensation heater keeps the temperature of the thermal mass of the machine above the ambient temperature.

What is a typical temperature setting for an anti-condensation heater?
Condensation may form at any ambient temperature.
Never use a thermostat with an anti-condensation heater.
For condensation protection you want to heat the iron mass of the generator 24/7/365.
We used anti condensation heaters on our generators in the tropics.

Supply voltage to anti-condensation heaters.
The heaters are typically connected for one half of rated voltage.
eg: 240 Volt rated heaters supplied with 120 Volts.
This combines economy of use with extremely long life.

Mounting of the heater.
The heater may be directly attached to the iron core.
Often the heater is mounted in an air duct close to and below the iron core.
Even though it is mounted in an inch or so away from the core the purpose is to heat the core.

But I saw a thermostat in a switch-gear cabinet.
Switch-gear mounted outside in cold areas is a special case.
You will often see an anti-condensation heater such as described above, with-out a thermostat, energized 24/7/365.
In addition the switch-gear often has moving parts that by act slowly in very cold weather.
A second heater may be fitted to keep the internal temperature of the cabinet above freezing.
The anti-freezing heater will have a much higher rating than the anti-condensation heater and will have a thermostat.
Two heaters:
An anti-condensation heater energized 24/7/365 without a thermostat.
A much larger anti-freezing heater with a thermostat.


@WaRoss - Thank you, I really like these posts you’ve been providing. As a Mechanical Engineer, I learned a lot of this “sparky stuff” through pestering colleagues and piecing things together as I worked with them on various projects.

Understanding basic design considerations across the breadth of a project does nothing but benefit everyone.

You can help yourself and help the site build content at the same time.
Ask for explanations even if you know the answer.
Myself or someone else will respond.
Thanks for the kind words.
ps: Ask your colleagues to do the same.

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