3 Phase Heater Preservation

What is your megger reading now? What is the voltage used by the megger? What is the insulation composed of? Would design/construction of the heaters allow forced airflow or nitrogen ?

Don't turn it on and pack it in rice.

I have found a few suggestions ....

1. Place the heater on a hot / warm surface for a time prior to installation.

2. Or the heater can be energized at 1/2 voltage for 5 minutes.

3. Build a simple box with a 25 watt light bulb in it to store the heaters in...

Reduced voltage can be obtained by jumping 2 legs on the heater together and supplying one phase of the incoming voltage to those 2 and then tying the remaining leg of the heater to neutral...This would depend on the wiring of the heater, but you get the idea....If you are not an electrician, and one isn't available, then I would stick to heating the heaters with external source...

110V 3Ph should give you approximately 500W heating. Just a couple of hours a day should keep the heater in good fettle.

If you're concerned that your insulation resistance is so low that current will travel through it then use an isolation transformer to put low voltage on the element. Be aware that the element will draw significant current due to the much lower resistance at lower off-spec temperatures.

Like it!!

An auto transformer as well might be a good idea as well to control the current to a low level and let it warm through slowly.....

I sometimes even use light bulbs of various wattages to work as resistances in some mains and battery circuits. As long as the normal working voltage of the bulb is correct higher than the voltage being used, they work just fine.

The heaters may need to be switched on say once a week for a short time, to maintain a good resistance to ground, even when not actually needed....

Thanks for the comments. One heater is just about hard down so that one may have to be removed and dried out manually (electric heat gun or oven).

We had a similar problem crop up recently and our heater supplier suggested operating the heater at a reduced voltage with the covers off so the element exceeds 100 deg C continuously for up to one week (that's week, not hour or day) to allow the element to naturally vent the moisture out, checking the insulation reading periodically.

Be advised that an electric heat gun is unlikely to do anything but waste your time.

Removing the covers and placing in an oven may be a potential option but our heater supplier did not mention this as an option at all. It may be possible but watch out for damaging low melting point plastics or similar attached to the element.

That sounds simular Jack of all Trades. Are you able to tell me the equipment you used and what your readings where before you started the temporary heating process?

We passed the information on to a customer of ours, we didn't work on the heater personally.

We have not had a response back from our customer but believe they will be removing all the covers and operating the 3 phase (400/415V) heater elements using single phase voltage (230V).

This is about the simplest way to safely dry out an element that has absorbed moisture and doesn't require an oven or specialist variac.