Air filter fan motors, portable gfci plugs...

Old 11-09-20, 09:57 AM
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Air filter fan motors, portable gfci plugs...

I have several portable hepa air filters with a "high efficiency permanent split capacitor motor". Power cord is two wires. The filter turns on with a manual switch, first position is high, then to medium and then to low. My understanding, and confirmed by the company, is that it's best to let it spin up for a moment in high before moving it to a lower speed - that this puts less stress on the motor.

I often run the fan in medium or low. If the power goes out and then comes back on the fan will start in the speed it was using prior to the outage. In order to avoid this and putting stress on the motor from starting in a lower speed I plug into a portable GFCI that will trip when the power goes out, even for a second. I can then turn the filter off, reset the GFCI and then start the motor up again. I've been doing this for over 10 years on all 4 units with no problem. The filters are run at least 12 hours a day and the one in question is run 24 hours a day - as recommended by the filter company - they say that is what they are designed for.

One of the filters (the one running 24 hours a day at medium. Occasionally at high for short periods) has died. Woke up a couple of days ago (earlier than normal which was fortunate) and saw that the motor was not turning but was on. GFCI plug was on. The top of the filter (metal) was warm. Not blazing hot, but way warmer than it should be. I turned it off, waited about 30 minutes and turned it back on. It barely started. Several hours later it started it again and it seemed to be a higher speed than normal - and there was little or no movement in medium. Clearly the motor is toast.

I'm sending it back for repair (they will put a new motor in it so it's worth doing) and told them about my using the GFCI. They said, "We never recommend plugging the units into any GCFI because it can harm the motor. All of our units have a ground on them to prevent them from blowing a fuse." I had spoken to them about this same thing a couple of years ago and they did not say not to do this and there is nothing on their site or the manual about not using a GFCI. I responded and asked for a more technical reason and am waiting to hear back. I also pointed out that many people likely are using GFCI outlets given they are in many rooms in ones house that have them now. Also the statement that all their units have a ground to prevent them from blowing a fuse is nonsense and I'm just ignoring that.

My questions:

1. Is there any way using a portable GFCI plug, as I am doing, cause a problem?

2. What do you think happened to the motor? Did it just wear out?

3. I am concerned that the motor was overheating and could have caught fire. While it was in the basement and there is a smoke alarm very close by, I'd still rather not be in this position. Is there anything I can add to the circuit that would trip it out if this sort of thing happened again?

4. Any other observations or suggestions?
Old 11-09-20, 10:04 AM
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Using a GFI will not hurt the unit.
If the filter ran 24 hours a day for ten years I'd expect that the motor just wore out.
Most motors are internally protected from overheating. Some have a heat sensor that opens on high heat and resets and some have a thermal sensor.... like a fuse... that will open.

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