Progressive surge suppressor failed?

**John303** · 05-31-2021, 12:21 PM

We are at a new site and my surge suppressor says L1 has high voltage, ~250 volts. But when I measure between either side slot to the middle slot I only see 125 volts on each leg. I suspect the suppressor has failed. Any thoughts before I try the smoke test? The electrician will be by tomorrow to double check as he just installed it, and we can wait to see what he says. I am leaning towards trusting the meter on this one. Sometimes the suppressor says 250 sometime 170 or a different value.

**Ynot4me2** · 05-31-2021, 12:44 PM

If you can wait then I'd wait. So your at a new site and your PI surge protector is also new? Have you used it prior to arriving at this site?

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**John303** · 05-31-2021, 01:35 PM

The surge protector is not new. My memory tells me it’s about five years old. It was working at the previous site.

**jungleb0y** · 05-31-2021, 02:39 PM

Have you tried your protector at a different site?

If it reads odd there and you measure with a volt meter between the receptacle with the half moon (ground) and the left and right blade slots (L1 & L2) and see between 110-120 volts ac with no fluctuation out of that range I wouldn’t really think twice about it.

You might also take a reading between the two center blades as well to make sure you don’t have any current on the neutral line as well.

**jungleb0y** · 05-31-2021, 02:55 PM

Oh ya know looking at your original post you say you are seeing 125 VAC on each line which is about the absolute max for appliances, anything over that they start having issues dissipating the extra heat and start making that magic smoke, which appears to be what your protector is talking about i.e. 125vac L1+125vac L2 = 250vac.

Thinking about this while typing the other replies you might also check the voltage between the neutral (center blade without the half moon) and L1 and L2 if you get odd readings there it could signify a broken neutral somewhere in the circuit which can cause those voltages you are seeing, usually I’ve seen them a little higher though around like 130VAC.

**John303** · 06-05-2021, 01:46 PM

To close the loop on this...the electrician came back and verified that everything was OK. He also hooked up the 20 amp receptacle on the RV box. Suddenly, the surge suppressor did not show an error and has been working for about a week now. Beats me....

**jkwilson** · 06-05-2021, 02:35 PM

Originally Posted by John303

To close the loop on this...the electrician came back and verified that everything was OK. He also hooked up the 20 amp receptacle on the RV box. Suddenly, the surge suppressor did not show an error and has been working for about a week now. Beats me....

My guess is there was a neutral problem that he fixed, maybe inadvertently. A bad or missing neutral is about the only way to have a high voltage on a single leg like that, and it will measure normal with nothing hooked to the outlet.