Problem plugging surge protected power strip into gfci outlet?

by David G   Last Updated June 17, 2018 19:21 PM

In my science classroom all outlets on the lab benches are gfci protected--that's great. I plug in multiple computers into some of these outlets and use power strips to do this, but it seems there might be a problem occasionally with this.

It seems that there might be a negative interaction between the surge-protected power strips and the gfci e.g. excessive tripping of gfci or even wearing out of the gfci. The electrician told our head custodian that it wasn't good to use surge-protected strips with gfci and I'm wondering if this is the problem and if so is there some way to mitigate it. But, maybe it's just a bad strip, maybe these old computers' power supply?

Edit: Before posting this question I spent ~30 minutes searching E-SE site for any information on possible interaction between these two components, to no avail. These 2 components are commonly used in residential and commercial electrical power distribution systems, yes? Ideally, the answer will provide specific technical knowledge on the design/functioning of these 2 components and explanatory/theoretical knowledge explaining why they might interact negatively.

HOWEVER, my question assumed 'generic' designs of surge protection circuits in inexpensive power strips and also generic designs of gfci. Perhaps this is a bad assumption?

Answers 4

If either the power strips or connected equipment have capacitors between the power conductors and ground, there would be some current to ground through the capacitors. If there are MOVs between power and ground, there could also be some leakage through those. Deterioration of insulation can also result in small intermittent leakage currents to ground before the insulation actually fails and trips the GFI or breaker every time the faulty device is plugged in.

Charles Cowie
Charles Cowie
August 11, 2016 15:32 PM

Surge protectors typically have three MOVs -- from hot to safety ground, from neutral to ground, and between hot and neutral. The connections to safety ground, if they leak any current, would indeed be the kind of unbalanced flow that the GFCI is designed to detect and cut off.

A properly designed surge suppressor shouldn't leak enough current to be a problem, under normal circumstances. However:

1) Any surge being shunted aside might cause the GFCI to pop. That's a case of everything working as designed, even if leaving the equipment unprotected by a surge suppressor would not blow the GFCI (but might blow the equipment).

2) MOVs do eventually take enough surges to start to fail. I'm not sure what the failure modes are, but if one of them starts leaking more than its spec calls for that too could trigger the GFCI. Again, though, that's the GFCI working as designed and telling you that the surge suppressor is no longer trustworthy.

So I don't see any reason not to try this combination. If it works, it will continue working modulo surges.

August 11, 2016 21:25 PM

It can be an accumulation of multiple devices.

Not enough from a single device but given you are using power boards, it is the sum of many small leakage currents on one circuit.

Should be possible to fault find, try substituting out the power boards for new or non surge protected model.

Also try using less computers and devices on one circuit. It may be an accumulation from multiple devices or one in particular may be causing issues.

Narrow your problem down.

August 11, 2016 21:39 PM

What about plugging a surge protected power strip into a surge protected recepticle/outlet?

June 17, 2018 18:39 PM

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