More GFCI Breaker Mysteries

[mercurous]

We have a set of outlets powered by a GFCI breaker. We plug one surge protector into the outlet and turn the surge protector off. We then start plugging equipment in (the surge protector is still off) and the GFCI breaker trips. We have tried different surge protectors and different outlets on the same breaker and this is a somewhat random occurence, sometimes everything works fine for a few hours, then it trips. We have switched out this (new) GFCI breaker with another new GFCI breaker. Same behavior. Switching out the breaker for a non-GFCI solves the problem but then we are unprotected (In a somewhat wet lab environment).

I assume that the surge protector switch just turns off the hot wire but leaves neutral connected. My take, is that for some reason, there is current (>15mA?) going through neutral (from ground?) and tripping the breaker. What can we do to solve this problem? Thanks.

 

[dpc]

Your best bet is to replace the GFCI breaker with local GFCI receptacles. GFCI breakers are more prone to nuisance tripping due to the longer run of the circuit and increase leakage current due to shunt capacitance and other leakage. We stopped specifying GFCI breakers (unless no other solution) many years ago.

But having said that, you may want to look at what you are plugging into the power strip. What type of equipment is it and how long are the cords? The longer the run of conductor downstream of any GFCI device, the more nuisance problems you will have. Of course, you could have a defective piece of equipment that is causing most of your problems.

You may need to get rid of the surge protector as well or try a different (higher quality) brand. These can have some leakage current, depending on the design, quality of components, etc.

 

[itsmoked]

mercurous: As dpc notes, surge protectors can cause the problem. They have capacitor "like" devices going from hot to neutral and often from hot to ground. This looks a lot like a problem to the GFI. They must protect the user from a very small current.

What I would do:

1) Temporarily use a NON-surge supressor power strip. See if the problem stops.

2) Use a standard breaker and a GFI outlet. See if the problem stops.

If the problem persists you have a faulty apparatus plugged in. This is not as rare as would be hoped.

What kind of things are you plugging in here? We might be able to quickly point at a likely culpret.

 

[DaveKillens]

Yes, many power bars just open the hot circuit, and leave the neutral and ground path closed.
It only takes 6 ma for a GFCI to operate.
I suspect some device plugged into the power bar has a slight path from neutral to ground. Personally, that is when I take out my ohmeter and check to discover where the offending device is.
If your location requires a GFCI, please do not attempt to use anything less for protection.

 

[NEWFIEBOY]

mercurous
I agree with dcp, it smoked and DaveKillens power bars and GFIC circuit breakers do not seem to work well together. As the guys pointed out the surge protector internal circuitry tricks the GFIC circuit breaker into thinking that a ground fault has occured and it trips off. You may not have much more sucess with a GFI outlet. If you still have a problem after you have tried the GFI outlet solution it may be worth your while to look at a UPS power supply. The UPS will block any line surges and will give you the added advantage of protection from brown outs and short time protection from black outs.

 

[mercurous]

Thanks for all your help guys. I will try those things out.