OT - Tripping GFCIs in shop

I raised this question some time ago regarding my GFCI outlets in my shop that trip during each and every electrical storm.

What I know is this....they are tripped during electrical storm activity and NOT rain/moisture. Don"t have this issue in the winter nor during just average rain. But come the lightening, they"ll trip in a heart beat.

Now I"m wondering this ---- the wiring is in the "attic" space of the shop. In other words, it runs across the roof trusses. The roof itself is metal. Is it possible that the electrical storms are creating an energy force that is magnified by the metal roofing causing them to trip? Sort of like creating a magnetized field. And if so, you think that grounding the roof will help?

I really like having all the circuits protected by GFCI. But this constant tripping is becoming a huge pain!

Thanks for any thoughts.

Hello 61-4010,
In my neck of the woods its the law.
If electrical storms are creating a spark in the vicinity of the wire, with a metal roof to boot. You may have to sink another ground for the panel, insure the existing groun is good, or you may need to run a ground for the roof?
Very interesting! Post back if you get it resolved
Guido.

You not using any surge surpressors are you? They divert the surge to ground and can trip or even blow up a GFCI.

Grounding the roof sure wouldn't hurt. Shouldn't be too expensive to run a ground to the roof. If it works, you've solved the problem. But you also need to make sure that the GFI's are of sufficient Amperage too. If they are close to being overloaded all the time, you might need to go up in rating, provided the wiring is the right gauge.

61-1040,

You probably already know this, but at the risk of stating the obvious, here goes.

Unlike a regular old circuit breaker that simply looks for excess current in a circuit, a ground fault circuit interupter is actually comparing the current flow in the "hot" wire to the current flow in the "neutral" wire. If the current flow in those two wires is not exactly the same, the gfci trips.

And it does so for good reason. The current in those two wires SHOULD be exactly the same. If it is not, it indicates that voltage is draining off to ground somewhere in the circuit (like a short inside a power tool that would cause a shock to a person that touchs it).

So, if your gfci is tripping, it's an indication that current is flowing in the circuit and that the current in the "hot" wire and the "neutral" wire are not the same.

Do these gfci's have things plugged into them when they trip during the electrical storm? That might be an interesting thing to check out. If so, and if it's possible for you to do so, you might unplug everything the next time a storm is coming and see what happens.

Good luck with your diagnosis.

Tom in TN

As previously stated.The shed electrical grounding system may have problems.
Also there maybe some cross connection between the grounding system and the neutral system. It's a "shock" to some but the two are different.

Mine does the same thing sometimes. Sometimes the lightening ruins the GFCI. My building is completely wired in conduit and the metal skin is attached to the roof. It is all bonded by bare copper to the ground rod. I would live with the nuisance problem before I removed the GFCI and replaced them with regular receptacles. Whether they are 15 or 20 amp GFCI should not make any difference as far as nuisance tripping. They are designed to trip on a 5 millamp difference in current between the hot and neutral.

Is it all the GFCI's, or just one. If you only have one swap it out with a known good one and see if that helps. If not, I'd run a seperate ground wire from the building to a second ground rod. That way the static charge coming off the roof during a storm shouldn't be an issue. Static charges build on a roof due to wind passing over the roof, so during a storm with lightening you usually have more wind and therefore more charge.

Make sure the second ground wire attaches to the roof. Draining off the charge will reduce the risk of lightening strike since it won't attract the charge in the clouds. Hope that helps. Gerard

Thanks everyone for the ideas. The GFCIs only trip during electrical storms never any time else such as during normal (non-rainy) days or even during just rain days with no electrical activity.

There are 2 GFCIs in the shop as I have the shop split between 2 primary circuits. Both trip pretty much at the same time. Load wise, they trip regardless of load. However, both circuits do have surge suppression power strips on them....so that may be an issue.

That said, I"m going to first remove the surge supression strips to see if that helps. If not, I"ll go the route of adding a ground to the roof. And then it that doesn"t help, I"ll go the route of adding another grounding rod for the panel.

Will repost as I make progress. THANK YOU AGAIN!

Lightning strike the power lines often.Gfci cant take this.If you look at a gfi that has been struck by lightning you you will see transitors blown apart.they do fail.

Wont work..Lightning strikes the power line.

Lightning strikes the power line.It nails TV sets,fence chargers,welders with diodes get hit often.They have to be unpluged.Lightning jumps across open switches with ease.My fence charger just got struck from the power line.Fuse cap was blown off and input tansformer has an open primary.

Hello 36 coupe,
The power lines he has run close to the roof, he does not really want to move them. But he may have no choice if it keeps up.
Proximity of a lightning strike to that metal will certainly zapp the lines. The GFCI only needs a tickle to trip off.
Guido.

Lightning can also strike roofs, trees, towers, or any tall thing. I should have added that as long as he was grounding the roof, he could install lightning rods. Still don't know if that is gonna solve his GFI problem.

If you have 2 circuits and they are running a common neutral, instead of one neutral for each circuit, you probably will have trouble. Dave

The power lines get direct hits.Ive seen light bulbs and fuses blowout of sockets.Dont not trust GFICs.I found many that wont test.I had a big electric drill that had leakage that you could feel.Dufus had used a piece of cardboard to insulate the switch.The GFIC did not trip on the drill.Open up a bad GFI and see all the small parts that can fail.Dont use GFI to run a fence charger.You will get constant tripping.Just looked at a fence charger that was destroyed on the power line side, no damage to fence side parts.