Question
Why not require GFI receptacles for washing machines ?
We need them on spas,hot tubs, garages, basements commercial kitchens, 6' from sinks, outside etc etc.
Why not the 4' tall x 3' wide x 3' deep box of steel we fill to the top with water
Think about it

IMO it will eventually be required.

I believe most of the present GFCI locations have had a 'body count' available to justify the requirement.

If someone can show the need by way of electrocutions from washing machines it would probably get into the NEC.


That is not all sinks, only 'wet bar sinks'

I disagree with you Bob, about the body count.

I think if GFI's can get past the inductive load problems the code writers will have less reason to not require them. Given better and less expensive technology in the future I would expect more requirement with or without more dead people.

For right now I would agree that they're not wanted where they're not needed because they can cause more problems than they solve.

Hey, you weren't a moderator. Were you?

Sam I agree to some extent.

But IMO the NEC is not really worried about nuisance tripping as evidenced by the commercial kitchen requirement. That includes refrigerators.

Also consider that pool pumps and the all the power tools on a job site work fine on a GFCI.

I like the job site tools one the best. I don't know how many times Iv'e been told that GFI's never nuisance trip because of that.

That is a good point though, and I agree the NEC guys don't care too much, but, is there like a difference in manufacturer or something that accounts for some applications not being a problem while others are?

Sam I am not sure what you mean here.

I believe that almost all GFCI tripping can be traced to a 'real' problem.

Every appliance is likely to have leakage current, running to many items from on GFCI is not a good plan as the cumulative leakage current.

Long branch circuits can also cause problems.

Then of course you could just have a faulty appliance.

My sump pump in my basement happens to be on a GFCI and it runs a 3 or 4 times an hour when it rains. It has never tripped the GFCI. When it does I will buy a new pump.

The engineered prints I work from will specify a separate GFCI receptacle for every location that needs one, no using GFCI breakers, or coming off the load side of another GFCI outlet.

This is also how we do job temps, normal breakers with a GFCI receptacle at the point of use.

Well, you seem to be on the side of those who would say that GFI's wont nuisance trip now.

Will they or wont they?

Some of those who say that they wont will site as evidence that they can run power tool from them.

If it is a current leak it is necessarilly not a nuisance trip.

I will say this much. I don't really know what causes the nuisance tripping. But my instinct tells me it's not always current outside the intended path.

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I don't really know what causes the nuisance tripping.
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In a word, inductance. A GFI trips when the source current to the load does not equal the return current from the load. One of the characteristics of inductance is that the current thru such a load cannot change instantaneously. Thus if you provide a unit step of source current to an inductive load, the return current from that load will have an inherent rise time (delay). During this delay there will be a difference in current between the source and the return. This difference in current is not leakage current to ground but rather a difference due to the characteristics of inductance. Nonetheless, the GFI doesn't know that and will theerfore (nuisance) trip. How much difference in current there is and the duration of the delay is dependent on the inductive
characteristics of the load.

Can you point me to an item that does produce this inductance tripping?

I see some fairly large pool pump motors running fine on GFCIs.

I don't find GFCIs tripping nearly as much as some claim.

The NEC handbook claims the nuisance tripping associated with refrigerators on GFCIs had to due with leakage current in the electric defrost circuits. They also claim this has been addressed by the manufactures.

Bob

I'm just explaining the theory of nuisance tripping due to inductance, not claiming that it is common. In fact I rarely see it associated with standard household appliances. I work in an industrial enviornment and I do see it occassionally. In fact just the other day I ran into it. One of the labs had supplied an X-Y stepper motor positioning table which also contained flourescent lighting via a GFI. With this load the GFI did not stand a chance, tripped constantly and there was NO leakage to ground. This was classic inductive load nuissance tripping. Nuissance tripping due to actual leakage current to ground is a separate issue and I agree that most houshold appliances, motors, tools etc. have overcome this problem

Yes I have had problems with fluorescents fixtures (about 20) around an indoor pool protected by a GFCI breaker.

We split the circuit in half and used two GFCI breakers, problem solved.

In my case it was the stepper motors and drives that contributed to the tripping more than the flourescent lights (although they didn't help )
Because the intent was to provide leakage current protection for the equipment and not personell, we were able to substitute a Class B GFCI device. Used an ELCI (Equipment
Leakage Circuit Interrupters) - Problem solved.

I seem to remember our NEMA rep stating that washing machines are now manufactured to specifically not trip GFCIs. I have an older washer (10years) on a GFCI of the same age, and it has never tripped while running.

PS. It was my wife's idea to put a GFCI for the washer. I told her that it was not required by code, but you know how that goes............

Rick Miell

I'm starting to think maybe I'm farther off than you are Bob. When Electric Ian mentioned inductance I started thinking Kirchoff's current law and it just doesn't seem to wash.

I'm at a loss. Why isn't there some kind of authoritative study or report on the whole issue by now? Or is there?

Mr Kirchoff says current will be the same if there is no other path. Inductance will make current lag voltage but the current in and out will be equal at any given instant ... minus leakage.

Things that trip GFCIs leak current.

And I can't see leakage being caused through induction, which is what I'm inclined to suspect, because the coil doing the inducting should have equal current on it's leads.

I agree with Bob 100%. Bob and I have argued the same point at several sites and have always always agreed.

Regarding washing machines: The will be required in the 2005 to be protected if they are within 6' of any sink. Bob mentioned the 2002 text, but the 2005 is different in 2 major ways:
1) 2005 applies to all sinks, not just wet-bar.
2) 2005 applies to all receptacles within 6' of the sink, not just those receptacles serving the countertop.

Also, the 2002 (and 2005) requires protection for all 125V 15 and 20A recpetacles in a commercial kitchen. There are certainly inductive loads in a kitchen, but I haven't heard of any nuisance tripping since the requirement.

Regarding current leakage: In my opinion, those who posted above saying that devices tripping GFCI's have leakage current are exactly right. Read the ROP/ROC to the 2002, and pay close attention to Mike Johnston (CMP 5)'s substantiation to get 210.8(B)(3) into the code. You want a body count?...read what he has to say. The reason there are no exceptions in the commercial kitchen rule is that one of the dead bodies in Mr. Johnston's case study happened because of a refrigerator with leakage current on the case...enough to kill a man. This man was mopping the floor of a commercial kitchen when he slipped on the water. In an effort to keep his balance, he grabbed the metallic handle of the fridge, and it was the last thing he ever did. He left a family behind.

So, if people what to talk to me about nuissance tripping, I say get a new appliance before it injures someone, or worse...

Just my two cents

The only time I ever personally encountered 'nuisance' tripping was on a commercial food processor in a co-op where I would cook. This was a small beast that used a 1/2 hp induction motor in its base (rather than the more common brush universal motors). It would trip the GFCI receptacle every 3 or 4 starts....then one day just after I'd pureed some soup and cleaned the machine up, it simply turned itself on and smoke started coming out of the base. It turns out that the waterproof boot on the main switch had cracked, and enough liquid had gotten in to short past the switch. To this day I don't know if it was in fact nuisance tripping, or leakage around the switch.

Regarding inductive loads and current balance: If you think of an ideal inductor isolated in free space, there is no way that more current could flow out on one leg than return on the other leg. But in this case the inductor is _not_ isolated in free space, and is not ideal. In particular there is capacitive coupling to ground all around the circuit. I would expect _some_ imbalance current caused by this capacitive coupling, since the two terminals of the GFCI are now part of several pretty complex circuits.

However I suspect a different issue. A GFCI is supposed to trip on current imbalance. However what a GFCI really does is measure the current induced in the secondary of a current transformer with all of the conductors being tested fed through the aperture. If the conductors don't equally couple to the transformer (leakage flux through the air rather than through the core), then even with perfect current balance, there will be some residual current measured detected by the transformer. I suspect that the inrush current to many inductive, or the starting current for many motors could create a total balanced current that is high enough to cause an false imbalance reading.

-Jon

I remember it being fairly difficult to convince guys that had their grandads crome plated drill or saw on the job site that the ground fault device was not bad. You know the suicide specials with the ground pin cut off the plug. They would trip the ground fault every time. I just don't think they all believed me when I told them the ground fault working correctly and saving their life. Maybe some of these guys just needed 10 or 15 ma of current to help push their brain impulses across some large synapses. I have heard that it is possible to kill brain cells, just don't remember how, or how I got home a few times either. Well I gotta go do the wash. Seems I can think clearer leaning against the washer, no GFI you know.

Ryan,

I'm a huge fan of GFCI protection. If it were up to me there'd be more GFI's, not less.

But they do nuisance trip. Whether the nuisance is actually a hazard, at least in my mind, isn't clear.

Winnie,

You said two things that make sense to me. I'm going to add a bit to one thought.

Capacitive coupling. If you had coupling at some point on a voltage divider (the resistance in the windings of a coil create a voltage divider) you would have unequal currents at the source.

The idea of flux imbalance at rather large currents. I actually keep a GFI circuit on my desk. It's a pretty nifty set up. The area where the current is sensed is neat and symetrical and it looks like, by virtue of the design, that stray flux wouldn't be a huge issue. But it could have an effect.

Here's s pretty good technical discussion on so called nuisance tripping:
http://www.marcspages.co.uk/pq/3342.htm

Ian,

I like it and I book marked it. It's in rather plain English and also fairly detailed at the same time.

It tends to confirm Winnie's capacitive coupling.

Maybe it's just me, but I can usually see the electrical dynamics of a problem a lot easier than I can this one.

No it's not just you Physis,. There are a lot of variables at work here. But I agree that this is a good "plain english" description of the capactive coupling variable. I also think that winnies explanation of percieved imbalance due to flux leakage caused by high inrush current characteristic of inductive loads also has merit.

I'm sure it's partly because your dealing with such a tiny piece of the forces in the circuit.

Here's the perfect example of nuisance GFI trips.
Okay, True, its not truly nuisance trips, as it's doing its job, tripping when like 5ma+ of current goes through ground, but it's a result of something functioning properly that its tripping. And it sure is a nuisance..

Computer power supplies. Every single one has a RFI Filter on the incoming power PRIOR to the switch. A computer can trip a gfi every time it gets plugged in. Before it even gets switched on.

Now, I have a particular problem with this. I do power distribution for large LAN events (big computer parties). Whenever we have to bring in a generator, more often then not, the power distro system I get with the generator is all GFI (which makes sense, as a portable power distro system like that is normally used outdoors)(the Hubbel Spider Boxes are a common favorite)

However, In my application, obviously generator power isn't 100% clean, and obviously a little more dirty then standard home power. So the RFI filters on all the computer power supplies, do their job, and send the dirt back on ground....

I'm sure you can see where this is going... Generator Power + GFI protected power distro system + RFI Filters on EVERY SINGLE APPLIANCE plugged into said power distro system.... It can get ugly.

Now, my question is, what Can be done to avoid this? Personally, I've considered using 3-2 prong adapters and tying the ground to neutral.. however, Im sure we all know the hazard that would create if the polarity got reversed Anywhere along the line... So it's not really an option. One idiot plugs their computer power cord in backwards because they cut the ground prong off at home, and their computer becomes a big direct connection to the hot side of a 120v plug... Even with polarization, someone would find a way.... Stupidity always does.

So.. In the end, Yes, the Real answer, is get a distro system that isn't all GFI protected... but does anyone out there know of a portable large-scale generator power distro system that isnt GFI protected? I'm talking generator sizes of 150KW+

"does anyone out there know of a portable large-scale generator power distro system that isnt GFI protected? I'm talking generator sizes of 150KW+"

Many theatrical distribution systems are available both with, and without GFI's, probhably more suited to what you're doing any way. But these are supervised systems, if you don't know what you're doing you can fry some stuff up good. (pull out nuetral under load.) Not a good idea for all access type events, where poeple just walk up and plug in. And first sign of inclimate wheather means it gets shut down. Almost makes sound like a GFI is a good idea huh?

yeha, these are open-access, 300+ person type events... the largest of which is just a little over 3000 people... but thats normally done by GE, and I just represent the house side of the project for that. they handle the main distro with their own equipment.

so the search continues...