Jump to content
Light-O-Rama Forums

GFCI trips.. "leakage to ground"? HUH?


carsonsig

Recommended Posts

Yeah i unplugged them completely and it still happened.

In hu if i turn controller 2 all on it trips one channel at a time doesnt do it, controller 5 seems to be doing the same thing.

Unit 2 is running strands on the oak trees, and inflatables lights.

Unit 5 is running the arches and candy canes.

Link to comment
Share on other sites

Bob Moody,

 

I usually have to agree with most of the post you make. But in this case, well I think you dont fully understand GFCI and how they work and what happens in the real world. First lets set the stage so they say. G & F is Ground Fault, there is a certain amount of current that is not returning on the neutral lead. So if not going back on the neutral lead, where did it go? Why to earth ground of course. And this is considered a fault. Now there are two ways to get current to earth ground. It is either by a clear current path such as a bare wire that touches ground. Maybe via the metal frame of a washing machine. And part of that circuit might be via a persons body. But A.C. is a tricky beast, and when we are talking about such low current levels. Well there is a electronic device called a capacitor. That now get this, allows an A.C. current pass through it. But will block D.C. current. Now a capacitor has two elements. There are two plates with leads attached to each plate. Now think of a metal tomato cage as one plate and each time a hot wire from your lights making contact with the cage as another plate. Oh I forgot to mention earlier, 3 element of a cap. is an insulator between the two plates. This would be the plastic jacket on the wire of your lights. So, we have what is called capacitive coupling leaking a very small amount of current. More mini treas or wire frames, more leakage. When you get to critical mass, POP!  Bob there have been enough people who have listened to my ranting about this that it has helped them solve their tripping GFCIs that I must be on to something. Not always, but enough times you cant discount this capacitive coupling.

  • Like 1
Link to comment
Share on other sites

Please refresh my memory. How are the candy canes held in place? IF metal mesh, is the mesh isolated from earth ground? And you mention the metal ring on the mega tree as the base of the tree. How is the metal ring held in place so that it does not blow around? You just posted saying that your show was running ok. But seems that once it started to rain you popped the GFCI. Fairly clear that something is getting wet and providing a path to ground.

Link to comment
Share on other sites

Having been a Biomedical Electronics Technician and an Amateur radio operator, I am somewhat familiar with capacitive coupling, but thank you for the refresher.

 

To the subject, nothing was ever said about earth ground not being the path to a current imbalance there has to be some alternate path leaking (redirecting) current for the imbalance between Hot and Neutral to occur. Point was that the operation of GFCI has nothing to do with Earth ground. A sudden or unintended path to Earth is the CAUSE for the imbalance in the Hot/Neutral Zero sum parity that normally exists. As a matter of point, you don’t even need Earth ground in a GFCI circuit. Adding GFCI to an older home with only a 2 wire system, for example, is a widely accepted method to provide some form of protection for the occupants (Sockets are specially labeled if they have no safety (Earth) ground). For the sake of argument, there is a specific difference when talking about ground in the terms of a grounded conductor and a grounding conductor.

A grounded conductor in the US (120VAC systems) is the neutral (a current carrying conductor). A grounding conductor is the Earth ground which is purely a safety conductor and under normal circumstances never carries current.

The ONLY point I was trying to make is that if you’re tripping your GFCI circuits then something is wrong and simply isolating the prop from earth (If that is the source of the imbalance)  only circumvents the protection provided by the GFCI.

 

While I generally don’t mind condescending and subtle pot shots, the comment Max-Paul made in "Bob there have been enough people who have listened to my ranting about this that it has helped them solve their tripping GFCIs that I must be on to something" ranks as one of the more asinine comments I've read.  Just because you say it enough times doesn’t make it correct and just because it appears to solve the issue doesnt mean its safe.

 

Bob

Link to comment
Share on other sites

The ONLY point I was trying to make is that if you’re tripping your GFCI circuits then something is wrong and simply isolating the prop from earth (If that is the source of the imbalance)  only circumvents the protection provided by the GFCI.

 

BUT if it is a cumulative leak to ground, as people are theorizing..a la 16 metal minis on one GFCi... popping it... then IS that a dangerous circumvention of the GFCI protection?  is there any setting where a cumulative leak to ground can be dangerous?  seems a bit nit picky... Or am I wrong?

Link to comment
Share on other sites

I can't comment regarding a cumulative leak to ground. I think we all agree that current flows through the path of least resitance.  That being a given I would think it unlikely unless there was some extremely high resistances involved that were all similar.

 

What I have experienced in my display:

28 Mini trees each wrapped with 300 mini incans running on two controllers each plugged into thier own GFCI and neither has ever tripped.

 

My yard grid on the other hand which is 40 strings of mini incans just laying on the ground, will trip its GFCI after a decent rain. I can sometimes use the leaf blower and blow over all the strings and thier plugs and this corrects the issue and I'm back online. Sometimes its just wait till tomorrow, let them dry and all is good. Since I keep these on seperate GFCI's if I lose the yard grid, the display continues with out it.

 

As I said from the start, I'm not an electrician or an engineer. But I at least try to ask why something happens and solve the root problem and not simply come up with what I beileve is a work around. If your trees are tripping circuits then shut down the LOR console, bring up the HWU, disconnect all 16 trees, set all 16 channels to full on and start adding them back one at a time until it trips. Then repeat the process starting at the other end (16 to 1) does it trip on the same tree? is it the same number of trees when it trips?

 

Remeber, GFCI is not a current limiting device. It wont necessarily shut down due to an overload (UNLESS the overload causes an imbalance in the hot and neutral lines. 30 amps Hot<->Neutral may melt the plug but not trip the circuit.. thats the breakers job)

 

Can a cumlative leak be dangerous? In my opinion, anytime you can come into contact and interrupt flowing current with your body.. it can be dangerous.

 

Nit picky... absolutely not..

 

Bob

 

Since I also dont have a grasp of "real world" applications I will point out the portable hair drier (blow drier). Since 1991, the federal governement has mandated that all portable hair dries be equiped with a GFCI. Notice, there isnt a ground wire. I dont reccomend you do this it will certainly irritate the owner of the drier... but its there to trip if you drop it in a sink or tub full of water.

Edited by bob_moody
Link to comment
Share on other sites

Power is relative. Not to disagree with any of the fine information from Max and Bob, just trying to add to everyone's confusion on the issue.

What I mean by power is relative is that power is measured as volts times amps. A GFCI is in fact reacting to a hot / neutral imbalance, which can also be caused by a high inrush at start up. Most Christmas lights are not going to create enough inrush current to imbalance the hot / neutral. However, many mins on the same circuit at the end of a long extension cord ran to get to the prop could have enough voltage drop to create this power inrush imbalance. I've heard some even take old strands that don't work and use as a cheap extension cord. Very bad idea for lots of reasons. But on this topic, again voltage drop is not good and 20awg or smaller extension cords causes amp draw to increase. Now, not to disput my own therory, but minis are incandescent lamps that can be dimmed. So the inrush would be negated as just a normal dimming curve designed into that old technology.

So this entire post by me means absolutely nothing.

Link to comment
Share on other sites

A GFCI is in fact reacting to a hot / neutral imbalance, which can also be caused by a high inrush at start up.

Actually .. a very interesting and valid point. If one were to read the specs on GFCI one of the issues causing false triggers is ...

line runs over 100' and motors...

The lines over 100' goes to your comment on voltage drop.

Startup on certian types of motors see a huge inrush current because when your starting them you are basically seeing a dead short until they (simple explination here) start turning ...

But .. I agree. I really doubt a .33 amp of incans will generate enough inrush current to drop a gfci...

Bob

Edited by bob_moody
Link to comment
Share on other sites

Yeah - we see nuisance GFCI tripping even when floor heat trace is installed on that circuit. No motor load, but intense inrush on the cable.

But still as I was typing, came back to incandescent dimming almost completely blows that theory up.

However, most LED mini-trees aren't tripping.

Humm....

Link to comment
Share on other sites

Maybe because the sockets are sealed?

Let me rephrase that so it doesn't sound like it reads.....

ARE the sockets sealed? That would certainly reduce the moisture points.

Bob

Edited by bob_moody
Link to comment
Share on other sites

Bob, it is clear you have a great deal of knowledge. But I feel that you are adding a bunch of gobbly goop to your post that has nothing to do with the issue. And as for the inrush. If there is an inrush of current on the hot lead, then there will be an inrush on the neutral as well.This is a closed loop. The only thing that could be involved is how voltage and current react in a inductive load or capacitive load. I suspect in Bob's case the grid on the lawn is more than likely a current leak via water and dirt making contact with plug, but possible in a light socket. I would suspect that it has very little to do with capacitive coupling.   Bob one way or another, good to see another amateur radio op on site..  Oh and do you think I did a background check on you? So, grow some skin and take it easy. I didnt really know your background and had no idea what you do and do not know. But dont get all flowery with me. Otherwise I will have to start telling you what I think of you. :P

Edited by Max-Paul
Link to comment
Share on other sites

Oh and do you think I did a background check on you? Lord I hope not... Its not worth the $29.95

 

So, grow some skin and take it easy. I have plenty thank you and .. I always do..

 

I didnt really know your background and had no idea what you do and do not know. Yet you still had no issue talking to me like I'm an idiot. But its not the first time .. I'm used to it.

 

But dont get all flowery with me. Otherwise I will have to start telling you what I think of you. :P I'm fairly sure that conversation in an open forum would get us both expelled..

 

73's

 

Bob

Edited by bob_moody
Link to comment
Share on other sites

Here's something I posted on another thread - old style GFCI's were also known to have "high frequency noise nuisance tripping"...

There seems to be many threads on GFCI tripping right now. So to follow-up, I rechecked my specs yesterday on the WT series I previously mentioned elsewhere. I wanted to see for myself exactly what features caused the sell price to be a little higher on this GFCI series than the normal indoor series GFCI receptacles (About a $2 higher than indoor only ). Knowing that they need to be installed in a weatherproof box or under the eave away from the elements any way, why state they are "better for outdoor use"?

They have rust resistant stainless steel straps and screws and have more durable cold impact resistant face and buttons, which are great features. New code calls for all dwelling receptacles to have tamper-proof shutters on the hot and neutrals - great for keeping bugs out.. Additionally, internally, Leviton has "Conformal coated PC board to protect critical components from moisture". Even if you don't want to fork out a buck or two extra for a weather-resistant model, newer models of GFCI receptacles, from most leading manufacturers, have addressed the high frequency noise nuisance trips previously found. So if you are experiencing a lot of tripping and you can't just seem to find it, and if your receptacles are over 5-6 years old, might consider changing them out.

(Be sure to turn the breaker off before attempting this or any other electrical work you are not qualified for, and / or call an electrician... Just covering my check-book here so I'll still have money for more controllers.....)

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
×
×
  • Create New...