GFCI and inrush

[sparrott4]

I have several problematic installations of low voltage lighting transformers where the GFCI nuisance trips. Here are some questions related to that. (Note - the installations are in coastal Florida)

1. Can inrush alone trip a GFCI? Note that the transformers involved carry loads varying from 800W to a 1000W. Also note that the addition of a 50 ft. extension cord between the GFCI and the transformer seems to prevent the GFCI from tripping - though not always.

2. Could electronic noise from the soft-start unit in the transformer cause the GFCI to trip?

3. Would a panel-mounted GFCI breaker at the mains panel be less problematic than using a GFCI receptacle near the transformer (outdoors)?

4. What is the absolute best, most robust outdoor GFCI receptacle?

Thanks for your help.

 

[ptonsparky]

Inrush alone does not trip a GFCI. They serve no overcurrent protection whatsoever.

Not sure about the soft start but enough other electronic devices do, so I wouldn't scratch that off the list.

The indoor protection would help with spiders, dust etc from fouling the GFCI electronics. Be it panel mounted or an inside receptacle.

I am partial to Leviton but a year or so ago I saw some P&S complete with gasket and slot protection for outdoor use at a trade show. Haven't seen another since.

 

[ELA]

It is possible for the GFCI to trip due to noise currents. Some are more robust than others. Your experiment with the extension cord could be an indication that added impedance between the noise source and the GFCI reduces the noise somewhat.
It is possible that a breaker would hold better as a result of being further away from the noise source.
You could try using an EMI filter between the GFCI and the noise source to test this further.

 

[iwire]

What is a 'noise current' and how would it trip a GFCI?

 

[sparrott4]

I just had a phone mtg with the engineer who designed the transformer and asked him the above questions. Here are his replies:

1. The GFI will not trip due to inrush.

2. The transformer does not produce the type of noise or emf that would trip the GFI.

3. The problem is almost certainly caused by moisture on the plug going into the GFI. Even a slightly damp plug carries enough current along its moist surface to trip the GFI.

3. It's also possible that moisture on the timer plug inside the transformer could trip the GFI, although this is highly unlikely because that plug operates an isolated relay.

4. When the contractor added the 50 ft. extension cord it fixed the problem because the new plug was dry, it had nothing to do with the additional length of cord.

Given this new wisdom, I have an important question for you guys:

What tips and techniques do you use to keep your plugs dry in a GFI outlet? Even waterproof covers apparently allow in small amounts of moisture since the seal isn't perfect. Is their some kind of sealant that one could put on the bottom side of the plug that would repel moisture or seal the plug-outlet interface?

 

[weressl]

I have several problematic installations of low voltage lighting transformers where the GFCI nuisance trips. Here are some questions related to that. (Note - the installations are in coastal Florida)

1. Can inrush alone trip a GFCI? Note that the transformers involved carry loads varying from 800W to a 1000W. Also note that the addition of a 50 ft. extension cord between the GFCI and the transformer seems to prevent the GFCI from tripping - though not always.

2. Could electronic noise from the soft-start unit in the transformer cause the GFCI to trip?

3. Would a panel-mounted GFCI breaker at the mains panel be less problematic than using a GFCI receptacle near the transformer (outdoors)?

4. What is the absolute best, most robust outdoor GFCI receptacle?

Thanks for your help.

1. no
2. some rectifiers generate harmonics that manifest in excessive ground leakeage 'current' that may trip the GFCI. Having said that it is entirely possible that they are designed with harmonic restraint.
3. I am not certain I can picture what you're asking but in general long leads running through a wet area progressively increase the potential for nuissance trip.
4. lemme know if you find out

 

[weressl]

Is their some kind of sealant that one could put on the bottom side of the plug that would repel moisture or seal the plug-outlet interface?

Willie-grease, slicker than Teflon. (Only buy the Clinton brand.)

 

[ELA]

What is a 'noise current' and how would it trip a GFCI?

Sounds like you are skeptical Bob?

Type "GFCI immunity to noise" into a search engine and read about improvements to GFCI's against noise or EMI if you like.
It used to be much more common for GFCIs to false trip due to noise. They have gotten better. You will find manufactures themselves claiming improvements that have been made.

It sounds like the OP is onto a different cause/solution.

 

[SG-1]

Is the power supplying the GFCI being turned on & off or is the GFCI always on ?

 

[hurk27]

I have several problematic installations of low voltage lighting transformers where the GFCI nuisance trips. Here are some questions related to that. (Note - the installations are in coastal Florida)

1. Can inrush alone trip a GFCI? Note that the transformers involved carry loads varying from 800W to a 1000W. Also note that the addition of a 50 ft. extension cord between the GFCI and the transformer seems to prevent the GFCI from tripping - though not always.

generally no, GFCI receptacles do not have over current protection, so high inrush is passed on to the OCPD at the panel,

2. Could electronic noise from the soft-start unit in the transformer cause the GFCI to trip?

Possible if the noise can mimic an imbalance in the GFCI most are immune to this though

3. Would a panel-mounted GFCI breaker at the mains panel be less problematic than using a GFCI receptacle near the transformer (outdoors)?

Both use the same design, but depending upon the grade of GFCI device could make a difference because of longer circuit conductors?

4. What is the absolute best, most robust outdoor GFCI receptacle?

I prefer the Leviton sure Lock, I find many of the cheaper brands have a problem with inductive kickback, this is known when a GFCI trips at the time you turn off an inductive load not when you are turning it on.

the cheapo Menard's GFCI's are notorious for this.

Thanks for your help.

It's included with your membership

 

[sparrott4]

Great responses - thanks everyone!

 

[sparrott4]

Willie-grease, slicker than Teflon. (Only buy the Clinton brand.)

Can you tell me where to find this?

 

[SG-1]

Can you tell me where to find this?

This product is available where ever it is sold. It is so slick I have not been able to get it from the shelf to the checkout.

 

[iwire]

Sounds like you are skeptical Bob?

Type "GFCI immunity to noise" into a search engine and read about improvements to GFCI's against noise or EMI if you like.
It used to be much more common for GFCIs to false trip due to noise. They have gotten better. You will find manufactures themselves claiming improvements that have been made.

It sounds like the OP is onto a different cause/solution.

Nothing personal I am just always skeptical when people use 'noise' or 'dirty' to describe electricity.

I Googled "GFCI immunity to noise" and what I found had more to do with the GFCIs ability to survive surges and 'noise'. Putting aside forum posts the only things I found in reference to 'noise' and false tripping appear to written by advertising people not technical people.


I have no problem believing RFI can trip GFCIs.

 

[ELA]

Bob,
I was in the business of EMC testing electrical equipment for several years.
EMC stands for Electromagnetic Compatibility. The slang term "noise" is often used to be generic for EFT (Electric Fast Transients), RFI (Radio Frequency Interference), EMI (Electromagnetic Interference) etc.

There are several manufacturers including Leviton that state that they have enhanced their immunity levels to EMI (Electromagnetic Interference) or "noise".
You can believe that this came from their technical people. They have nothing to gain by stating it unless there were known issues in the past and they want to demonstrate that they have improved.

Most people insist that the only way to trip a GFCI is by creating a differential current greater than 6 ma. That is not the only way.

In the field of EMC it is known that any piece of equipment that contains Integrated Circuits may be susceptible to common mode interference that can result in abnormal behavior.
We used to subject equipment to what are known as Electrical Fast Transient testing and RF common mode testing. Both of these tests would often cause equipment to Hiccup or malfunction temporarily.

Just because a piece of equipment is designed to react to differential currents does not mean that it cannot be upset by EMI in the common mode.

When people post here with what they feel may be false tripping I would agree that in most cases the trip is probably due to a valid differential current flow. I just point out that a nuisance or false trip is possible under the right conditions.

 

[sparrott4]

Willie-grease, slicker than Teflon. (Only buy the Clinton brand.)

Oh, now I get it...took awhile...did a google search...came up with a lot of Clinton stories...was puzzled by that, still looking for the grease...then I put it together, felt stupid...probably a good thing to be humbled once in a while.

 

[wirenut1980]

Oh, now I get it...took awhile...did a google search...came up with a lot of Clinton stories...was puzzled by that, still looking for the grease...then I put it together, felt stupid...probably a good thing to be humbled once in a while.

LOL! Don't feel bad. It was fun to read though.:grin:

 

[weressl]

Oh, now I get it...took awhile...did a google search...came up with a lot of Clinton stories...was puzzled by that, still looking for the grease...then I put it together, felt stupid...probably a good thing to be humbled once in a while.

Well, don't feel bad. I tried to give a hint with the grinning face. E-mail communication is much more difficult as it is missing 80% of the face-to-face communication value. What it means that tonal, body and facial inflections accompanying a statement in some cases comprise up to 8-% of the message to be conveyed.