Higher amperage GFCI Breakers

[ForceFed70]

Hi guys,

The other day an electrician was telling me that there is often a minimum cable length required between a higher ampacity GFCI breaker and it's load.

Can anyone confirm this? Or better yet, explain why it's required?

The subject came up because I was talking about how I had installed a 100A outdoor subpanel for the central AC, landscaping lighting, outdoor plugs, and a future hot-tub. We were talking about requiremetns for how far the tub had to be away from the panel and whether the GFCI breaker itself could qualify as a disconnect. He said I may need to coil some cable, or take "the long way" to ensure I had enough cable length to meet the requirement for the GFCI to work properly.

Any thoughts? Thanks!

 

[tfi racing]

Never heard of this one,the closest you may have your GFCI breaker to your tub is 3m(10iish feet,so you can't reach it while in the water-nothing to do with its function),have yet to see any nuisance tripping on any of the tubs I know of or have installed due to cable length.

 

[Executive]

Some preassembled spa units have a GFCI breaker inside the access panel under the edge of the tub. Someone's looking to run up the price on the job...

Chris

 

[ForceFed70]

Hmmm. Yes, I know there is code limitation for how far away the breaker/disconnect must be.

The electrician I was talking to knew that I had no immediate plans to install a tub, and also knew that when I do the install I will do the electrical myself. So really doubt he was trying to run up the cost of the job.

 

[Executive]

Hmmm. Yes, I know there is code limitation for how far away the breaker/disconnect must be.

Article 680.41 of the NEC calls for an Emergency Switch for Spas and Hot Tubs that must be located at least 5 feet away from the spa or hot tub. This is not the breaker or disconnect. Article 680 in general has requirements for minimum distances for all electrical equipment. These requirements also take into account barriers and walls which allow a lesser measurement in most cases.

The NEC also allows a prefabricated spa or hot tub to have self contained disconnect and GFCI protection as I mentioned above. There is no specific limitation for how far away the breaker/disconnect must be.

Chris

 

[FluxCore]

For many particulars cited in codes, you have to have sufficient engineering background and experience to understand the 'spirit and intent' of the code.

"Spirit and intent" are easily interpreted and met when dealt with by qualifed and skilled installers who are up on the most recent materials available, and also well versed in old school applications......Code can be daunting and cause huge cost and unnecessary expense and needless trouble unless you talk the talk, and walk the walk.

First approach all code requirementswith an open mind and try to determine WHY it exists....Most code is written in blood and after loss of life and property

 

[jeff000]

Article 680.41 of the NEC calls for an Emergency Switch for Spas and Hot Tubs that must be located at least 5 feet away from the spa or hot tub. This is not the breaker or disconnect. Article 680 in general has requirements for minimum distances for all electrical equipment. These requirements also take into account barriers and walls which allow a lesser measurement in most cases.

The NEC also allows a prefabricated spa or hot tub to have self contained disconnect and GFCI protection as I mentioned above. There is no specific limitation for how far away the breaker/disconnect must be.

Chris

Op is in bc, so subject to the cec rather than the nec.

Prefab inside the tub is okay here too.
Inspectors won't call much for a hot tub as long as it's reasonable.

Just make sure you don't double up your GFCI, causes strange things to happen.

 

[Executive]

Op is in bc, so subject to the cec rather than the nec.

Prefab inside the tub is okay here too.
Inspectors won't call much for a hot tub as long as it's reasonable.

Just make sure you don't double up your GFCI, causes strange things to happen.

Never been to Canada so I'll defer to the Red Seal brigade.

Double GFCI is no mystery. The more sensitive device will trip first. That's it. No strange things at all.


Chris

 

[Executive]

For many particulars cited in codes, you have to have sufficient engineering background and experience to understand the 'spirit and intent' of the code.

"Spirit and intent" are easily interpreted and met when dealt with by qualifed and skilled installers who are up on the most recent materials available, and also well versed in old school applications......Code can be daunting and cause huge cost and unnecessary expense and needless trouble unless you talk the talk, and walk the walk.

First approach all code requirementswith an open mind and try to determine WHY it exists....Most code is written in blood and after loss of life and property

"Spirit and Intent" are easy to interpret. The NFPA publishes a report prior to each new Code cycle called the Report on Committees. It's available to anyone who asks and explains what each code article says and more importantly: why. Funny, many experienced electricians don't know this.

I teach Code and take my job very seriously. Whatever you do remember: knowledge is power and can save a life. Ask as many questions as it takes to do the job correctly or call in a pro who can get it done right.

Chris

 

[ForceFed70]

Thanks All.

I didn't get the impression that it was a code requirement (min cable length). Just that the GFCI wouldn't work properly is the cable to the tub was too short. Didn't really make sense to me which is why I'm asking here.

 

[FluxCore]

Thanks All.

I didn't get the impression that it was a code requirement (min cable length). Just that the GFCI wouldn't work properly is the cable to the tub was too short. Didn't really make sense to me which is why I'm asking here.

I'm not familar enuff with the NEC on GFCI breakers to know if there even IS a requirement that their load conductors be longer than some minimum length....I do know however, that due to their principle of operation, it is important that conductors be of same gauge and close in length to each other.

 

[Executive]

I'm not familar enuff with the NEC on GFCI breakers to know if there even IS a requirement that their load conductors be longer than some minimum length....I do know however, that due to their principle of operation, it is important that conductors be of same gauge and close in length to each other.

Please explain this "principle of operation" and how conductor length is a factor in GFCI function. (Hint: conductor length is irrelevant, it's about current measurement)

Chris

 

[nehog]

Please explain this "principle of operation" and how conductor length is a factor in GFCI function. (Hint: conductor length is irrelevant, it's about current measurement)

Chris

Actually conductor length can be relevant, but the difference between the two conductor's lengths would have to be extreme. Note this is only the difference in the two lengths, not the length of both.

As to the wire size issue, again a bit of extreme engineering is needed before it becomes significant. For example, if the line conductor was 10 AWG and the neutral conductor was 12 AWG, it is unlikely this will make a difference (as long as current is limited to the smaller wire's capacity.)

Also all these factors are only significant for pass-through GFCI devices (not the typical outlet based units) where you run the conductors through the GFCI's torrid.

http://maxwell.byu.edu/~spencerr/websumm122/node70.html is one reference.

IMHO the length reference is likely due to the proximity of the load/device to the GFCI such that one cannot be in contact with both at the same time (enabling one to be part of the fault circuit while attempting to reset the GFCI.) The reasoning there is that some GFCIs may present a substantial current pulse on reset before a second trip due to a continued ground fault condition. That power pulse would be potentially hazardous.

 

[FluxCore]

A quote from here:

http://www.inspectpros.com/GFCI.htm


"If the wires are of substantially different length, the GFI may trip. (Occasionally, amateur electricians become creative with wire routing, and route the hot wire and neutral via different routes. This is a code violation, and might also cause a GFI to trip.)"

Gents, I've seen some VERY creative single wire loop attempts that somehow powered things, but would never work with a GFCI....And then there is the cases where hot is fed stranded, and neutral is solid, then ground either stranded and/or solid all in the same circuit. Yup, I've seen it....I'm just saying it's good engineering practice to keep your conductor lengths, type and gauges common to each other and properly sized.

 

[Executive]

Actually conductor length can be relevant, but the difference between the two conductor's lengths would have to be extreme. Note this is only the difference in the two lengths, not the length of both.

A quote from here:

http://www.inspectpros.com/GFCI.htm


"If the wires are of substantially different length, the GFI may trip. (Occasionally, amateur electricians become creative with wire routing, and route the hot wire and neutral via different routes. This is a code violation, and might also cause a GFI to trip.)"

Interesting.
I'm still waiting for someone to post a legitimate example from a credible source as to why conductor length can trip a GFCI.

A GFCI operates by comparing the current on the ungrounded conductor with the current on the grounded conductor. If the two differ by more than 5 mA, in the case of GFCI for protection of personnel, the device trips.

Conductor length has nothing to do with GFCI operation.

Chris

 

[nehog]

...

Gents, I've seen some VERY creative single wire loop attempts that somehow powered things, but would never work with a GFCI....And then there is the cases where hot is fed stranded, and neutral is solid, then ground either stranded and/or solid all in the same circuit. Yup, I've seen it....I'm just saying it's good engineering practice to keep your conductor lengths, type and gauges common to each other and properly sized.

FWIW, I've never seen a 'creative routing' of conductors for an outlet, but I'm sure someone has done it! I have run mixed 12 and 10 AWG (had 10 in the color I needed, and no 12) without any impact. We're talking single conduit installation of two (actually three) conductors.

Interesting.
I'm still waiting for someone to post a legitimate example from a credible source as to why conductor length can trip a GFCI...

Credible? Well, how's your math?

And again, AFAIK, conductor length is meaningless except for the safety aspect, and mixed gauge wiring is only significant when high current pass through GFCIs are being installed and there is a significant difference in the two wire sizes.

 

[ForceFed70]

I gave this some more thought last night and here's my thinking:

We know that long runs can cause nusiance GFCI tripping. This is due to a tiny amount of leakage current within the cable between the hot and ground conductors. The longer the cable/conductors the more leakage we will see. This is part of the reason why GFCI's are built with a threshold current (typically 20 mA?) instead of just tripping with the detection of any leakage.

The only reason why I can think of why too short of a conductor would be a problem would be because there is little/no leakage current caused by the cable. Meaning the full 20mA would have to be a legitimate ground fault before tripping instead of the manufacturer expecting 10mA of leakage from the cable and thus only a 10mA current actual ground fault being required to trip the breaker.

Seems a bit far fetched, but is the only thing I can think of.

 

[ForceFed70]

Interesting.
I'm still waiting for someone to post a legitimate example from a credible source as to why conductor length can trip a GFCI.

A GFCI operates by comparing the current on the ungrounded conductor with the current on the grounded conductor. If the two differ by more than 5 mA, in the case of GFCI for protection of personnel, the device trips.

Conductor length has nothing to do with GFCI operation.

Chris

As I mentioned in my post above, cables themselves cause leakage. There is no such thing as a perfect insulator. So even in a healthy cable you will have a very small current flowing between the hot/neutral/ground conductors. The longer the cable, the more the leakage. At some point the leakage will be enough to trip the GFCI.

Also, I assume by "ungrounded conductor" you mean the hot conductor, and "grounded conductor" you mean the neutral and are refering to a 120V circuit? Otherwise, I think you're a little confused on the operation of a GFCI.

 

[Executive]

As I mentioned in my post above, cables themselves cause leakage. There is no such thing as a perfect insulator. So even in a healthy cable you will have a very small current flowing between the hot/neutral/ground conductors. The longer the cable, the more the leakage. At some point the leakage will be enough to trip the GFCI.

Also, I assume by "ungrounded conductor" you mean the hot conductor, and "grounded conductor" you mean the neutral and are refering to a 120V circuit? Otherwise, I think you're a little confused on the operation of a GFCI.

An ungrounded conductor is the proper name for a hot conductor. A grounded conductor is the proper name for a neutral in a single phase or three phase wye system. A grounding conductor is the bare or green wire what most people call "a ground".

I guess I'll have to turn in my Master License, give up my 30 years of experience in the trade, 18 years teaching the National Electrical Code, and look for a new line of work.

My definition of a GFCI is spot on.

I've been posting here trying to lend my expertise to guys who obviously don't have a clue. I'm not looking for an on-line argument but in all my years, I have never seen an intact conductor of any length leak sufficient current to trip a GFCI.

I have about a dozen textbooks, handbooks, white papers, and the UL "white book". I guess my definition of how a GFCI operates is wrong along with all of them.

Good luck.

Chris

 

[ForceFed70]

An ungrounded conductor is the proper name for a hot conductor. A grounded conductor is the proper name for a neutral in a single phase or three phase wye system. A grounding conductor is the bare or green wire what most people call "a ground".

I guess I'll have to turn in my Master License, give up my 30 years of experience in the trade, 18 years teaching the National Electrical Code, and look for a new line of work.

My definition of a GFCI is spot on.

I've been posting here trying to lend my expertise to guys who obviously don't have a clue. I'm not looking for an on-line argument but in all my years, I have never seen an intact conductor of any length leak sufficient current to trip a GFCI.

I have about a dozen textbooks, handbooks, white papers, and the UL "white book". I guess my definition of how a GFCI operates is wrong along with all of them.

Good luck.

Chris

Yeesh. If you read my post again, I never said you had it wrong so long as I understood your terminology. Nor did I say your terminology is wrong.

You may be a master electrician, but you have no idea what my qualifications are. And yes, I am qualified to talk about this. Let's not try to turn it into a **** waving contest.

As a Master electrician, you must know that what I said about all cables having leakage is correct. So I'm not sure what you are argueing with me about here. A long enough cable will leak enough current to trip a GFCI, that cannot be disputed. The real question is how long would that be? Maybe it's 200ft, maybe it's 10,000ft. I dunno, but I'm sure it depends on the type of cable and the condition. I'm sure it can be calculated if we had the specifications for the cable. I'm going to see if I can find something.

 

[FluxCore]

LOL, guys......ease up.

 

[nehog]

As I mentioned in my post above, cables themselves cause leakage. There is no such thing as a perfect insulator. ...

Virtually all 'leakage' is capacitive and not insulation breakdown. If you are getting insulation breakdown, that should be addressed, but capacitive leakage between the hot and the ground (which are next to each other in most cables, as the ground sits between hot and neutral) can be a factor. Were I to detect insulation leakage, I'd be strongly motivated to replace the cable--as the leakage could only get worse, eventually leading to failure.

(Insulation leakage would typically be in nano amps, and I doubt anyone here has the tools/equipment to measure such leakage until it got excessive...)

 

[jeff000]

Never been to Canada so I'll defer to the Red Seal brigade.

Double GFCI is no mystery. The more sensitive device will trip first. That's it. No strange things at all.


Chris

Wish it was always that simple. 800a GFCI main to a cdp, 6 100 GFCI breakers in the cdp. I chased ghost tripping for weeks before we got the ok to put normal breakers in the cdp. This was 3phase 600v. I'd have the main trip then a breaker then the main. We repulled feeds, changed breakers. This isn't the first time I'd had issues like that. Never dealt with double gfi in a single phase, but I'd still avoid it.

 

[ForceFed70]

Virtually all 'leakage' is capacitive and not insulation breakdown. If you are getting insulation breakdown, that should be addressed, but capacitive leakage between the hot and the ground (which are next to each other in most cables, as the ground sits between hot and neutral) can be a factor. Were I to detect insulation leakage, I'd be strongly motivated to replace the cable--as the leakage could only get worse, eventually leading to failure.

(Insulation leakage would typically be in nano amps, and I doubt anyone here has the tools/equipment to measure such leakage until it got excessive...)

Yes, I agree. Sorry to be misleading earlier.

Although I've heard that underground cables (oil impregnated, whatever) exhibit a lot more leakage. Not sure if that's because of moisture or cable design.