I met the neon guy at a restaurant today where he had installed 6 tubes of neon and I was there to hook up his transformer. He told me that ALL neon transformers today are made with a built in GFI, that I had to run a dedicated GFCI circuit to his transformer, the built in GFI was too sensitive and that a GFCI breaker would trip before the transformer GFI would thus preventing the restaurant owner from having to climb above the ceiling to reset the GFI, and finally he said I had to jumper from the grounding conductor to the grounded conductor on the transformer or that the GFI would not work at all. I told him if I bonded the two conductors together that there would be current traveling on the metal case of the transformer and anything that was in contact with. He disagreed. I asked him if the GFI in the transformer is so sensitive then wont it trip long before a breaker GFI? He just said "well thats the way we been doin'em and they work fine". Well I tapped off an existing circuit that was only loaded to 4 amps, didn't install a GFCI breaker, and didn't tie the grounding and grounded conductors together. Is this what any of you would have done. I'm going back tomorrow so let me know if you think any changes need to be made. Thanks.
The neon guy
- Thread starter ih8shorts
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russ
Senior Member
- Location
- Burbank IL
Re: The neon guy
There is no way you're supposed to bond the grounded conductor to the equipment ground.
The transformer ground fault is for the load side of the transformer. I don't see how a line side ground fault circuit interrupter helps to keep it from tripping.
There is no way you're supposed to bond the grounded conductor to the equipment ground.
The transformer ground fault is for the load side of the transformer. I don't see how a line side ground fault circuit interrupter helps to keep it from tripping.
hbiss
EC, Westchester, New York NEC: 2014
- Location
- Hawthorne, New York NEC: 2014
- Occupation
- EC
Re: The neon guy
I agree with Russ. Probably nothing more needs to be said but what I would do is have a look at the transformer manufacturers website just for the heck of it. Most of these things are electronic now.
-Hal
I agree with Russ. Probably nothing more needs to be said but what I would do is have a look at the transformer manufacturers website just for the heck of it. Most of these things are electronic now.
-Hal
curt swartz
Electrical Contractor - San Jose, CA
- Location
- San Jose, CA
- Occupation
- Electrical Contractor
Re: The neon guy
Actually if you tied the EGC to the grounded conductor you wouldn?t have any current flowing on the EGC since the GFCI breaker would trip as soon as you turned it on.
I agree with Hal, check with the manufacture to see if they have any specific requirements.
Actually if you tied the EGC to the grounded conductor you wouldn?t have any current flowing on the EGC since the GFCI breaker would trip as soon as you turned it on.
I agree with Hal, check with the manufacture to see if they have any specific requirements.
hurk27
Senior Member
- Location
- Portage, Indiana NEC: 2008
Re: The neon guy
A ground fault on the secondary side of any transformer will not trip a GFCI on the primary side as all transformers are isolating and current stops at source (transformer). also a ground fault will need a return path before there will be a fault and I have never heard any one grounding any secondary HV leads from a neon transformer. If only one lead is faulted you will now have a grounded circuit if the second lead is faulted then you will have a ground fault. This is just like a ungrounded delta but at a higher voltage. If there is GFP (30ma.) protection built in the transformer it will be on the secondary side of it.
[ November 15, 2004, 12:26 AM: Message edited by: hurk27 ]
A ground fault on the secondary side of any transformer will not trip a GFCI on the primary side as all transformers are isolating and current stops at source (transformer). also a ground fault will need a return path before there will be a fault and I have never heard any one grounding any secondary HV leads from a neon transformer. If only one lead is faulted you will now have a grounded circuit if the second lead is faulted then you will have a ground fault. This is just like a ungrounded delta but at a higher voltage. If there is GFP (30ma.) protection built in the transformer it will be on the secondary side of it.
[ November 15, 2004, 12:26 AM: Message edited by: hurk27 ]
jimwalker
Senior Member
- Location
- TAMPA FLORIDA
Re: The neon guy
I think that neon man needs to just do his job and let you do yours.If he was qualified to wire them then you would not be there.All the above post already told you correctly about gfci.If his sign trips its own gfci then it has problems that need to be fixed.
I think that neon man needs to just do his job and let you do yours.If he was qualified to wire them then you would not be there.All the above post already told you correctly about gfci.If his sign trips its own gfci then it has problems that need to be fixed.
sandsnow
Senior Member
- Location
- Southern California
Re: The neon guy
Neon is something I've done some looking into since we have channel letter signs going in all over our city. I can tell you this guy is absolutely full of ..... If he installs his system correctly, then the secondary ground fault will never be needed. The reason it's there is because so many moron installers kept starting fires.
Not all XFMRS have secondary groundfault. XFMRS with built in electrode receptacles (socket for the end of the neon) do not. XFMRS for outline lighting 7500 volts and under are not required to have it.
UL doees require secondary groundfault for any XFMR used in a listed electric sign regardless of voltage.
Grounding the secondary does occur in a midpoint grounded secondary. The XFMR is built for the purpose, not just any will do. The two HV leads run real short to the electrodes(ends of neon tubing), the tubing is run equal footage each way, then the two returns to the XFMR can be long and no danger of arcing to ground since those leads connect to the grounded midpoint.
For you who said the primary won't see the secondary fault. We had one inspector in our area who insisted that all neon XFMRS required primary fusing (an inline fuse) We did a little demo at one of our meetings and shorted the secondary and the fuse did not blow. Still didn't convince him. :roll:
Neon is something I've done some looking into since we have channel letter signs going in all over our city. I can tell you this guy is absolutely full of ..... If he installs his system correctly, then the secondary ground fault will never be needed. The reason it's there is because so many moron installers kept starting fires.
Not all XFMRS have secondary groundfault. XFMRS with built in electrode receptacles (socket for the end of the neon) do not. XFMRS for outline lighting 7500 volts and under are not required to have it.
UL doees require secondary groundfault for any XFMR used in a listed electric sign regardless of voltage.
Grounding the secondary does occur in a midpoint grounded secondary. The XFMR is built for the purpose, not just any will do. The two HV leads run real short to the electrodes(ends of neon tubing), the tubing is run equal footage each way, then the two returns to the XFMR can be long and no danger of arcing to ground since those leads connect to the grounded midpoint.
For you who said the primary won't see the secondary fault. We had one inspector in our area who insisted that all neon XFMRS required primary fusing (an inline fuse) We did a little demo at one of our meetings and shorted the secondary and the fuse did not blow. Still didn't convince him. :roll:
hurk27
Senior Member
- Location
- Portage, Indiana NEC: 2008
Re: The neon guy
Physis I think the short circuit current would be much higher than the rated FLA. of the transformer and this would put a even higher load on the primary. But still not enough to open the OCPD. I think most transformers today have a thermal fuse in them?
[ November 15, 2004, 07:08 PM: Message edited by: hurk27 ]
Larry what I should have said was That the primary wouldn't see an inbalance of current between the hot and neutral that would be needed to trip a GFCI breaker. And if the secondary was shorted it would increase the current on the primary, Just not enough to trip the circuit breaker.
Physis I think the short circuit current would be much higher than the rated FLA. of the transformer and this would put a even higher load on the primary. But still not enough to open the OCPD. I think most transformers today have a thermal fuse in them?
[ November 15, 2004, 07:08 PM: Message edited by: hurk27 ]
Re: The neon guy
Wow, thanks for all the great replies. I just wanted to make sure the GFCI wasn't needed on the primary side. I can remember on one job where the neon tubing was taken out and the transformer was left still connected to a circuit whose breaker was off. Well someone turned the breaker on and the neon wiring arced to the FMC that was protecting it and a stream of sparks dropped onto the ceiling tile. The arc burned itself clear but the paper on the insulation in the ceiling was starting to smoke. After that I realized how quickly an electrical fire can start.
Wow, thanks for all the great replies. I just wanted to make sure the GFCI wasn't needed on the primary side. I can remember on one job where the neon tubing was taken out and the transformer was left still connected to a circuit whose breaker was off. Well someone turned the breaker on and the neon wiring arced to the FMC that was protecting it and a stream of sparks dropped onto the ceiling tile. The arc burned itself clear but the paper on the insulation in the ceiling was starting to smoke. After that I realized how quickly an electrical fire can start.
sandsnow
Senior Member
- Location
- Southern California
Re: The neon guy
I know I didn't say so, but it was 10+ years ago. I don't remember what it was. 15,000 volts is the typical size in vogue at the time. 10 amp would be max permitted by code at 250% with a 30 milliamp XFMR. Nowadays people use a 9,000 volt XFMR. He was right that we needed some kind of protection to stop the arcing, but was invoking Art. 450 which does not apply.Originally posted by physis:
You weren't using a 30 amp fuse were you?
At some value it would take out the fuse because there is primary current. 10 milliamps at 7500v would put .625 amps on the primary.
physis
Senior Member
Re: The neon guy
Yeah Larry, my point was only that you're dealing with pretty small amperage with those.
Wayne, again you got me thinking about something different. I don't know how much good a thermal fuse is gonna do. There's not much power there to be dissipated into heat.
[ November 15, 2004, 08:49 PM: Message edited by: physis ]
Yeah Larry, my point was only that you're dealing with pretty small amperage with those.
Wayne, again you got me thinking about something different. I don't know how much good a thermal fuse is gonna do. There's not much power there to be dissipated into heat.
[ November 15, 2004, 08:49 PM: Message edited by: physis ]
hurk27
Senior Member
- Location
- Portage, Indiana NEC: 2008
Re: The neon guy
Sam think about it @ 95 watts yes it will heat the transformer from within. short out a neon transformer and it will get hot. Even a 10ma 10 volt doorbell transformer will get hot enough to blow the thermo-fuse. some of these neon transformers are over 300 watts.
Sam think about it @ 95 watts yes it will heat the transformer from within. short out a neon transformer and it will get hot. Even a 10ma 10 volt doorbell transformer will get hot enough to blow the thermo-fuse. some of these neon transformers are over 300 watts.
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