427.22 Fixed Electric Heating (Heat tracing)

[Lady Engineer]

Hi guys,

I'm doing the CA work for a water treatment pumping station. Now, I know usually I provide a GFEP/GFP breaker for every heat tracing circuit. However, this is considered an industrial application.

But I'm sure it meets the requirements of both conditions of NEC 427.22. Due to the fact that, it must also have an alarm indication of ground faults.

Now the panel that supplies the heat tracing is 208/120V, 3ph, 4W. Does the GFP have to be on the same panel, or can it be before the step down XFMR?

Also FYI, the water treatment plant is served with MV coming in at 4160V, and is transformed down to 480V via a unit substation.

Thanks,

Patty

 

[raider1]

If the GFP is located on the line side of a step down transformer it will not function to detect ground faults on the secondary of the transformer.

Also keep in mind that the term ground fault protection of equipment as used in 427.22 is incorrect. Ground fault protection of equipment is designed to protect equipment from damaging arcs. But the ground fault protection required for fixed electrical heating equipment is designed to limit the leakage current from the heating cables according to the UL whitebook for equipment ground fault protection. According to the UL whitebook equipment ground fault protection has a trip threshold of 50 milliamps.

I am submitting a proposal for the 2014 NEC to clarify the difference between equipment ground fault protection used for heat tape and ground fault protection of equipment used to protect services and feeders from damaging arcs.

Chris

 

[Lady Engineer]

If the GFP is located on the line side of a step down transformer it will not function to detect ground faults on the secondary of the transformer.

Also keep in mind that the term ground fault protection of equipment as used in 427.22 is incorrect. Ground fault protection of equipment is designed to protect equipment from damaging arcs. But the ground fault protection required for fixed electrical heating equipment is designed to limit the leakage current from the heating cables according to the UL whitebook for equipment ground fault protection. According to the UL whitebook equipment ground fault protection has a trip threshold of 50 milliamps.

I am submitting a proposal for the 2014 NEC to clarify the difference between equipment ground fault protection used for heat tape and ground fault protection of equipment used to protect services and feeders from damaging arcs.

Chris

D'oh! Yes, because the transformer isolates the load. Duh..sorry.

Yes, that does make sense. Let me read this again, because should have ready my NEC hand book instead.


Thanks! I hope they clear it up, because without the handbook, it looks like GFP for the equipment protection, not leakage.

 

[raider1]

D'oh! Yes, because the transformer isolates the load. Duh..sorry.

Yes, that does make sense. Let me read this again, because should have ready my NEC hand book instead.


Thanks! I hope they clear it up, because without the handbook, it looks like GFP for the equipment protection, not leakage.

Exactly the reason I am making the proposal. The term ground fault protection of equipment is defined in Article 100 that the GFP is designed to protect the equipment from damaging arcs not to limit leakage current.

Chris

 

[Lady Engineer]

Exactly the reason I am making the proposal. The term ground fault protection of equipment is defined in Article 100 that the GFP is designed to protect the equipment from damaging arcs not to limit leakage current.

Chris

Wow, nice going Chris. I would have not know this. Thanks again...

 

[Sierrasparky]

I thought the breakers had a 30 milliamp setting. or was that part of what you wanted to clarify?

 

[Lady Engineer]

I thought the breakers had a 30 milliamp setting. or was that part of what you wanted to clarify?

I looked this up in the handbook. I think GFP has the 30ma-50ma setting. But the GFEP needs a 6ma-50ma setting for heat tracing, unless I'm mistaken.

 

[raider1]

I thought the breakers had a 30 milliamp setting. or was that part of what you wanted to clarify?

According to the UL Whitebook equipment ground fault protective devices have a ground fault setting of 6ma to 50 ma. Also the ground fault protection trip level should ba marked on a breaker.

Chris

 

[raider1]

I looked this up in the handbook. I think GFP has the 30ma-50ma setting. But the GFEP needs a 6ma-50ma setting for heat tracing, unless I'm mistaken.

Keep in mind that Ground fault protection of Equipment as required in 230.95 and 215.10 may have a ground fault setting of up to 1200 amperes.

Chris