AFCI for GFP

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sgunsel

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Any reason an AFCI breaker can't be used for electric heat tracing?
They are a lot more common and less $$$ than other GFP devices.
 
The specs I have seen, at least for the newer combintion types, indicate they will trip at 30-50 ma ground fault current.
 
30 - 150 ma? Not defined in section 100, but many are adjustable from 30 - well over 100 (maybe 150) ma.
 
I dug this up:
Arc-fault detection does not replace other aspects of circuit protection. Short circuits from essentially bolted conditions must be still cleared instantaneously. Long term overloads must still be cleared on an inverse-time basis, with greater overloads clearing more rapidly. Although the arc-fault detection mechanism will be inside a typical molded-case circuit breaker, its sensing mechanism is strictly in addition to the conventional components. AFCI protection doesn't substitute for GFCI or GFPE protection, either. These devices are residual current devices: They measure the total current in a circuit, going to the load and returning from the load. If the vectorial summation of all currents does not equal zero, these devices detect the amount of that residual current and trip above a predetermined point. AFCI protection does not duplicate any of these functions, although a manufacturer may well marry some of them within the same device. An AFCI detects and clears arcing faults whether line-to-line, or line-to-neutral, or line-to ground. In spite of outward similarities in appearance, don't confuse an AFCI circuit breaker and a GFCI circuit breaker.
Click to expand...
http://ecmweb.com/mag/electric_illustrated_changes_nec_7/


[Search for TIPS on the page linked above]


Basically, AF and GF look for different characteristics in a circuit that initiate the "trip".
 
Your reference is 10 years old. There may have been improvements. My question is: if the manufacturer of the device states it will clear a 30 ma ground fault, is there any reason it can not be used for GFPE protection of electric heat tracing? Obviously, if the device does not have the capability, it can't be used.
 
celtic said:
Basically, AF and GF look for different characteristics in a circuit that initiate the "trip".
Click to expand...

sgunsel said:
Your reference is 10 years old. There may have been improvements.
Click to expand...
:-?

Improvements to what?
These devices look at different characteristics entirely differently.
If there were to be any "improvements", it would result in further disparity between the types of sensing AF or GF.

Even if the reference were 100 years old, it would not change the fact that an AFCI device is not a GF device.

sgunsel said:
My question is: if the manufacturer of the device states it will clear a 30 ma ground fault, is there any reason it can not be used for GFPE protection of electric heat tracing? Obviously, if the device does not have the capability, it can't be used.
Click to expand...

An AFCI device is not a GF device.
A GF is not an AFCI device.

An AFCI is looking for arc faults - not ground faults.
A GF device is looking for ground faults - not arc faults.


You need to understand what each of these devices actually do.
Rather then rehash much of what has already been discussed, here is a link to a thread already in progress:
Combination AFCI Breakers ??

Buck Parrish said:
How many people think the Combination AFCI breakers are GFCI and AFCI, together in one breaker ?
Click to expand...
 
In aprevious post to this forum, someone stated..."AFCIs are compatible with GFCIs. There's even a 50ma GFCI function built into the AFCI compared to a 5ma unbalanced current that trips the GFCI."

Maybe this is not true. I have looked at several AFCI manufacturers information and have not been able to verify that they actually incorporate this function. It would seem to be an easy addition compared to the sophistication required to recognize parallel and series arcs.
 
Celtic, as I understand it, the AFCI breakers in use today also contain 50mA of ground fault protection. Whether it is good enough for a heat tracing product would depend on the listing requirements of the heat tape, IMO.
 
I'll go with that George...if documentation showing the AFCI is suitable as GFPE can be produced.
 
celtic said:
I'll go with that George...if documentation showing the AFCI is suitable as GFPE can be produced.
Click to expand...
I doubt if you find an AFCI that is listed for use as a GFPE device, but all AFCIs have a 30 to 50 mA ground fault trip unit. In most cases the ground fault device, and not the fancy arc signature recognition device causes the AFCI breaker to open the circuit. It is almost impossible to have a 5 parallel arcing fault without also having a 30 mA ground fault. In most cases the AFCI does not even detect a poor or glowing connection, (some times called a series arcing fault) until the heat from the fault has caused enough damage to turn the fault into a ground fault or parallel arcing fault.
 
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