GFCI Required for Removable Heaters?

[CeCo3]

We have a machine with a large metal casting head heated by multiple groups of heating element cartridges. The heaters are 240V/500W metallic types with a stainless 5-foot flexible conduit attached to protect the two wires back to the heating source. The heaters are periodically removed to facilitate cleaning. Although power is to be removed when the heaters are out of their receptacles, it is possible for someone to make a mistake. To better protect against electrical shock, we are replacing the heaters with types from the manufacturer that have a dedicated ground wire bonded to the metallic case.

We also want to improved the convoluted power distribution scheme in this machine and centrally locate all related components in a new enclosure. Circuit breakers, SSRs, disconnect, fuses and pilot lamps would all be in one box. The existing design utilizes dedicate 2-pole GFCI breakers for each heater group. With grounded heaters, I no longer see a requirement for the GFCI type breaker. My plan is to use standard DIN rail 2-pole breakers.

I don?t want to endanger anyone with my preferences or violate an accepted practice or regulation. Does the NEC address this issue?

 

[CeCo3]

31 hits so far and no takers. Hmmm....

a. I'm considered in over my head by other members, or
b. No one has a suggestion
c. No one understands the question
d. I wasn't polite enough
e. I violated some message board rule and have already been shunnned

I have thick skin. Please advise and thank you in advance.

 

[RICK NAPIER]

While additional grounding is generally a good idea it does not replace the protection afforded by GFCI protection. If the GFCI protection has not been a problem I would see no reason to consider removing it.

 

[renosteinke]

No need to fear this board; if anyone has an issue, you can be sure they will speak up!

OK ... as I understand it, you want to remove existing GFCI protection as part of your electrical 'clean-up' program.

From a code perspective, there are two matters to address: where did the GFCI decision first originate, and why was it there. If the GFCI protection was part of the original assembly, or was reccomended by the equipment maker, I'd advise keeping it there.

Otherwise, I can't speak for your location, or why someone felt a need to provide the 'extra' safety.

Grounding and GFCI's attempt to provide for a safer installation by using completely different
approaches. They compliment each other, rather than compete.

Now I ask, "why does he want to remove the GFCI protection?" Here, I am going to make some guesses.
First, I suspect that your GFCI protection is provided by preakers in ordinary panels. Your mention of DIN rails makes me think you are building your own control panel. So, is your issue that Allen-Bradley doesn't have a GFCI breaker? If so, I think you are being hasty.

I have access to many control panels that have 'ordinary' breakers mounted in them. Square D (and I'm sure others) have bases available specifically for mounting their QO breakers on backplates (QOMB-1, QOMB-2). With these bases, I see no reason you cannot use a GFCI breaker in your box.

 

[CeCo3]

Rick & renosteinke,

Thank you both for the replies. Unfortunately, I do not have a complete machine history and cannot determine the facts surrounding the GFCI addition. Old timers here say they were definitely added. This is actually what prompted my question on the board.

First, I suspect that your GFCI protection is provided by preakers in ordinary panels.

Your assumption is correct. The GFCI breaker panel is remotely located and a bit of a pain to get to. The disconnect is in yet another panel and unnecessarily powers down other controls.

Your mention of DIN rails makes me think you are building your own control panel. So, is your issue that Allen-Bradley doesn't have a GFCI breaker?

Correct again. My plan was to have everything heater related in one nice package (disconnect, circuit interruption, SSR control, etc.). Yeah, I am surprised not to find GFCI's in smaller packages and just smart enough to realize there may actually be a reason why MY idea is not a standard...

If so, I think you are being hasty.

Hasty? Not yet. Hes-i-tant. Safety IS important.

If the GFCI protection has not been a problem I would see no reason to consider removing it.

Overall it has not been. Once in awile we get heaters in that have slight leakage current (to the metallic case). No problem if it is just one, but if several heaters in the ganged group exhibit this, then we end up with false tripping of the GFCI. Interruptions to the process are problematic (controlled environment).

I have access to many control panels that have 'ordinary' breakers mounted in them. Square D (and I'm sure others) have bases available specifically for mounting their QO breakers on backplates (QOMB-1, QOMB-2). With these bases, I see no reason you cannot use a GFCI breaker in your box.

This is a good idea and had not crossed my mind; a very good suggestion indeed. Itl pushes the space limitations, though. (Proposed box is near point of use and can't go any bigger.) If I keep GFCI, which is most likely at this point, then I will retain the existing remote box and just reroute the power source from the new disconnect.

I would still like to know if the code addresses this issue, either specifically or subjectively.

Again, I appreciate your time, guys. I feel welcome.

CeCo3

 

[rcarroll]

I would still like to know if the code addresses this issue, either specifically or subjectively.



CeCo3

I can't find anything in Art. 210 or chapter 4 heating section that requires GFI protection.
Of course, if the listing requires it, you need it. But, you would have seen that.

 

[ceb58]

Once in awile we get heaters in that have slight leakage current (to the metallic case). No problem if it is just one, but if several heaters in the ganged group exhibit this, then we end up with false tripping of the GFCI.

I would say that if you have current leakage then you dont have false tripping of the GFCI. It is doing it's job. Other than equip. mfg. instruction I can't think of a requirement for GFCI. Although you must remember the NEC is a minimum requirement. If you have had some heaters leak in the past then it is safe to conclude you will have some leak in the future. If it has been working with the GFCI in the past then I see no reason to discontinue it's use. Aside from a safety stand point it is a good indicator of a problem with the system before it gets out of hand.

 

[CeCo3]

Of course, if the listing requires it, you need it. But, you would have seen that.

True. I've come up dry on any written requirement for them or anything similar.

I would say that if you have current leakage then you dont have false tripping of the GFCI. It is doing it's job.

I agree. I should have said nuisance tripping. That of course leads to questions about how much leakage per element and per group is acceptable. There are six breakers, one for each group (or heat zone). I don't believe the number of heaters per breaker was calculated; rather they just slapped a GFCI in place of each standard breaker, did a quick check and ta-da, here we are years later still dealing with nuisance (in my mind) tripping.

If the heaters were permanently installed in the zones (like boilers), we wouldn't be having the conversation, the GFCIs would be gone. It's when we have them pulled out and someone mistakenly applies power that we have a risk of having an energized metallic surface with no effective bonding path in place (currently as we use the two-wire heaters). That's why we're switching to 3-wire heaters from the manufacturer. (Of course if they left the power on the heater bucket could get real hot real fast.)

During process operation, heaters go out once in awhile and we replace them and their respective fuse on the fly without interrupting the process. When the GFCI pops, the whole zone goes down, a temp alarm activates and we have to explain and document the deviation because of our industry. That is my primary driver for our conversation.

Thanks guys.

 

[ceb58]

It's when we have them pulled out and someone mistakenly applies power that we have a risk of having an energized metallic surface with no effective bonding path in place (currently as we use the two-wire heaters). That's why we're switching to 3-wire heaters from the manufacturer. (Of course if they left the power on

Do you not have LOTO procedures for working on the equipment? What about OSHA guidelines?

 

[CeCo3]

Yes, we do have LOTO in place and the new disconnect will accommodate LOTO.

 

[ceb58]

Yes, we do have LOTO in place and the new disconnect will accommodate LOTO.

Then I would say that since you are switching to 3 wire heaters and you will have lockable disconnecting means then you could forgo the GFCI protection.

 

[boboelectric]

Seems to me,if the power was left on to the heaters,it would be more of a burn hazard.

 

[CeCo3]

Seems to me,if the power was left on to the heaters,it would be more of a burn hazard.

The process runs at approximately 50?C (122?F) which isn't too terribly hot under normal conditions. A potential problem arises when the heaters are removed because the thermocouple gets pulled as well. Once they are no longer joined in the metallic head-AND -power gets applied, then we can have some hot fun as the temp controller tries to maintain temperature setpoint. If LOTO is followed, that shouldn't happen.

Our LOTO is well-enforced at the plant, leaving forgetfullness or dereliction as the only real opportunities for power to be applied when the heaters are pulled.

Then I would say that since you are switching to 3 wire heaters and you will have lockable disconnecting means then you could forgo the GFCI protection.

Yeah, that's what I was thinking and what prompted my original question.

I have access to many control panels that have 'ordinary' breakers mounted in them. Square D (and I'm sure others) have bases available specifically for mounting their QO breakers on backplates (QOMB-1, QOMB-2). With these bases, I see no reason you cannot use a GFCI breaker in your box.

I was looking at the wrong bases in response to this suggestion earlier. I see now that the ones you were referring to would actually fit in the new box.

 

[hurk27]

article 427 is about as close as you might find in requiring any ground fault type of protection, but these GFP's operate at 30+ma's, and are more for fire protection than for shock hazard, we used to call them class B type GFP's the only problem I can see is if the heaters are pulled and still energized, and the EGC is lost, there could be a shock hazard if one of the elements had gone to ground, which if a heater element goes to ground closest to the center of an element it wont always operate any over current devices, so having ground fault protection can be a plus, if a system of disconnect can be designed so that power has to be removed before removal of the heaters then there would be no problems, this can be done by short cord with twistlock receptacles, but other wise, maybe some one was shocked and that is why they went to using the GFCI's, there could be liability issues if so.

 

[CeCo3]

I decided to keep the GFI design. Found an A-B breaker that will suffice, was less expensive than the Square-D and a little smaller: 1492-MCGA215. Got them ordered just before the prices went up.

Anyhow, just thought I'd provide "closure." Thanks for all the help everyone.

CeCo3

 

[boboelectric]

Sounds to me like another "Safety Man" thinking too much!

 

[tom baker]

Does the NEC even apply to this?
Certainly the GFCI makes for a safe installation. Heat trace is allowed to use GFPE, which is a 30 or 50 mA trip to ground. That protection is for fires. But I do very short runs of heat trace with a GFCI as GFPE is a lot more expensive.