Sealtight Bonding Fittings

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BPoindexter

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C1D2 Group B,C,D have motors installed. We have an internal equipment ground that is pulled in with the circuit conductors. Rigid Aluminum Conduit all the way from the MCC to the motor where we have a short section of sealtight that connect to the motor. Had a debate over the use of the 'bonding' fittings with the external jumpers installed. If there is an internal ground pulled then do we need to also install the jumper and what does the NEC exactly mean by "Liquidtight flexible metal conduit with listed fittings."?

Are the listed fitting required to be listed for bonding per 250.100 (250.92)? Or are we just talking about the fittings being NRTL listed?
 

rbalex

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C1D2 Group B,C,D have motors installed. We have an internal equipment ground that is pulled in with the circuit conductors. Rigid Aluminum Conduit all the way from the MCC to the motor where we have a short section of seal tight that connect to the motor. Hada debate over the use of the 'bonding' fittings with the external jumpers installed. If there is an internal ground pulled then do we need to also install the jumper and what does the NEC exactly mean by "Liquidtight flexiblemetal conduit with listed fittings."?

Are the listed fitting required to be listed for bonding per 250.100 (250.92)?Or are we just talking about the fittings being NRTL listed?
Normally I don’t get too finicky about terms, but with grounding/bonding you can’t be too careful – even if I know what you mean. First, there is no such thing as a “ground” conductor of any kind; it is either a bonding, grounding or grounded conductor. The most common distinction is “grounded” conductors (usually neutrals) are intended to carry current under normal conditions; bonding and “grounding” conductors (usually equipment grounding conductors[EGC] or grounding electrode conductors [GEC]) are not. Of course, it doesn’t help that, usually, all of them are ultimately “grounded.”

There have been several unsuccessful attempts to rationalize these terms; usually by redefining equipment grounding conductors to some concept of equipment bonding conductors.

That said, "Liquidtight flexible metal conduit with listed fittings" simply means the fittings are NRTL listed and suitable for LFMC. It's already a requirement of Section 350.6. If listed, they will automatically be suitable for “bonding” in “ordinary” locations. (A UL term for “general purpose” in both indoor and outdoor applications). In “classified” locations the NEC has some additional requirements. If we assume the raceway system is the actual EGC, then a properly installed “grounding” conductor (or equipment bonding jumper [2011 NEC]) included in the raceway fulfills all the requirements of 501.30.

Personally, I believe Section 501.30 is gross overkill for Division 2. Although I agree “[t]he locknut-bushing and double-locknut …” alone is not appropriate when using raceway as the EGC in Division 2.
 

BPoindexter

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Thanks Bob- yep my bad for terminology... EGC is what I am talking about. So then listing is simply that and as long as the LFMC is not the sole fault path and has an internal EGC sized properly for for the OCPD we do not need the bonding jumper on the outside. What about where it connects to the motor- is a bonding type locknut/bushing per 250.94 required or is the "listed" fitting sufficent?
 

rbalex

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I?ll be citing the 2011 NEC.

We are actually dealing with two issues here. The ?easy? one is providing a low impedance ground-fault current path. Assuming the installation is otherwise compliant, with or without the internal EGC an all metal raceway system will do just fine.

The ?tough? issue is preventing possible arcing between sections of the interlocked metal tape of FMC or LFMC. In ?ordinary? locations it?s no big deal of course, assuming the overall installation is properly installed; but in a hazardous location? Well, a bonding jumper, either external or internal, won?t necessarily prevent arcing across the sections either.

Section 501.30 refers you to 250.102 which still permits either an internal or external equipment bonding jumper. Section 250.102(E) further refers you to 250.119 and 250.148 for internal conductors, which effectively turn them back into EGCs. They should be called equipment bonding conductors in that case. It seems every "clarification" by CMP5 muddies the issues even more.

In Division 2, again assuming the rest of the installation is compliant, a brief arc is no big deal since there isn?t supposed to be any volatiles to ignite anyway. (That?s why we have a Division 2) Otherwise, we should just make it Division 1 compliant and FMC/LFMC wouldn?t be acceptable in the first place (problem solved).

The wire connection at the motor needs to be compliant with Section 430.12(E).
 

BPoindexter

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To be honest i have spent very little time in the 2011. We are still using the 2008 but will be adopting the 2014 1Q of next year. So I am guessing the terminology will match that in the 2011 which means I have some required reading to do ;)
 
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GoldDigger

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To be honest i have spent very little time in the 2011. We are still using the 2008 but will be adopting the 2014 1Q of next year. So I am guessing the terminology will match that in the 2011 which means I have some required reading to do ;)
Lucky man! You will be going directly from the unclear language to the "re-clarified" "clarifications" without even noticing why folks were having trouble with 2011.
That means that you will have a totally fresh misunderstanding of those issues. :)
 

rbalex

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To be honest i have spent very little time in the 2011. We are still using the 2008 but will be adopting the 2014 1Q of next year. So I am guessing the terminology will match that in the 2011 which means I have some required reading to do ;)
The 2008 NEC will ultimately lead to the same conclusion with the Section 501.30 reference to 250.102.
 

BPoindexter

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OK perhaps I can ask my question a bit more clearly.

501.10(B)(2) allows LFMC with 'listed' fittings.

501.30(B) Refers to 250.102 but in any case does not allow the LFMC to be used as the EGC in the case where the ciruit OCPD is over 10A and it is a power utilization load.

501.30(A) States that "The locknut-bushing and double-locknut types of contacts shall not be depended on for bonding purposes, but bonding jumpers with proper fittings or other approved means of bonding shall be used. Such means of bonding shall apply to all intervening raceways, fittings, boxes, enclosures, and so forth..." and also refers you to 250.100.

250.100 States "...shall be ensured by any of the bonding methods specified in 250.92(B)(2) through (B)(4). One or more of these bonding methods shall be used whether or not equipment grounding conductors of the wire type are installed."

So from this information I have the understanding that LFMC in this case must have an internal EGC installed to the motor or have fittings listed with an external bonding jumper.

So my questions are:

If I have an internal EGC that is terminated in the motor terminal housing do I need an equipment bonding jumper for the fitting at the motor housing? In other words do I need to use a bonding type locknut or a bushing with a jumper to the motor per 250.92(B)(4)?

If an external jumper is used then is an EBJ inside the motor terminal housing required? I believe that we still have the issue of bonding the motor terminal housing to the LFMC in this case so the answer is yes?

So it appears (to me anyway) that the external jump is useless and serves no purpose if an internal EGC is installed because the fitting at the terminal housing still needs to be bonded to the terminal housing.

Am I reading this correctly?

Yep GoldDigger this is a convolution and then some.... :slaphead:
 

rbalex

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Despite many, many attempts to do otherwise:

90.1 (C) Intention. This Code is not intended as a design specification or an instruction manual for untrained persons. (Underline mine)

Basically that means you won?t necessarily find everything you want know in one place. In some cases, you may not find it at all ;)

I have already said I believe Section 501.30 is overkill for Class I, Division 2 except for the restrictions on locknut-bushing or double-locknut for bonding. Nevertheless, it says what it says.

In Classified locations, Section 500.8(E) requires threaded entries made up wrench tight to enclosures OR Section 501.30 requires bonding jumpers for non-threaded enclosures.

Excluding 501.30(B) Ex, threaded or not, FMC or LFMC must have a bonding jumper - internal or external . A properly installed internal one is effectively an EGC.
 

BPoindexter

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Excluding 501.30(B) Ex, threaded or not, FMC or LFMC must have a bonding jumper - internal or external . A properly installed internal one is effectively an EGC.

So if you have an external bonding jumper you still have a simple locknut connecting the LFMC fitting to the motor terminal housing. Would not you still have to have an EBJ from the fitting to the motor inside the terminal housing?
 

rbalex

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I'm doing this from an iPad, so bear with me.

With an FMC/LFMC external bonding jumper to a threaded enclosure, you'll probably need a union somewhere in addition. That would be sufficient. All NEMA/UL listed unions are both explosionproof and listed for grounding/bonding.

To an unthreaded enclosure you would need a grounding bushing inside the motor JB with a bonding jumper installed per Section 430.12(E).
 
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