bonding jumper/liquid tight fmc

[brother]

Just wanted to hear from others on this issue. There is liquid tight flex metal conduit ran on both ends of rigid metal conduit. The flex goes to the box. There is a ground pulled inside the conduit, However i believed it was required to run a 'bonding jumper (ground wire)' on the outside of the pipe (where the flex meets the rmc) to the j box following along the ltfmc because the ground continuity cannot be maintain with just the flex because flexibility is required even under the 6ft.

Another says no, so long as there is one ran on the inside, Searching code, but havent found it yet. What say you all experts?? Just seems to me that the sections in the middle (rmc) doesnt have the continuity to me.

 

[resistance]

I don't know I f fully understand the question, but i believe you are referring to NEC 250.102(E).

 

[brother]

I don't know I f fully understand the question, but i believe you are referring to NEC 250.102(E).

ok, basically, there is 20ft of rigid metal pipe in the center and theres ltfmc on both ends that go to j boxes. isnt there suppose to be a b-jumber from on the ends of the rmc from the rmc to the j box??

I hope i made this clear enuff, im not good at putting up pics online.

 

[resistance]

ok, basically, there is 20ft of rigid metal pipe in the center and theres ltfmc on both ends that go to j boxes. isnt there suppose to be a b-jumber from on the ends of the rmc from the rmc to the j box??

I hope i made this clear enuff, im not good at putting up pics online.

I shouldn't be on here seeing that I'm half sleep!!!
Ok, see 350.60, then 250.118

 

[iwire]

ok, basically, there is 20ft of rigid metal pipe in the center and theres ltfmc on both ends that go to j boxes. isnt there suppose to be a b-jumber from on the ends of the rmc from the rmc to the j box??

It depends.

Do either of the sections of LFMC qualify as an EGC per 250.118? The ampacity of the circuit and the length of the LFMC both have an impact here.

Is there an wire EGC in the raceway from one enclosure to the other?

 

[brother]

It depends.

Do either of the sections of LFMC qualify as an EGC per 250.118? The ampacity of the circuit and the length of the LFMC both have an impact here.

Is there an wire EGC in the raceway from one enclosure to the other?

It does NOT meet the requirements of 250.118, and yes there is an egc installed in the raceway. but i still think it needs one on the outside.

 

[M. D.]

Let me see if i'm following .. Are you saying that should an ungrounded conductor , come in contact with interior metal of the flex,.. or conduit the flex will not be able to handel the fault current imposed???

 

[wwhitney]

Let me see if i'm following .. Are you saying that should an ungrounded conductor , come in contact with interior metal of the flex,.. or conduit the flex will not be able to handel the fault current imposed???

I think the concern is that the rigid conduit has flex at both ends, and if the flex isn't rated as an EGC, does he need a jumper to bond the rigid conduit?

Cheers, Wayne

 

[resistance]

If you have an EGC installed in the conduit (complete-- from box to box), then no EGC is needed outside the conduit.


Just a side note:
I believe the articles I listed above addressed some of what you seem to be asking.

 

[Dexie123]

It does NOT meet the requirements of 250.118, and yes there is an egc installed in the raceway. but i still think it needs one on the outside.

I'm not sure why you'd need another way of bonding the LMC. If it's got a egc that is bonded to the box(es) that it's being taken to, why would you need another?

 

[brother]

I think the concern is that the rigid conduit has flex at both ends, and if the flex isn't rated as an EGC, does he need a jumper to bond the rigid conduit?

Cheers, Wayne

that is correct, even though i believe it would in reality clear the fault (the flex atached to rigid is tight) i do not believe its code. I believe a jumper is needed from the rigid conduit to the box, cause there is flex at both ends.

At least thats how i read the code sections.

 

[M. D.]

I'm not sure why you'd need another way of bonding the LMC. If it's got a egc that is bonded to the box(es) that it's being taken to, why would you need another?

I would say 250.90,..If the flex is not capable of handling the fault current likely to be imposed.

 

[resistance]

Well doesn't this take us back to 250.102E

 

[M. D.]

Not sure ,..how about 250.96 (A)

 

[resistance]

It does NOT meet the requirements of 250.118, and yes there is an egc installed in the raceway. but i still think it needs one on the outside.

and you are correct--if it doesn't meet 250.118, and based on what I read from the last articles I posted (250.118 being one).

 

[M. D.]

Another location that supports the idea is 250.4(A) 3/4/5/

 

[iwire]

It does NOT meet the requirements of 250.118, and yes there is an egc installed in the raceway. but i still think it needs one on the outside.

I believe we agree.

If neither section of LFMC qualifies as an EGC you have to find a way to ground the section of conduit in the middle.

IMO the best way to deal with this is to use a box to change from the LFMC and the other raceway.

 

[Flex]

would a bonding bushing in the box at each end do the trick?

 

[resistance]

would a bonding bushing in the box at each end do the trick?

Nope! **Read Brother's set-up in earlier post

 

[M. D.]

And what if the fault occurrs in the flex??? I guess that is not "likely"