Bonding Jumper Size

[yfz450rr]

I'm running a 4/0 ground to building steel in a 1 1/4 EMT conduit. There is an expansion joint where I will transition to steel flex then back to EMT. The details show a bonding jumper across the expansion joint and the flex. Is that bonding jumper across the expansion joint required to be a 4/0? or can I use a #6.

What about communication conduit? What size bonding jumper would I be required to use?

 

[Dennis Alwon]

I believe you will need a 4/0 bonding jumper. I am not sure you will need a jumper for the communication conduit. Let's see what the others say

 

[petersonra]

I'm running a 4/0 ground to building steel in a 1 1/4 EMT conduit. There is an expansion joint where I will transition to steel flex then back to EMT. The details show a bonding jumper across the expansion joint and the flex. Is that bonding jumper across the expansion joint required to be a 4/0? or can I use a #6.

What about communication conduit? What size bonding jumper would I be required to use?

take a close look at 250.64(E).

As long as the flex is "electrically continuous", I am not sure there is a requirement to bond it at all.

Presumably using flex with the wire woven through the armor would make it "electrically continuous".

If not "electrically continuous", it appears to me you need a 4/0 jumper.

are conduits for communications circuits even required to be bonded to anything?

 

[augie47]

I can't anything specific to GEC & flex, but since 250.118 limits then grounding capability of a 20 amp circuit it seems logical that one would need to bond across it.... not that logic and the NEC are hand-in-hand.

 

[yfz450rr]

take a close look at 250.64(E).

As long as the flex is "electrically continuous", I am not sure there is a requirement to bond it at all.

Presumably using flex with the wire woven through the armor would make it "electrically continuous".

If not "electrically continuous", it appears to me you need a 4/0 jumper.

are conduits for communications circuits even required to be bonded to anything?

I am required to bond the communication conduits at both ends with a ground bushings to the cable tray or the grounding bus bar in the IT room, by the specifications. I was just wondering if the size of the bonding jumper would be the same if I bond a 1 inch conduit or a 4 inch conduit. #6 is minimum according to the detail.

 

[Dennis Alwon]

I believe the bond for the conduit at the ends only needs to be sized based on the overcurrent protective device. Table 250.122 Not sure what you would do with communication cable.. I would assume #12 but that is a guess.

 

[Dennis Alwon]

Here is something from art 800

800.100(A) Bonding Conductor or Grounding Electrode Conductor.
(1) Insulation. The bonding conductor or grounding electrode
conductor shall be listed and shall be permitted to be
insulated, covered, or bare.
(2) Material. The bonding conductor or grounding electrode
conductor shall be copper or other corrosion-resistant
conductive material, stranded or solid.
(3) Size. The bonding conductor or grounding electrode
conductor shall not be smaller than 14 AWG. It shall have a
current-carrying capacity not less than the grounded metallic
sheath member(s) and protected conductor(s) of the communications
cable. The bonding conductor or grounding electrode
conductor shall not be required to exceed 6 AWG.

 

[Canton]

I'm running a 4/0 ground to building steel in a 1 1/4 EMT conduit. There is an expansion joint where I will transition to steel flex then back to EMT. The details show a bonding jumper across the expansion joint and the flex. Is that bonding jumper across the expansion joint required to be a 4/0? or can I use a #6.

What about communication conduit? What size bonding jumper would I be required to use?

EMT to FMC to EMT, all being metallic I cannot find anything in the code "requiring" a bonding jumper. As Augie pointed out, it is true FMC can only be used as an EGC for circuits up to 20 amps with some restrictions. That being said you can see the weak link for your GEC.

But...if a bonding jumper is used, it must be properly sized...so your #6 bonding jumper on your spec detail would be a code violation and should be the same size as your 4/0 GEC in the pipe.

 

[Smart $]

EMT to FMC to EMT, all being metallic I cannot find anything in the code "requiring" a bonding jumper. As Augie pointed out, it is true FMC can only be used as an EGC for circuits up to 20 amps with some restrictions. That being said you can see the weak link for your GEC.

Yet this is not an EGC application nor is the GEC a circuit conductor.

AFAICT there is no requirement for a bonding jumper around the FMC. It is essentially no different than a GEC junction box at both EMT-FMC transitions... which wouldn't require a bonding jumper (though the GEC would be required to be bonded to each junction box). You could actually run FMC the entire distance and it would only require bonding to the GEC where not connected to an enclosure. The purpose of bonding is to prevent a choke effect during a lightning strike with high frequency surge current through the GEC.

But...if a bonding jumper is used, it must be properly sized...so your #6 bonding jumper on your spec detail would be a code violation and should be the same size as your 4/0 GEC in the pipe.

FWIW, the detail doesn't spec a #6... just #6 as the minimum.

 

[Canton]

Yet this is not an EGC application nor is the GEC a circuit conductor.

AFAICT there is no requirement for a bonding jumper around the FMC. It is essentially no different than a GEC junction box at both EMT-FMC transitions... which wouldn't require a bonding jumper (though the GEC would be required to be bonded to each junction box). You could actually run FMC the entire distance and it would only require bonding to the GEC where not connected to an enclosure. The purpose of bonding is to prevent a choke effect during a lightning strike with high frequency surge current through the GEC.



FWIW, the detail doesn't spec a #6... just #6 as the minimum.

In my opinion the minimum of the bonding jumper would be the same size as the GEC....or 4/0 as the OP stated.

 

[Smart $]

In my opinion the minimum of the bonding jumper would be the same size as the GEC....or 4/0 as the OP stated.

With the bonding jumper spec'd, I agree.

 

[yfz450rr]

Thanks guys.