Sizing bonding jumpers for myer hubs.

[Dsg319]

I seen a post relating to this I thought, but I can’t find it. So I’m going to ask anyways.
How does one properly size bonding jumpers, say from myer hubs to the rest of the panel case. In my company I’ve always just seen #10 or #12 used, probably because it’s small easy to work with and convenient.
But how does one properly size the conducter to be used say if you had a distribution panel with, #2 feeder and other smaller branch circuits.
If I am correct I know that if Under 250volts you don’t have to worry about it, but most the gas company’s we work for spec out for everything to be continues and bonded regardless of voltage.

 

[Dennis Alwon]

Bonding jumpers are sized by Table 250.102(C)(1)

 

[Dsg319]

Thank you!

 

[Dsg319]

Bonding jumpers are sized by Table 250.102(C)(1)

But what if you daisy chain all the myer hubs together, with different sized conductors. Do you just go with the largest or is there a way to calculate it to an average?

 

[Dennis Alwon]

I am not sure what you have there. Are these service raceways or just feeders and branch circuit raceways?

 

[augie47]

Please note 250.102(C) is for service and supply side bonding jumpers and 250.122 is for feeder and branch circuit bonding jumpers.
If you have multiple hubs and are bonding on the load side of overcurrent devoces you can use one jumper sized to the largest device. See 250.102(D)

 

[Dsg319]

I am not sure what you have there. Are these service raceways or just feeders and branch circuit raceways?

Just feeders and branch.

I’ll build a senerio . 100amp distribution panel with 1.5in rigid conduit entering with #2 feeders. Than 3, 1” conduits leaving with 20amp branch circuits. If I were to daisy chain all the hubs I’d only have to take the larger bonding jumper to the 1.5” myerhub and after that reduce down to what I would need for the 20 amp branch circuits right?

 

[Dennis Alwon]

So why are you bonding them. I assume you are using metal conduit??? Do you have an equipment grounding conductor run in the conduits also?

As Gus stated for feeders and branch circuits you would use T 250.122

 

[Dsg319]

Yes we have rigid conduit, and EGC but the gas company specs out for grounding type myer hubs to be bonded. However I’ve never known there to be a specific size conducter for them. I know what we’re doing is basically for looks and to please the customer.

 

[Dennis Alwon]

I would use T 250.122 for bonding the raceways based on the largest conductor in any of the raceways - that is assuming you are bonding them as a continuous run.

 

[Dsg319]

For example in this photo it is not yet done. The largest EGC in the box is a number 8. So if I was I daisy change all the hubs would I have to use #8 on them all, even the conduit hubs with a smaller EGC, or just to that specific conduit it comes from?

 

[Dsg319]

Stole this pic off the web. Obviously I don’t know Conductor sizes but can tell the bonding conductor is significantly smaller.

 

[kwired]

Stole this pic off the web. Obviously I don’t know Conductor sizes but can tell the bonding conductor is significantly smaller.

Seems to be pretty good chance that jumper is not large enough.

If those raceways contain parallel sets, even more likely.

Add: 99.99% of the time would need to be size of the green pulled in the raceway.

 

[infinity]

Stole this pic off the web. Obviously I don’t know Conductor sizes but can tell the bonding conductor is significantly smaller.

I agree with Kwired that bonding jumper is not sized properly. At the minimum it should be the same size as the EGC.

 

[Dsg319]

Seems to be pretty good chance that jumper is not large enough.

If those raceways contain parallel sets, even more likely.

Add: 99.99% of the time would need to be size of the green pulled in the raceway.

That’s what I was under the impression of.

 

[Dsg319]

Thanks everyone.

 

[Dennis Alwon]

The green bonding conductor in the pic doesn't even look as large as the egc in the conduit. Anyway the OP is not talking parallel runs so the bond can be sized based on T250.122 based on 250.102 (D) as Gus stated

 

[Carultch]

Please note 250.102(C) is for service and supply side bonding jumpers and 250.122 is for feeder and branch circuit bonding jumpers.
If you have multiple hubs and are bonding on the load side of overcurrent devoces you can use one jumper sized to the largest device. See 250.102(D)

What happens when the size specified in either 250.102(C) or 250.122, which ever is applicable, is too large to fit in the bonding bushing lug?

I could see this as a likely situation, when you have a large quantity of parallel sets.

 

[infinity]

The green bonding conductor in the pic doesn't even look as large as the egc in the conduit. Anyway the OP is not talking parallel runs so the bond can be sized based on T250.122 based on 250.102 (D) as Gus stated

Dennis, why would parallel conductors change anything? Wouldn't the EGC in each raceway need to be "full size" anyway?

What happens when the size specified in either 250.102(C) or 250.122, which ever is applicable, is too large to fit in the bonding bushing lug?

I could see this as a likely situation, when you have a large quantity of parallel sets.

You change the lug, done all of the time because they never seem to be large enough.

 

[Carultch]

You change the lug, done all of the time because they never seem to be large enough.

What if it is beyond the capabilities of lugs that can be mounted by the bonding bushing screws? I could see this happening if a 500 kcmil EGC is prescribed.