Jumper to the box

[jap]

If upsizing wire for voltage drop say from #12 to #10 for a 20 amp circuit, yet using the conduit as the EGC, then does the ground jumper to the box at the device locations also have to be upsized to #10?

Jap>

 

[Dennis Alwon]

Imo, a #12 would suffice but I am not sure the code addresses that except for this in the 2020 NEC

Exception:
Equipment grounding conductors shall be permitted to be sized by a qualified person to provide an effective ground fault current path in accordance with 250.4(A)(5) or (B)(4).

So the question becomes "Are you qualified"? haha

 

[jap]

I guess it would depend on whether you consider the jumper to be from the box to the device, or, from the device to the box.

I'm going for it with the #12.

Jap>

 

[infinity]

The exception that Dennis posted says EGC's not bonding jumpers. Since the EGC is the raceway there is no reason why a #12 bonding jumper on a 20 amp circuit would not be large enough to clear a fault.

 

[jap]

The exception that Dennis posted says EGC's not bonding jumpers. Since the EGC is the raceway there is no reason why a #12 bonding jumper on a 20 amp circuit would not be large enough to clear a fault.

Well put as usual.

Thanks,

Jap.

 

[Jim_SWFL]

The #12 bonding jumper would not prevent clearing the fault.

On a similar but longer circuit, where you had to go to #8 or #6, couldn't you splice back to #12 before terminating at the end device, if for instance the end device couldn't not accept a #8 or #6 wire? This arrangement would also be adequate to clear a fault.

 

[jap]

The #12 bonding jumper would not prevent clearing the fault.

On a similar but longer circuit, where you had to go to #8 or #6, couldn't you splice back to #12 before terminating at the end device, if for instance the end device couldn't not accept a #8 or #6 wire? This arrangement would also be adequate to clear a fault.

When you upsize the wire for voltage drop you also upsize the EGC proportionally when pulling a wire type EGC.

That is if you're pulling one.

In the case of using the conduit as the EGC, I see no limit as to the amperage of the circuit or feeder that the conduit will service as far as being the EGC for that circuit or feeder.

At the point of termination, when using the conduit as the EGC, since we don't have a wire type EGC, it then falls back to the size of the "bonding jumper" to insure a properly sized ground fault return path from the device, back to the conduit.

Sometimes I just need to hear from others where they feel that transitional point in size actually is to see if they see it the same way I do.

Jap>

 

[LarryFine]

If upsizing wire for voltage drop say from #12 to #10 for a 20 amp circuit, yet using the conduit as the EGC, then does the ground jumper to the box at the device locations also have to be upsized to #10?

I'd say the jumper only needs to be sized to suit the device.

 

[jap]

In this instance it's a 120v back lit sign circuit left in a j-box for the sign guys.

Which triggered my thinking of the size of the stinger.

I'm almost sure they wont go out of their way bond the EGC in their MC Cable to the box.

Maybe though.

Jap>

 

[Jim_SWFL]

In the case of using the conduit as the EGC, I see no limit as to the amperage of the circuit or feeder that the conduit will service as far as being the EGC for that circuit or feeder.

In the end, we agree.

But there are limits. In your case, if you are only going up one wire size, I doubt you are approaching the limit.

For reference, see table 22.10 in Soares Grounding and Bonding.

 

[jap]

In the end, we agree.

But there are limits. In your case, if you are only going up one wire size, I doubt you are approaching the limit.

For reference, see table 22.10 in Soares Grounding and Bonding.

In what scenario would a completed run of EMT or rigid of any size not be sufficient to be used as an EGC ?

Jap>

 

[Jim_SWFL]

In what scenario would a completed run of EMT or rigid of any size not be sufficient to be used as an EGC ?

For 1/2" EMT, 246 feet if you want to open a 20A breaker at 500% or 100A. Not sure if that length accounts for fittings, etc.

https://www.nema.org/docs/default-source/technical-document-library/steel-conduit-and-emt-proven-to-meet-the-nec-reg.pdf

 

[jap]

That's an interesting read.

Jap>

 

[Tulsa Electrician]

If you have an 2020.
Give 250.109 a read(new).