EGC Sizing

[Therealcrt]

20 amp circuit 120 V it’s roughly 350 to 400 feet from the panel. I’m upsizing the hots to number 4 copper to accommodate Voltage Drop I know I need to upsize my equipment grounding conductor as well. Do I first see what number 4 copper amps city is rated for then go back to table 250.122 and adjust equipment grounding conductor based off of that amperage.? Which would be 85 A for number4 and the minimum size equipment grounding conductor would be number 8 copper?

 

[infinity]

No. A 20 amp circuit typcially requires #12 ungrounded conductors and 12 EGC. The ratio between those two is 1 to 1. Your upsized conductors would need to maintain the same ratio so #4 ungrounded means #4 EGC.

 

[wwhitney]

No, for a 20A circuit, EGC size = ungrounded size (usually both #12), and that is the relationship that is to be respected when you upsize the ungrounded conductor. So with #4 Cu ungrounded you need #4 copper EGC.

Cheers, Wayne

 

[Therealcrt]

No. A 20 amp circuit typcially requires #12 ungrounded conductors and 12 EGC. The ratio between those two is 1 to 1. Your upsized conductors would need to maintain the same ratio so #4 ungrounded means #4 EGC.

Where is the evidence that backs that up? EGC is based on OCPD right? 20a #12 sure but what if it was a 30am circuit or a 40a circuit where #12 is also permitted as the EGC? The Hots would be naturally larger in those situations so the ratio wouldn’t be 1:1 so why would it be 1:1 on a 20a circuit when upsizing conductors due to VD

 

[Therealcrt]

Not arguing just curious I want to know the fact

 

[Elect117]

250.122(B)

They are both correct.

 

[ggunn]

I will add one thing: if the EGC is already larger than it needs to be, the existing wire isn't the starting point for upsizing. You start with the minimum size EGC from table 250.122 and proportionately upsize from there at the same ratio as the CCC upsizing.

 

[Therealcrt]

I will add one thing: if the EGC is already larger than it needs to be, the existing wire isn't the starting point for upsizing. You start with the minimum size EGC from table 250.122 and proportionately upsize from there at the same ratio as the CCC upsizing.

What do you mean if the EGC is already larger than it needs to be?

 

[infinity]

Where is the evidence that backs that up? EGC is based on OCPD right? 20a #12 sure but what if it was a 30am circuit or a 40a circuit where #12 is also permitted as the EGC?

#12 is not permitted as the EGC on 30 or 40 amp circuits. You need to take a look at Table 250.122 and the words not exceeding. As mentioned by others 250.122(B) will give you the information regarding proportional increase in size.

 

[winnie]

There is a bit of a loophole/inconsistency in the rule for increasing the size of the EGC.

If you increase the size of the circuit conductors then you are required to increase the EGC by the same proportional cross section. For a 20A circuit, the calculation is easy because the EGC is the same size as the circuit conductors.
250.122(B) Increased in Size. If ungrounded conductors are increased in size for any reason other than as required in 310.15(B) or 310.15(C), wire-type equipment grounding conductors, if installed, shall be increased in size proportionately to the increase in circular mil area of the ungrounded conductors.

The loophole is that voltage drop is a design issue, not a code requirement. You could install larger conductors and a larger circuit breaker that matches the conductors, and then use the normal size egc associated with that circuit breaker. This might trigger other requirements, not going into depth.

Jonathan

 

[don_resqcapt19]

There is a bit of a loophole/inconsistency in the rule for increasing the size of the EGC.

If you increase the size of the circuit conductors then you are required to increase the EGC by the same proportional cross section. For a 20A circuit, the calculation is easy because the EGC is the same size as the circuit conductors.
250.122(B) Increased in Size. If ungrounded conductors are increased in size for any reason other than as required in 310.15(B) or 310.15(C), wire-type equipment grounding conductors, if installed, shall be increased in size proportionately to the increase in circular mil area of the ungrounded conductors.

The loophole is that voltage drop is a design issue, not a code requirement. You could install larger conductors and a larger circuit breaker that matches the conductors, and then use the normal size egc associated with that circuit breaker. This might trigger other requirements, not going into depth.

Jonathan

What code language would permit that?

 

[wwhitney]

What code language would permit that?

Winnie means "install larger conductors than typical for your required circuit size, due to voltage drop concerns," then "install a larger circuit breaker than required for your circuit, but matching the installed conductor size," and then "install the normal size EGC associated with that circuit breaker." Typically you'd need an additional OCPD near the load to provide the proper size circuit at the load.

E.g. in the OP, you could use a 20A breaker, #4 ungrounded, and #4 EGC. Or you could use a 70A breaker, #4 ungrounded, and #8 EGC, along with a 20A breaker near the load. If the extra breaker is not otherwise needed, probably more trouble than it is worth just to downsize the EGC from #4 to #8.

Cheers, Wayne

 

[don_resqcapt19]

Winnie means "install larger conductors than typical for your required circuit size, due to voltage drop concerns," then "install a larger circuit breaker than required for your circuit, but matching the installed conductor size," and then "install the normal size EGC associated with that circuit breaker." Typically you'd need an additional OCPD near the load to provide the proper size circuit at the load.

E.g. in the OP, you could use a 20A breaker, #4 ungrounded, and #4 EGC. Or you could use a 70A breaker, #4 ungrounded, and #8 EGC, along with a 20A breaker near the load. If the extra breaker is not otherwise needed, probably more trouble than it is worth just to downsize the EGC from #4 to #8.

Cheers, Wayne

missed that

 

[Eddie702]

I thought the EGC was sized base on the breaker size feeding the circuit? We were always told the rating of the circuit is based on the breaker or fuse size...not on the wire size so If the conductor is upsized for whatever reason the egc remains based on the breaker size.

If I am wrong tell me. #14 is a #14 egs, #12 is 12, #10 is good to up to 60 amps

 

[infinity]

I thought the EGC was sized base on the breaker size feeding the circuit? We were always told the rating of the circuit is based on the breaker or fuse size...not on the wire size so If the conductor is upsized for whatever reason the egc remains based on the breaker size.

If I am wrong tell me. #14 is a #14 egs, #12 is 12, #10 is good to up to 60 amps

Look at 250.122(B). Increased in size means that they have a proportional increase in the EGC. From your post:

"#14 is a #14 egs, #12 is 12". The ratio is 1 to 1.

 

[ggunn]

What do you mean if the EGC is already larger than it needs to be?

Sometimes for whatever reason someone will run a larger EGC than the minimum. In that case if you upsize the CCCs and need an upsized EGC to go with it, you calculate the new EGC size starting at the minimum, not whatever it happens to already be.

 

[solarken]

20 amp circuit 120 V it’s roughly 350 to 400 feet from the panel. I’m upsizing the hots to number 4 copper to accommodate Voltage Drop I know I need to upsize my equipment grounding conductor as well. Do I first see what number 4 copper amps city is rated for then go back to table 250.122 and adjust equipment grounding conductor based off of that amperage.? Which would be 85 A for number4 and the minimum size equipment grounding conductor would be number 8 copper?

Is the conduit run in a building or buried? If in a building, can you use THHN in EMT? Then make the EMT be the EGC, and just go with L1 and N at 4AWG and no wire-type EGC. Use the $1.13 or so per foot of avoided cost of the 4AWG EGC toward the conduit cost. Alternatively, if your utility typical line voltage generally runs above 120V, go with 6AWG (x3) and live with the 5% voltage drop at 15A, knowing it will not likely be an issue.