10s and 12s

[don_resqcapt19]

If it was oversized for a motor, then the 12 g is OK

250.122 d

That section only says that you don't have to size the EGC for motor circuits to the rating of the branch circuit ground fault and short circuit protective device if that device is an instantaneous trip circuit breaker or a motor short-circuit protector. If that is the case then you can size the EGC based on the rating of the motor overload device. If the branch circuit OCPD is a fuse, or thermal magnetic breaker, then the EGC must be sized based on the rating of the branch circuit OCPD.
Don

 

[dezwitinc]

They were strictly convenience outlets.
Three 15 amp duplex on the circuit.

 

[chris kennedy]

20 amp circuits fed with #10 hot and #10 neutral with a #12 ground.
This installation was obviously done this way because the installer did not have any or enough #12 on hand.

There are no exceptions to 250.122(B) for what the installer had on the truck.

I've seen this done, and have never seen anybody get busted for it.

 

[don_resqcapt19]

There are no exceptions to 250.122(B) for what the installer had on the truck.

Actually that type of excuse was the reason the words "for voltage drop" were removed from the code. There was no way for the inspector to prove the reason that an oversized conductor was used.
Don

 

[iwire]

I have the answer but its based on something non-enforcable.

Get over it already.....

That book is good one to have but it's answers are no more or less accurate then you can find here, at the job, in other books.

 

[iwire]

have never seen anybody get busted for it.

Come on up here, I have had inspectors give me a heads up ahead of time that they expect compliance with 250.122(B).

For site lighting this can be a big deal, run 4 AWG to compensate for voltage drop (or any reason) on a 20 or 30 amp circuit and you had better have pulled a 4 AWG EGC along with it.

 

[iwire]

number 12Ga grounding conductor is all that is required for a 20A protected circuit period.

That is false.

With 15, 20 and 30 amp circuits the size ratio of the circuit conductors to the EGC is 1 to 1.

250.122(B) requires we maintain the ratio when increasing the circuit conductor size.

Run 6 AWG for the circuit conductors and the EGC will have to be 6 AWG as well if supplied by a 15, 20 or 30 amp circuit.

 

[kbsparky]

... Run 6 AWG for the circuit conductors and the EGC will have to be 6 AWG as well if supplied by a 15, 20 or 30 amp circuit.

But install that same #6 AWG wire on a 60 Amp breaker, and all you need is a #10 EGC.

What is wrong with this picture?

 

[Dennis Alwon]

But install that same #6 AWG wire on a 60 Amp breaker, and all you need is a #10 EGC.

What is wrong with this picture?

Here is a response I made on a similar thread months ago.

An Interesting Paradox When​

Upsizing The EGC​

I want to feed a sub panel that will have a calculated load of 55 amps. I will be using conduit with THHN wire. Table 310.16 says that for 55 amps at 75C I could use #6 copper and I could fuse it at 70 amps (if I wanted to).

Table 250.122 states the minimum size EGC would be #8 but because of VD I have decided to upsize my wire let's say to #3 copper (which has an ampacity of 100 amps). Now I have to upsize my EGC proportionally. Article 250.122(B).


Conductor Ratio
Chapter 9 Table 8
#6 is 26240 cir mil
#3 is 52620 cir. Mil

52620/26240= 2 times greater


EGC Ratio
Chapter 9 Table 8
#8= 16510
16510*2= 33020 cir. Mils

Thus I would need a #4 EGC


If, instead, I decide to fuse the sub panel at 100 amps instead of the 70 amp breaker, I can keep my #8 EGC.

This seems odd to me. Why does keeping the 70 amp breaker size change the scenario then if I change the breaker to 100 amps? Remember both breaker sizes are within the limits of Table 250.122 for the #8 EGC.

 

[ptonsparky]

Less than 15 amp load at 3000' if I use 2-2-2-4 it is a violation when protected at source by 15 amp fuse. Put a in 60 amp fuse and I am good to go. Doesn't make sense

 

[infinity]

Less than 15 amp load at 3000' if I use 2-2-2-4 it is a violation when protected at source by 15 amp fuse. Put a in 60 amp fuse and I am good to go. Doesn't make sense

Making sense or not the requirement is there in black and white. It's funny that the NEC doesn't require us to do anything about voltage drop but requires the EGC to be up sized. I could have a circuit with 3-#12 conductors and 100 volts at the end and be compliant with a #12 EGC. The fact that I only have 100 volts is OK. Doesn't make much sense.

 

[e57]

Situation:
Circuit breakers are 20 amp.
20 amp circuits fed with #10 hot and #10 neutral with a #12 ground.
This installation was obviously done this way because the installer did not have any or enough #12 on hand.
It is a short circuit (less than 75') so voltage drop was not a consideration.
Is this a violation because the ground was not increased proportionately to the circuit conductors?

Re-pull the 10's with 12's if in conduit - If in metallic conduit your #12 EGC is superfluous - yank out the EGC too while you still can use metallic conduit as the ground. Apparently you won't be able to in 2008????? Are they killing 250.118 by advise from the copper industry?

 

[peter d]

The fact that I only have 100 volts is OK. Doesn't make much sense.

I think it does make sense. Voltage drop does not really fall under practical safeguarding in 90.1(A).

Without any fires or a body count, mandating limiting VD won't get elevated to code rule status.

 

[JohnJ0906]

yank out the EGC too while you still can use metallic conduit as the ground. Apparently you won't be able to in 2008????? Are they killing 250.118 by advise from the copper industry?

The only change I see in 250.118 ('08) is listed fittings required for FMC,LFMC, and FMT

 

[infinity]

I think it does make sense. Voltage drop does not really fall under practical safeguarding in 90.1(A).

Without any fires or a body count, mandating limiting VD won't get elevated to code rule status.

I agree and prefer to keep VD limited to a FPN. My point was that if you don't increase any of the branch circuit conductors you can keep the EGC possibly smaller than necessary to open the OCPD.

 

[danickstr]

The code has obvious errors as pointed out by this EGC mismatch WRT oversized wires and panel EGC requirements.

What is the problem with an EGC encountering "voltage drop" as it safely carries the tiny curent load it was designed for?

I really don't see a one wire size increase to allow for voltage drop as being a reason to increase EGC size, and might wait and see if the inspector wants it changed if it is already in place.

 

[Cow]

If he were to remove the ground and use the metallic(?) conduit as an EGC all would be well. Seems like you're taking a step backwards though, common sense says to leave it.

 

[Pierre C Belarge]

The code has obvious errors as pointed out by this EGC mismatch WRT oversized wires and panel EGC requirements.

What is the problem with an EGC encountering "voltage drop" as it safely carries the tiny curent load it was designed for?

I really don't see a one wire size increase to allow for voltage drop as being a reason to increase EGC size, and might wait and see if the inspector wants it changed if it is already in place.

What is the "tiny current load it was designed for" mean in regards to how you have made in your statement here.
If you have a ground fault with an effective ground fault current path with lets say a 20 amp circuit, how much current is it possible for the 12 AWG EGC to carry? Lets also assume this circuit is directly off the service panel.

Also, take a look at the note after Table 250.122 and while you are at it, take a look at the title to the same table.

 

[electricguy61]

What is the "tiny current load it was designed for" mean in regards to how you have made in your statement here.
If you have a ground fault with an effective ground fault current path with lets say a 20 amp circuit, how much current is it possible for the 12 AWG EGC to carry? Lets also assume this circuit is directly off the service panel.

Also, take a look at the note after Table 250.122 and while you are at it, take a look at the title to the same table.

Pierre:

Do you agree that #12 is all that is required for a circuit protected at 20amps? That's the way I read 250.122

 

[Pierre C Belarge]

Guy61
Yes, I do agree as per 250.122 that a 12 AWG EGC is what is required for a 20 amp circuit that is supplied with a 12 AWG phase conductor.

code does not require the increase in size of phase conductors for voltage drop, that is a design issue.
If an installer should install a long run for a 70 amp circuit, supplied by 6 AWG, and does not upsize the conductors, also installing an 8 AWG EGC, there is a possibility that the impedance of the ground fault current path could be such as to impede the opening of the overcurrent device or at least increase the time it would take for the OCPD to open.