lighting circuit

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eager2learn

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Mennifee,Ca
situation = 1 circuit - 3/4" p.v.c. conduit - length of circuit is 625' from breaker to end of line fixture - hot is #8 awg, neutral is #8 awg

question = would a #10 awg ground be suitable for this type of installation under these circumstances
 
JT,

So the wire size was increased for voltage drop, per 250.122 any increase in the circuit

conductors must be done in the EGC.

So you would need #8 for the EGC.
 
benaround said:
JT,

So the wire size was increased for voltage drop, per 250.122 any increase in the circuitconductors must be done in the EGC.

So you would need #8 for the EGC.
Click to expand...

Can you show your work to prove a #10 will not suffice?
 
celtic said:
Can you show your work to prove a #10 will not suffice?
Click to expand...
No need to show any work...the code rule in 250.122(B) requires that the EGC be at least the same size as the ungrounded conductors for circuits protected at 30 amps or less.
(B) Increased in Size. Where ungrounded conductors are increased in size, equipment grounding conductors, where installed, shall be increased in size proportionately according to the circular mil area of the ungrounded conductors.
Click to expand...
 
celtic said:
Can you show your work to prove a #10 will not suffice?
Click to expand...

The math is simply for wire sizes #14, 12, & 10. If you must increase the size of the ungrounded conductors then the egc must also be upsized proportionately. This means that any of the EGC sizes mentioned above will increase to the size of the ungrounded upsize.

This does not hold true for other sizes.

George did a nice explanation here
 
Dennis Alwon said:
The math is simply for wire sizes #14, 12, & 10. If you must increase the size of the ungrounded conductors then the egc must also be upsized proportionately. This means that any of the EGC sizes mentioned above will increase to the size of the ungrounded upsize.

QUOTE]

Dennis,

I have to disagree, if you have a 15,20, or 30 amp OCPD no matter what size wire is used

must be increased. Example; #4 on a 20a c.b. the EGC would need to be #4. Do you feel

this is incorrect ?
Click to expand...
 
benaround said:
Dennis Alwon said:
The math is simply for wire sizes #14, 12, & 10. If you must increase the size of the ungrounded conductors then the egc must also be upsized proportionately. This means that any of the EGC sizes mentioned above will increase to the size of the ungrounded upsize.

QUOTE]

Dennis,

I have to disagree, if you have a 15,20, or 30 amp OCPD no matter what size wire is used

must be increased. Example; #4 on a 20a c.b. the EGC would need to be #4. Do you feel

this is incorrect ?
Click to expand...

Yes I agree that if the ungrounded conductors are increased in size that the egc must be increased. My point is that for wire sizes #14-10 they will increase to the size of the increased ungrounded conductor. This is not true necessarily for other sizes. Thus as in George's example a #6 increased to a #1 would only require a #4 egc not a #2 or a #1.

If you increased a #12 to a #1 you would need a #1 EGC. If you increased it to 3/0 you would need a 3/0 EGC.
Click to expand...
 
Dennis,

OK, This is good. When I read your post #7 I saw ' this does not hold true for other sizes',

When I went back and reread it, it was perfect. thanks for the reply. :)
 
I'll admit I was a little befuddled by Dennis' comment of:
The math is simply for wire sizes #14, 12, & 10.
...
This does not hold true for other sizes.
Click to expand...

Looking at T250.122, the logic behind Dennis' comment became obvious...painfully obvious :)
 
The key word here is proportionately sized according to Circ mil area. You stated you had a 20amp OCP. The egc is a #12. You increased your ungrounded wire size from a #12(6530) to a #8(16510) or 2.53 times bigger. Increase your # 12(6530) x 2.53=16520.
A #8 EGC is required.
 
slect said:
The key word here is proportionately sized according to Circ mil area. You stated you had a 20amp OCP. The egc is a #12. You increased your ungrounded wire size from a #12(6530) to a #8(16510) or 2.53 times bigger. Increase your # 12(6530) x 2.53=16520.
A #8 EGC is required.
Click to expand...

I agree but that is the long way around to get the answer for 15, 20 & 30 amp circuits. Those particular circuits require ECGs that have a 1 to 1 ratio with the circuit conductors.

Run 4 AWG for a 15, 20 or 30 amp circuit and you immediately know that the EGC will be 4 AWG as well.
 
I agree, and understand completely. But now he understands the math behind the article and can use for other sizes in the future. Thanks
 
Question.

Say that I need to power a A/C compressor with a Minimum Circuit Ampacity of 30A....Maximum 35A.

I have a spare piece of #8NMB that is the correct length, so instead of buying a piece of #10, I want to use the #8.

Does this rule mean that I can't use the #8 cable?

Note for those not familiar....Both cables have a #10 Grounding conductor.

Just curious
steve
 
hillbilly said:
Question.

Say that I need to power a A/C compressor with a Minimum Circuit Ampacity of 30A....Maximum 35A.

I have a spare piece of #8NMB that is the correct length, so instead of buying a piece of #10, I want to use the #8.

Does this rule mean that I can't use the #8 cable?

Note for those not familiar....Both cables have a #10 Grounding conductor.

Just curious
steve
Click to expand...


What size OCPD ?
 
Dennis Alwon said:
benaround said:
If you increased a #12 to a #1 you would need a #1 EGC. If you increased it to 3/0 you would need a 3/0 EGC.
Click to expand...

iwire said:
Run 4 AWG for a 15, 20 or 30 amp circuit and you immediately know that the EGC will be 4 AWG as well.
Click to expand...

So if we decide to run a 6 AWG for a 35 amp circuit alongside, maybe a higher voltage, and #6 is 1.59 times the size of a #8, we can upsize a #10 (10380 cmil) to #8 (10380 x 1.59 = 16504, smaller than #8 at 16510).

We then have a #8 gounding a 35 amp, and a #4 grounding a 30 amp circuit.

I think you guys are right, these sizes are just an unfortunate possibility sometimes.
Click to expand...
 
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