Pairing #8 AWG

[Sparky2222]

I understand pairing identical wires for large amperage Service Drops. My question is can twin #8 AWG conductors be used for a Single Phase 240 volt circuit (about 100') be used for a 50A Class A Motor Home service? Possibly protected with a 40A breaker for safety.

John Rowe

 

[infinity]

Short answer no. Parallel conductors must be a minimum of #1/0.

Welcome to the Forum.

 

[bwat]

Already answered, but here's the NEC reference if you're curious where it came from:

310.10(H)(1) General. Aluminum, copper-clad aluminum, or copper
conductors, for each phase, polarity, neutral, or grounded
circuit shall be permitted to be connected in parallel (electrically
joined at both ends) only in sizes 1/0 AWG and larger
where installed in accordance with 310.10(H)(2) through
(H)(6).

 

[oldsparky52]

If you tie 2 #8's at each end of the circuit and fuse them at 40-amps, what's the harm? (I understand it's a violation of the wording of 310.10) but each of the conductors are not protected at a higher ampacity than it can handle alone.

 

[norcal]

If you tie 2 #8's at each end of the circuit and fuse them at 40-amps, what's the harm? (I understand it's a violation of the wording of 310.10) but each of the conductors are not protected at a higher ampacity than it can handle alone.

It's still paralleling conductors smaller then 1/0.

 

[Dennis Alwon]

If you are going to fuse it at 40 amps then why parallel?

 

[winnie]

There is exactly this exception to the paralleling rule for 400 Hz systems.

You are permitted to parallel conductors smaller than 1/0 to reduce voltage drop in a 400Hz system, but the OCPD has to be sized for the individual conductor, not the formed parallel set. I would see no problem with a similar setup for 60Hz system, but code does not permit this.

-Jon

 

[roger]

I would see no problem with a similar setup for 60Hz system, but code does not permit this.

-Jon

Same here, maybe just a CMP oversight.

Roger

 

[roger]

So to get around 310.10(H)(1) just double the conductor (do not cut it) and connect both ends to the breaker, you have one conductor.

Roger

 

[jap]

This post sounds like a voltage drop concern to me.

JAP>

 

[Dennis Alwon]

I understand pairing identical wires for large amperage Service Drops. My question is can twin #8 AWG conductors be used for a Single Phase 240 volt circuit (about 100') be used for a 50A Class A Motor Home service? Possibly protected with a 40A breaker for safety.

John Rowe

If 40 amps works and it is 100' then I wouldn't worry about it. I would probably pull #6 for 50 amps.

 

[jap]

At 100 feet, and, if piped to the 50a RV outlet , I'd pull #8's, land it on a 50 amp breaker and let it rock and roll.

JAP>

 

[wwhitney]

Same here, maybe just a CMP oversight.

I submitted a PI for 2023 to expand Exception 1 to cover any application, with the substantiation:

"The current language is unnecessarily restrictive as to the applications that are permitted for parallel
conductors smaller than 1/0 AWG. When the conditions specified in the exception are met, there is no
safety downside to using parallel conductors in smaller sizes. Thus in keeping with the goal of
"Practical Safeguarding" as specified in 90.1(A), there is no reason to restrict paralleling conductors in
small sizes when each conductor is protected at its individual ampacity."

The CMP response:

"Resolution: No substantiation for opening up this exception further. Currently allowed applications are
low current."

I guess if you disagree you will soon have a short window of time to provide a Public Comment on my Public Input 3480-NFPA 70-2020 (if I've got the lingo correct).

Cheers, Wayne

 

[jap]

All technical jargon aside,,, I'm fine with the minimal size of 1/0 for paralleling.

Been that way forever.

Generally at that size you're still dealing with a feeder, plus, paralleling branch circuits or even feeders at less than 150 amps just seems odd.

JAP>

 

[bwat]

To the OP: Why are you thinking of paralleling 8s and not just going to a larger size? It's what you have already?

 

[ptonsparky]

So to get around 310.10(H)(1) just double the conductor (do not cut it) and connect both ends to the breaker, you have one conductor.

Roger

The argument has been made that changing the characteristics of the other conductor means they are no longer in parallel. Ranks right up there with your suggestion

 

[oldsparky52]

So to get around 310.10(H)(1) just double the conductor (do not cut it) and connect both ends to the breaker, you have one conductor.

Roger

Somebody will say it's a "ring" circuit and those are not allowed (so I've heard).

 

[roger]

Somebody will say it's a "ring" circuit and those are not allowed (so I've heard).

I've heard that too but I have used them in many LV lighting installations.

Roger

 

[synchro]

The argument has been made that changing the characteristics of the other conductor means they are no longer in parallel. Ranks right up there with your suggestion

You could also put the conductors at a right angle to each other, and then obviously they would not be parallel.

 

[epelectric33]

Not only is it a code violation, but I would expect that the OCPD (breaker/fuse/etc.) is not rated for (2) #8 to be landed on it. Doesn't matter if you can fit the the (2) #8s in or not if the termination is not rated for multiple conductors.