Pairing #8 AWG

[ptonsparky]

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

I keep hearing that, too. A ring circuit certainly does not meet the definition

 

[roger]

No problem, just splice them to a single conductor at the breaker.

Roger

 

[wwhitney]

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

Another one of my PI's was to change the language in 310.10(H)(1) to "(electrically and physically joined
at both ends)" The panel response was "Electrically joined conductors will also be physically joined."

So I think that dispels the idea that ring circuits with more than one device, and certain switching arrangements, are prohibited by 310.10(H)(1). "Electrically joined" at both ends doesn't just mean that there's a current path between the two ends (non-overlapping with the current path between the other two ends); the two ends have to be physically connected to each other.

Cheers, Wayne

 

[roger]

I guess I was typing when you posted Tom.

Roger

 

[roger]

Another one of my PI's was to change the language in 310.10(H)(1) to "(electrically and physically joined
at both ends)" The panel response was "Electrically joined conductors will also be physically joined."

So I think that dispels the idea that ring circuits with more than one device, and certain switching arrangements, are prohibited by 310.10(H)(1). "Electrically joined" at both ends doesn't just mean that there's a current path between the two ends (non-overlapping with the current path between the other two ends); the two ends have to be physically connected to each other.

Cheers, Wayne

Parallel conductors would have four ends.

Roger

 

[wwhitney]

Parallel conductors would have four ends.

Agreed for 2 parallel conductors, but I don't see the point you are trying to make.

Cheers, Wayne

 

[ptonsparky]

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.

That is what a Blue or Grey wire connector is for.

 

[roger]

Agreed for 2 parallel conductors, but I don't see the point you are trying to make.

Cheers, Wayne

Seems to me their wording should say "each end" for it to be correct, by saying "both ends" it seems to be describing a ring circuit specifically.

Roger

 

[don_resqcapt19]

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.

I submitted a proposal to permit any combination of conductors to be paralleled as long as the OCPD rating did not exceed the rating of the smallest conductor of the set. It was rejected, but there is no technical reason not to permit that.

 

[Sparky2222]

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

Yes, we have alot of #8 stranded and would like to use it for a single 240v 50A RV plug-in. At 120' x 3 conductors (Red, Black, and Neutral) plus a ground wire, seemed like an OK approach from a safety standard; Code (Law) not withstanding. This is all because of potential voltage drop at high amperage surges, especially rare sudden motor startups like all A/C units kicking in at once (not a steady load).

 

[Sparky2222]

That is what a Blue or Grey wire connector is for.

As for overcoming the two conductors under a single lug terminal, as you hint, why not make a #6 pigtail at each end of the paired wires to attach to CB and load device such as the 50A RV outlet?

 

[kwired]

I submitted a proposal to permit any combination of conductors to be paralleled as long as the OCPD rating did not exceed the rating of the smallest conductor of the set. It was rejected, but there is no technical reason not to permit that.

Be nice if they would clarify if they intend "conductors in parallel" to mean any conductors that end up in parallel or only those intended for the purpose of creating an effective conductor of higher ampacity.

In the latter case it it important to maintain same overall impedance of each element of the set to assure equal distribution of current through each element. With smaller conductors you may need even more precision or you possibly change impedance enough to disturb the balance.

Something like a ring circuit with overcurrent protection set for the conductor shouldn't be a problem here, but wording is such it can be interpreted as being parallel conductors.

 

[Sparky2222]

Be nice if they would clarify if they intend "conductors in parallel" to mean any conductors that end up in parallel or only those intended for the purpose of creating an effective conductor of higher ampacity.

In the latter case it it important to maintain same overall impedance of each element of the set to assure equal distribution of current through each element. With smaller conductors you may need even more precision or you possibly change impedance enough to disturb the balance.

Something like a ring circuit with overcurrent protection set for the conductor shouldn't be a problem here, but wording is such it can be interpreted as being parallel conductors.

If the parallel wires are an exact match and bonded together at both ends, is the amperage rating maximum defined by the NEC tables or does Voltage Drop lower the ampacity of the CB to be used?

 

[jap]

The amperage rating of a conductor is determined by several different things.

The size of the conductor or circular mils being one of them.

Paralleling conductors simply makes wire management easier on larger amperage installs since your dealing with 2 or more smaller conductors rather than 1 large conductor.

Voltage drop does not lower the ampacity of a CB being used.
Voltage drop is the result of too much resistance.
Resistance due to distance being one of them.

The whole point of upsizing to a single larger conductor, or, paralleling 2 or more smaller conductors above what is normally needed to carry the amperage of a given circuit is done to reduce the resistance of the conductor itself which affects it's voltage and current carrying capability at any given amperage.

JAP>

 

[kwired]

If the parallel wires are an exact match and bonded together at both ends, is the amperage rating maximum defined by the NEC tables or does Voltage Drop lower the ampacity of the CB to be used?

Paralleled conductors for the purpose of creating an effectively larger conductor need to be same size, type and other characteristics need to be same so that they end up being equal impedance - this equal impedance is important because it will cause current to divide equally among them. Say you have 2 3/0 copper in parallel to create a 400 amp conductor, if current doesn't divide equally the individual conductors are still only intended to handle 200 amps, but if you have a 400 amp load that splits 275 on one and 125 on the other because of differences in the conductors, then the overloaded one can have insulation break down eventually because it is overloaded but has nothing to individually protect it from overcurrent.

 

[LarryFine]

To add, the closer to the max (before calcs call for next size up) that shared conductors are loaded, the more likely it is that a relatively small imbalance can create some amount of overload on the lowest-impedance conductor, termination quality included.


Let me know if that needs to be re-stated.