solid vs stranded THHN

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nick h

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I completed my apprenticeship program in NYS working mostly in commercial and industrial applications. We pulled stranded THHN for all of our branch circuits ran in conduit. The only time we would use solid THHN was in control panels. I recently moved out to Montana and it seems like everyone uses solid wire. I'm referring to 20A and 15A circuits pulled through conduit. Several months ago someone saw me pulling stranded wire and told me it was a code violation to used stranded wire in a commercial building...i've had several people tell me the same thing since. Am i missing something?? I've never seen solid wire used, and since moving out here thats all i see, and i have people telling me with absolute certainty that i'm wrong. I've never come across anything in the code book saying you cant but then again i havnt looked specifically for it because I've never questioned it up until now.
 
>>>Ask those who say stranded wire is a violation for the code section. Perhaps its a state rule to use solid?

Stranded wire is easier to pull in, and many years later, easier to pull out . Copper wire gets harder over the years, I don't know the reason for this.
I find stranded is easier to shove into the boxes
But stranded wire is a bit slower to make up at the devices, and can be unwieldy pulling in, as it wants to jump off the spools.
When I started I was self taught so used solid, but then started working with some apprenticeship electricians and made the switch to stranded.
 
When i first saw it i assumed they were doing it for ease of installation with devices. It just seems like pulling it in would be a lot harder, and like you said pulling it out could be downrite impossible. That's a good idea i will look into if there are any local code amendments.
 
As a design engineer, I most often see the specifications call for solid for some sizes (typically #10 or smaller) and stranded for larger sizes. I have no technical basis for such a requirement. But the NEC is silent on this issue, and anyone telling you there is a code violation here is simply wrong.
 
I suspect it is just one of those local preferences. There seem to be a lot of them an most are not code amendments.

I don't recall off hand if you are allowed to back stab with stranded. It is certainly easier with solid. Places where back stabbing is common probably prefer solid. There are a fair number of electricians who don't like back stabbing and blame it for all kinds of ills that it probably does not deserve.

Personally I do not like trying to connect stranded wire to receptacles and switches. It seems like when this is tried without a ring tongue terminal there is always a whisker or two that sneaks out. Not an issue with solid.
 
I would say 99% of my jobs specified solid for #10 and smaller, it is not hard to pull.

Roger
 
We haven't pulled solid copper conductors in decades except for when someone requires it in the spec. No one has ever given me a reason why it's better and IMO they cannot because it isn't. Especially today where everyone wants to value engineer down to the smallest possible size conduit packed to the max. We had a job several years ago where they specified #10 solid conductors, the wiring pulling crew had to fill some 1" EMT runs and needed a tugger to get the wire in. It pulled with so much force that it started to straighten out the offsets in the EMT. :slaphead:
 
tom baker said:
Stranded wire is easier to pull in, and many years later, easier to pull out . Copper wire gets harder over the years, I don't know the reason for this.
.
Click to expand...

It's possible that solid copper wire will get harder to pull out after it's been pulled in due to work hardening, especially if there are a number of bends. There is something known as age hardening of metals but I'm not aware that it would occur in this case. Accumulated dirt, tarnish, or corrosion on the interior of the conduit over time could significantly increase friction and increase the pulling force, especially with solid wires that will experience more sideways force around bends.
 
For those who find it difficult to land stranded wire on device screws, there are a few tricks:

Reverse-twist the strands which keeps them together better

Pinch the loop closed with needle-node pliers while tightening

Leave a ring of insulation on the tip of the wire strands

Use solid wire pigtails to join with the stranded wires
 
LarryFine said:
For those who find it difficult to land stranded wire on device screws, there are a few tricks:
.....
Use solid wire pigtails to join with the stranded wires
Click to expand...

If you wirenut a single solid wire with stranded, do you find that the stranded sometimes spins around the solid (which then remains straight and doesn't twist itself)? As a result the wirenut doesn't get a good grip on the solid wire.
It may be more effort than it's worth, but it seems that slightly kinking or twisting the end of the solid slightly first seems to prevent this.
 
synchro said:
If you wirenut a single solid wire with stranded, do you find that the stranded sometimes spins around the solid (which then remains straight and doesn't twist itself)? As a result the wirenut doesn't get a good grip on the solid wire.
Click to expand...

No, I make sure the stranded wire is well-twisted first. I also make sure the wires remain in their relative positions with my fingertips as I screw on the wirenut.

When wiring more than one stranded wire, I twist them into one larger wire before adding them to the solid(s).
 
synchro said:
If you wirenut a single solid wire with stranded, do you find that the stranded sometimes spins around the solid (which then remains straight and doesn't twist itself)? As a result the wirenut doesn't get a good grip on the solid wire.
It may be more effort than it's worth, but it seems that slightly kinking or twisting the end of the solid slightly first seems to prevent this.
Click to expand...

Lead the stranded slightly longer than the solid, just like the directions for the wirenut specify, and you'll rarely have to monkey with it further. Of course, the more conductors you have, and the sizes and mix of them, will change things, but leading the stranded to be a bit longer is the first rule.
 
LarryFine said:
No, I make sure the stranded wire is well-twisted first. I also make sure the wires remain in their relative positions with my fingertips as I screw on the wirenut.

When wiring more than one stranded wire, I twist them into one larger wire before adding them to the solid(s).
Click to expand...

That's what I used to do (relative position until the spiral bit). Also the twisting the stranded together 1st, and also would twist the solids together if more than 1 solid.

I would also "tug" the individual conductors while holding the wirenut to look for a conductor that might have gotten pushed out slightly.
 
nick h said:
I completed my apprenticeship program in NYS working mostly in commercial and industrial applications. We pulled stranded THHN for all of our branch circuits ran in conduit. The only time we would use solid THHN was in control panels. I recently moved out to Montana and it seems like everyone uses solid wire. I'm referring to 20A and 15A circuits pulled through conduit. Several months ago someone saw me pulling stranded wire and told me it was a code violation to used stranded wire in a commercial building...i've had several people tell me the same thing since. Am i missing something?? I've never seen solid wire used, and since moving out here thats all i see, and i have people telling me with absolute certainty that i'm wrong. I've never come across anything in the code book saying you cant but then again i havnt looked specifically for it because I've never questioned it up until now.
Click to expand...

Ok, here it is.

Stranded requires less pulling tension. Stranded tends to jump off the reel and kink up requiring a helper. Stranded is difficult to wrap around the screws of devices to make a reliable connection. Backstabbing, mmm no, I don't think so. :jawdrop:

So stranded gets one thumbs up :thumbsup: and two down :thumbsdown::thumbsdown:.



Solid can be more difficult to pull. Solid pulls smoothly off the reels unattended. Solid terminates easily on the screws of devices. God forbid but you can backstab with it.

So solid gets one thumbs down :thumbsdown: and two thumbs up :thumbsup::thumbsup:.



So to me solid, for the work I do, is the clear winner.

But it's all a matter of preference, and anybody that tells you that using one or the other is a code violation doesn't know what they are talking about.

Edit to add:
nick h said:
The only time we would use solid THHN was in control panels.
Click to expand...

Actually my experience is just the opposite and I myself prefer using stranded in panels.

-Hal
 
Certainly a matter of preference and what type of work you do. I seem to do lots of work where pulling solid is very difficult, i.e. two - three full boats of #12 in a 3/4 with 3-4 bends. Sure it would be nice to have only 1 or 2 full boats with only two bends, but that is not realistic most of the time. Usually for other than resi I use higher grade devices that have clamps so terminating is no big deal.
 
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