Trick to using stranded wire?

[Jon_E]

I've started wiring my shop and ran into a little problem over the weekend. I started by installing a double duplex receptacle (120V) and a single 240V receptacle adjacent to my panel. I am using surface mounted square boxes, EMT conduit and #12 THHN stranded wire. I have a bunch of older receptacles, none of which have the backwire feature (not the stab-type, I won't use them), but they all have regular wire-mounting screw terminals. I found that no matter what I did, I could not get a clean-looking connection between the stranded wire and the screw terminal. I think I did OK after a few failed/aborted attempts but I don't like it at all. I don't have any solid wire to run pigtails, either. I never considered how difficult this would be, as I have never used stranded wire in line-voltage circuits before. My entire house is NM-B (Romex) and it is all solid wire.

Any special tricks or tips to using stranded wire on receptacles and switches that have screw terminals, or should I just set these aside for use in solid-wire circuits and buy some new commercial-grade receptacles with backwire plates?

 

[mobiledynamics]

tin it or get comm spec ones.

 

[sberry]

I done these by the hundreds. Make the strip a little long and pre twist left handed. You will figure it out.

 

[wyliesdiesels]

I've started wiring my shop and ran into a little problem over the weekend. I started by installing a double duplex receptacle (120V) and a single 240V receptacle adjacent to my panel. I am using surface mounted square boxes, EMT conduit and #12 THHN stranded wire. I have a bunch of older receptacles, none of which have the backwire feature (not the stab-type, I won't use them), but they all have regular wire-mounting screw terminals. I found that no matter what I did, I could not get a clean-looking connection between the stranded wire and the screw terminal. I think I did OK after a few failed/aborted attempts but I don't like it at all. I don't have any solid wire to run pigtails, either. I never considered how difficult this would be, as I have never used stranded wire in line-voltage circuits before. My entire house is NM-B (Romex) and it is all solid wire.

Any special tricks or tips to using stranded wire on receptacles and switches that have screw terminals, or should I just set these aside for use in solid-wire circuits and buy some new commercial-grade receptacles with backwire plates?

First thing i would do is use spec grade outlets.

Next to that what u can do is leave a short piece of insulation on the end of the wire as u strip it, then wrap the wire around the screw terminal in the clockwise direction.

I have done that method many times without issues.

 

[n8n]

as others have said the neatest easiest way to do it is to buy receptacles that have the little square washers under the side screws. Many spec grade receps are like this. PRobably not too costly if you buy them from a real supply house not the big box.

 

[sberry]

I do leave a piece of insulation on occasion but as I said I usually make a longer strip and can just actually pinch the wire in an eye as I tighten. I use pigtails, have hundreds of these with the 50 cent recepts and never a problem.
Got one on the chop saw, 1000's of hi power motor starts, not hundreds but 1000's and a 30A breaker.
The benches have recepts with 1000's of plug in cycles. I always got to wonder when someone says they changed them all,,, I cant even remember last time I had to change a recept. Replaced old switches but never new ones and not due to load but wear.

 

[sberry]

A word of warning, some new gfci I got were deaper and even with a raised cover don't fit in old shallow 4x4, have to use a deep. But a few boxes, some handi even and some connectors and a box of cheap recepts make it a no brainer and easy to add something in a place3 you find you may need it.
I have done this and more than once, do some planning but don't get too complicated and make it easy to add something if and when needed vs pull double circuits every 4 ft with 3 spares just in case. Not every wire and plug will see 20A. I got a guy go in to a panic when he sees a 50 ft circuit and cant believe I use 14,,, yes,,, but the load is on a switched wire and 2A.

 

[sberry]

as others have said the neatest easiest way to do it is to buy receptacles that have the little square washers under the side screws. Many spec grade receps are like this. PRobably not too costly if you buy them from a real supply house not the big box.

They are probably cheaper at a box for those not in the business and don't have a pal who sells them real wholesale. There isn't much anyone really needs from a jobber that cant be scored from common stuff at Lowes etc. If it is then its something an amateur probably should think real careful if he really needs or not.
I tried to use every fitting they ever invented when I started this, today I am near the other end and do it with as much common as possible and you wont be left with a pile of weird expensive fittings when done.
I got one piece of rigid pipe in my building and as it turns out wouldn't have needed that.

 

[rlitman]

I done these by the hundreds. Make the strip a little long and pre twist left handed. You will figure it out.

That's an option. Outlet screws are cupped on their underside. If you can maintain the wire's twist as you shape the hook on the end (and be sure to install the hook so that the screw pulls the wire in clockwise), then it can be made to work.

...Next to that what u can do is leave a short piece of insulation on the end of the wire as u strip it, then wrap the wire around the screw terminal in the clockwise direction...

That'll work, but then I'd want to snip off that excess.

as others have said the neatest easiest way to do it is to buy receptacles that have the little square washers under the side screws. Many spec grade receps are like this. PRobably not too costly if you buy them from a real supply house not the big box.

Yeah, those square washers would be great. Or a proper back wire like they have on GFCI outlets.

Or, if you're not happy with any of the above, you can crimp on fork terminals.

 

[n8n]

A word of warning, some new gfci I got were deaper and even with a raised cover don't fit in old shallow 4x4, have to use a deep. But a few boxes, some handi even and some connectors and a box of cheap recepts make it a no brainer and easy to add something in a place3 you find you may need it.
I have done this and more than once, do some planning but don't get too complicated and make it easy to add something if and when needed vs pull double circuits every 4 ft with 3 spares just in case. Not every wire and plug will see 20A. I got a guy go in to a panic when he sees a 50 ft circuit and cant believe I use 14,,, yes,,, but the load is on a switched wire and 2A.

My local supply houses (Dulles Electric and Dominion Electric) don't care where I work. I have bought from them for work and also for personal use and they don't care other than that if it's for work I have a PO number handy. otherwise they just run my credit card and say "have a nice day."

 

[dw1]

The little piece of insulation at the end of the wire (That wylie and sberry) are talking about, helps keep the strands of wire together. Strip about an inch of insulation off, then strip about 1/4" or so and pull it to the end of the wire, twist the stranded wire left handed or ccw then make a loop and put under the screw, it works great and has been used for a very long time, other than that, get a better recept or use lugs.

 

[raddksn]

"Make the strip a little long and pre twist left handed. You will figure it out"
I think what sberry is saying twist the strands counter clockwise and make the loop clockwise! This works verry well

 

[sberry]

I took a pic of a job I did today, see if it turns out. I took some out and they were still really tight after 20 yrs.

 

[Movover]

Sta-Kon fork terminals .. you need a good crimper though. Thats what my electrician used in my building, and what he says they use in a lot of commercial places

 

[SEV22XS]

Sta-Kon fork terminals .. you need a good crimper though. Thats what my electrician used in my building, and what he says they use in a lot of commercial places

As former apprentice on a lot of commercial jobs this is what I would use and did use to terminate a stranded wire connect stranded wire was never meant to be wrapped around or under a terminal screw. Klein a makes a pair crimpers that work great for doing the connections.

 

[Bottlecapdigger]

Sta-Kon fork terminals .. you need a good crimper though. Thats what my electrician used in my building, and what he says they use in a lot of commercial places

This is what we have always done in industry. I have also heard of the left hand twist that is also mentioned. BCD.

 

[ForceFed70]

So.. why did you use stranded in the 1st place? Seems like a lot of headache for little/no benefit.

 

[sberry]

I like stranded and use it.

 

[ForceFed70]

I like stranded and use it.

OK, so perhaps you can answer the question. Why? Why do you like it?

I've worked with both and can't think of anything good to say about stranded other than it's ability to flex easily and handle vibration better - neither of which are considerations for household wiring.

Yet on the other side I find it harder to work with and more expensive. So for me it's a no brainer - solid conductor unless we're talking 10ga or bigger.

 

[Jon_E]

So.. why did you use stranded in the 1st place? Seems like a lot of headache for little/no benefit.

First - as I said in my original post - surface mounted EMT and boxes. Never heard of anyone running solid wire through EMT and Romex is not allowed in conduit.

Second - I got the #12 THHN for less than $20 each for a 500 foot roll, and bought eight rolls on craigslist. So it was a deal.

Third. I'm just asking for advice, just trying to get an idea of how other people deal with it. I thought it would have been easier. I have not bought any backwire receptacles yet and also have not used the wire twist methods described in this thread, so if they work like these other guys claim, I'll be all set.

 

[alfredeneuman]

Sta-Kon fork terminals .. you need a good crimper though. Thats what my electrician used in my building, and what he says they use in a lot of commercial places

Technically, the UL listing on the receptacle can be for use with solid wire only (for backstabbing), or with solid or stranded wire only.

They're not listed for use with crimp connectors.
(Nobody pays much attention to this though, except inspectors)

 

[sberry]

Its easy to install in boxes, the connections don't seem to loosen, wire nuts very well and tight.

 

[wyliesdiesels]

OK, so perhaps you can answer the question. Why? Why do you like it?

I've worked with both and can't think of anything good to say about stranded other than it's ability to flex easily and handle vibration better - neither of which are considerations for household wiring.

Yet on the other side I find it harder to work with and more expensive. So for me it's a no brainer - solid conductor unless we're talking 10ga or bigger.

When pulling through conduit such as EMT, stranded is way easier to pull vs solid. Thats one of the big reasons to use stranded.

First - as I said in my original post - surface mounted EMT and boxes. Never heard of anyone running solid wire through EMT and Romex is not allowed in conduit.

Second - I got the #12 THHN for less than $20 each for a 500 foot roll, and bought eight rolls on craigslist. So it was a deal.

Third. I'm just asking for advice, just trying to get an idea of how other people deal with it. I thought it would have been easier. I have not bought any backwire receptacles yet and also have not used the wire twist methods described in this thread, so if they work like these other guys claim, I'll be all set.

That is an old wives tale and is BS. NM-b wire aka Romex IS allowed in conduit. One of the many urban legend codes that wont go away!

 

[psu927]

If you use 4" square boxes, you can put 2 receptacles in each box. pre-wire the receptacles with solid wire and then wire nut the tails together with the stranded tail in every box.

 

[sberry]

I am not a fan of solid to strand, it can be done but this is way overblown here, millions of these connections are made this way each day. They can be done tight.

 

[ForceFed70]

When pulling through conduit such as EMT, stranded is way easier to pull vs solid. Thats one of the big reasons to use stranded.

Thank-you. That makes a lot of sense. I once spent my summer off (school) as an electricians helper for a large commercial project using all EMT. I spent weeks fighting with solid wire and must have went through a bottle of that nasty yellow lube every day. Wonder why they didn't go with stranded? Sounds like it would have made my life easier. Probably a case of me being cheaper than the wire.

 

[sberry]

I did a pull with 5 circuits the other day. Split in a couple Jboxes going different ways. It would been a problem with solid.

 

[augustus]

these are all good tips/methods above, if you still have trouble, you can cheat a little and pinch the wire loop tight around the screw with needle nose pliers as you screw it down.

 

[Jon_E]

Today I asked a master electrician what his secret was for working with stranded wire. He told me that I should use the Sta-Kon crimped terminals, he uses them all the time. Second best would be to do the trick about leaving a bit of insulation on the end of the wire and twist/loop the wire around the screw with the insulation still on. Not nearly as good or neat of a connection though. Sta-kons are cheap so I'm gonna head to the local electrical wholesaler and pick up some of them and a good crimp tool.

 

[jeffmoss26]

I have pulled a lot of solid wire out of conduits doing building renovations. It really had to be a pain in the **** to install in the first place!

 

[rlitman]

Technically, the UL listing on the receptacle can be for use with solid wire only (for backstabbing), or with solid or stranded wire only.

They're not listed for use with crimp connectors.
(Nobody pays much attention to this though, except inspectors)

I do not believe this is completely correct.

Yes, cheap receptacles are UL rated to be used directly with #12 or #14 stranded or solid under the screws, and #14 solid only in the back stabs.

But Sta-Kon terminals CARRY THEIR OWN UL rating. They are appropriate for the specified wires under screw terminals, when crimped with an approved tool.

 

[alfredeneuman]

The issue isn't with the crimp connectors themselves, even if they carry their own listings, but with the receptacles.
UL tests every specific combination individually before they list a product.
Every individual test costs money. If the manufacturer of the receptacle won't pay to have the particular test done, it isn't listed with that combination.

(One example of this is with panels that won't be listed with any other breakers other than their own. For instance Siemens circuit breakers are exactly the same physically and electrically as Murray breakers, but the Murrays aren't listed for the Siemens panel because nobody will pay for the tests)

 

[Charles (in GA)]

All of the #12 in my building is solid THHN in 1/2 conduit and never really had an issue pulling it, some runs as long as 70 ft or so, pulling by myself.

Charles

 

[Aceman]

We only use stranded. The trick is to use quality spec grade side wire devices with pressure plates. That just leaves the ground to deal with since those don't usually come with pressure plates. For those, a quality fork connector is what we use.

I never liked using crimps on the hot and neutral connections just so I could use a cheaper receptacle with just a screw connection and no pressure plates. Those crimps just add one more potential failure. Instead of one side wire connection(on a quality recep), you now have two connections. A crimp connection attached to a screw connection.

One other thing we always do(other than residential) is everything gets pigtailed always. No passing through one recep to the next.

 

[Jon_E]

Thanks for the helpful advice, gentlemen. Another question, while I'm here:

I am running all of my circuits, as I said, in EMT with metal boxes and box covers. Even though I'm running a ground back to the electrical panel, should I still be connecting each box to the ground wire with a ground screw in the back of the box? It appears to me that it would be redundant, since the whole system is grounded already. Or not?

 

[alfredeneuman]

If used, the ground wire must be bonded to each box that has a device or splices in it.

 

[Norcal]

Thanks for the helpful advice, gentlemen. Another question, while I'm here:

I am running all of my circuits, as I said, in EMT with metal boxes and box covers. Even though I'm running a ground back to the electrical panel, should I still be connecting each box to the ground wire with a ground screw in the back of the box? It appears to me that it would be redundant, since the whole system is grounded already. Or not?

If you do not bond the grounding conductor at every point where it's spliced, it would be better if the grounding conductor was omitted & relied on the code compliant method of using a metallic conduit as a grounding conductor.

 

[raddksn]

If used, the ground wire must be bonded to each box that has a device or splices in it.

this!!!

 

[rlitman]

If used, the ground wire must be bonded to each box that has a device or splices in it.

If it is a splice box, you should have a grounding screw, or bond somewhere. If it is a receptacle box, the receptacle may provide appropriate ground bonding through its screw.

 

[n8n]

If you do not bond the grounding conductor at every point where it's spliced, it would be better if the grounding conductor was omitted & relied on the code compliant method of using a metallic conduit as a grounding conductor.

Most of the receptacles that have the square washers under the screws are also self grounding, so if you are using metal boxes you can just wire nut a pigtail to the ground wire splice and then put the pigtail under the box ground screw.