Using stranded wire with screw terminals

[KrimsonNekros]

I'm starting my second year of my apprenticeship, and this an issue I keep getting conflicting information on. Is it permissible to wrap stranded wire around a screw terminal?

The older journeymen I work with all say it is, and typically recommend leaving a bit of insulation on the end to help keep the strands together. The newer journeymen tend to be more in favor of using fork terminals. No one is able to point me in the direction of a code article, or a local statute one way or the other. Is there any code on this, or would this fall under the verdict of the AHJ?

 

[ActionDave]

Welcome to the forum.

Short answer in this case is, trust the old journeyman. Most devices are required to be able to be used with solid and stranded wire. None that I know of allow fork connectors.

The strip of wire at the end of a piece of stranded is not required, but it helps keep things neat.

 

[Smart $]

Here's a few other related threads:

http://forums.mikeholt.com/showthread.php?t=150516
http://forums.mikeholt.com/showthread.php?t=88409
http://forums.mikeholt.com/showthread.php?t=146409

 

[Ponchik]

I agree with the more seasoned journeyman.

I always wrap the strands counter clock wise and make sure it is a tight wrap, then dress it under the screw and make sure no strands are sticking out. Personally, I never leave the insulation on.

 

[GoldDigger]

I suspect that what you call counter clockwise is what most call clockwise. It all depends in which part of the wire you start bending at.
Or if you are talking about the twist of the individual strands, yes, twisting CCW will make that twist tighten as you bend the whole wire CW around the screw, instead of requiring you to retwist after bending.

 

[texie]

I'm starting my second year of my apprenticeship, and this an issue I keep getting conflicting information on. Is it permissible to wrap stranded wire around a screw terminal?

The older journeymen I work with all say it is, and typically recommend leaving a bit of insulation on the end to help keep the strands together. The newer journeymen tend to be more in favor of using fork terminals. No one is able to point me in the direction of a code article, or a local statute one way or the other. Is there any code on this, or would this fall under the verdict of the AHJ?

Since you are an eager apprentice, you dazzle them and tell them that according to UL category RTRT that covers receptacles, the screw terminals are rated for solid or stranded conductors.
Just google "UL White Book" and download a free copy from UL's website. It is a very useful tool and something all electricians should learn to use.

 

[jumper]

I suspect that what you call counter clockwise is what most call clockwise. It all depends in which part of the wire you start bending at.
Or if you are talking about the twist of the individual strands, yes, twisting CCW will make that twist tighten as you bend the whole wire CW around the screw, instead of requiring you to retwist after bending.

Goldy, ya gotta lay off some that coffee.

 

[fmtjfw]

Since you are an eager apprentice, you dazzle them and tell them that according to UL category RTRT that covers receptacles, the screw terminals are rated for solid or stranded conductors.
Just google "UL White Book" and download a free copy from UL's website. It is a very useful tool and something all electricians should learn to use.

And if you really want to impress them also quote WJQR which states (for standard snap (wall) switches:
"Terminals of the wire-binding screw, setscrew, or screw-actuated back-wired clamping types are suitable for use with solid building wires unless otherwise indicated either on the device or in the installation instructions.
Terminals of a flush snap switch are permitted for use with Listed field-installed crimped-on wire connectors or an assembly, if so identified by the manufacturer."

Which prohibits the use of stranded conductors and allows the use of fork crimps.

 

[fmtjfw]

And the White Book ties back into the NEC with 90.7 which invokes, not by name the UL WB, and 110.3(B) which tells you to follow it.

 

[Ponchik]

I suspect that what you call counter clockwise is what most call clockwise. It all depends in which part of the wire you start bending at.
Or if you are talking about the twist of the individual strands, yes, twisting CCW will make that twist tighten as you bend the whole wire CW around the screw, instead of requiring you to retwist after bending.

I do mean CCW. I look at the tip of the wire and twist it opposite way. Most of the stranded wire that I have seen are twisted CW.

Or maybe I should have said "twist the opposite direction"

 

[Smart $]

I do mean CCW. I look at the tip of the wire and twist it opposite way. Most of the stranded wire that I have seen are twisted CW.

Or maybe I should have said "twist the opposite direction"

I think GD is pointing out that you wrap the wire around the screw CW (i.e. the wire end is clockwise from the rest of the wire under the screw; the actual wrapping can be done in any manner that works). However, the wire strands are re-twisted from CW to CCW. You wrote, "I always wrap the strands counter clock wise...", which is quite misleading.

 

[KrimsonNekros]

And if you really want to impress them also quote WJQR which states (for standard snap (wall) switches:
"Terminals of the wire-binding screw, setscrew, or screw-actuated back-wired clamping types are suitable for use with solid building wires unless otherwise indicated either on the device or in the installation instructions.
Terminals of a flush snap switch are permitted for use with Listed field-installed crimped-on wire connectors or an assembly, if so identified by the manufacturer."

Which prohibits the use of stranded conductors and allows the use of fork crimps.

What is the WJQR?

Since you are an eager apprentice, you dazzle them and tell them that according to UL category RTRT that covers receptacles, the screw terminals are rated for solid or stranded conductors.
Just google "UL White Book" and download a free copy from UL's website. It is a very useful tool and something all electricians should learn to use.

I'll grab that and take a look thanks.

I do mean CCW. I look at the tip of the wire and twist it opposite way. Most of the stranded wire that I have seen are twisted CW.

Or maybe I should have said "twist the opposite direction"

How does this help? It seems counter-intuitive to have the strands at the tip twisted the opposite direction of the rest of the wire.

 

[Ponchik]

I think GD is pointing out that you wrap the wire around the screw CW (i.e. the wire end is clockwise from the rest of the wire under the screw; the actual wrapping can be done in any manner that works). However, the wire strands are re-twisted from CW to CCW. You wrote, "I always wrap the strands counter clock wise...", which is quite misleading.

OHHHH I see.

:ashamed1::ashamed1:

 

[jap]

if you get too conflicted with wrapping stranded wire around the screw, you could always resort to back-wired receptacles and put the wire under the pressure plates instead.

Jap>

 

[don_resqcapt19]

What is the WJQR? ...

Go here and type WJQR in the UL Category Code 'box" at the top. Also check the box that says "display guide information only". If you don't check that you will get a list of every company that has a product listed under that category code.

Another handy way to look up the UL Guide Information is to go here. You can select the code you are using, and the code section and get a listing of the categories that are used in that code section.

 

[GoldDigger]

if you get too conflicted with wrapping stranded wire around the screw, you could always resort to back-wired receptacles and put the wire under the pressure plates instead.

Jap>

But the restriction in the UL listing applies to pressure plate as well as to screw, unless so indicated, where switches are concerned.

 

[Aleman]

So....reading through this thread I see both that you cannot use fork connectors and that you can use a fork connector.
Which is correct?

I have used a bunch of fork connectors because I don't like using stranded under screw terminals. But I will
try the CCW twist and maybe save me some work. The local shop doesn't sell rear loaded 20 amp receptacles or switches.
From what I have seen most people leave some insulation on the ends of the stranded.

 

[Smart $]

So....reading through this thread I see both that you cannot use fork connectors and that you can use a fork connector.
Which is correct?

Both

They appear to be UL approved for use with snap switches... but no mention regarding receptacles. Doesn't mean you can't use on receptacles, just no instruction will say you can... so approval will be at AHJ discretion.

From what I have seen most people leave some insulation on the ends of the stranded.

Most times I snip the tail off at the back edge of the receptacle. When I do not... I tape it to the main wire run. I've seen several occasions where not-taped insulation will come off when manipulating the receptacle into the box, or after pulling out for whatever reason and putting 'em back in.

 

[iwire]

They appear to be UL approved for use with snap switches... but no mention regarding receptacles. Doesn't mean you can't use on receptacles, just no instruction will say you can... so approval will be at AHJ discretion.

Moderator Jim D recently pointed out at least one brand and grade duplex receptacle that was listed for fork terminals. However I think currently that was a rare exception and certainly not common.

 

[Besoeker]

I'm starting my second year of my apprenticeship, and this an issue I keep getting conflicting information on. Is it permissible to wrap stranded wire around a screw terminal?

The older journeymen I work with all say it is, and typically recommend leaving a bit of insulation on the end to help keep the strands together. The newer journeymen tend to be more in favor of using fork terminals. No one is able to point me in the direction of a code article, or a local statute one way or the other. Is there any code on this, or would this fall under the verdict of the AHJ?

I can't tell you about code. Different country..........
I just think that a crimped fork terminal has to be a better and more reliable method.
In my field, industrial, it would be a minimum standard acceptable to the customer.
And the kit goes all over the world.