[OP]
Contributor
Just a quick question:
I will be wiring some 220 and 110 outlets in my garage, running stranded THHN through EMT conduit. I plan to put crimp connectors at the ends of the wires. Should I use spade/fork connectors or ring connectors to connect the wire to the outlets? Also, should I / can I use crimp connectors to connect the wire to the circuit breaker?
Thanks.
Member
Either is fine at the receptacles but not required. Simply twist the strands tightly together before tightening the screws and you will be fine.Originally Posted by Brian W Evans
No crimp type connector should be used at the breakers; the lugs on them are designed to clamp directly down on the bare wire.
Member
I am not an electrician, but think that the crimp-on spade/fork connections would leave a weak spot where the wire can slip out of the connector. The only way this seems safe would be if you soldered the wire into the connector. I am not sure if the code allows this.
My personal favorite is to use outlets with a clamp instead of the type where you have to wrap the wire around the screw. I think this type would be required for stranded wire. Here is an example that specifies compatibility with stranded wire http://www.homedepot.com/p/Eaton-15-...-BOX/203492664
Steve
Member
Code forbids connections that are dependent on solder. I suspect many would say that if you added solder to a connection, you felt it was dependent; so if probably isn't allowed.
However... I have used crimp-on spades a number of times with stranded and have never had a problem. Unless you expect there to be pulling on the connection (and there never should be!) I just don't think it is a problem.
Contributor
I would not use crimp connectors at all. It is done, on occasion, but would be highly unusual. Certainly the breakers and outlets you have are listed for use with stranded wire. As Scott says, twist the strands and you'll be fine. It's done that way all the time.
IF you insist on using terminals, you need a GOOD crimp tool (not the notches in the wire stripper...), you need terminals that are listed and rated for the application (ie - not auto-parts-store terminals; ones that are rated Cu/Al and to >250V), and you need to use them as directed (ie - not putting two wires in one crimp if the crimp is only rated for one, etc).
Member
Strip the wire and twist the strands in the opposite direction and then bend your hook. When you tighten the screw it will naturally pull the strands under the screw.
I'm with Steve. Use receptacles that are push and clamp style. Much easier to use with stranded wire.
NOW you tell me...
Member
Retired electrician here (44 yrs). Do not use any terminals at the breaker, the lugs there are designed to screw down on the copper wire. Don't use any terminals at the devices either. As Alan says just twist the wire backwards and hook it around the screw terminal. My preferred devices have the clamping style, loosen the screw, push in wire from back and then tighten screw which pulls up a lug tight on the wire. Do not use the device as a splice i.e. wires on both screws in and out. The correct way is a splice and then pig tail to the device. And whatever you do never use the stab in connectors on the back, the ones where you don't have to tighten any screws, you just stab them in. Not with stranded, not with solid, not ever! I have removed dozens of these with melted insulation on the wires inserted into these, it's a terrible connection.
[OP]
Contributor
Thanks for all of the replies. I will give the twist method a shot. My personal experience as a non-electrician is that I end up chasing wayward strands that get bent or broken in the process of twisting, which is certainly my bad technique. I will also look for the clamp-style outlets, which does sound like an ideal solution.
Jay, thanks for reminding me about the pigtails. I knew that but the temptation is always there to get things done quickly.
Member
I had a recessed lighting fixture in my kitchen fail. I didn't know what to do about it, so I ignored it. A week later it started to work again, only to fail permanently in 6 month. (http://www.noralighting.com/Product.aspx?pid=7669)
I worked up the nerve to open it up and found the hot wire going from the quick connector in the junction box to the light was completely out. It was tinned stranded wire.
But the crazy thing was that it was burnt around the insulation and the wire was about 75% burnt through. I cut it off, stripped a new end, and put it in a new connector.
I am making a wild guess that it was pushed in too far, so it wasn't making good connection with the conductor, was arcing and burning the wire and insulation.
But:
1) How did it survive 10 years like that, seeming to work fine
2) How did it get out of the connector? If it was in too far, how did it come out completely?
Or do you have a better explanation for what caused my problem?
A bigger issue, is that I have 20 of these fixtures, some of them in 16' ceilings; all 10 years old. Am I likely to have problems with more of them?
Any help here would be much appreciated.
Member
Stab in connectors of all types are terrible. We always cut those connectors off and use a proper wire nut. Think about how little contact is made between a round wire and the flat surface of the pin inside one of those connectors, which could be potentially carrying 12-13 amps. A little heat starts to develop and over time more heat, tiny arcing, bigger arcing, total failure! Hard to say about failure rate Wade, but if another one starts to have problems I'd change them all.
I don't read anything good about those stab connections. But if they are so bad, why are the allowed by code?
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