Fine Stranded Wires in a Circuit Breaker

I have to run fine stranded wires from a #10 SOOW wire to a breaker and to the bus bars in my main panel.

That just doesn?t seem like a very secure connection. I?m thinking of tinning the wire.

Is there any problem with doing so?

No problem at all says a retired union electrician.

Does the breaker have a "clamp" style connector, or does a screw just tighten down on the wire?  The clamp style seems to give a little better connection with fine wire like you are describing.  One thing that I always do is after tightening the screw/clamp or just a screw down is to grab the wire and wiggle it in a 360 degree motion a few times.  Most of the time you can get another 1/4 turn - 1/2 turn on the screw.......says a Non-retired union Electrician! 

I've tinned wires a couple times over the years on other projects.

An ounce of prevention is worth a pound of cure.

No problem at all or two other methods:
1. Just twist them real tight
2. Use a spade type crimp on terminal

Jack L

I have read an article on the "dangers" of doing that but... Well I frankly do not recall which was better. With fine stranded I think I'd tin them..

Oh the danger.. wire breakage due to vibration.  But it seems that would happen anyway.

Thanks guys.

My breakers and bus bars have just a screw clamping against the wire - hence my concern.

I think the problem with tinned wire breaking from vibration is more with wires that have been heated to the point that the solder flows too far up the wire. I know not to do that.

The problem with tinned wires occurs when the breaker heats up, doesn't trip and melts the solder. I don't know how possible that is in the real world but I would not worry about it. When you have fine wires it is easy to nick a few of them when stripping the wire. A few nicked wires reduces the current carrying capacity of the wires and leads to the wires heating up sooner than if none of the wires were nicked. Once again I have no idea how prevalent this is in the real world but since I am very good at not nicking wires I would not worry about it.

Starnd wire is fine as long as the right gauge is used. In the industrial industry it is almost all strand wire. Your mains are almost always strand wire. Just make sure when tightening you back off a 1/4 turn and tighten again 2 or three times. This will get it tight. More so on bigger gauges

Fast and easy, do anywhere. Pin connector.

Jim18655 said:

Fast and easy, do anywhere. Pin connector.

Click to expand...

I went looking for those but I could not find them because I did not know they were called pin connector. Thanks. )

The wires are tinned and installed.

Thank You to all who responded.

Tom

Heli_av8tor said:

I have to run fine stranded wires from a #10 SOOW wire to a breaker and to the bus bars in my main panel.

That just doesn’t seem like a very secure connection. I’m thinking of tinning the wire.

Is there any problem with doing so?

Click to expand...

yes, plenty.. here is what your union man doesn't know..

it's called thermal expansion of dissimilar materials.
what happens with a soldered joint is the differential expansion of copper and solder causes the wire to change shape and this is
called "cold flow".. the wire over time will loosen in the terminal and give rise to a high resistance contact that will heat more and eventually work loose. no code ever, with the exception of some military applications has ever specified soldered joints for a mobile application. the union man is generally static drinking coffee and reading news papers.. so mobile is not in his vocabulary.

please, NEVER solder a mobile connection, the strands of wire close to the solder that wicks up the cable suffer mechanical stress
as well and eventually break. so what's the correct solution ?

The correct way of terminating fine strand copper in a screw terminal is to strip twice the length of insulation, twist the wire together with fingers and then bend the cable over itself so providing a sacrificial layer for the screw to cut into. I learned this over 40 years ago as a rookie sparky with cheap ass Chinese terminal blocks that cut cables like a guillotine !! the screws have a concave end due to the production process and this acts as a cutting edge, so the simple solution of doubling the cable allows the screw to cut into the doubled over piece about half way through and provide a secure connection. when you do this, make sure the doubled over piece faces the screw. also, in the event the wire is too big for the terminal you will have to resort to a pin crimp as suggested by an earlier post.



If you have soldered your cable, please take the time to cut it off and do it the right way..

I went looking for those but I could not find them because I did not know they were called pin connector

Click to expand...

I think the proper technical name is an "electric wire ferrule", and these are a crimp-on type.

https://en.wikipedia.org/wiki/Electric_wire_ferrule
https://www.youtube.com/watch?v=os66cID30Ek

solarman said:

yes, plenty.. here is what your union man doesn't know..

it's called thermal expansion of dissimilar materials.
what happens with a soldered joint is the differential expansion of copper and solder causes the wire to change shape and this is
called "cold flow".. the wire over time will loosen in the terminal and give rise to a high resistance contact that will heat more and eventually work loose. no code ever, with the exception of some military applications has ever specified soldered joints for a mobile application. the union man is generally static drinking coffee and reading news papers.. so mobile is not in his vocabulary.

please, NEVER solder a mobile connection, the strands of wire close to the solder that wicks up the cable suffer mechanical stress
as well and eventually break. so what's the correct solution ?

The correct way of terminating fine strand copper in a screw terminal is to strip twice the length of insulation, twist the wire together with fingers and then bend the cable over itself so providing a sacrificial layer for the screw to cut into. I learned this over 40 years ago as a rookie sparky with cheap ass Chinese terminal blocks that cut cables like a guillotine !! the screws have a concave end due to the production process and this acts as a cutting edge, so the simple solution of doubling the cable allows the screw to cut into the doubled over piece about half way through and provide a secure connection. when you do this, make sure the doubled over piece faces the screw. also, in the event the wire is too big for the terminal you will have to resort to a pin crimp as suggested by an earlier post.



If you have soldered your cable, please take the time to cut it off and do it the right way..

Click to expand...

Wow, I guess I need to remove all of the computer/circuit boards in my car/truck/motorcycles because they are certainly "mobile"!  And I'm not sure how or even why you felt like you had to try and throw a slam in there against union Electricians....maybe there is a tinge of jealousy or ?????  I spent thirty years in a steel mill and I can tell you one thing, you don't have a clue if you think that's all that union Electricians do.....drink coffee and read newspapers.  If you don't like unions, that's your choice, but find some other place to throw your Digs at them.

And I would be fairly certain that I've worked on Electrical equipment over the years there that you wouldn't have a clue about, much less know how to repair it!  The man that thinks he knows everything is many times that man that knows nothing.

The OP didn't refer to any screw terminal connection or mobile. He said he was running a number 10 Gauge wire to a breaker and bus bar. Not sure how that got side tracked.

xrated said:

Wow, I guess I need to remove all of the computer/circuit boards in my car/truck/motorcycles because they are certainly "mobile"!  And I'm not sure how or even why you felt like you had to try and throw a slam in there against union Electricians....maybe there is a tinge of jealousy or ?????  I spent thirty years in a steel mill and I can tell you one thing, you don't have a clue if you think that's all that union Electricians do.....drink coffee and read newspapers.  If you don't like unions, that's your choice, but find some other place to throw your Digs at them.

And I would be fairly certain that I've worked on Electrical equipment over the years there that you wouldn't have a clue about, much less know how to repair it!  The man that thinks he knows everything is many times that man that knows nothing.

Click to expand...

firstly, I agree with you, I don't know what union men do now, but when I started out as a journeyman in a union shop, this was typical common humor.
I left all that behind after changing my career path and graduating with an MSEE and later a PE
secondly, like you, I don't know everything, never said I did. I DO know my own field of electrical engineering very well though and I will turn the tables
on you and say that I have probably designed equipment that you won't have a clue about.!

looks like i hit a nerve here.. perhaps a sense of humor is required or some physical stress relief of a certain kind ?  ;D ;D

Ghostman said:

The OP didn't refer to any screw terminal connection or mobile. He said he was running a number 10 Gauge wire to a breaker and bus bar. Not sure how that got side tracked.

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breakers and buss bars have screw terminals and mobile was implied as

1. SOOW cable is intended for mobile use ( 10 AWG suggests a 30 Amp shore line )
2. this is an RV forum.

either way, fixed or mobile, soldering is undesirable and bad practice for this type of connection.

solarman said:

firstly, I agree with you, I don't know what union men do now, but when I started out as a journeyman in a union shop, this was typical common humor.
I left all that behind after changing my career path and graduating with an MSEE and later a PE
secondly, like you, I don't know everything, never said I did. I DO know my own field of electrical engineering very well though and I will turn the tables
on you and say that I have probably designed equipment that you won't have a clue about.!

looks like i hit a nerve here.. perhaps a sense of humor is required or some physical stress relief of a certain kind ?  ;D ;D

Click to expand...

So, if you don't know, why would you make a blanket statement about a group of people?  And actually, I've got a very good sense of humor, but I also have a very low tolerance for for people that categorize folks into a certain group just because they have seen a few bad examples and they think that everyone in that group is the same.  There are hard working folks everywhere....and there are lazy bums everywhere also....just don't lump me into a certain group because of what others do.  And yes, nerve hit!  I've always prided myself on being a smart, hard worker and very proud of my affiliation with and in the Electrical trade.......Rant off!

xrated said:

So, if you don't know, why would you make a blanket statement about a group of people?  And actually, I've got a very good sense of humor, but I also have a very low tolerance for for people that categorize folks into a certain group just because they have seen a few bad examples and they think that everyone in that group is the same.  There are hard working folks everywhere....and there are lazy bums everywhere also....just don't lump me into a certain group because of what others do.  And yes, nerve hit!  I've always prided myself on being a smart, hard worker and very proud of my affiliation with and in the Electrical trade.......Rant off!

Click to expand...

You are going to have to understand there are some hard core union haters in this world. When I first got on this board we had a dilly of a union hater hanging out regularly here. I made the mistake of mentioning I was a retired union electrician and from that point on he made a point of trying to disprove many of my statements. I finally stopped mentioning my union credentials and fortunately the union hater no long hangs here.