toasted buss bar & wire

[ChrisOlson]

I agree that screw type terminals have issues, and i try to avoid them altogether for anything carrying any current. Crimp, lug and post is a better solution.

There's nothing really wrong with screw type lug or bus bar terminals.  They are designed for solid wire but can be used with stranded wire with no issues as long as you use a ferrule or tin the wire.  For me, tinning has always worked as good as a ferrule.  The tinning also insures a clean connection that will stay clean with age.

[niel]

resthome,
i wouldn't recommend tinning as the slightest bad connection or over current condition would melt the solder and accelerate a bad connection condition. in a worst case the solder will explode like molten shrapnel or drip down to the next wire/buss below.

mike,
in my opinion you have too many strands in your wires. these busses were meant for solid wires, but a few strands won't hurt. going 20, 30, 40, etc. and up is asking for trouble. i don't believe that was the case on that buss as it appears the buss may have been over loaded with current. maybe a short or misswired at some point. i see the set screws are all discolored from excessive heat even in the middle. some of the wires on the buss next to that one are discolored too. magnify your images and look more closely to see what i'm talking about.

[ChrisOlson]

i wouldn't recommend tinning as the slightest bad connection or over current condition would melt the solder and accelerate a bad connection condition. in a worst case the solder will explode like molten shrapnel or drip down to the next wire/buss below.

Solder melts at 216°C.  The maximum temp rating of the wire is 90°C.  If you melt solder off a tinned connection or have solder "explode like molten shrapnel" you got one hell of a lot bigger problem than a bad connection on a bus bar.

[Resthome]

i wouldn't recommend tinning as the slightest bad connection or over current condition would melt the solder and accelerate a bad connection condition. in a worst case the solder will explode like molten shrapnel or drip down to the next wire/buss below.

Solder melts at 216°C.  The maximum temp rating of the wire is 90°C.  If you melt solder off a tinned connection or have solder "explode like molten shrapnel" you got one hell of a lot bigger problem than a bad connection on a bus bar.

+1

[niel]

Solder melts at 216°C.  The maximum temp rating of the wire is 90°C.  If you melt solder off a tinned connection or have solder "explode like molten shrapnel" you got one hell of a lot bigger problem than a bad connection on a bus bar.

yes, it's called "an over current condition" like i mentioned and that could be a short. reading is fundamental even for M Es.

[zoneblue]

Yes i think its pretty likely that bus bar had some amps through it at some stage. I very much doubt that bat+ bar was ever intended for anything other than a few small ancilliary loads.

[dgd]

Yes i think its pretty likely that bus bar had some amps through it at some stage. I very much doubt that bat+ bar was ever intended for anything other than a few small ancilliary loads.

Small ancillary loads probably needs to be on the label in the epanel. I have seen this +ve bus used to connect two Classic 150s that can easily output 85+ amps each on a good day.  #4 multistrand cable was used into the larger holes in the block and when the screw was tightened most of the strands were diverted either side of the screw.
I thought this was a bit ugly and then all that current going to the +ve connector on the breake via a length of #6 few strand cable.
I try to avoid these type of bus bars much preferring the types with a row of studs and nuts to take ring type copper connectors crimped onto the multistrand copper cables. Tighten these down with a spring lock washer and there is no re-torqing required.
Althought with several power making/using devices that +ve stud on the 175/250A breaker can get a little busy.
dgd

[ChrisOlson]

yes, it's called "an over current condition" like i mentioned and that could be a short. reading is fundamental even for M Es.

I'll ignore the last comment - for now.  And stick to the topic.  The issue is not over current.  That's why breakers and fuses are used on circuits to prevent over-temping your wire beyond it's max rating.  The issue is proper termination of stranded cables in set screw bus bars and lugs.

John Wiles on what the problem is:
http://www.nmsu.edu/~tdi/pdf-resources/CC104.pdf

[niel]

the breakers won't stop all shorts and i'm not saying it was shorted, but it looks that way.

i'll ignore that my initial comments weren't directed to you as i addressed mike and resthome.

[ChrisOlson]

Just looked it up.  UL486 testing includes tinned stranded cable in set screw lug terminations.  Tinning is an approved method of termination under both UL486 compliance and NEC.  Crimped on solid pin terminations, however, are not approved for use in set screw lugs.

Amazingly, UL486 allows for 5% shear of the strands after the screw is torqued to the specification and held at spec torque for five seconds.

[Resthome]

the breakers won't stop all shorts and i'm not saying it was shorted, but it looks that way.

i'll ignore that my initial comments weren't directed to you as i addressed mike and resthome.

I guess I'll have to ignore your comment then, for now anyway.

As for breakers and fuses protecting your wires from shorts. I have a breaker at the Classic for the Battery and PV and a proper sized fuse near the battery bank. So if the Classic lets out smoke and it's typical failure would be a short I'm as protected as I can be. And my stranded wire is Marine grade tinned cooper for less chance of corrosion in a marine environment. It is also more fatigue-resistant as vibration is always present on a boat and will possible fatigue and crack coarsely stranded wire. And last there is no way of avoiding the screw terminals block on the Classic itself.  So different environments require different solutions.

[ChrisOlson]

And my stranded wire is Marine grade tinned cooper for less chance of corrosion in a marine environment. It is also more fatigue-resistant as vibration is always present on a boat and will possible fatigue and crack coarsely stranded wire. And last there is no way of avoiding the screw terminals block on the Classic itself.  So different environments require different solutions.

It's the same way with all the wiring in our sailing yacht - all marine tinned copper.  There's a specific specification that wire has to meet and marine surveyors and USCG inspectors are pretty good at finding one wire in the boat that you "cheated" on and didn't use the right wire.  If it's in there, they'll find it and write it up.

In checking on UL486, it's kind of interesting.  You have lugs and you have terminations, but they are not the same thing.  As an OEM when you install a conductor into a lug and then submit that assembly to UL, what you get back is a device with a 'listed termination'.   UL then allows you to provide a lug and the proper instructions so that a field installed conductor maintains the 'listing' for the termination.

I assume this is the way the MidNite boxes are listed - they have labels in them with the proper torque specs, which bars or lugs are UL Listed for fine strand cable, etc..  In Mike's case where he had a connection overheat due to high resistance at the bus bar, technically his install should meet the termination requirements for Class B stranded wire.  Whether or not the termination was torqued correctly, I don't know.  The spec calls for using a torque wrench (not guessing) and when the proper torque is reached it must be held at the torque spec for an additional 5 seconds.

Tinning is allowed for stranded wire in set screw lugs, and is one of the tests under UL486 on the heat and pull test.  When you tin the wire the termination is considered to meet UL486 as long as the torque specs are adhered to, and even allows the use of fine stranded cable in lugs and bus bars not listed for fine strand because tinning effectively turns a stranded cable into a solid wire.  It is interesting that they make a distinction between tinning and solder dipped.  Tinning is tested and approved - solder dipped is not.  If you use a ferrule on stranded wire in a set screw lug, then the ferrule itself has to be UL Listed.

It's no mystery that Mike's wire termination got burnt and damaged from high resistance connection at the bus bar - more than likely caused by the classic problem  of strand shear during tightening of the screw, and failure of the connection to stay tight with age.  Simply tinning the wire end totally solves both problems.  I think it's important for folks to see that it can happen, and also to learn the proper methods of terminating wire in these types of bus bars so it doesn't happen to them.

[Resthome]

And my stranded wire is Marine grade tinned cooper for less chance of corrosion in a marine environment. It is also more fatigue-resistant as vibration is always present on a boat and will possible fatigue and crack coarsely stranded wire. And last there is no way of avoiding the screw terminals block on the Classic itself.  So different environments require different solutions.

It's the same way with all the wiring in our sailing yacht - all marine tinned copper.  There's a specific specification that wire has to meet and marine surveyors and USCG inspectors are pretty good at finding one wire in the boat that you "cheated" on and didn't use the right wire.  If it's in there, they'll find it and write it up.

So true !! A lot of folk try, and some get away with using welding cable for invertor to battery cables on boats.

Great comments on this topic, Chris. And good torque screwdrivers aren't cheap. Any leads on a good quality torque screwdriver at a reasonable cost?

[ChrisOlson]

Great comments on this topic, Chris. And good torque screwdrivers aren't cheap. Any leads on a good quality torque screwdriver at a reasonable cost?

Well, I have to admit that I've always torqued those screws using the "feels tight" test.  Stick a screwdriver on it and tighten it up until it feels like it's tight.

After seeing what happened to Mikes bus bar and reading UL486 I'll change my tactics.  Those torque specs are published for a reason.

It's easy enough to adapt a screwdriver bit to a beam or click type 3/8" drive torque wrench.  Ever seen one of those impact driver screwdrivers?  They are usually 3/8" drive on the impact part that you hit with a hammer.  The adapter has a 3/8" square drive with usually a hex screwdriver bit that snaps in.  That can be put on a 3/8" drive inch-pound torque wrench, even with a 3/8" drive extension if needed to reach inside the box, and apply the proper torque to the screw.  And it's fairly economical.

[Resthome]

Thanks Chris I though about that also. Would like to have a good quality torque screwdriver just have to get the correct one as they vary as to the range they cover.

Maybe Ryan will pop in here and let us know what model they are using in some of the MN Video. I think they mentioned it in the video but no access to the video here on the boat. Internet connection too slow.