DC Breakers with Stud Connections

[hogback]

I inherited some surplus Carling DC 125A breakers that I'd like to use between my bms and inverter/charger. Some of the breakers came with some scrap/cut wire with lugs attached, which were attached to the breaker studs. The studs have two nuts and two washers each (plus one star washer against the plastic breaker housing), and in the case of the previous user, the wire lugs were sandwiched like this: starwasher-nut-washer-lug-washer-nut. I'm not sure how I should properly torque my lugs with this stud mounting system. It seems like if you torque the outer nut with respect to the inner nut, the whole connection must be relying on current running through the threads, which doesn't seem right, and is certainly never recommended for battery terminals. If you remove all the nuts/washers, the studs just disappear into the plastic, and there is no terminal plate/metal to secure against. The Carling datasheet has no instructions. Has anyone else used stud connected breakers like this before? Any tips? Thanks!

 

[MisterSandals]

Those are some mighty fine breakers! Midnite solar uses them for their higher rated applications.
I have used one with a lug sandwiched between the nuts/washers and had not issues.

How many did you inherit?

 

[hogback]

Probably 12 pairs or so. They were 'scrap' from a sunpower rummage sale. These are the breakers that are used between the 'sunpower' battery units and the rest of the sunpower sunvault system, which is like their tesla powerwall equivalent. I have some batteries too, but I couldn't get their bms's to stay on, so I'm going to rip them out and replace with the newest jk units. I have one cludged so far.....

I think these are what schneider sells as well, which makes sense as sunpower uses xwpros in their sunvault all-in-one box.

 

[hogback]

I'm pretty sure the nuts and washers are aluminum. They seem 'fluffy' and light and are non-magnetic. Noalox recommended?

 

[MisterSandals]

I'm pretty sure the nuts and washers are aluminum. They seem 'fluffy' and light and are non-magnetic. Noalox recommended?

I like a thin coat on all contact surfaces. Put a little on, spread all over (and beyond) the contact surface and wipe most of it off is how I’d describe my use.

Probably overkill in environmentally controlled area but a must for anywhere with moisture and salt.

 

[Steve_S]

Those are the same Big DC Main Breakers that Midnite Solar Uses, they are TOP Notch !
Torque: MNEDC125 Breaker 30 In-Lbs (3.4NM)
REF: https://www.midnitesolar.com/pdfs/torque_values.pdf
SPECS SHEET: https://www.midnitesolar.com/pdfs/EA1-X0-17-708-22A-ZB.pdf

Use ONLY Tinned lugs connecting to these.
Technically you do not need any No-Alox type grease unless you are in a humid zone but IF you use it, DO NOT get any on the threads (skewed torque readings) only on the contact surface of the lug and a VERY THIN LIGHT COAT ONLY ! NO Gobs !

 

[hogback]

Thanks. Yes, I have tinned copper lugs for connecting, but not crimped any yet. The thing here is that the threads are necessarily where the current flows into the stud, as the lug would be crimped between the two nuts, and not against any sort of brass/copper mating surface on the back of the plastic. It looks like whoever installed these last replaced some of the stock washers and nuts with galvi steel, but I've found all of those and will replace with whatever is proper. I think that asking midnite is probably the better bet than trying to get ahold of carling. Looks like the midnite spec is an abridged version of the carling one, and neither mentions material or assembly instructions beyond the torque.

Of note is the anti flash divider between the breakers, of which I cut of a bit to get the breakers to fit in the 6/6 raceway I bought for them. Maybe not smart, but I did cut holes in the top of the raceway to account for the arc vent clearance in the dimensional drawings.

 

[hogback]

Nuts actually appear to be tinned (or some other grey metal/alloy coating) brass. Compared to some known aluminum nuts I have, these seem more dense. Abrading the surface makes them appear slightly yellow, but that could be the low color temperature of my headlamp.