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-   -   Replacing 4/0 welding cable on Moly? (http://talk.craftweb.com/showthread.php?t=12675)

Josh Bernbaum 09-17-2020 02:04 PM

Replacing 4/0 welding cable on Moly?
 
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It's been 10 years of running current from the transformer to the elements on my Moly through the 4/0 welding cables that came with one of Steve's old furnaces I'm still running. I've done the maintenance over the years, albeit less than regularly, making sure connections are all tight and cutting back the cable-ends to expose bare copper many many times (thankfully there was a lot of excess slack). But I noticed when starting to change my pot, now that I'm shut off, that I've never seen a cable end as badly overheated as the one in the attached photo. The bolt to the lug for that one did appear to be loose, so perhaps that was the culprit, but regardless the ends of these cables just keep getting hard and crusty over time.

I think I read here once that 350 mcm was recommended over the 4/0 welding cable. I had trouble finding that post if I'm remembering that info right, and so just wanted to make sure I'm not harming anything by going up a cable size (before I drop a lot of $ on this copper). I think I'll have to get larger lugs too.

Thanks in advance.

Pete VanderLaan 09-17-2020 03:07 PM

You do want 350 MCM or you want a hydraulically connected end as well. If you go with the Burundy clamp, I might have a few. I certainly still have straps. You get that cable from Specialty Hardware in Seattle., It will run around $9-10 dollars a foot. It will ship UPS and looks like a Michelin tire when it arrives. Get the burundy clamp for a 600MCM or you'll have trouble getting the wire in the clamp. Lots of Noalox.

Make sure your connectors are tight in the transformer as well and pay attention to any cracking in the insulation there as well. I had a short at the trans once and was fortunate that the resultant aluminum clamp did not go down in the windings when it melted. That would have meant a new transformer.

Rollin built a big copper plate above his moly and distributed power from there and it seemed to work quite well.

Josh Bernbaum 09-17-2020 04:05 PM

Ok, thanks Pete. I think I have been using Burndy lugs all along, these right?:

https://www.grainger.com/product/22C...200917144844:s

I'm not sure why you refer to them as hydraulically connected though. Maybe I'm missing something. The ones I have been using have the set screw attachment, which, granted, needs to be checked for tightness, but they seem to rarely be loose there for me. It's more the element strap connections that seem to loosen up where the nuts and bolts are.

Also, is this the Seattle place you recommend?:

http://www.hscseattle.com

If so, I'm wondering how their 350 mcm might differ from what I could have my local electrical supply order in, and maybe save 3000 miles of shipping. The 4/0 welding cable I have been using has dozens and dozens of fine copper strands, maybe closer to 100, which seem to allow it to be quite flexible which seems to be a good thing for this application. But my guess is not all cable has as fine strands inside, and if it were thicker copper wires inside it probably wouldn't bend as well so that it will stay where I lay it and drape it around the top of the furnace. Is that what's special about the Seattle company's cable?

Pete VanderLaan 09-17-2020 06:14 PM

Local shops won't have the big wire in stock. So you'll likely pay more.

I can only recommend what I used when I sold cable. The hydraulic connectors were used by some people over the last fifteen years or so, or however those guys who professionally squish clamps onto wire. I never had access to people who did that, so I used the Archimedian screw type clamp you are talking about. Mt experience with those clamps was it was a one shot deal tightening it down. It was not going to come apart again in any meaningful condition. I have a box with a bunch of those larger connectors and haven't paid a lot of attention to them. Burundy is manufactured in Manchester NH but it will take a real electrical supply house to get them. It ain't a Home depot item. Again, you want a 600 MCM clamp.


Your link to Seattle hardware is the one. The cable is used on electromagnets in the harbor salvage. I stick with what I know. If you need element straps, I've got them. Just compare prices if you decide to shop around. Get ,lengths about three feet longer than you need so you can strip them back when they fail.

Lawrence Tuber 09-18-2020 10:41 AM

Lugs
 
Here's a way less expensive source for lugs, these are the ones I use:

https://lugsdirect.com/#!/S500-41-63...olt/p/78077485

Josh Bernbaum 09-18-2020 11:40 AM

Thanks Lawrence, good find on that website.

Josh Bernbaum 09-18-2020 11:43 AM

Thanks Pete, I'll be looking into cable options and pricing next.

Mark Rosenbaum 09-18-2020 01:18 PM

Why would one source be 5x the other?
The more expensive one is tin coated. Does that make a difference?

Pete VanderLaan 09-18-2020 01:27 PM

I should have been clearer about flexibility on the 350 MCM cable. It's extremely flexible, again used on electromagnets which can really swing around in maritime salvage.


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