Industrial Control Panel - flexibility of larger conductors

[johnd_12500]

We typically use THHN and MTW wiring for control panels and either works well. In larger gages, such as 4/0 the THHN is very stiff and hard to work with. MTW is much more flexible but it almost too finely stranded. A power distribution block we have allows wire class B and C. THHN that I have seen is Class B. Class C would be more flexible but I am having trouble finding any. MTW is so finely stranded its about Class K and not usable on this component.
Any suggestions on a 4/0 that is more flexible than the typical, THHN, 19 strand wire, that meets UL Class B or C?

 

[infinity]

Can you use dual rated welding type cable? If the fine strands are a problem there is a metal foil that is used with fine stranded conductors and standard terminals. I'll see if I can find a photo.

 

[johnd_12500]

From what I've seen the welding cable is the s uper fine stranded cable, similar to MTW. For the power block I'm using it just had a set screw that clamps directly onto the wire. On the fine stranded stuff it causes strands to back out and go every which way which is probably why they only approve Class B & C for this component.

You bring up a good point about treating the end of the wire with something to keep the fine strands in check. I haven't seen ferrules big enough for 4/0. Back when we used to dip the ends of the wire in molten solder.. I'll search for the metal foil you mentioned. Thanks.

 

[petersonra]

Can you use dual rated welding type cable? If the fine strands are a problem there is a metal foil that is used with fine stranded conductors and standard terminals. I'll see if I can find a photo.

I don't think the metal foil is listed for that purpose.

But these days there are plenty of terminals listed for fine stranded wires. Also distribution blocks.

 

[infinity]

The metal foil is not listed for that purpose.

But these days there are plenty of terminals listed for fine stranded wires.

I've seen on factory installations from transfer switches. Are you saying that it is not listed for the purpose? Right from the manufacturer:

 

[petersonra]

It's possible they got some dispensation from UL for that specific application.

But you cannot normally take copper foil and wrap it around the strands of wire and call it good.

 

[infinity]

It's possible they got some dispensation from UL for that specific application.

But you cannot normally take copper foil and wrap it around the strands of wire and call it good.

When I saw this I assumed that it was some type of listed product. We had over a dozen factory wired units built this way.