Is fine stranded wire ok for main supply line?

Question

I’m changing the load panel in a mobile home with additions to gain additional circuits.

Outside a few feet from home is the service pole with meter and a 100 amp disconnect.

I became concerned about the entrance wire because it is a fine stranded wire like automotive battery cables or like welding equipment wiring. The picture shows the work in progress and it is complete now but I wonder if this type wire is anything to be concerned about especially since I will be adding to the load draw with a central heat pump.

In the red square you can sort of see the fine strands that the entrance wire has. I can’t get better pictures until I return to this vacation home.

To clarify I was expecting the wire to be stranded like this

But what I have is very similar to this

Edit: Returned and pulled old wire out. It was in a heavy rubber jacket that had writing on it indicating it was mobile home wire like one uses for a camper at at campground. It stated it was for 50 amps.

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Replaced with #1 copper wire on hots and neutral and #3 copper on ground.

Answer 1

A terminal problem

Beyond the potential labeling/marking (or lack thereof) issues with this wire, there is a serious problem with this setup: equipment terminal lugs are not suited for fine stranded wire (anything finer than what UL calls Class C stranding) unless the equipment is specifically listed for use with specific fine strandings, which is not true for light duty loadcenters.

As a result, what we have right now is a 110.3 violation of the loadcenter's listing and labeling, atop anything else that's going on with the wire itself. Given that the wire appears to be in conduit, simply replacing the run with the correct stuff is the best option, as that will cure any issues with labeling/marking as well, and also gives you the chance to adjust conductor sizing as-needed.

Answer 2

I can call it right now.

I don't see any markings on the wires. Now, perhaps the wires come out of a multiconductor cable, whose cable sheath has markings that indicate it is one of the NEC/UL rated types of wire legal for mains wiring. But if not...

Wires without insulation markings are no wires at all.

You don't even know what you're looking at here. You don't know what insulation temp column you should be pulling out of for 310.15(B)(16). You don't know if it's 600V insulation. We don't know if the insulation will hold up over time, in the environmental conditions, or with the heat of the wires working normally. For all we know it could be Chinese car battery cable.

Given that it's all 4 colors, there's a fair chance it's cable in sheath, or was shucked from cable in sheath (there go the markings). This is why you can't shuck NM to get wires for running in conduit.

Answer 3

I won't comment on the legalities since I'm not from the US and I'm not deeply familiar with their codes, but from a safety point of view my big concern would be the insulation.

It's difficult to be 100% sure from a photo but those conductors look like rubber to me. Rubber insulation was phased out from fixed-wiring wires/cables a long time ago, but it's still used to this day on some types of flexible cord.

The problem with rubber is it can oxidise over time leading it to harden, then when the cables are manipulated to modify the installation it can crack.

Answer 4

Yes there is fine stranded wire, it is not common because it is more expensive. I use it on equipment that has a high vibration or regular movement because the fine wire holds up better in those conditions than heavier strands. thick strands tend to break with movement. Since this is a mobile that might be why this type wire was used but it goes back to the size of the wire if it will do the job or not, fine or heavy strands don't matter it's the gauge or size that is the limiting factor.

Answer 5

If you are asking if it is OK to use stranded wire VS solid wire, then yes, stranded is OK, as long as the current rating of wire is appropriate.

Stranded wire is easier to bend and thus easier to wire panels with. (In fact, it is the only option when you reach certain sizes, because you would need a hammer to bend a solid core wire).

One important thing:
Stranded wire cannot be used directly in most screw terminals (lugs).
You need to clamp an special endpiece before screwing it in, otherwise the screw ends mashing the tiny wires aside, sever some, generally make a mess.

In Your panel, you appear to be missing those endpieces -> fix.