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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.

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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 enter image description here

But what I have is very similar to this

enter image description here

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.

. enter image description here

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

  • When you get back there, can you get us better pictures, especially showing any markings that are present on those feeder wires? – ThreePhaseEel Mar 31 at 20:10
  • Also, would you be able to get us a very close-up of the end of a representative wire? Your photo doesn't show nearly enough to let me count strands... – ThreePhaseEel Mar 31 at 20:20
  • @ThreePhaseEel yes I will edit in better pictures in a week or so. In your experience have you seen very finely stranded wire used fir this application? – Kris Mar 31 at 21:27
  • it's not common for sure, and if it was fine stranded, then it's a 110.3 labeling/listing vio as loadcenter lugs aren't listed to accept it, but it's definitely possible – ThreePhaseEel Mar 31 at 22:10
  • I see Mr. Snippy has been in the panel and cut back all but the minimum possible wire length. Better to leave enough length to allow hot+neutral to reach any space in the panel. Neutral too because GFCI+AFCI. – Harper Mar 31 at 23:21
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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.

  • Thank you I was not comfortable with how the lug was capturing the soft bundle of strands now I am certain I will change the cable . – Kris Apr 2 at 1:51
  • +1 This is the best answer to the headline question and is most likely to help others with the same question in the future. – statueuphemism Apr 2 at 14:10
  • Thanks again I got the old stuff out and new outside panel and wire done today. Edited question with what I found. – Kris Apr 18 at 0:07
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    @Kris -- I think we're all glad for the end result of this, given what you found! (50A wire on a 100A breaker with no OCPD at the other end of the line...zoinks) – ThreePhaseEel Apr 18 at 0:26
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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.

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    We do know it has held up over time since the original setup of mobile home was in 1969. What I don’t know is if it will hold up in the future with a heat pump being added to the mix. There was no ac in this house only a small electric furnace which was rarely used since it is a summer destination. I’m thinking I will replace the short run from outside disconnect to panel. – Kris Mar 31 at 23:47
  • Is there an NEC/UL rated wire that is fine stranded and legal for use as service entrance cable? – Kris Mar 31 at 23:58
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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.

  • I’m thinking grand dad who had a big woodworking shop with some large three phase machines may have used some reclaimed wire here. I will verify the size of the wire before final decision is made to replace or not. – Kris Apr 1 at 14:29
  • It was mobile home wire in a heavy rubber jacket. I edited the question. – Kris Apr 17 at 23:42
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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.

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