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I am wiring my new home. Can I run 4/0 aluminum THHN Service entrance from my Meter Socket to my main panel inside of the house 43' away through the attic without conduit or do I need conduit?

The cluster of 4 wires is roughly 1.5” in diameter. The cluster is not bound together with an outer sheath but the wires are twisted together. I have pulled my permit as is required but the inspector is hard to track down unless you want an inspection scheduled. I’d rather not have to do it over.

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    Is there a main breaker next to the meter? Because while your "main panel" in a practical sense (where all or nearly all branch circuits are connected) can be anywhere, it is normal to have an actual main breaker ("meter main") next to the meter or to keep that meter -> main breaker/panel very very short (typically just to the other side of a wall). The reason is that if any part of that 43' feet of wire got damaged there would be no overcurrent protection and the meter (and your house) could go BAM! Mar 28, 2023 at 3:19
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    I would check with your inspector before you start. diy.stackexchange.com/questions/70167/…
    – JD74
    Mar 28, 2023 at 3:37
  • Yeah, inspectors HATE dealing with DIYers with code questions. They feel it's your job to learn Code, and you're in the right place here. They are happy to clarify things which truly are fuzzy/wobblers/matter of interpretation that show you did your homework. Mar 28, 2023 at 3:41
  • Yes, per local code there is a 200amp main shutoff at the meter. I have an NEC book but this particular item is not clear to me.
    – Travis
    Mar 28, 2023 at 11:13
  • In my town, the inspectors would rather be asked before you start, as long as it's just one or two reasonable questions rather than "teach me how to do this" or "tell me how I can get away with doing something stupid."" I'd assumed this was common, as it's less work for them to prevent a mistake than to force rework and have to inspect it a second time. But there will be exceptions.
    – keshlam
    Mar 28, 2023 at 13:00

1 Answer 1

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The service entrance wiring is totally unfused

Service entrance wiring runs from your weatherhead or underground splice point, through the meter, and onward to the main breaker.

If the wires shorted together, no breaker anywhere will protect it.

This wire is also not grounded.

As such, the service entrance wires are not allowed to take "the grand tour of the house" as it were. Code requires they be absolutely as short as possible - typically with the main panel being on the other side of the wall from the meter pan.

So "hard no" on the idea of sending these wires totally unfused through the house.

NEC 2020 changes everything, though.

As the 2023 NEC edition has come out, many states are getting serious about adopting NEC 2020 and most have.

NEC 2020 requires an outside disconnect - the concept is to give firemen an easy way to cut power. But the effect is that the reasonable way to comply with the rule is a Meter-Main. This is a "meter pan" with a main breaker added.

Even if you're not on NEC 2020, the effect of the rule has been to change the economies of scale of meter-mains so they're pretty cheap now. So go ahead and use one.

Wow! That nicely solves the "unfused wiring" problem above! This main feeder is allowed to take the grand tour of the house if it wants.

It is not service wire since it's past the main breaker. It is feeder, so it needs 4 wires. But it sounds like you have that.

Individual wires need conduit. If you want cable, use cable.

Individual THHN, XHHW or USE/RHW wires need to be inside a conduit. If you want to cross the house without use of a conduit, use a cable that is approved for direct use indoors per NEC Chapter 3.

The first one that comes to mind is SE-R.

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