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redpoint5 03-24-2019 03:04 PM

Electrician Question - Connecting detached garage
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My parents have 2 electrical meters and pay the monthly connection fee on both meters, but the property only has 1 habitable house (house2)

Attached shows the current electrical connections in yellow, and the proposed connection in orange, with the idea to eventually eliminate the House1 meter and electric service.

My question is, what type and gauge of wire should be run from house2 to the garage 100 ft away? There's already a 1" buried conduit running from the house2 panel to the garage. BTW, the garage is used as a shop, so 240v is needed for a compressor.

Can we run house2 > garage > barn from the house2 service panel, about 400 ft total? The barn electrical requirements are minimal, just needing 120v for minimal lighting and an outlet.

I'm pitching the project to my parents as a way to reduce the monthly connection fee for the redundant service, but my interest is for everything to be electrically connected so I can run data over electrical for surveillance cameras.

redpoint5 03-24-2019 07:26 PM

Just realized this should probably live in the DIY forum.

me and my metro 03-24-2019 09:03 PM

Before you start are both services 200 amp and are you with PGE or someone else?

ksa8907 03-24-2019 09:26 PM

Speaking to the wire choice: when I ran power to my garage for my L2 charger, it was approximately 75 feet between the existing panel and the new sub panel. I used 10 gauge rated for direct bury. I read a few places that even in conduit it had to be direct bury rated, I forget the industry spec. With 10 gauge I'm good up to 30 amps at 100', it was a compromise, I really should have gone with 8 gauge.

So it really depends how much load you're going to have. Also, my project was diy and it still cost me around $2-300 iirc. It may be cheaper to just keep both services.

oil pan 4 03-24-2019 10:21 PM

It all depends on the air compressor.
The minimum you should run a few hundred feet is 10 gauge.

The max you can run in 1 inch conduit is three current carries in 4 gauge and a smaller ground. 4 gauge will limit you to around 70 amps at 100 feet.

Direct burial wire is UF-B.

redpoint5 03-24-2019 10:42 PM

I'm not certain what house1 service is, but house2 is very likely 200A since it was installed just 10 years ago. House1 was built in the 19th century, so who knows when the last time service was upgraded. It has a fuse box instead of a breaker panel. The utility is PGE.

We've got a section of direct burial 10/3+G that is probably long enough, so maybe it's best to just use that. I doubt we need more than 30A to the garage. I should find out what is already running from house1 to the garage.

I'll have to look at what breakers are in there already. There's no sub-panel, and I don't know if one is required by code. We might have a sub-panel available though if one is needed.

So, if we run 10 gauge to the garage, can we also keep the existing run to the barn? As it is, I think it's just a single outlet running to the fuse panel of house1. Probably 10 gauge running to the barn, as that would explain how we have a leftover section. It's direct buried at 3 ft with no conduit. An online calculator says 10 gauge 120v at 400 ft has a 13v drop at 15 amps. That seems acceptable for a single outlet providing minimal lighting.

I know it's a big no-no, but I'm going to try running cat5 in the same 1" conduit to the garage. Don't need a lot of bandwidth, just 2 PoE IP cams. If it sucks, I might try shielded cat6.

ksa8907 03-24-2019 10:52 PM

I think I see better what you're after. I would put in the sub panel in the garage and also drop another ground rod at the panel, it will actually benefit the main service by having a 2nd ground separated by some distance.

Now, I can just about promise it would not meet code but yes, I believe you can feed power back to house 1 then on to the barn from the new sub panel in the garage.

redpoint5 03-24-2019 11:15 PM

Kinda don't care about code beyond the garage. Won't be selling the property in the foreseeable future, and the wiring was always makeshift.

That old house had the fixtures with pull chains on the sockets, along with an outlet. My dad routed strings through eye screws to these sockets so we could turn lights on where entrances were rather than having to walk to the socket to turn them on.

So, it sounds like the project cost might be nothing if the section of 10 gauge can be used in the existing conduit, and assuming we've already got a sub panel. I'm sure we've got a spare ground rod laying around somewhere too.

So, if 10 gauge is acceptable for 30 amp service at 100 ft distance, does that mean I use a 30 amp breaker in the house2 main panel?

oil pan 4 03-25-2019 12:52 AM

A lot of places require a grounding point at each structure with a panel.
A 30 amp breaker should be fine for 100 feet.

freebeard 03-25-2019 02:32 PM

My opinion is worthless, but I will note that my VW mechanic moved shop and when he ran power underground to his new building, the inspectors made him pull up ~100ft of aluminum wire and replace it with copper. So there is that.

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