I have a detached garage I want to run a 100amp subpanel. The total wire length from main to subpanel should be less than 90ft(garage is about 50 ft away from house). I have to run from the main panel across part of the unfinished area of the basement to the cloesest exterior wall and then trench underground to the garage.

I plan on running conduit underground when the cable leaves the house but conduit would be near imposible for the inside run since I have to snake around a couple obstructions. I know I could put a juntion box in and change wire types when I leave the house but wanted to find an economical way to do this with one continuous run of wire.

My local county code says Aluminum wire can only be used for service entrance and feeder applications. Is a subpanel a feeder application? If so what wire should I use if I can use aluminum? Should I go bigger than #2 aluminum?

I looked into copper but without spending a ton the best option was to use Romex through the basement and junction box to THHN inside of conduit to the subpanel.

Yes a subpanel would need a "feeder", so aluminum should qualify.

To run cable inside you can use SER 4 wire aluminum feeder cable. In conduit, you can use aluminum wire with XHHW insulation.

#2 is fine, but if there are any larger motors, you may want to consider using #1 to hel reduce voltage drop. The #2 will exceed the recommended 3% if the load gets close to the maximum of 80 amp load on the panel.

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Originally Posted by kman1

I have a detached garage I want to run a 100amp subpanel. The total wire length from main to subpanel should be less than 90ft(garage is about 50 ft away from house). I have to run from the main panel across part of the unfinished area of the basement to the cloesest exterior wall and then trench underground to the garage.

I plan on running conduit underground when the cable leaves the house but conduit would be near imposible for the inside run since I have to snake around a couple obstructions. I know I could put a juntion box in and change wire types when I leave the house but wanted to find an economical way to do this with one continuous run of wire.

My local county code says Aluminum wire can only be used for service entrance and feeder applications. Is a subpanel a feeder aplication? If so what wire should I use if I can use aluminum? Should I go bigger than #2 aluminum?

I looked into copper but without spending a ton the best option was to use Romex through the basement and junction box to THHN inside of conduit to the subpanel.

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Thanks for the answer but can I run either of these cables the both inside without conduit and outside with conduit for the entire run or do I have to use two different cables?

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Originally Posted by kman1

Thanks for the answer but can I run either of these cables the both inside without conduit and outside with conduit for the entire run or do I have to use two different cables?

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Please explain, which cables?

By cables I meant the wire types you recommended. Can either of them be used in my application for the whole run or do I have to buy two different types and splice them together when I change from the basement part of the run where there will be no conduit to the outside part where it will be buried underground in conduit.

The feeder from my main panel will run down to the basement, then across the basement ceiling to the back of the house. There it will exit the back of the house to a conduit buired according to code to the garage. Is there one type of aluminum feeder wire that can go the whole way from the main panel to the subpanel without having to splice it that can run across the basement without conduit and then go into conduit? I'm trying to see if there is a cheap enough way to run the feeder without having to put a junction box in the middle of the run?

Can someone help me out if I am not wording my question correctly? Thanks, Kevin

I believe he wants a single cable type which can be placed in conduit underground and used inside with only clamps (no conduit) such that it is a single run, without splices in junction boxes.

The cable in the basement should be the Romex or SER cable. This will stop at a junction box at the point the conduit will continue on outside. Individual conductors must be pulled through the conduit and spliced to the cable at the junction box.

The only cable that can be continuous through the basement and direct buried is UF cable. This cannot be pulled through conduit unless the conduit is oversized, since UF cable is flat and does not pull easy through conduit, not made for that purpose. It can be buried directly in earth thou.

This may not be practical due to the cost of UF cable.

Could he run the flexible plastic conduit in the basement, smurf?

You know, actually, that is a good idea. I did not think of that. Using some sort of flexible conduit would allow conductors to be pulled from the panel to the end of the line, with no splices.

I will say, if I had one to do tomorrow, I would probably still use cable inside, and splice at the conduit. But that's me, old fashioned and stubborn.

Wire pulling is, quite frankly, a b**** (female dog). Pulling through straight conduit it can be a challenge if not set up right, but manageable. I have pulled through long runs of flex, and that is no fun at all.

I wonder what the opinion would be of other professional electricians.

It's a bit of a weird run from the main panel in the house. It goes down from the main panel a couple of feet, then snakes through some block to the basement. Then across the ceiling around a steel beam and some ducts then through more block to a crawl space and out then through the wall to the outside for the buried section.

I'm guessing even the flex conduit would be a pain for what I'm doing inside the house. I was trying to avoid the splice especially if I went with aluminum to save a couple bucks. I figured the fewer junctions the better. Let me know if you come up with anything else. Thanks

I talked with one of the inspectors in my area and he tells me I can use SER Aluminum for the entire run without having to splice in the middle. He said I can do this because it will be fused since it is going from my main panel to a sub panel.

I will run Ser from my main panel through the basement without conduit and then continue the run underground in conduit to the detached garage. He said be careful of tight bends and I might have to use a raceway?
Does this sound correct? I want to meet code and have the job done right. I am going to have an electrician do the permit and the work but I have talked with a few and get different answers.

Conduit is raceway. Raceway is the generic term for any enclosure to run wiring, to include conduit, Wiremold, wire trough, etc.

I think, since I am assuming you are asking him the questions and not an electrician, he is setting you up to fail, or there is something he does not understand.

He gave you a clue to be careful if you pull SER cable through conduit.

The size conduit needed to pull SER cable will need to be grossly oversized to be able to pull SER cable through it, esp through sweeps, elbows, and wait till you try to get it through an LB fitting, if you use one.

No electrician, including me, would pull SER cable through conduit for any decent distance, other that through a short sleeve through a wall or floor.

If you use #2-4 Al SER cable, you will need at least 2" PVC, maybe larger. And I assure you, who ever pulls the cable will have a great deal of problems, if not damaging the conduit itself in the process.

What does your electrician say about this? I understand you want this done to code, the electrician that you hire will be the permitee, and will be fully and completely responsible for the insuring the entire installation be installed to comply with code.

I'm not a professional sparky, but I've run and pulled a lot of cable. I like the idea of one solid run to the sub panel. I just don't like splices in that large a feed. Nothing wrong with it, it's just my personal preference. I really like labman's idea of using flexible conduit. It seems to me that if you can run cable around your obstacles, you should be able to get flexible conduit too. It may take a bit more work and ingenuity, but you would have a cleaner install IMO...

The electrician was first on that told me he wanted to use aluminum wire and could do the whole run without a splice. I asked him how he could do that and he said he would use "Se" wire. He hasn't started the job yet but I wanted to make sure he knew what he was doing.

The run would start at my main panel then snake down into the basement through some cinderblock then across the ceiling of the basement around a few obsticles, then make a left turn through a cinderblock wall to a crawl space then out through another wall to the outside.

The first part where where it comes from my main panel there is about 18 inches from the bottom of the panel to the start of the cinder block and then goes into the top of the cinderblock and then comes out the side of a block into the basement if that makes any sense. That's where it would be the hardest to use conduit. Maybe I should just ask him to use Romex inside the house and put in a junction box somewhere?

He is licenced and is pulling a permit for the job.

If I had the job, it would be done by now, with Romex in the basement, and conduit in the ground, with a junction box where the two meet in the basement, with splices, that will never fail.

Plain, simple, off the shelf products, and no back breaking work involved.