Since that is stranded copper, you only need #4AWG for 100 amps. At least under the 2020 NEC. Quite a bit less.
Pull a permit and ask the inspector.
Mike
Originally Posted by Scott Winter
Since that is stranded copper, you only need #4AWG for 100 amps. At least under the 2020 NEC. Quite a bit less.
Pull a permit and ask the inspector.
Mike
New house here, Aluminum for 200 amp service. Installed in 2" PVC 2 feet deep as we have rock and more rock. If installed correctly, no issue with aluminum. And probably 25% of copper even with PVC. But 35' run? Copper and why not go 100amp. I've only 60 amps into my shop and it does push load if I run several items at once.
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Sixteen years ago, I ran 4/0 RUD aluminum cable 192 feet inside 2" Schedule 40 conduit for a 200 AMP service to my garage, office, workshop. I also used sand under the conduit and on top of conduit before backfilling the trench The electric company advised it was overkill. After reading about Jordan's issues I'm happy I went the extra step. No problems so far.
Contributor
I would get a larger then needed subpanel and install a whole house surge protector in the subpanel. Square D makes a surge protector that plugs into two slots and just has one wire that connects to neutral. All those big motors will cause surges inside the house wiring.
With any surge protector place it as close to the infeed as possible
Contributor
When I built my house the location of the transformer made it too far away to use 0000 wire. The vault the transformer is on had to be where it is because of it's distance to the next vault down the line. So the option would have been to install another vault or jump up to a thicker gauge. I could have gone with mcm 300 but it was close so I just went with mcm 350. I found it was easier to lay the cable out and then slide each section of the conduit onto the cable. By doing so I noticed that the inside edge of the conduit can be sharp enough to damage the cable so I sanded the edges on each section.
For my garage I went with 100 amp sub panel. I know of nobody who ever said "I went too big" on a lot of things including power to a sub panel. I forget the size wire I used, 0 I think, but ran aluminum in conduit. I don't think I would ever directly bury service cable. Too much of a chance of it getting damaged in my opinion. Conduit (at least pre pandemic) is too cheap for the insurance it gives you. I wouldn't go with 60 amp subpanel. In a garage you could have a 3hp dust collector and a 5hp planer going when the 5hp air compressor turns on. For an extra few bucks why worry?
Contributor
There must be posts on this somewhere, but the question of service size: In a one person shop, how many machines are likely to be running at one time and under what current draw?
I might be running a jointer/planer, but it might not be drawing full current. I do have an electric shop heater that might run continuous. And compressors and DC might be in the background when a machine kicks on. But even my tablesaw rarely sees full load. Ditto on the band saw. So even multiple motors are unlikely to pull full current simultaneously.
I have 60A available to me, so far it has not kicked out. I tend to prioritize having low voltage drops - all my 220V I wire with 10awg, whether the machine needs 30A or not (tend to not like having different size plugs). Reduces low voltage drops from surges (maybe?).
Currently my tablesaw, bandsaw, jointer/planer are all 4hp. (Euro machines). An electric shop heater. A 2hp DC. And a 5hp compressor although I can ensure the compressor doesnt kick on when running other equipment. A radio and some LED lights. Is the most I can think of at any one given time (welders and powder coat oven would be completely separate).
My prior shop I put in 200A to the shop and upgraded to 200A for the house (yep, 2 200A services to the transformer). 200+ft underground 0000 Al in conduit on sand buried 2ft (code for my area). I never had to blink with that but was it necessary? Nope. Also running a second empty conduit while the trench is open seemed a good idea, but I never ended up using it. There was a satisfaction knowing it would never be an issue, but thats just engineer psychology not logic - some design philosophies say wasting resources/material to create unnecessary overkill is bad design....
Al in conduit underground seems no issue, and would be considerable savings.
Moderator
"Need" and "Practical" have to be rationalized here. Many folks indeed can do just fine with a 60 amp sub. But the cost to install a 100 amp sub isn't materially all that much more and gives more headroom for unanticipated needs. That's why I chose to do that in my temporary shop. 60 would have been fine, but because the sub is literally next to the main panel, there was nearly zero difference in cost other than with the actual breaker to doing 100 vs 60. Permit was the same. Panel was nearly the same. The $200 for the licensed electrician to do the hook up to the main panel was the same (I chose to do pay for that service even though I normally do my own work and was going to to run the circuits myself) Etc. The one variable is distance for the feeder cable and cost for that cable is currently high. I lucked out there as the electrician I hired to do the hookup had a hunk of SER that he included at no charge, but it was only a few feet.
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The most expensive tool is the one you buy "cheaply" and often...
Member
Aluminum wire = Fire
Moderator
Aluminum is very common for service entrance and panel feeders. It's used even more right now for that application because of the cost of heavy copper service entrance and feeder cable. It's not a fire hazard in that context and there are specific measures taken to insure that from a code and practical standpoint.
Aluminum in circuit wiring, however, isn't a thing anymore exactly because of hazards it created long ago.
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The most expensive tool is the one you buy "cheaply" and often...
Contributor
That's a ridiculous statement that shows a near complete lack of knowledge on the subject.
Contributor
One thing I forgot to mention, just because a inspector approved it does not make it correct or code compliant, and they can't be sued because they have immunity.
Contributor
Yeah, not so much, but it is still code compliant. The issue was its coefficient of expansion was markedly different than copper. So any termination or connection with copper was problematic. It was also more malleable than copper.
Since the ‘70’s, changes were made. Only special aluminum alloy that mimics the expansion rate of copper, or copper clad aluminum is used.
Additionally, any device or connector must be rated for Al, like alumicons.
It is wise to treat the connection or termination with an anti-oxidation compound, like noalox.
And, you need to remember that aluminum is not rated the same as copper. For instance, the 100 amp panel under discussion would be #3 copper, but #1 aluminum; a 20 amp circuit would be #12 Cu or #10 Al.
Last edited by Charlie Velasquez; 12-10-2021 at 6:11 PM.
Comments made here are my own and, according to my children, do not reflect the opinions of any other person... anywhere, anytime.
Contributor
Jim,
my subpanel is about 2’ from the main. When we built the house, the electrical contractor wanted $900 to wire it to the main. My general contractor called that an, “I don’t want to do it” price.
Moderator
That was definitely an "I don't want to do it" price! Sheesh. I paid the guy $200 and he made really good money for the less than an hour he was there and that included the short hunk of SER. I did have the sub already mounted so all he had to do was drill a hole through a stud, crimp out a big enough hole in the bottom of the main panel and do the deed. That was before he went to do his "big" job for the day...kinda the "absorb the coffee" work before doing heavier lifting.
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The most expensive tool is the one you buy "cheaply" and often...
Contributor
I had purchased the sub, mounted it and had the wire. This is on a basement wall so no studs to drill. When I did it, I put a few blocks under the wire to stabilize it.That was definitely an "I don't want to do it" price! Sheesh. I paid the guy $200 and he made really good money for the less than an hour he was there and that included the short hunk of SER. I did have the sub already mounted so all he had to do was drill a hole through a stud, crimp out a big enough hole in the bottom of the main panel and do the deed. That was before he went to do his "big" job for the day...kinda the "absorb the coffee" work before doing heavier lifting.
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