Sub-panel

[Frank Pratt]

I'm sticking with copper even though the cost is higher.

On the advice of the utility company and two electricians I installed 650' of 2-2-2-4 mobile home feeder underground to a future barn site but used it only for a couple of low amperage circuits (lights at the sub panel and from there another 400' of #10 copper underground to the electric gate opener). I was wary of using aluminum underground because I had heard horror anecdotes but was assured it would be fine.

After about 8 years it failed. dropping voltage drastically over a few days, eventually killing three of the four conductors.

I replaced the run with #2 copper thwn in conduit. The initial cost benefit of the aluminum vs copper was negated by the cost of doing the job twice.

For my shop I ran 250' of #1 copper underground in conduit and fed with a 100amp breaker. That wire provides more capacity than I need in the shop but who knows what other sub-panels I might decide to run from there or what the next owner of the property might do with the building when I kick off.

JKJ

Aluminum wire will last just as long as copper, providing there is no damage to the insulation. Even a small nick exposing the aluminum to moisture in the soil will lead to corrosion. The metallic aluminum turns to a white powder, swelling & bursting the cable jacket. If there is no insulation damage and the wire is terminated in the correct manner, it will last indefinitely.

The damage may have occurred prior to burial, or perhaps a sharp rock did the job. Around here, even if the service cable is approved for direct burial, it is usually installed in PVC conduit as physical protection.

[John K Jordan]

...The damage may have occurred prior to burial, or perhaps a sharp rock did the job. Around here, even if the service cable is approved for direct burial, it is usually installed in PVC conduit as physical protection.

I knew that and I was very careful with the handling and installation and put down a layer of fine dirt with no rocks below and above. I wondered if it came with insulation damage or defect - I did not inspect every inch. One story described the decay even in conduit. Lesson learned for me, use copper and always use conduit. I always run UF cable in conduit too for physical protection.

One thing I liked about using individual #2 thwn rather that the four conductor bundle was the handling. The mobile home service feeder bundle was on a huge reel and difficult/dangerous to handle on a hill. I fabricated an axle to hold the reel on forks on the front of the tractor and drove backwards to unspool next to the trench. By contrast, I put two much smaller diameter spools of individual #2 at once on a long piece of pipe and held it up off the ground with the excavator thumb and unspooled by pulling by hand.

JKJ

[Frank Pratt]

I knew that and I was very careful with the handling and installation and put down a layer of fine dirt with no rocks below and above. I wondered if it came with insulation damage or defect - I did not inspect every inch. One story described the decay even in conduit. Lesson learned for me, use copper and always use conduit. I always run UF cable in conduit too for physical protection.

One thing I liked about using individual #2 thwn rather that the four conductor bundle was the handling. The mobile home service feeder bundle was on a huge reel and difficult/dangerous to handle on a hill. I fabricated an axle to hold the reel on forks on the front of the tractor and drove backwards to unspool next to the trench. By contrast, I put two much smaller diameter spools of individual #2 at once on a long piece of pipe and held it up off the ground with the excavator thumb and unspooled by pulling by hand.

JKJ

As long as the wire is rated for wet locations & the insulation is not compromised, degradation simply does not happen. Not in our lifetimes anyway. After backfill, performing a high voltage insulation test would reveal any insulation damage, Course, by then, it's already covered up.

[Mike Cutler]

The OP's stated purpose for the small, auxiliary shop structure should be reasonably served by a 40-50 amp subpanel, IMHO. He stated it would be for hand-tool woodworking and already has a larger shop setup.

Jim
Sp many folks start out that way, only to find themselfves10 years down the line kicking themselves for not pulling a bigger service.
If he's already got the conduit in the ground, fill it.
A friend ran a direct burial,30 amp service two years ago to a detached "garage/shed". I told him to run 100 amps in conduit. Now he wants to learn to weld and is going be running a new service.
It's kind of fun poking at him about it.

[Marc Fenneuff]

The NEC is available online for free from the National Fire Prevention Association’s website. You have to register, but registration is free.

I’ve browsed the NFPA website before, looking for the NEC, and haven’t found it. Any tips?

[Jim Becker]

Mike, in general, I don't disagree that there can be regrets with not installing for higher usage in the future. My shop building originally had (marginal) 50 amp service which I upgraded to 200 amps. (the previous owners only used the building as a garage, so that wasn't inappropriate) That said, there is some information we don't know about the OP's current services, such as whether or not the main shop has separate service or is a sub off the residence, etc. So to me, for the small shed intended for "quiet" woodworking, the 40-50 amp sub-panel still makes logical sense based on what we know. Of course, in the end...it's the OP's choice.

[Dan Rude]

The link for the NEC on the NFPA is https://www.nfpa.org/NEC/About-the-N...ical-standards Dan

[John Lifer]

My Shop has a small 60 amp subpanel. PO ran it and had plenty of outlets and a couple of light circuits and one 240 circuit which looked like he probably did a bit of welding (not much, but some). It is barely adequate for me, I've kicked a single breaker occasionally with the DC I have, but nothing else, but I sure wish it was a 100 amp.....
I don't want to run the 150 feet again in my rocky soil. Do it once, and never regret the initial cost. It will soon be forgotten.

[Charlie Velasquez]

My Shop has a small 60 amp subpanel. PO ran it and had plenty of outlets and a couple of light circuits and one 240 circuit which looked like he probably did a bit of welding (not much, but some). It is barely adequate for me, I've kicked a single breaker occasionally with the DC I have, but nothing else, but I sure wish it was a 100 amp.....
I don't want to run the 150 feet again in my rocky soil. Do it once, and never regret the initial cost. It will soon be forgotten.

The 60 amp sub panel may not be the issue with your dust collector. Unless you tripped the breaker that feeds the sub panel you had enough amps, it was that specific circuit that was too small. You can run as many circuits as you wish to use those amps to your best advantage. Remember, a sub panel supplied by a 60 amp two pole breaker on the main panel allows you to use 60 amps on each leg.... I think....

If your dc has the option of running at 120 or 240 you may want to set it to run at 240. The equipment may or may not run better, but 1) it will distribute the amps over both legs of your panel and 2) if the wire size on your 120v circuit is currently barely adequate, the reduced amps per leg will mean your wire size is now actually oversized and should eliminate that overload situation.

[Tom M King]

i have a scientist friend who bought a Tesla. He wanted a 240v charging circuit in his garage. There was no prewired circuit for 240v, but he found that he had two 20 amp 120v circuits, with each coming from a different leg of the main panel. I'm not saying try this at home, but it worked for what he wanted to do.

[Frank Pratt]

i have a scientist friend who bought a Tesla. He wanted a 240v charging circuit in his garage. There was no prewired circuit for 240v, but he found that he had two 20 amp 120v circuits, with each coming from a different leg of the main panel. I'm not saying try this at home, but it worked for what he wanted to do.

To do this legally, or for that matter, safely, both conductors in the 240V circuit must be part of the same cable assembly or in the same conduit. And they must be fed from a 2 pole breaker, not separate single pole breakers. If he can afford a Tesla, he can afford to put in the correct circuit to charge it.

[Mike Henderson]

i have a scientist friend who bought a Tesla. He wanted a 240v charging circuit in his garage. There was no prewired circuit for 240v, but he found that he had two 20 amp 120v circuits, with each coming from a different leg of the main panel. I'm not saying try this at home, but it worked for what he wanted to do.

I agree with Frank - you don't have to be a scientist to figure that wiring situation out. But 20 amps is not much to charge a Tesla - it would take a long time. The Tesla will not pull 20 amps from a 20 amp circuit. I think it's 85% but I don't remember exactly.

I had a guy come into my home to do some polishing on my stone floor. He had two 120V plugs on his polisher and he went from outlet to outlet until he hit two plugs from different sides of the panel. And he certainly wasn't a scientist.

Better to put in a legal 50 amp circuit and get the Tesla charged in a reasonable amount of time.

Mike

[Tom M King]

He probably has done it correctly, by now. I haven't seen him in a long time, and that was right after he had bought the car. I just thought it was funny.