New shop: running wire to a sub-panel

[Roger Feeley]

We got our final inspection approval just today. Yay!!!! That means I can start installing the electrical for my shop.

The guys at the electrical supply sold me aluminum wire to wire an 80 AMP sub-panel. that stuff is pretty thick.

I feel pretty comfortable running the wire from the main panel to my sub-panel. I'm a little apprehensive about the aluminum part. Do I have to be careful about not bending it too much or anything? I think the total wire run will be less than 5 feet since the two panels will be side by side.

FYI, the main panel will be dead. There are three levels of panels here. We have the main panel in the main house with a 120A breaker supplying my new house (in-law quarters). There is a sub-panel in the new house that I think of as my main panel but it's really a sub-panel. Then there is my shop sub-panel. Confused?

main house(120A)--->pool house(70A)--->Safety shutoff switch with 70A fusable links--->shop panel--->my stuff.

I will shut down the 120A breaker in the main house so I can do the final connection between the safety switch and the pool house panel.

[Frank Pratt]

With aluminum, you want to be careful when stripping it that you don't score the aluminum. Scoring creates a weak point which can lead to breakage when the wire is flexed. Copper is much less susceptible to this. The lugs that the Al wire connects to must also be rated for Al (that's almost a given).

An approved oxide inhibitor must also be used on the connections. Be sure to follow the directions on the package.

Bending the cable a reasonable amount is not an issue.

Here's a tip to terminating: when tightening the wire in the lug, when you have it snug, bend/twist the wire back & forth gently a couple of times. Then finish tightening. That relaxes the strands in the lug & makes a better connection.

[George Bokros]

Personally I would not use aluminum. I know the utility in my area brings the power into the panel with aluminum but I would not use aluminum for any wiring in my house. When I put in my shop sub panel I used cooper, more costly but I feel more comfortable with cooper.

[John Lankers]

I have to agree with Frank in regards to the installation of aluminum wire and also with George, I would not want aluminum in my shop or house - to much potential for trouble down the road.

[Art Mann]

There is "trouble down the road" for the vast majority of houses nationwide. I just haven't seen that many house fires due to aluminum lately to be worried about it.

[Chris Padilla]

The feeder from the mains on the side of my house to the the house main inside the house is aluminum. Everything else is copper. House was built in 1975. Still there. :)

[Arthur Fleming]

I would set a date in the calendar for two months from when you install the aluminum, kill all the power, and retourque the aluminum connections. They can loosen up after the initial installation. Also I believe as of Jan 1, 2017 the NEC requires all connections to be done with a tourque wrench/screwdriver. With the Panels side by side the cost savings of aluminum over copper should have been negligible, money is the only advantage aluminum has over copper. Supply house should have explained that. When installed correctly aluminum is very safe, and I doubt you will have a continuous load, unless this is a business, and not a hobby. Frank is very correct in stripping the insulation very carefully, and not scoring the aluminum. Keep us posted on the shop (pictures good :) )

[Bruce Wrenn]

120 amp main panel, with a 70 amp sub already on it. You need a SERIOUS up grade on your main panel. Something in the 200-400 amp range. Unless you want to turn everything off in main house and pool heater when in your shop. Mama ain't gonna go for that!

[Darcy Warner]

I feed the 400a 480v sub panel in my shop with aluminum in parallels.

Way easier to pull that size wire, way less than copper sized for 400a in parallel.

Nothing wrong with aluminum feeders.

[Jim Andrew]

Think Arthur has a point here, and agree, just a few feet of aluminum vs copper not worth the trouble for small savings.

[John K Jordan]

Hmmm. I don't like aluminum either, I've heard too much about potential problems. Will it be underground, direct burial? Two friends who work for the power company told me they've seen problem where a rock worked into the insulation and caused the aluminum to disintegrate. Consider putting in conduit.

I ran 250' of #1 AWG copper underground to my shop, in conduit. I didn't see where you mentioned the distance but be sure to do the voltage drop calculations carefully. I wanted a solid 100 amp capacity in the shop but my wire size choice was oversized according to some advice (opinions) I got. What bothered me was they were guessing instead of calculating and they said the voltage drop wouldn't hurt anything. The electrical service is something you only do once and compared to the cost of the shop and the equipment, the cost of the wire is trivial.

Is 70A in the shop enough? It depends on what you want in the shop. Will you use electric heat and cooling, either now or some day?

If you decide to use copper you might have a fight returning the aluminum. 45 years ago when I built my first shop I was ignorant and the supply house sold me the wrong kind of cable. When I went back they said sorry, can't return it, not our fault, that's why we are not allowed make recommendations. But they HAD and I was very persistent. If the distance is short I'd just buy the copper even if they wouldn't give a refund on the aluminum.

JKJ

[Curt Harms]

There is "trouble down the road" for the vast majority of houses nationwide. I just haven't seen that many house fires due to aluminum lately to be worried about it.

True. AFAIK (not a sparky) termination is where people get in trouble with aluminum. Not tightened properly, no anti-oxidant paste, that sort of thing. Years ago I recall replacing an electric water heater. Aluminum to copper connection, ordinary wire nuts, no paste, was not a pretty sight.

[Bruce Wrenn]

You said you got final inspection today. Why isn't electric included in inspection. Are you doing wiring WITHOUT A PERMIT? Not a good idea!

[Rollie Meyers]

When torquing conductors, the proper way is to torque to the manufacturers specs, and LEAVE IT ALONE, do not retorque the conductors as too tight is just as bad as too loose, if just have torque it again, then trim off the cable & re strip & terminate the conductor.

Just another note, anti-oxidant is only required if the manufacturer requires it on aluminum alloy conductors as the NEC requires compliance with listing and labeling instructions, but anyone who says there is a blanket requirement to use anti-oxidant is wrong, that being said I use it on AL alloy conductors, which properly installed is just fine, improperly installed copper is just a much of a hazard as improperly installed aluminum alloy conductors.

[Robert Engel]

Roger,

I am not an electrician but I have had electricians do the same type work you are doing.

A few points:

1. AL is standard for service wire. I've asked several electricians about it they all say there is nothing wrong with it/no advantage over copper other than a) price and b)AL will corrode and break if the insulation is compromised. It also stretches more than copper and gets hotter than copper under load but this is made up by larger wire size. Yes, a lot of old timers prefer copper but when you price running a couple hundred feet CU vs. AL its quite a diff.

2. There is no way to know if you need a main service panel upgrade. It depends on what you have (AC/HW heater, etc.) and what the draw is. I would consult your electrician about this.

3. AL wire MUST be put in conduit, even if only running 5 feet. I think any electrician will tell you never do direct burial with AL.

4. 50-60A is going to be adequate for just about any hobby shop that doesn't have multiple machines/huge HP machines running all at once. But once again it all depends on what machines you have and what you'll be doing. Thinking ahead is the key. You will want dedicated circuits for a dust collector or compressor (whether 120 or 240V) or 240V arc welder, etc. This really determines what sub panel you need because every 240 circuit takes 2 spaces.

5. You'll probably be OK but I would feed the shop subpanel directly from the main panel instead of through a sub panel.

My shop used to be fed by 60A to a subpanel 120 feet from the main panel. I ran an entire shop including 3HP Planer, 3Hp tablesaw many lights and all the other machines you commonly see. I never had an issue *until* I lost one of the hots, which was caused by burying the cable instead of using conduit. Electrician said probably a root stretched wire or small nick in insulation caused AL wire to oxidize and eventually corrode through.

Since then I had an entirely new 200A service run to my barn/shop (only because I wanted capability of putting a mobile home on my property). They used AL wire in conduit 225 to the pole.

[Frank Pratt]

As Rollie stated, not all terminations with aluminum wire require anti-oxidant. Only if the manufacturer states that it isn't required. But I've never encountered residential electrical panels or breakers that met that criteria.

A further comment on torquing the connections. If the wire is inserted in the lug & the lug is simply torqued to spec, then subsequent movement of the wire (eg; when work is later done in the panel) can loosen the termination. If manipulation of the wire is done as part of the torquing process (as I previously explained) then that issue is eliminated.

When the insulation of an underground aluminum conductor is broken, even a tiny puncture, the aluminum will gradually turn to powder. Then one day you'll notice the lights flicker & go out. When this happens the wire will look grotesquely swollen, to the point where the insulation is split wide open & there will be no metallic aluminum, just that white powder.

I've had to repair lots of direct buried cable that was damaged only slightly but then failed. Usually fails within a year or two. The last repair was a 350' run of 750 MCM that was in conduit. The guy that drilled the holes for some bollards pierced the conduit with the tip of the auger, only about a 1/2" hole in the conduit. But it nicked 2 of the conductors.




When torquing conductors, the proper way is to torque to the manufacturers specs, and LEAVE IT ALONE, do not retorque the conductors as too tight is just as bad as too loose, if just have torque it again, then trim off the cable & re strip & terminate the conductor.

Just another note, anti-oxidant is only required if the manufacturer requires it on aluminum alloy conductors as the NEC requires compliance with listing and labeling instructions, but anyone who says there is a blanket requirement to use anti-oxidant is wrong, that being said I use it on AL alloy conductors, which properly installed is just fine, improperly installed copper is just a much of a hazard as improperly installed aluminum alloy conductors.

[Mike Henderson]

Personally I would not use aluminum. I know the utility in my area brings the power into the panel with aluminum but I would not use aluminum for any wiring in my house. When I put in my shop sub panel I used cooper, more costly but I feel more comfortable with cooper.
Aluminum would not be my choice, either. I had a house where they used aluminum from the meter to the main box. One day, the main circuit breaker tripped. I went out and checked it and the breaker was hot. The aluminum had corroded and formed a resistance connection. When electricity flows through a resistor, the resistor gets hot - and the heat had tripped the breaker.

So I went and bought copper, pulled the meter and replaced the aluminum with copper. Then I called the power company and told them to come put a new lock on the meter. They were not happy and told me I had to pull a permit and get it inspected. I wasn't concerned about the safety of what I had done so I put a small tip on my oxy/acetylene unit and welded the wire of the old lock back together. Unless you looked really hard, it was hard to see it had been removed.

Mike

[Robert Hayward]

http://photos.imageevent.com/bayward/latheturning/websize/Wire%201a.jpg

Picture of an aluminum wire from the meter can to the house panel. About a 3' run and all three wires looked like this. The aluminum had gotten hot enough over who knows how much time the wire insulation was bubbled and brittle. This came from a home that was about 40 years old at the time. The wire pictured had not been handled or made to look like it does, it came out of the electric panel just like you see it.

[Eric Keller]

Interesting discussion. My subpanel is about 100 feet of wire away from the main panel. I put it in at peak copper pricing, and to be honest I don't think copper was an option for wire that big, because they didn't want to spend the money to stock it and their customers wouldn't have bought it. Obviously, aluminum has a really bad reputation so I asked them about it and they told me not to worry. I haven't looked at my feed recently, but the last time I was in the panel it looked fine. I did use antioxidant though, they recommended it.

[Frank Pratt]

Let's be clear about one thing. Aluminum feeders, if properly installed & terminated are no more problematic than copper. Full stop. And it's not at all difficult to do properly. Just make sure you know what you're doing.

So for short runs, I say go for the copper. For longer runs, you're just throwing your money away using copper. But if it makes you feel better to use it, that's just fine too.

[Roger Feeley]

The 70A is overkill. It shouldn't be a problem. This is an in-law quarters off the main house. (pool heater is on the main house and is gas).

-- All the lights in the place are LED including the shop.
-- We have an induction stove.
-- It's just the two of us.
-- Heat pump
-- We do have an electric hot water heater.
-- The clothes dryer is ventless and is essentially a heat pump.

I don't think I will ever draw the full 70A. I wanted to add a TIG welder someday and thought it would be nice.

The main house is 400A and we brought over 125 to our house.

[Roger Feeley]

Thanks to all:

My understanding of the permitting process is that if I pull a permit for my shop sub-panel, I have to have an electrician do all the shop wiring. I would also have to have an inspection every time I move or add something. That's just not happening. So this little panel will be off-book.

The distance is very short. The sub-panel will be right beside the main panel for the house. Total wire run is just a few feet.

Based on the good advice here, aluminum no longer intimidates me. But I do have an electrician friend back in Kansas City. I may try to skype with him to make sure I did things right.

I got some anti-oxidation stuff.

This whole thing is belt and suspenders. I will have a 70A breaker feeding a safety shutoff with 70A fusable links feeding my shop sub-panel.

[Mike Henderson]

Thanks to all:

My understanding of the permitting process is that if I pull a permit for my shop sub-panel, I have to have an electrician do all the shop wiring. I would also have to have an inspection every time I move or add something. That's just not happening. So this little panel will be off-book.

The distance is very short. The sub-panel will be right beside the main panel for the house. Total wire run is just a few feet.

Based on the good advice here, aluminum no longer intimidates me. But I do have an electrician friend back in Kansas City. I may try to skype with him to make sure I did things right.

I got some anti-oxidation stuff.

This whole thing is belt and suspenders. I will have a 70A breaker feeding a safety shutoff with 70A fusable links feeding my shop sub-panel.
Here in California, the homeowner can pull the permit and do the work. You can hire someone to help you do the work. What you can't do is pull the permit and then let and unlicensed person do the work. Meaning: Some unlicensed person comes to you and tells you s/he will do the work on contract (for a fixed price) as long as you pull the permit - and you don't do any of the work.

And just because you did the initial work on a permit doesn't mean you absolutely have to have a permit to do anything else. Technically, the law says you do, but very, very few people pull a permit to move an outlet, for example.

Mike

[Rollie Meyers]

Here in California, the homeowner can pull the permit and do the work. You can hire someone to help you do the work. What you can't do is pull the permit and then let and unlicensed person do the work. Meaning: Some unlicensed person comes to you and tells you s/he will do the work on contract (for a fixed price) as long as you pull the permit - and you don't do any of the work.

And just because you did the initial work on a permit doesn't mean you absolutely have to have a permit to do anything else. Technically, the law says you do, but very, very few people pull a permit to move an outlet, for example.

Mike,

In CA if you hire other then a licensed contractor you better have workmans comp coverage, if any thing happens you're going to be on the hook. They do ask when applying for a permit.