Electric to a shop. Alum vs. copper

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  #1  
Old 03-03-11, 09:55 AM
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Electric to a shop. Alum vs. copper

Well it's time to get electric service to my shop. I had planned for this when I built my house and buried conduit from the panel of my home to my shop building just never had the money to pay for the copper wire to get it done. My question is can I run 4-0 alum from my house panel to my shop panel? If so how many strands will I need to run? I will be running a couple of 220v plugs out in the shop along with 110v and lights. Copper is just so dang High I hate to spend the money if it's no big deal to run the alum. Any help would be great
 
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Old 03-03-11, 10:03 AM
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#4/0 aluminum is probably supreme overkill for a home shop -- that would be enough to power a good sized commercial shop.

First what size service does your home have, is there space in the main panel, and do you have major electrical loads like electric heat, spa, instant water heater?

Let us know a few details and we can help with your shop. What size is the conduit you buried? About how big is the shop? What types and sizes of tools (appx. motor horsepower) do you plan to use or any metal working tools (welder, plasma, etc)? Will this be a one-man shop or multiple tools at the same time? Do you plan for electric heating or air conditioning in the shop?
 
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Old 03-03-11, 10:28 AM
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sorry should have given more detail. The house has 200amp service panel and is total electric. HVAC, Hotwater tank and well pump. When I built the house I had the electrican run the drop and conduit to the shop so I should be good with the house panel. The shop is a 30X40 one man shop. I have a 220v welder that I will want to run and maybe a large compresor and thats about it other than hand tools, radio and maybe a small window unit a/c. and of course lighting which I plan on keyless fixtures.
 
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Old 03-03-11, 10:28 AM
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Yes that is a big service...either way you need 4-wires to sub feed a box. Two hots, a neutral, and a bonding wire from box to box. Usually a 100 amp service is MORE than enough, in fact I have a 30 now with provisions for 100 later if needed. But if you want 200 amps there are ways you can do that but not cheap.
 
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Old 03-03-11, 11:24 AM
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I would go 100A service to the shop -- more than enough for welding and air compressor.

Install a 100A double-pole breaker in the main panel and from that run (3) #1 aluminum conductors (probably type XHHW) in black, tape the ends of one them white as the neutral. Also pull a #6 green or bare ground. At the shop, install at least a 20 space 100A main breaker panel with an add-on ground bar kit and unbond the neutral per panel instructions. Drive two 8' ground rods at least 6' apart and connect them to the subpanel ground bar with bare #6 copper (this one must be copper) wire and brass acorn clamps on the rods.

Aluminum wire is perfectly fine to use in this situation, you just need to pay a little more attention to the connections. When you strip the wire to put it in a lug, shine it up a little with emory paper or fitting brush and generously apply Noalox paste to the bare aluminum with a flux brush. You can get a tube of it (aluminum non oxidation grease) for a couple bucks in the electrical aisle. Torque the lugs to manufacture specs. The panel label will have the rating in inch-pounds for the lugs (divide by 12 if your torque wrench is in foot-pounds).
 
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Old 03-03-11, 12:43 PM
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dang the one thing I didn't do put in ground rods for the shop any ideas? I need to check my breaker box I have been buying pats and stuff for a while and have had it hanging out there for a while. Thanks for all the info and help.
 

Last edited by planman23; 03-03-11 at 01:10 PM.
  #7  
Old 03-03-11, 01:09 PM
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Would he really have to drive rods for this? If he uses 4 wire cable and bonds the boxes properly it would seem that is not needed. I realize however that every area is different though on these things. Here we would not need it.
 
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Old 03-03-11, 01:10 PM
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Ground rods can be driven with some time and effort. A lot depends on your soil. An 8 lb maul works.
 
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Old 03-03-11, 02:03 PM
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Is it ok to place the ground rods outside the shop? The inside floor is concrete. The shop is a wood ploe barn with a metal skin is it cool to run the ground wire through the metal skin? I like the option of not having the ground rods. Tell me more
 
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Old 03-03-11, 02:14 PM
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Oh absolutely, the ground rods go outside the building. Generally put them right outside the panel and run the #6 copper out beside the service conduit. You can even tie wrap it to the conduit. It can go out through any penetration in the building skin as long as it is reasonably protected (i.e. not going to chop it with the lawn mower). If it is in an area subject to damage, sleeve the #6 in PVC conduit from the building exit to a few inches under the soil. You only need to drive the rods so the head is just under the soil. If you have mulch or similar landscaping you can cover the head with that.

A maul, sledge hammer, fence post driver, pretty much whatever method you need to use to get the rod in without destroying it. If you really need to pound it put the acorn clamp on first otherwise you won't be able to fit it on over the mushroomed out end of the metal rod. Sometimes it also helps to dig about a foot deep hole and soak in a couple buckets of water to soften up the soil.

Rods are mandatory for all outbuildings with a subpanel. The purpose is primarily lightning protection whereas the ground wire between buildings is to trip the main breaker if you ever have a major short and the subpanel main breaker jambs, fails, etc.
 
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Old 03-03-11, 04:01 PM
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I agree with everything posted here. Ground rod is no big deal to install and is required by 2008 code. I suggest running #6 solid copper to it. It will never get damaged then.

I also agree with running 100 amp to your building for many reasons above which you will not find a 200 amp breaker for the panel in your house. #3 copper or #1 aluminum will do you fine unless it is a long way to the shop.
 
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Old 03-03-11, 06:38 PM
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Install a 100A double-pole breaker in the main panel and from that run (3) #1 aluminum conductors (probably type XHHW) in black, tape the ends of one them white as the neutral. Also pull a #6 green or bare ground.
The grounding conductor you pull from the main panel in the house can be #4 aluminum XHHW rather than #6 copper to save a few bucks. The grounding conductor from the shop panel to the ground rods outside MUST be copper, #6, as was stated.
 
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Old 03-04-11, 09:47 AM
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Thank you for all that replied. I think I just found a new how for all my projects!!
 
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Old 03-05-11, 07:03 PM
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Originally Posted by pcboss View Post
Ground rods can be driven with some time and effort. A lot depends on your soil. An 8 lb maul works.
I've seen ECs use a small electric jackhammer without the bit to drive them in a matter of minutes with no sweat. That's something you can usually rent for about $20 an hour at a rental yard. Might be something to consider if you have particularly nasty clay type soil. Also, are dual rods required for an outbuilding or is that just the main?
 
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Old 03-05-11, 07:49 PM
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Originally Posted by JerseyMatt View Post
I've seen ECs use a small electric jackhammer without the bit to drive them in a matter of minutes with no sweat. That's something you can usually rent for about $20 an hour at a rental yard. Might be something to consider if you have particularly nasty clay type soil. Also, are dual rods required for an outbuilding or is that just the main?
Yes, roto hammers set to hammer will work very well when driving a rod, there are also ground rod driving accesories available.

As far as I know, dual rods are not a requirement. The requirement is resistance of 25 ohms or less at both the main and outbuilding. If the resistance is too high, a second rod is one way to lower it.
 
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Old 03-05-11, 07:59 PM
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Since the equipment needed to measure the ground rod resistance is fairly expensive (and consequently fairly rare) it is usually cheaper to just install the second rod since then no proof of ground rod resistance is required.

I gotta get a picture of what "they" did at my sister's house regarding the ground rods, I swear nobody will believe it.
 
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Old 03-06-11, 05:48 AM
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I also found somewhere on the internet to take a 1/2'' pipe and connect a garden hose to one end, and hammer the other end to a sort of point to predrill a hole then drop the ground rod in a hole, although it does not have good contact with the ground initially.
 
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Old 03-06-11, 01:12 PM
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Originally Posted by Justin Smith View Post

I also found somewhere on the internet to take a 1/2'' pipe and connect a garden hose to one end, and hammer the other end to a sort of point to predrill a hole then drop the ground rod in a hole, although it does not have good contact with the ground initially.

That's a REALLY bad idea. :NO NO NO: Defeats the entire purpose of the ground rod if it doesn't make good contact. They are designed to be pounded in, not dropped into a hole. :NO NO NO:
 
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Old 03-06-11, 02:01 PM
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Originally Posted by JerseyMatt View Post
That's a REALLY bad idea. :NO NO NO: Defeats the entire purpose of the ground rod if it doesn't make good contact. They are designed to be pounded in, not dropped into a hole. :NO NO NO:
I would suspect the ground would settle down and make good contact to the rod.

Really, installing a ground rod is not a big deal unless your on rock. Just stand it up and beat it in. Only takes about 5-10 min.
 
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Old 03-06-11, 04:37 PM
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That's a REALLY bad idea. :NO NO NO: Defeats the entire purpose of the ground rod if it doesn't make good contact. They are designed to be pounded in, not dropped into a hole.:NO NO NO:
A good rain and mud will settle in around the ground stake.
 
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Old 03-06-11, 06:00 PM
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Since the equipment needed to measure the ground rod resistance is fairly expensive (and consequently fairly rare) it is usually cheaper to just install the second rod since then no proof of ground rod resistance is required.
True, $1200 to $1500 is a lot to spend on one piece of equipment for a small residential shop, but many commercial contractors spend a lot more than that on tools. Most contractors of any size that I am familiar with have one.
 
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