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splice aluminum and copper

Posted by jca1 (My Page) on
Sun, Mar 2, 08 at 16:22

I have spliced #6 copper to #6 aluminum. I was given three connector lugs and told to tape them and I'd be OK, along with a junction box. I did it with no problem but I'd like some reassurance from you real sparkies here. I held the lugs with pliers and tightened the screws in as tight as I could with a regular screwdriver, used that black goo on the aluminum wire, and taped the lugs with about 8 wraps of electrical tape. Then I just pushed and pushed until they all fit into the junction box, which I think could have been a little bigger. The ends of the aluminum wire seemed to almost bend at 90degree angles when I pushed everything into the box, is this OK? Should I have done anything different?


Follow-Up Postings:

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RE: splice aluminum and copper

Us real sparkies would need to know what kind of lugs. How many wires? Also, how big is the box? Is this above ground or buried? Are the conductors in cable or conduit?

The devil is in the DETAILS


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RE: splice aluminum and copper

Don't know what kind of lugs they are, but they are about 1.5" long I guess, have a solid piece in the middle that prevents the copper and aluminum wires from touching, and have one flat blade set screw on each side to hold the wires. Splice is above ground, in my crawlspace. The junction box is probably 2.5"deep, and at least 4"x4". Three wires, two hots and a neutral, plus a ground from the panel to ground the metal box, but no ground from there on. The wires are in cable, copper is 6-3w/grnd NM, aluminum is three #6 wires(one with green stripe for neutral) for UG. This is feeding a outbuilding from a 50A breaker in my house panel(not hot yet, breaker not in) and there is a ground rod at the bldg. A 100A box was used on the bldg, with all the neutrals and grounds on the same bar along with the ground rod, and three 20A breakers feeding one light and 6 recep.'s.


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RE: splice aluminum and copper

Just a couple of considerations, the copper and aluminum wire have different ratings. Typically Aluminum wire is next size larger for a given current.

Check with your local inspector, you may have to connect the branch panel to the same ground system as the rest of your home forcing you to run four wires.

Sounds like you used the the wrong lugs, you need to be sure they are rated for copper and aluminum, not all are.

Personally I do not like connecting two different metals together and avoid doing it whenever possible.


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RE: splice aluminum and copper

jcal, you're a good fella...but a touch masochistic? I mean, it's like beatin' yourself in the head with a hammer because it feels so good when you stop. Almost any way to avoid this splice would be preferable to what you've contemplated and/or attempted, and nothing about this gives me a good feeling. Is it absolutely, positively too late to go back to the drawing-board? I hope not.


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RE: splice aluminum and copper

Let me try to revise this a little bit, so far thanks for all the advice. I had #6 copper already pulled into the main panel for future use in case I ever wanted to wire up an electric range. I have now used this wire to feed power to this new shed. because of the price of CU wire of this size I decided to go with AL. I used a 4x4x2.5 junction box, mounted under the house,( want to replace with a 6x6) and these butt connectors of some sort, just can't find the name, but they are rated for CU and AL, and have a divider in the middle of the connector to keep the two wires from touching each other. They are not split bolts or wire nuts, and look like the same material used to make the lugs in a panel box. I will remove the electrical tape and re wrap with rubber tape, then with vinyl over that, but I'm having a hard time understanding why this connection is such a bad idea. I would really like to hear the reasons so I can better understand the problem, I mean if this is going to burn my house down then yes I want to redo it no doubt, etc.
Again, thanks for sharing your knowledge.


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RE: splice aluminum and copper

jca1 are you suggesting that there is no ground wire from main to sub panels? Just a local ground at the sub?

I'm pretty sure (not 100%) that that is a violation.


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RE: splice aluminum and copper

Well, there is no ground wire pulled from the main panel, and yes there is a ground rod at the out building. I personally am not really concerned about this right now, what I am concerned with is the connection of the Cu and Al wires under the house and what if any real hazard this type of connection could cause. Now don't misunderstand me, I appreciate everything all of you share with me and am not refusing to listen or attempt in any way to say "I know better than you" about any of this, because I do not. I do however believe that our local code have not yet enforced the ground wire deal yet so I am OK, and have had many outbuildings wired this same way in the past so I feel safe with that as is, plus I only need 45 amps and no 240V circuits so I could easily use the red wire as a insulated ground, and only feed on side of the outbuilding panel, is that right? As is I plan to use a 50A breaker in the main panel to feed both sides of the shed panel but that is way overkill. I need to supply current to one, 1 60w light fixture, a microwave, blender, 110v window ac, a 110v 6 gallon w.h., and a gas oven, so thats what 1A+12A+8A+9A+13A+maybe 3A or 46Amps total, given all of them running at once which is highly unlikely, is that correct?


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RE: splice aluminum and copper

jcal, even though you say you have done it this way in the past, the safest way to do it would be to ahve a ground running from the main all the way to the sub. Also, like someone else mentioned, check on the ampacity of 6awg AL, it may not be the same as 6awg copper.


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RE: splice aluminum and copper

"Three wires, two hots and a neutral, plus a ground from the panel to ground the metal box, but no ground from there on."

Driving a ground rod in at the outbuiliding and not grounding the sub back to the main isn't a good idea, even if it isn't a code violation in your jurisdiction. The resistance in a ground rod is much higher than a direct wire connection to the main panel ground.

" I could easily use the red wire as a insulated ground" NO, NO, NO, NO, NO!
Major code infraction everywhere!

#6 CU and #6 AL have different ampacities. #6 AL is equal to #8 Cu.


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RE: splice aluminum and copper

If there are any metallic connections (phone, water, cable tv) between the buildings you MUST pull the ground as well.

Just what sort of Al cable are we talking about here anyhow?

What you 'feel safe' doing isn't as important as the code.


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RE: splice aluminum and copper

ronnatalie, #6Cu=65A, #6AL= 50A so I'm using a 50A breaker.

Have no other metallic paths between buildings

thanks everyone.


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RE: splice aluminum and copper

You didn't answer the question? What sort of wire is this. If the cable is 60 degree rated you're not getting 65 for copper or 50 for aluminum. You also have to use something appropriate for wet locations (if in conduit) or direct burial (if you're doing that).


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RE: splice aluminum and copper

jca1....".......aluminum is three #6 wires(one with green stripe for neutral) for UG....."

A GREEN striped wire is for a Ground..........

What is the aluminum cable designation ?

You have WATER and GAS and you still don't have any metallic paths between the buildings ?


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RE: splice aluminum and copper

water will be pvc pipe

gas will be located at the building via a small Lp tank

Not sure about wire designation, but I got it from the electric supply house and he checked the charts for his wire to make sure it was good for 50A, and actually said it could be protected at 55A. It is UG wire.

Anything you can share to help me understand I appreciate, I'm certainly not an electrician. My other shed(no longer wired) was wired this same way for 10+ years, thats why I feel safe. That doesn't mean it wasn't wrong or a disaster waiting to happen, so please educate me. If the only safe way is for me to dig this wire up and redo it with a 4th wire then I want to do that. I want my family to be safe, so please don't anything I say or don't say by accident to be me saying "I know better" cause I don't. I'm looking to understand why I need to do whatever I need to do and have always found valuable advice on this forum, so thanks for the help.


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RE: splice aluminum and copper

Jcal, it's already been stated waht you need to do to make this safe. You need to run 6/3 WG for the WHOLE RUN, to have the ground running from the subpanel back to the main panel.


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RE: splice aluminum and copper

Read the FAQ link found at the top of the forum or in the bottom bar of each thread, and look under Subpanels. That explains the grounding requirements for subpanels such as yours with and without ground wire to the main panel.

As I understand it, you are legal and reasonably safe without the ground wire between panels when there is no other metallic connection between the buildings. It is preferable to have that ground wire both for a slight improvement in safety and to meet the requirements with a future phone line or something making a metallic connection.


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RE: splice aluminum and copper

Man I read this whole thread through again, now I even think I sound hard headed. Anyway thanks for the help, I know what I need to do now and sorry if I agitated anyone, especially you electricians who have spent years learning what you could never teach me on a one page thread, much less so when I act so dense. I guess I was looking for the answer so hard that I read right past it about 400 times, cause it wasn't worded the way I envisioned it. Basically what ya'll said is that in the case of a fault current and a compromised neutral, the ground rod will become the grounded conductor in place of the neutral, but not allow enough current flow to trip the breaker, because of the resistance of the earth itself, so that fault current will simply flow into the earth seeking the source and energizing anything metal along the way, pretty much, right?

By the way, last weekend I replaced the Junction box with a 6X6X4, re-did the connections, rubber taped them until they looked like 3/4" pipe, then super 33 taped them for several more wraps. Now I'll dig the ditch back up and add a ground wire, then stop beating myself on the head with this hammer.


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RE: splice aluminum and copper

I don't know about lugs but I just saw that ideal makes a special wirenut just for this purpose.


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RE: splice aluminum and copper

I don't know about lugs but I just saw that ideal makes a special wirenut just for this purpose.

Really, I was unaware that IDEAL made a wire nut or any similar product that would take anything bigger than #8.

The purple "winenuts" are actually more properly their "Twister" Al/Cu. It can't take bigger than #10.


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Slight Correction

OK, Buchanan makes a B-cap that can take two #6 coppers.


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RE: splice aluminum and copper

If this is a separate building just bond the neutral and ground at the building. there is no need to dig this up just to install a ground wire that isn't even required by the 2005 N.E.C. for existing installations as per 520.32B exception, although you will need to ground this as a new service. 3 wires to an outbuilding is a pretty standard set up for anything installed before the 1999 code.


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RE: splice aluminum and copper

There's no "exception" in 250.32B. The code just proivdes two ways of compliance either run the grounding conductor or in the case where a few conditions (which DO appear to apply to the original poster as I inquired earlier) you can work with just the grounded (NEUTRAL) conductor.

There's no exception or provision otherwise to do things different for "EXISTING" installations, not that this would qualify as EXISTING anyhow.


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RE: splice aluminum and copper

Ron, Your right I was looking at the 2008 Code in which there is an "EXCEPTION" for existing wiring. I misunderstood and thought the underground wiring for Jcal was existing.


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RE: splice aluminum and copper

jcal,something else to consider.....when making a connection with aluminum and copper,you need to coat the 2 conductors with a corrosion inhibitor-like "noalox"


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RE: splice aluminum and copper

You need to read the entire thread. He is NOT joining copper to aluminum. He's putting a copper wire and aluminum wires into separate terminals on a junction block. The block's listing doesn't require anti-ox to be used, though it's not a bad idea.


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RE: splice aluminum and copper

Wow.. this whole thing sounds confusing... But the code is like the bible. Every Inspector has their on interpretation of the code book. The inspector of this county says its ok to do it this way and in the next county this inspector disapprove of it and want you to do it his way. Even though the code says you can do it this way but being that the inspector has the last say so.. He wants it done his way. Some states that I know of still uses the 2000 code book and some still uses the 2005 and some are now beginning to use 2008. Its all depends on that State's Head Electrical Inspector of which code book they are using. Now, I can explain why things are the way there are. Now. remember this, even though there is a 100A sub feed panel but it is only getting 50amps from main main panel because its on a 50a breaker. Head you used metal Ridget conduit leading to the sub feed panel back to the metal junction box in the crawl. You need not worry about needing the ground rod because the metal box is bound by the panel and the connector of the metal conduit bonds the junction box. In sub feed panel you would have to separate the ground and neutrals if it was done that way. # 6 aluminum is rated for 50 amps. #6 copper is rated for 55 amps now the amps varies depending on the temperature rating of your wire. Now, here are one reason why there should be 4 wires at a sub feed panel. The ground wire is use as an escape way for wasted energy to flow back to ground ( the earth) If ever notice that your lights are extremely bright an not normal or your power tool is running too fast, its because there is no ground. No where for the access energy to escape so it makes your tools and light bulbs run abnormal. The reason why you use the rubber tape is because over a period of time the joints generate heat, standard black tape will melt and you will have expose hots touching neutrals and grounds together causing a fire. So, the heavy duty rubber is tolerant to the high heat. Then you cover the rubber with standard electric tape to keep the rubber from coming undone. The bolt that you used sounds like a different type of split bolt. Same concept but design differently. I'm sure the the entire bolt was all metal. Ok you are right the aluminum wire is not touching the copper wire. If I'm right that zinc metal piece that separate the two metal is also a conductor. Over a period of time aluminum does corrode much faster than copper. Corroded aluminum makes a bad connection which also creates sparks and then fire. The gel is used to keep the aluminum cool and extend its life a little longer than normal. Older homes catch fire because of aluminum wireing that gets over heated and catch fire in the walls. Ok.. enough for now...


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RE: splice aluminum and copper

Ok.. enough for now...

Thank goodness for that.

What in the world possessed you to drag up a nine-month-old thread? Are you under the illusion that the OP (person asking the original question) is holding his breath waiting for your supplemental wisdom?

Is this a school project? Or maybe the first chapter of 300-page one-paragraph book entitled "What I (think I) know about wiring"?

What purpose does this post serve? Please, please don't make this a habit.


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RE: splice aluminum and copper

So what's wrong with late posts, tt? I am reading for the first time here the end of July 2009, another 9 months. And all the pieces are new to me.

Posts are for everyone, not just the one who originated a post.

I looked this up because I decided to use a piece of insulated copper wire between my HV fence charger and the "hot" wire, which is aluminum...and wondered how the connection would hold up. I'm made the splice, both small guage, about 16 gauge I'd estimate... but the current is only milliamps


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RE: splice aluminum and copper

"The block's listing doesn't require anti-ox to be used, though it's not a bad idea."

Make SURE the block has a listing for this use.

Their are a bunch of things floating around by Tyco and others that are ONLY ALLOWED in manufactured housing.

The NEC requires a listing by a recognized lab for acceptance of the part.
Tyco likes to call out all sorts of test the parts passed and standards they comply with, without ever stating what the actual listing of the part allows.


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