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Old 05-23-2009, 12:00 PM   #1
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Splicing Aluminum to Copper Wire


I've got a 2 foot section or so of aluminum wire cut out from the line that supplies my house air conditioner. The air conditioner looks like its on its last straw so I'd prefer to wait to replace the entire run of wire until we replace the air conditioner at the same time.

For now, though, I'd like to splice in a section of copper wire just to get the circuit running again. I know that something different needs to be done in this situation, because of the aluminum oxidizing or the different coefficients of thermal expansion of aluminum vs. copper, so my question is what do I need to do to make it safe?

Thanks!
-Dave

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Old 05-23-2009, 12:37 PM   #2
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Splicing Aluminum to Copper Wire


I would replace the whole run now. You have to do it anyway, right? If your not sure what wire size you need on the new one, do a little research.

They make splices for AL to CU. What size wire do you have? And where is this splice located?

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Old 05-23-2009, 12:47 PM   #3
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Splicing Aluminum to Copper Wire


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Originally Posted by J. V. View Post
I would replace the whole run now. You have to do it anyway, right? If your not sure what wire size you need on the new one, do a little research.

They make splices for AL to CU. What size wire do you have? And where is this splice located?
I'm not exactly sure what size the existing aluminum wire is, but it is on a 40A breaker. I've got a few feet of 6 guage wire left over from wiring up a new oven that I was going to use for the splice.

The splice is located in the basement...easily accessible. I will make it within two junction boxes. The only thing I was concerned with about replacing the whole run, besides the cost, is the fact the current wire is a 3 wire, and I would want to go with a 4 wire for the new, so where would I attach the new ground wire? I doubt the AC unit has a 4th terminal as it is over 20 years old...
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Old 05-23-2009, 01:23 PM   #4
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Splicing Aluminum to Copper Wire


I've never seen an AC that required a 4 wire. They are all straight 240V.

SPlice your wires in jboxes with blue wirenuts. Crank them down tight with channellocks and you'll be fine. It's not legal but, in some areas of the country (Texas and Georgia), selling vibrators is illegal. I claim that it's safe. You can make your own choices.

If you want to go all crazy, get some double lugs, rubber tape and big jboxes.

Replace the feed when you can.
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Old 05-23-2009, 01:29 PM   #5
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Splicing Aluminum to Copper Wire


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I've never seen an AC that required a 4 wire. They are all straight 240V.
So what about how the older dryer and ovens installations use 3 prongs, where as the newer ones use 4 prongs? Would it not be the same thing with an air conditioner?

And how about that goop that they sell that is some sort of anti-oxidant for the aluminum? Is that needed?
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Old 05-23-2009, 03:09 PM   #6
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Splicing Aluminum to Copper Wire


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So what about how the older dryer and ovens installations use 3 prongs, where as the newer ones use 4 prongs? Would it not be the same thing with an air conditioner?

And how about that goop that they sell that is some sort of anti-oxidant for the aluminum? Is that needed?

No. A dryer or an oven circuit are 120/240 volt. A AC condenser is straight 240. No neutral needed.

there are split bolts designed for the joining of the two wire materials and yes, although it is not code, anti-oxidant should be used on the aluminum. After joining the wire, you would wrap with black tape and then with 3M 130c and then black tape again.

Or, you could use polaris connectors. faster and easier and for a couple splices, not a big enough cost difference to care about. Be sure you purchase connectors rated for aluminum and copper.

I am actually surprised 220/221 recommending big blue nut. As he states, they are not legal nor recommended (by the manufacturer( for such a use). The two items I listed are.
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Old 05-23-2009, 03:12 PM   #7
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Splicing Aluminum to Copper Wire


Insulated Polaris connector
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Old 05-23-2009, 04:05 PM   #8
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Splicing Aluminum to Copper Wire


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I've never seen an AC that required a 4 wire. They are all straight 240V.....
Then you have never seen an all-in-one gas or oil fired unit. Mounted outside, with the ductwork running under the house, they have all the guts of any standard furnace, as well as the cooling compressor and condenser.

Many of them require 120/240 volts to operate, and thus need a 4-wire circuit. The oil burner motor assembly is what usually requires the 120 Volt supply.

Usually you will see these units in a mobile home application, but they can be used in permanent structures as well.
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Old 05-23-2009, 05:09 PM   #9
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Splicing Aluminum to Copper Wire


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No. A dryer or an oven circuit are 120/240 volt. A AC condenser is straight 240. No neutral needed.

there are split bolts designed for the joining of the two wire materials and yes, although it is not code, anti-oxidant should be used on the aluminum. After joining the wire, you would wrap with black tape and then with 3M 130c and then black tape again.

Or, you could use polaris connectors. faster and easier and for a couple splices, not a big enough cost difference to care about. Be sure you purchase connectors rated for aluminum and copper.

I am actually surprised 220/221 recommending big blue nut. As he states, they are not legal nor recommended (by the manufacturer( for such a use). The two items I listed are.
Ok, I would prefer to do it correctly (even if it's only temporary), until I end up replacing the whole run. And heck, maybe I won't have to replace it if the AC lasts another couple years until we move...

But I'll head out to Home Depot tonight to see if I can find either of the two things you mentioned. But what is the difference between the 3M 130c tape and regular tape/why is it needed? I'm not at all challenging what you said, I just like to know the "why" of things.

And maybe since we're sort of on the topic, could you or someone clear up a little confusion I have regarding 240 volt circuits?...I used to think that 3-wire 240 volt circuits had two hots and one neutral, and lacked a ground. Now I know (I think) that they in fact have two hots and a ground, and lack a neutral. Why is a neutral not needed? And if it was ok for dryers and ovens back in the day to not have a neutral, why has code changed and what benefit does the 4th (neutral) wire now provide?

I understand why some appliances would need a 120/240 supply, but I thought that was possible simply by having two hots, and the appliance then split it up to be either 120 or 240 volts, as needed. I also now understand that modern AC units may be straight 240 so they don't need a neutral (although I don't understand why), but why is it that modern dryers and ovens all of a sudden DO need a neutral? I mean, they were still operating on a split 120/240 volt supply before the code changed, right?
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Old 05-23-2009, 05:41 PM   #10
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Splicing Aluminum to Copper Wire


Dryers and ranges have always required a neutral. The exception was that you could connect the ground to the neutral under certain conditions: supply originated from the service panel, and three insulated conductors or SE type cable.

The neutral is required because the appliances require 120V and 240V to operate. The 120V is between either hot and neutral, the 240V is between the two hots.
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Old 05-23-2009, 07:30 PM   #11
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Splicing Aluminum to Copper Wire


unless im missing something dont grd and neu both tie into the same bar essentially making them the same thing although on a 120 v application its sheilded as current can flow thru it
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Old 05-23-2009, 09:08 PM   #12
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Splicing Aluminum to Copper Wire


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unless im missing something dont grd and neu both tie into the same bar essentially making them the same thing although on a 120 v application its sheilded as current can flow thru it
current DOES flow through the neutral. It should not flow through a ground conductor unless there is a problem. What the diff is, when using the 3 wire system, there was no ground wire. The problem with that is, should the neutral wire become disconnected somewhere between the panel and the appliance or even become a higher resistance than a person touching the appliance and some ground source, since the frame of the appliance is connected directly to the neutral, that frame now becomes energized and if a person were to touch it and a ground source, they could be electrocuted.

Quote:
But what is the difference between the 3M 130c tape and regular tape/why is it needed? I'm not at all challenging what you said, I just like to know the "why" of things.
No offense taken. 130C is a rubbery insulating tape. While the standard black tape (Temflex 1700, jap wrap, 33+, whatever) is a thinner tape, it does not do so well on corners and points of the split bolt. The 130C is bulkier and protects those corners and such better should they be pushed against the back of the box or whatever. The overwrap of 33+ is because the 130C is stretchier and does not always stick to itself well, at first. I have seen it start to unwrap on its own. The 33+ is also a bit better against abrading actions as it is smoother and a bit harder than the 130C. The inner wrap of jap wrap is because if you have ever taken a split bolt apart without an inner wrap of something such as jap wrap, you would understand but it can be near impossible. The 130 C tends to become one big ball of rubber, gooey rubber.

I actually wrap the inner wrap with the sticky side of the tape facing out after an initial sticky in wrap only where the insulation of the two conductors is. Then twist it sticky side out and completely cover the split bolt. This way, there is not adhesive to overcome if you should have to remove the split bolt.. Less mess.

In the old days varnished cambric would be used instead of the inner wrap of tape. It is a good method but more difficult and finding cambric is getting harder all the time.
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Old 05-23-2009, 09:12 PM   #13
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Splicing Aluminum to Copper Wire


Quote:
And maybe since we're sort of on the topic, could you or someone clear up a little confusion I have regarding 240 volt circuits?...I used to think that 3-wire 240 volt circuits had two hots and one neutral, and lacked a ground. Now I know (I think) that they in fact have two hots and a ground, and lack a neutral. Why is a neutral not needed? And if it was ok for dryers and ovens back in the day to not have a neutral, why has code changed and what benefit does the 4th (neutral) wire now provide?
it is 2 hots and a neut. The 4th wire (ground) is because of what I explained in the last post. The frame is now totally isolated from any current for safety.

Quote:
I understand why some appliances would need a 120/240 supply, but I thought that was possible simply by having two hots, and the appliance then split it up to be either 120 or 240 volts, as needed.
you have 240 between the 2 hots. You get 120 from one hot and the neutral.

Quote:
I also now understand that modern AC units may be straight 240 so they don't need a neutral (although I don't understand why), but why is it that modern dryers and ovens all of a sudden DO need a neutral?
dryers always needed a neutral. They use the 120 for the time and sometimes the motor. The heating element is the main reason for the 240 volts.

Quote:
I mean, they were still operating on a split 120/240 volt supply before the code changed, right?[
yep but an AC unit typically doesn't. There was an exception provided previously but that is not common, at least from what I have seen.
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Old 05-24-2009, 03:52 AM   #14
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Splicing Aluminum to Copper Wire


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I am actually surprised 220/221 recommending big blue nut. As he states, they are not legal nor recommended (by the manufacturer( for such a use). The two items I listed are
I have not fallen victim to the AL/wirenut scare. I have researched it and I believe it is hype. AL wiring does have it's share of problems but failures in properly wirenutted connections are rare.

It pisses me off when a customer has to spend 4 bucks a piece for a simple wirenut with nolox in it. It does nothing to the connection, it just pays for insurance premiums for the MFG. Nobody wants anything to do with AL wiring but Ideal came up with preinstalling nolox (it can't be done correctly in the field lol) and charging 4 bucks a piece for a 20 cent wirenut.

This is, as always, my opinion.
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Old 05-24-2009, 09:50 PM   #15
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Splicing Aluminum to Copper Wire


Ok so I got the AC hooked up and working...it sure is nice considering the past few days, it has been over 85 inside the house.

I didn't end up using a split bolt, and I don't think what I used is a polaris connector, but I'm not sure. They are marked as a "splicer reducer," and came in these little plastic bags with two in each bag. They were 5 bucks a bag and I had to get 3 bags unfortunately for 6 splices. But they are marked for aluminum and copper wire, and are basically a rectangular block of aluminum about the size of a stick of chapstick, with a hollow cylinder running the length of the block, with a set screw on each end to secure the inserted wire.

I used anti-oxidant on the aluminum side of each connection and wrapped each hot splice over and over again with black tape. I couldn't find any of the 130c tape at Home Depot, so hopefully the tape I used will suffice (I believe mine is scotch 700). I made sure to wrap the corners extra.

This was actually a pretty big pain in the butt, and took me a couple hours. Also it ended up costing about 30 bucks to "band aid" the problem, when I could have just spent 100 bucks or so and gotten a 250' roll of 8/2 w/ground, and then had plenty of wire left over to use for whatever in the future. Also it wouldn't have taken much more time to replace the whole run.

Thanks a lot for the help with it all, and let me know if anything I did doesn't sound right...

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