View Full Version : Heavy gauge wire splice - AL to CU


scott45
06-26-2012, 12:16 PM
I've got stranded 4ga aluminum wire (2 hots and a neutral) coming into my house from a sub panel in the garage and, because I'm short on wire, I need to connect this wire to some stranded 6ga copper NM-B I've got.

I picked up the pictured hardware from HD and want to confirm I won't be asking for a fire in my crawl space if I use it.

The plan is to put three splices in one 4" box and have each splice shrink wrapped and suspended in the box. There will be no ground in the box, just two hots and a neutral. I expect I'll need to apply the terminal grease stuff where the copper connects to the aluminum connector.

Thoughts?

rlitman
06-26-2012, 01:18 PM
That's the right connector. I just think that a 4" box would be a little tight for all that. Especially one that shallow. Can you find one twice as deep? It's going in a crawl space, so a little bigger box won't get in the way.

Make sure you clean the aluminum right when you strip it. Then coat it immediately with something to prevent oxidation. Oh, and be sure to strip it with something that does not nick the metal. A tiny nick will open up into a crack where the whole end of the wire can fall off.

pattenp
06-26-2012, 01:23 PM
You're fine with what you got to splice the wires together with. The box may be too small. You need to leave at least 6 inches of wire after it enters the box. So you may have a problem folding it back into the box after you make up the splice connections. You also need to use antioxidant past on the AL wire connections. The metal box needs to be grounded, and again as said in another post you should have an equipment ground wire that goes from the garage to the house.

scott45
06-26-2012, 01:59 PM
Make sure you clean the aluminum right when you strip it. Then coat it immediately with something to prevent oxidation. Oh, and be sure to strip it with something that does not nick the metal. A tiny nick will open up into a crack where the whole end of the wire can fall off.

Clean the aluminum with what?
A tiny nick can cause the end to fall off? Seriously? What sort of device strips wire without putting the tiniest of nicks in it?

You need to leave at least 6 inches of wire after it enters the box. So you may have a problem folding it back into the box after you make up the splice connections. You also need to use antioxidant past on the AL wire connections. The metal box needs to be grounded, and again as said in another post you should have an equipment ground wire that goes from the garage to the house.

Why do I need to have x number of inches worth of cable folded into this box? This is really heavy gauge wire and my vision of me trying to manhandle 6 heavy wires in almost any sized box makes me shudder. What if there weren't any folds and the wires came in the box, hit the connector and then went straight out the other side? Everywhere a wire went through the box it would be clamped down and immovable. I would have a loop of wire on both sides of the box in case someone ever needed to repair the connections.

Falcon67
06-26-2012, 03:25 PM
This has a 2-2-2-4 splice in it - IIRC, that's a 6" box in all directions. No, it's not easy. Start with one in and one out, loop so that the ends meet as required, trim the ends carefully, goop the ends and put in the splice.
http://raceabilene.com/misc/NewShop/Power5.jpg

matt151617
06-26-2012, 03:26 PM
That looks like a 1/2" NM bushing. You'll need one bigger than that.

And you said you only have 3 wires coming from the subpanel, is it an attached garage?

I don't have it available right now but you need to look up the NEC box fill chart and calculate how much space you'll need. Usually it's quite a lot, espeically for thicker wires.

rlitman
06-26-2012, 03:33 PM
Clean the aluminum with what?
A tiny nick can cause the end to fall off? Seriously? What sort of device strips wire without putting the tiniest of nicks in it?



Why do I need to have x number of inches worth of cable folded into this box? This is really heavy gauge wire and my vision of me trying to manhandle 6 heavy wires in almost any sized box makes me shudder. What if there weren't any folds and the wires came in the box, hit the connector and then went straight out the other side? Everywhere a wire went through the box it would be clamped down and immovable. I would have a loop of wire on both sides of the box in case someone ever needed to repair the connections.

240 grit sandpaper is what's often recommended, but scotchbrite is good too. You need to remove any oxide layer, before making a connection, although if it was just cut and stripped, it should be pretty clean.

You want to nick the insulation, without going through to the wire. Then use pulling pliers to pull the insulation off, tearing it at the nick. Nicking the wire is bad form with copper, but dangerous with aluminum.

The wire is supposed to make the loop INSIDE the box. If you get the deepest 4 square box you can (they come over 3" deep), I think you should be ok. You could add a deep mud-ring extension to the box, to make it deeper too.

Somebody here could possibly run the calculations based on the wire sizes and tell you what the minimum allowable interior volume the box can have. It is all spelled out in the NEC.

The last time I had to deal with this, I was making four connections (there was a ground wire) with 6ga copper and split bolts in a similar sized box. The split bolts take up much more room, especially because of the space the tape takes up. These splices with the heat shrink should be easy enough to fit in there.

pattenp
06-26-2012, 03:45 PM
NEC 300.14 requires that you have a certain amount of length of wire to work with in a junction box when making splices or connections. That's the main reason it takes such a large box when doing splices on large wire. I had to splice some 2-2-2-4 and it took a 8" x 8" x 4" box to fit the loop in and not fight the wire.

........
Why do I need to have x number of inches worth of cable folded into this box? This is really heavy gauge wire and my vision of me trying to manhandle 6 heavy wires in almost any sized box makes me shudder. What if there weren't any folds and the wires came in the box, hit the connector and then went straight out the other side? Everywhere a wire went through the box it would be clamped down and immovable. I would have a loop of wire on both sides of the box in case someone ever needed to repair the connections.

MrMark
06-26-2012, 04:12 PM
You said you weren't going to ground the box. That is a mistake. Anything metal needs to be grounded, especially that box. You will need a ground lug kit to ground the box.

hh76
06-26-2012, 04:15 PM
you're gonna need a bigger box. Notice how the butt splices are nearly the same length as the box? You'll need room for the wire to exit on each side of the splice, and you shouldn't kink it.

You'll be swearing the entire time you try and stuff those wires in there, and there's a good chance that you'll damage the wire.

If you're not planning on grounding the box, go with pvc. Get yourself an 8x8, and save yourself a lot of trouble.

scott45
06-26-2012, 04:36 PM
This is a detached garage so there's no ground wire between it and the house and is also why there's only three wires coming to the house. The sub panel in the garage has a piece of #4 copper running to a ground rod.

Pattenp - The attached hastily drawn sketch on the post-it note is how I would like to do the box if it doesn't seriously violate any NEC code. Sounds like it may...

If I go with a big 'ole PVC box then I would only need to ensure the connections inside don't touch each other, right? No need for a ground on a plastic box I'm guessing.

MoonRise
06-26-2012, 04:45 PM
You WILL need a bigger box for:

- meeting NEC space/fill requirements

- being able to physically fit and manipulate those wires

Table 314.16(B) requires a minimum 5 cubic inches for each #6 conductor. Add in the clamp 'fill', plus the #4 aluminum from 300.14 needing minimum 6 inches 'free' for connection/movement/etc and you need a pretty darn big box to fit everything into.

+ 1 on the use of the anti-oxidation paste/grease/goop.

Metal boxes MUST be 'properly' grounded (Article 314.4).

pattenp
06-26-2012, 04:59 PM
You've already seriously violated NEC by not having an equipment ground from the house main panel to the garage sub-panel. Having a grounding electrode does not satisfy the equipment ground conductor requirement. Running the wires straight through as in your diagram without leaving the required extra length is a NEC violation. If you use a plastic box you don't need to ground it. You will still need to insulate the splice connections with tape or shrink tube. Well... duh yeah on the bold part.

This is a detached garage so there's no ground wire between it and the house and is also why there's only three wires coming to the house. The sub panel in the garage has a piece of #4 copper running to a ground rod.

Pattenp - The attached hastily drawn sketch on the post-it note is how I would like to do the box if it doesn't seriously violate any NEC code. Sounds like it may...

If I go with a big 'ole PVC box then I would only need to ensure the connections inside don't touch each other, right? No need for a ground on a plastic box I'm guessing.

kkenney
06-26-2012, 05:00 PM
dont forget

Conductors 4 AWG or Larger. Installation shall comply
with 300.4(G).

300.4(G) Insulated Fittings. Where raceways contain 4 AWG
or larger insulated circuit conductors, and these conductors
enter a cabinet, a box, an enclosure, or a raceway, the conductors
shall be protected by an identified fitting providing
a smoothly rounded insulating surface, unless the conductors
are separated from the fitting or raceway by identified
insulating material that is securely fastened in place.

kkenney
06-26-2012, 05:10 PM
Boxes and conduit bodies enclosing conductors 4 AWG
or larger shall also comply with the provisions of 314.28.

314.28 Pull and Junction Boxes and Conduit Bodies.
Boxes and conduit bodies used as pull or junction boxes
shall comply with 314.28(A) through (E).

(A) Minimum Size. For raceways containing conductors
of 4 AWG or larger that are required to be insulated, and for
cables containing conductors of 4 AWG or larger, the minimum
dimensions of pull or junction boxes installed in a
raceway or cable run shall comply with (A)(1) through
(A)(3). Where an enclosure dimension is to be calculated
based on the diameter of entering raceways, the diametershall be the metric designator (trade size) expressed in the
units of measurement employed.
(1) Straight Pulls. In straight pulls, the length of the box
or conduit body shall not be less than eight times the metric
designator (trade size) of the largest raceway.

When transposing cable size into raceway size in
314.28(A)(1) and (A)(2), the minimum metric designator
(trade size) raceway required for the number and size of
conductors in the cable shall be used.

sickjuice
06-26-2012, 05:12 PM
There are so many things wrong with your little sketch but the only one I'm going to bother mentioning is the one that could burn down your house. Running the single conductors thru separate holes in a metal enclosure will cause inductive heating which will heat things up to a dangerous point depending on how heavy your load is.
Disregard that if your running proper single conductor cables and terminating them properly per single conductor rules but I'm guessing since you have to ask how to splice wire that is not the case

scott45
06-26-2012, 06:21 PM
Thanks for all the input everyone. Sounds like little tiny box is out due to being way out of code and having the possibility of burning down my house.

So I get a larger PVC box that's big enough to bring all my wires in through one hole, splice them, fold them around a bit and bring the copper out the other end of the box.

Now, the issue of needing to bring a ground wire from my house to my detached garage. If I've got to have a ground rod (or two) at the garage to handle all the ground wires in the garage, why bring a ground down from the house as well? Is there some measure of extra protection there?

matt151617
06-26-2012, 08:06 PM
Now, the issue of needing to bring a ground wire from my house to my detached garage. If I've got to have a ground rod (or two) at the garage to handle all the ground wires in the garage, why bring a ground down from the house as well? Is there some measure of extra protection there?

Ground rods are mainly for lightning protection. The ground wire back to the main panel is the real ground. Oh, and it's required by code...

Also, I hope the #6 Romex you bought is 6/3, otherwise, you can't use it.

scott45
06-26-2012, 08:36 PM
One more wire to run down through that silly trench then... ah well. At least I can just drop it in the hole and connect up the ends.

The #6 is 6/3 with ground - should be exactly what I need.

jbberns
06-26-2012, 09:26 PM
One more wire to run down through that silly trench then... ah well. At least I can just drop it in the hole and connect up the ends.

The #6 is 6/3 with ground - should be exactly what I need.

Let me guess. You didn't run it in conduit and you didn't use direct burial wire? Do you have to get this inspected? The NEC is the minimum for safety. You need to do a lot more research.

scott45
06-27-2012, 07:39 AM
I did screw things up at first but now I've got direct burial in there and I've run it through the conduit I had leftover, just so it got used.

I'm planning to just drop the copper ground wire into the trench next the conduit unless someone on here tells that is also against the rules.

Per my inspector the trench won't be inspected but even so I'd like to do things as right as I possibly can.

gayler
06-28-2012, 03:57 PM
Is It just bare copper, or is it direct burial wire?

scott45
06-29-2012, 08:32 AM
Haven't bought it yet but was going to do bare copper. Seems like it would be a better ground to have it exposed to the earth for the entire run but there's probably some reg against that... :sad:

matt151617
06-29-2012, 03:17 PM
If not in conduit you would have to use at minimum #6 copper ground. I know the inspector said the trench won't be inspected, but you still better check with them to be sure they don't start questioning multiple bare ground wires exiting the panel.

jbberns
06-29-2012, 04:55 PM
Sorry to say this. I don't want to be mean, but you don't need to be doing any electrical work.

Rtw5150
06-30-2012, 12:31 AM
Sorry to say this. I don't want to be mean, but you don't need to be doing any electrical work.

I think you're right. To the OP, it is obvious you bit off more than you can chew and are in over you're head. Call an electrician and make sure its done right and is safe for you, your family and any other families whose house's are in close proximity to yours.

scott45
06-30-2012, 12:36 PM
I think I'm beginning to agree that I may have bit off more than I should have here. I've done plenty of electrical work indoors but only to the extent that simple circuits were run or fixed. I've not ever installed a sub panel, buried anything in a trench or spliced together large wire.

Perhaps this isn't the best project to cut my teeth on... What should a residential electrician charge me to come in, make sure what I have is up to code and maybe finish off the last splices I've got here?

Rtw5150
06-30-2012, 09:20 PM
I think I'm beginning to agree that I may have bit off more than I should have here. I've done plenty of electrical work indoors but only to the extent that simple circuits were run or fixed. I've not ever installed a sub panel, buried anything in a trench or spliced together large wire.

Perhaps this isn't the best project to cut my teeth on... What should a residential electrician charge me to come in, make sure what I have is up to code and maybe finish off the last splices I've got here?

That's more of a localized thing, where I'm from everything needs to be in pipe and wire. I'll tell you one thing though, I wouldnt use those splices you bought, GB is not quality material by any means. I'm sure Home Depot carries Burndy split bolts get 3 of those, a roll of rubber tape (or mastic pads) and a roll of 33. It will make a much higher quality splice.

rlitman
07-02-2012, 07:41 AM
I'll tell you one thing though, I wouldnt use those splices you bought, GB is not quality material by any means. I'm sure Home Depot carries Burndy split bolts get 3 of those, a roll of rubber tape (or mastic pads) and a roll of 33. It will make a much higher quality splice.

That is HORRIBLE advice. Split bolts are an awful choice for aluminum.
What he has is probably the best thing he's going to find.

pattenp
07-02-2012, 08:17 AM
+1. I wasn't going there when I saw that comment, but since you said it, I agree, bad advice.

That's what the splice/reducers are made for.

That is HORRIBLE advice. Split bolts are an awful choice for aluminum.
What he has is probably the best thing he's going to find.

Rtw5150
07-02-2012, 05:08 PM
That is HORRIBLE advice. Split bolts are an awful choice for aluminum.
What he has is probably the best thing he's going to find.

They make split bolts specifically made for joining copper to aluminum, there's a tab in the center to seperate the two of them. I've used them hundreds of times and never had a failure. The 100 amp service drop at my sisters house was installed with them in 1998, two years ago I was over there and my brother in law was showing me his new Flir camera, I had him go over the service drop as well as the lugs in the meter housing, the Burndy showed no temp change anywhere near it, all the lugs were showing they were heating up.

If you think those Gardner Bardner junk splices are the best he's going to find .I'm guessing you've never seen an Ilsco splice, I personally think they are better than a Burndy but the engineers at Com Ed prefers we use Burndy's which is fine by me since a #3 Ilsco runs about $12 each.

How many split bolts have you had fail?

rlitman
07-02-2012, 06:05 PM
The splices in the original post were Thomas and Betts. Ilsco splices are great, but he's not doing something underground. Anyway, protecting the splice from the elements is not as important as a solid mechanical all aluminum connection. It doesn't matter who machines an aluminum tube, with an aluminum set-screw threaded into it.

The separated brass or copper split bolts are not appropriate for aluminum wiring. The brass or copper expands and contracts at a thermal different rate than the aluminum, leading to the connection loosening over time.
There are split bolts that are made entirely of aluminum. Those are suitable for aluminum, however with their tendency to strip the threads, I would suggest that they be only used with a torque wrench, as they require quite a bit of torque to get tight, but just a little more will cause the thread to skip. The set-screw connections are not quite as sensitive to this.

A Burndy crimped connection on aluminum wiring is ALWAYS the best option, but the tool for this is way out of the reach of someone doing just one connection like this, so lugged connections are the best you can get otherwise.

We go over all the connections at work every 6 months with the flir. Getting false flir heat readings on an aluminum lugged connection is very easy. Believe it or not, the IR from your body heat will reflect off the aluminum like a mirror, making it extremely difficult to get a real reading from an aluminum terminal block. I'll often have to position myself behind a door or panel, and even then I will have to move the camera around to get my hand out of the shot. If you look closely enough at the reflection, you will begin to notice your profile and features as you move around. Ignore this, and you'll think the terminal is well hotter than ambient temperature, when it's just you that's warm. :)

In the past few years, we have not noticed any real heat coming from an aluminum lugged connection. We did have an issue with a crimped all copper connection on a DC system (540V float voltage, 4/0 wire, hydraulically crimped onto a copper lug, and bolted to the batteries with a stainless bolt, torqued into place). Flir showed the bad crimps (incomplete crimps let the acid fumes get between the many wires, causing it to have a high resistance and heat up under load, with no other visible signs of damage).

Oh, and I use copper split bolts all the time at work, and they're great, at the data center I work at, we're very picky about using only copper for everything.
No, I've never had a split bolt fail. But I have seen non-premium tape split on one (never had that issue with Scotch 88).

PRH44
07-02-2012, 09:03 PM
Excellent points by both rtw5150 and rlitman. I do agree with rlitman on the fact it doesn't really matter who machines the components. However we all know that quality control can lack in different manufactures.
The main concerns we have when terminating aluminum is crepe, oxidation and galvanic corrosion.
Take a look at set screw terminal such as the Blackburn by Thomas and betts in the OPs photo.
http://www.garagejournal.com/forum/attachment.php?attachmentid=193611&d=1340730805
This type of connector appears to be a great choice on the surface. It is made of an alloy that it is compatible for both aluminum and copper, contains a ridge for adequate separation between the aluminum and copper conductors.
Now the short fall of this style connector as with many lugs commonly used and have a UL listing, is the fact the set screw twist directly on the conductor.
With this arrangement it important the the proper torque setting is adhered to as an over torque can cut through some of the stranding. The fact that it is a blind termination prevents observation of such action.
Be sure to use a screwdriver that fills the slot's width as this style will twist out easily.

Looking at an alloy split bolt.
https://www.ilsco.com//Images/ProductImages/AK.jpg
heat treated to prevent galling and tin plated for low contact resistance. It is rated for aluminum and copper. We see a mechanism for separation of the copper and aluminum conductor. We also see a saddle if you will for both conductors to rest on. The saddle will only squeeze and not twist, protecting the conductors.
The conductors are partially visible during this process allowing the installer to witness the compression.
Down side of the split bolt, labor intensive, requires skill to insulate properly and it takes up more space.
While both types are good connectors they have their advantages .
For ease of use speed and size, the set screw barrel connector is good.
For a large smooth non twisting contact surface area the split bolt is the choice.
Regardless the following steps should be followed when terminating aluminum conductors.

1. When stripping avoid ringing the conductor.
2. Clean and apply oxide inhibitor per instructions.
3. Use torque settings by manufacture, if unavailable default to UL 486B torque values, Use lugs of the appropriate size based on the AWG in use. Both combined will reduce crepe to negligible level.
4. use lugs and hardware of the appropriate materials to prevent galvanic corrosion.
5. Alway insert the conductor to the proper depth to avoid push out and increase surface contact area.

Rtw5150
07-02-2012, 09:26 PM
My bad, I thought those were GB crimps, I didn't notice the T&B bag, I still wouldn't use them. About 10 yrs ago one of our apprentices was telling us about a demonstration the instructors were giving them on those style connectors. They put the body of the connector in a vise, put the proper size cables in, set them with a torque wrench, set it on a shelf, came back in a week and checked the torque settings. Not surprisingly they were sloppy loose. I, myself won't use them, ever.
The Ilsco's I was referring to are not the underground they are for above ground, molded in rubber, you pull the plug out and it has a mechanical lug (with the hex head set screws) I have a lot more confidence in those.
Like you noted anything can fail if improperly installed, I just think you should start with the highest grade parts available, one less component to worry about. I think the best connector in this situation is the one the licensed electrician (that the OP decides to hire) thinks is the best! Lol

taumac
07-02-2012, 09:37 PM
I got a stupid question.... if those are bare and not insulated would they possible come in conact with metal box and electifly the box?

PRH44
07-02-2012, 09:54 PM
:shocking: Oh yea and a big flash

matt151617
07-03-2012, 06:16 AM
I got a stupid question.... if those are bare and not insulated would they possible come in conact with metal box and electifly the box?

That could happen... you'd be crazy to not insulate them a bunch of times over. Lots and lots of tape, plus rubber tape or shrink wrap. I used shrink wrap, then about 1/4 of a roll of 33+ tape. The 33+ tape pretty much seals to itself and makes a solid coating.

Of course, if you use a metal box, it has to be grounded, so it shouldn't electrify the box, and hopefully the breaker would trip.

rlitman
07-03-2012, 10:12 AM
That could happen... you'd be crazy to not insulate them a bunch of times over. Lots and lots of tape, plus rubber tape or shrink wrap. I used shrink wrap, then about 1/4 of a roll of 33+ tape. The 33+ tape pretty much seals to itself and makes a solid coating.

The set screw barrel splice kits come with a pre-cut piece of heat shrink tubing, and make a UL compliant splice using everything included.
The advantage to something like that, is that the splice stays very small.
I would be more comfortable adding about two layers of Scotch 88 on top of that (33+ is just as good, I just happen to prefer the feel of 88, but you should never use an inferior tape for insulation purposes) too.

Split bolts are another story. They have edges and corners that can pierce the tape over them.
The traditional method of taping would be to first wrap them in a layer of friction tape to cover any sharp edges, then two layers of rubber self-sealing insulating tape that extends onto the wire, then a cover layer in either friction tape or electrical tape, to protect the rubber layer from damage.
Covering in about 1/3 roll of Scotch premium tape (33+ or 88) would be an acceptable alternative.
All said and done, you'll end up with a golf ball sized splice, or larger.

Back to the issues with the actual connections:

Yes indeed, you must use a well fitting screwdriver for the set-screws. A Craftsman cabinet screwdriver is simply NO GOOD. Proper screwdrivers will be hollow ground with parallel faces. Basically a gunsmithing screwdriver in design. I use Wera insulated screwdrivers (insulated, because it's what I have).
Use the wrong screwdriver, and you may damage the aluminum.

The screw should "squeak" when it gets tightened right. That's the sound of the screw jumping forward in ever so tiny increments because of high static friction. If it doesn't make the sound, it is more likely to back out.

It is important to select the smallest barrel that fits the wire being used. Larger or lugs will leave space around the wire that the set-screw must pass through, leaving less thread engagement for the screw, and more room for the individual strands to wiggle out from under the screw. This is also an issue if the strands in the wire are fine. Thicker strands hold up fine under a screw. If it fits well, it makes for an excellent connection.

Now, about split bolts. The nut only contacts threads on about 1/2 of the full circle, so it is very easy for the threads on one side to jump. With copper, it is bad enough, but with aluminum it is downright scary to me. The total thread engagement is less than with that tiny set-screw, believe it or not.
This really requires careful preparation, and a torque wrench.

Previously, i've only seen all aluminum split bolts rated for co/alr.
The tin plated copper split bolts that I knew of were not rated for aluminum wires. I see now that some are indeed rated AL9CU. I'll admit freely, aluminum is not my thing. I avoid it like the plague.
Ok, that sounds like it may be a good option too then, but while the plating may take care of the corrosion issues, it doesn't fix the thermal expansion/contraction issues that can cause the bolt to loosen.

The spacer bar is designed to prevent galvanic corrosion. This is only an issue in wet locations (the outdoor box in question would fall into this category though, as would an overheat triplex install, etc.).

But all said and done, I would still recommend a set-screw connection in a pre-made split kit, before I told a do-it-yourselfer to grab split bolts. Even if they can be made to work just fine, they're not nearly as simple to get right.