Any home electicians? AL to Copper Q?

[don911]

I'm doing a kitchen remodel and am hooking up some existing 220 to a cooktop and wall oven.
I have existing 10 gage copper wire and 6 gage AL wire. My cooktop needs 40 amps and my oven 30amps. According to my wiring book, my cooktop will need 8 gage wire and oven will need 10.

My plan is to use the existing 10 gage copper and run it to the oven. Should be fine.

For the cooktop, I plan to run new 8 gage copper from the cooktop up to a junction box and mate with the existing 6 gage AL. I've seen some scary pics of heat generated from bad AL/copper connections. I plan to use the proper AL/copper lugs for the connection but am wondering about the gage change from 8 to 6.
Any thoughts on possible issues going from 8 gage copper to 6 gage AL?

Also, I would have expected the oven to have higher amps than the cooktop. Seems odd that the oven can use smaller wiring. Normal?

[Superman]

I'm not an electrician, don't play one on TV and didn't sleep at a Holiday Inn Express last night but I will tell you what I think I know about Al wiring. I used to work with electrical inspectors. Their concern was that over time, the Al connections would loosen. Perhaps Al expands and contracts more than copper. At any rate, over the many years, the connections would become less tight, resulting in resistance, resulting in heat. Aside from that problem, I'm not sure Al is that bad. But.....loosening connections is plenty enough of a problem. I got the impression that if someone went in there every decade or so and retighened the connections, Al would be fine. But who wants to do that?

[don911]

Yes, as far as I know, loose connections are the problem. I believe that's the problem if you put the wires together with those twist cap connectors. Over time, they can loosen up. There are AL to copper lugs that solve that issue. The lug hard fastens each wire separately.

[RickM]

Accepted connector: \





Here's another accepted connector: http://www.alcopstore.com/

[VINMAN]

25 yrs in the electrical field...
If it as all possible, I would replace the AL wiring. The 6ga AL and the 8 copper have the roughly the same ampacity, but you still have the expansion issue.
I went through my house and tore out all the old Al wiring. Almost every connection had an issue.

[Danny_Ocean]

1) Replace the AL wiring, sleep better at night.

2) Stepping-up a wire gauge is better than installing the minimum requirment.

3) An oven typically has two large, slow-heating elements (usually only one of which is used at a time (broil vs. bake). Cooktop has 4 (or more) rapid-heating elements, which could all potentially be in use simultaneously. I would suspect a cooktop draws more amps than an oven.

[masraum]

Also, if you are really determined to use the Al wire, use lots of "no alox" I think it's called. It's a special goop that you put on the connection to reduce oxidation build up which is the big problem. I've got Al wiring in my house. I hate it. When we moved in every wall socket in the place was replaced with the correct co/alr recepticles. Even with that, I occasionally get one that stops working. I take it apart, clean the wires and put it back together tightly. I've seen sparks come out of a socket that has oxidized over time. It's exciting to say the least.

[Porsche_monkey]

I would dump the aluminum if possible. My entire house is wired with aluminum from the 70's. No issues, but I have treated every joint with no-alox.

If you keep the aluminum use no-alox and be sure not to knick the wire, they tend to crack and break off when this happens.

[don911]

Thanks for the replys. I'd like to dump the AL wire but it would be quite a bit more work. I'm not sure why they used it for the one 220. Maybe it was added as an after thought.
I could run new wire under the house to the c/b panel. Might be the safer way to go.

[HardDrive]

If you have access to the crawl space under the house, then I would do a fresh run.

Count your blessing friend. I have a mix of knob/tube + 60 years of someones drunk brother in law making 'updates' to my wiring. I've been here 5 years doing renovations, and come across stuff all the time that makes me say, "ARE YOU KIDDING?!?!?"

The electric heater that heats our tile floor in the master bathroom? It shares a ciruit....with the freaking garbage disposal in the kitchen! Sometimes I feel like tracking down the previous owners....and hurting them.

[RickM]

Originally Posted by don911

I'm not sure why they used it for the one 220.

Aluminum is still used quite a bit in commercial settings. IIRC, the new home of the NJ Devils used it for all it's electrical infrastructure, which carries much more than 220v. Seems that aluminum is simply not conducive to residential type applications.

[Porsche_monkey]

I think aluminum is fine now. When it was first used there were quality issues and the wire was brittle. My home has zero problems, but my brother had a house that was slightly older, and I was over there once a month fixing outlets.

And aluminum may be good enough for the New Jersey Devils, but am sure that the mighty Toronto Maple Leafs are 100% copper. Okay maybe 75% sure.

[RickM]

FWIU the arena save mucho bucks by switching the spec from copper to aluminum. Hasn't hurt their game either

[Mo_Gearhead]

If I were splicing AL to CU I would ALWAYS use a suitable 'crimp' connector.
Heat/expansion cycles are different in the two metals and bolted/screw connections can loosen/fail over time.
JMO