Subpanel wiring

[Sean Hughes]

Hopefully someone here can lend me a hand with this. Our range has been changed from an electric to gas. The line feeding it was hardwired into the range. It's aluminum standed wiring with 2 hots and a ground. The opposite side of the wall is my garage and I'd like to change this line into a subpanel for the garage. Will this work with what is already there? The line is setup at the main with a 50 AMP breaker. The stamping on the sheathing of the wire is as follows, Alcan S Stubby Type SE Cabble Style U Typre XHHW CDRS 600 Volts 2 CDRS 4 AL 1 CDR 6 AL. Thanks for your help

Sean

[Matt Meiser]

It sounds to me like it has 2 #4 conductors and 1 #6 conductor. You need 3 conductors + the ground. Since its aluminum, I personally would want the peace of mind of new wiring any way.

[Ken Garlock]

Sean, I see two things. You need a forth wire to produce a separate equipment ground back to the main panel. You cannot tie neutral and equipment ground together in a sub-panel. Second, I would not do it because of the aluminum cable. I am not sure, but I think that aluminum wire is illegal in most places. You might want to check with your codes department there in West Chester.

Say hello to my money over at QVC. :D :D

[Ken Fitzgerald]

Sean...........I lived in a new house trailer for about 18 months in the mid-1970s. 5 months after I moved into base housing, that trailer burned to the ground. The fire was caused by faulty electrical wiring. I used to sit at night watching tv and see the outlets "sparking". The next day I'd notify the owner and tighten the connections to eliminate the sparking. I had a pregnant wife and two children at the time.

I won't have aluminum wiring in any building I own. I just built a new shop and I ran copper even on the incoming wires to the meter box.

I won't use aluminum. JMHO.

[Sean Hughes]

Thanks for the replies. Yes QVC is about a half mile from my house. If I were to replace the wiring, would 8/3 do the trick? Cost?

[Ken Garlock]

Regarding your cable size, take a look at this site (http://www.jhlarson.com/ind_tables/ind_table.htm). It has information regarding permissible current loads for various size wires. There is alot of other good 'stuff' there also.

I think I would go with at least 6 Ga.

[Bryan Somers]

About aluminum wire

What Ken and Ken said!!!

Is your main panel in the garage? If so it should be a fairly easy change over to run copper to a subpanel. If not the wire is probably run up to the attic or down to you crawlspace and then over to the range.

[Sean Hughes]

The main is in the basement on the other side of the house. probably a 50 foot run in all.

[rick fulton]

Sean...........I lived in a new house trailer for about 18 months in the mid-1970s. 5 months after I moved into base housing, that trailer burned to the ground. The fire was caused by faulty electrical wiring. I used to sit at night watching tv and see the outlets "sparking". The next day I'd notify the owner and tighten the connections to eliminate the sparking. I had a pregnant wife and two children at the time.

I won't have aluminum wiring in any building I own. I just built a new shop and I ran copper even on the incoming wires to the meter box.

I won't use aluminum. JMHO.

Ken -

Dude your scaring me. I am about to install a new 50 amp range in my kitchen and a 50 amp breaker in my box. The existing circuit has a 40 amp breaker. Per an NEC wire chart at Home Depot, my 4 conductor 6 gauge XHHW type aluminum wire is rated at 50A. Replacing the line from the box to the kitchen would be a major PITA. I think it is the only AL wire in the house. Maybe its time to call an electrician or electrical contractor.

Thanks!
rick

[Rob Russell]

I wouldn't worry about aluminum wiring - if the wire is protected from oxidation and the terminals where the conductors land are properly torqued.

The aluminum wire horror stories you hear about were largely caused from the "aluminum romex" that was used to wire dwellings. I ran SER with aluminum XHHW conductors for the subpanels in our addition and I'm not losing a bit of sleep over it.

Ox-Gard is the brand of anti-oxidant paste that I bought at the local (orange) big box store. You put a bit onto the ends of the conductors after you've stripped the insulation off. The paste prevents the oxidation that aluminum can get over time.

Sean,

You could use that circuit to feed 240v only circuits in your garage. I'd check with the local inspector to see what they'd want. It's possible that they would allow you to install a 240v-only panelboard that could only be used for 240v loads. If they approve it, you can install it.

Without running new cable (replacing the 3-conductor completely, not just running an additional wire for the neutral) you're stuck with 240v only - you can't run a normal subpanel.

Rob
Addy protocol - unlicensed but experienced amateur, homeowner electrician.

[rick fulton]

Rob -
Thanks for the info. I have a new outlet that says its OK with AL. I will look for Ox-Gard before completing the hookup.
Thanks again.
rick

[Frank Hagan]

I wouldn't worry about aluminum wiring - if the wire is protected from oxidation and the terminals where the conductors land are properly torqued.

The aluminum wire horror stories you hear about were largely caused from the "aluminum romex" that was used to wire dwellings. I ran SER with aluminum XHHW conductors for the subpanels in our addition and I'm not losing a bit of sleep over it.

Ox-Gard is the brand of anti-oxidant paste that I bought at the local (orange) big box store. You put a bit onto the ends of the conductors after you've stripped the insulation off. The paste prevents the oxidation that aluminum can get over time.

Sean,

You could use that circuit to feed 240v only circuits in your garage. I'd check with the local inspector to see what they'd want. It's possible that they would allow you to install a 240v-only panelboard that could only be used for 240v loads. If they approve it, you can install it.

Without running new cable (replacing the 3-conductor completely, not just running an additional wire for the neutral) you're stuck with 240v only - you can't run a normal subpanel.

Rob
Addy protocol - unlicensed but experienced amateur, homeowner electrician.

You just have to make sure the connections are to outlets, etc. that have terminals that are rated for use with aluminum wire. I just installed an oven this weekend and it had specific instructions for joining the copper wires to aluminum. Follow those instructions and you're OK.

[Rob Russell]

You just have to make sure the connections are to outlets, etc. that have terminals that are rated for use with aluminum wire. I just installed an oven this weekend and it had specific instructions for joining the copper wires to aluminum. Follow those instructions and you're OK.

Frank,

Very valid point - thanks for the reminder. The terminals on your devices must be rated for aluminum conductors. It will be right on the device as to whether it's rated for aluminum or not.

Most people don't do it, but for aluminum wire, I'd make sure I torqued the connections to the manufacturer's specs. That means having a torque wrench calibrated in the proper range.

Also, if you happen to have one of those houses with "aluminum romex" and want to connect copper wire to the aluminum, there are special purple wire nuts specifically made for joining aluminum and copper conductors. Warning - they know they have you over a barrel on these, so these purple wire nuts are stupidly expensive.

Rob

[Ken Garlock]

SNIP -
Without running new cable (replacing the 3-conductor completely, not just running an additional wire for the neutral) you're stuck with 240v only - you can't run a normal subpanel.

Rob
Addy protocol - unlicensed but experienced amateur, homeowner electrician.

Rob, educate me. Why is running a separate 4th wire not a good thing? Is it an NEC rule? confused:

[Rob Russell]

Ken,

NEC Article 300.3(B) Wiring Methods, Conductors, Conductors of the Same Circuit states "All conductors of the same circuit and, where used, the grounded conductor and all equipment grounding conductors and bonding conductors shall be contained within the same raceway, ... cable, or cord, unless otherwise permitted in accordance with 300.3(B)(1) through (4)." Just to be clear, "Grounded" is the proper term for the "Neutral" conductor - Grounding is the term for the Equipment Grounding Conductor.

Exception 300.3(B)(2) Grounding and Bonding Conductors states "Equipment grounding conductors shall be permitted to be installed outside a raceway or cable assembly where in accordance with the provisions of 250.130(C) for certain existing installations ... . Equipment bonding conductors shall be permitted to be installed on the outside of raceways in accordance with 250.102(E)."

Sean's existing circuit is run with #4 SE cable. That has 2 insulated #4 conductors and the outer braid is considered to be #6. The outer braid can only be used as an Equipment Grounding Conductor - it must have insulation to be used as a Grounded Conductor (aka "Neutral Conductor"). I took a quick look for the code section that says the current-carrying conductors must be insulated, but can't find it right now. Anyway, he could add an additional conductor if he were adding an Equipment Grounding Conductor because that's allowed as an exception to 300.3(B), providing he followed the rules for adding such a conductor. Unfortunately, an EGC isn't what he needs - he needs a Grounded/Neutral conductor. There is no exception, at least that I know of, that would allow him to run a separate Grounded/"Neutral" Conductor.

Rob

[Ken Garlock]

Rob, good answer, thanks for taking the time to respond. I thought the smaller 6 ga. would be a problem somewhere, and it was.:)

[Rob Russell]

Rob, good answer, thanks for taking the time to respond. I thought the smaller 6 ga. would be a problem somewhere, and it was.:)

Actually, the size of the conductor isn't the problem - it's the fact that the grounding wrap is uninsulated.

Hypothetically, if the SE cable had (2) #4 and (1) #6 conductors and they were all insulated conductors, Sean could pull an additional #6 conductor for his Equipment Grounding Conductor and treat the whole thing as if it were #6.

[Jerry Olexa]

IMHO, replace the aluminum wire with standard. You'll sleep better at night.

[Chris Padilla]

FWIW, a "big honkin'" Al cable feeds the house sub-panel at my place...built in the ealry 70s. I think Al is/was cheaper than Cu so that may be the reason. Each terminal point has this goop all over it, too. :) Al is not as conductive as Cu and so you'll find that amperage ratings are higher for the same guage wire in Cu over Al--especially in the heavier gauges.

Cu = 5.8e7 mohs/meter
Al = 3.5e7 mohs/meter

[Ken Garlock]

Actually, the size of the conductor isn't the problem - it's the fact that the grounding wrap is uninsulated.

Hypothetically, if the SE cable had (2) #4 and (1) #6 conductors and they were all insulated conductors, Sean could pull an additional #6 conductor for his Equipment Grounding Conductor and treat the whole thing as if it were #6.

Oh for Pete's sakes. I guess we have hit the brick wall that a ground is a ground until it isn't. Ah, the wonders of a committee at work. I'll bet that the electrons don't know or care if the ground conductor is insulated. Take a look at a utility pole, bare copper wire down the side of the pole and into the earth for the 'white' side of the high tension line ( 7 or 14 KV.)

No need to answer, I am just releasing frustration.:)

[Rob Russell]

Oh for Pete's sakes. I guess we have hit the brick wall that a ground is a ground until it isn't. Ah, the wonders of a committee at work. I'll bet that the electrons don't know or care if the ground conductor is insulated. Take a look at a utility pole, bare copper wire down the side of the pole and into the earth for the 'white' side of the high tension line ( 7 or 14 KV.)

No need to answer, I am just releasing frustration.:)

Well, it's OK to be frustrated, but I think you missed my point.

"Neutral" conductors must be insulated. Because the EGC wrap in SE cable is uninsulated, it can't be used as a neutral.

It's perfectly acceptable for the grounding wrap to be bare wires (in most cases), but it means the wrap can only be used as an EGC.

[Frank Chaffee]

Sometime in the early eighties, and shortly before the expiration of the Rural Electrification Act, I got electrical service to a rural site (yippie!, well and septic can follow!, no more outhouse or carrying water!!!, no more squinting at the fine print in the dim light of kerosene lamps).

Wisconsin Power and Light (who btw had an office in town that was open to we public citizen electric power users, and thru whom I had direct access to our local empowered decision-maker Leroy; could speak with him face-to-face, meet with him on my land, and get the lowdown from him w/o punching thru menus to finally reach a representative in another part of this country or even another, ).

I got poles to the edge of our land and paid extra for additional underground footage to our house site.

The power company provided actively resisting electrons thru buried # gauge sized aluminum, while I had to use some ought #’ed gauge copper to traverse the several inches thru the exterior wall from the meter socket to my service entrance.

I think we could all take this as a hint that aluminum wiring may not be safe for homeowner use, even if we or our electricians use anti-oxidants and aluminum rated fixtures. Once upon a time I bought a mobile home in Arizona and did so only after thoroughly checking that the wiring was all done with copper.

The Coefficient of Thermal Expansion of aluminum is far greater than that of copper, and therefore heat produced by resistance expands and allows contraction in aluminum to a greater degree.

My personal and quite dramatic experience of this phenomenon was when I grasped a cast bronze splice clamp while coiling an aluminum extension cord to my welder and received a burn. Although the aluminum wire was heavily sized, over the period of a couple of years it had expanded and contracted so many times that it had become deformed, and resistance thru the clamp had increased.

Frank

[Chris Padilla]

The Coefficient of Thermal Expansion of aluminum is far greater than that of copper, and therefore heat produced by resistance expands and allows contraction in aluminum to a greater degree.
Frank

I looked up some numbers, Frank, in my college Physics book, as you got me curious:

Coeff. of Linear Expansion in per degree C
===============================
Cu = 1.7e-5
Al = 2.4e-5-->Al will expand linearly 41% more than Cu--Is that much?

So a 30.48 m length of Al and Cu at 20 C, will be 30.502 m and 30.496 m at 50 C, respectively.

Or, to convert it into numbers all of us here have a better feel for, a 100' length of Al and Cu at 68 F, will be 100' 7/8" and 100' 5/8" at 122 F, respectively. Now I rounded a bit for the fractional inch part but suffice it to say that the difference between the two is a tad higher than a 1/4" (0.252 inches).

I think the 122 F isn't far off...I've felt the mains at my house before on a day with lottsa stuff running in the house and I pulled my hand away very quickly.

It is greater, definately, but over a 100', that 1/4" could make a difference. As Rob alluded to, the Al will just need a bit more care in its installation in regards to torque and oxidation but I don't think it is anything to be scared of. After all, the copper line is expanding and contracting too, just not as much.

However, the miain benefit with copper is its almost doubling of conductivity or nearly halving of the resistance of aluminum.