Subpanel Electrical Fire

Same question to you. Why do electric utilites use aluminum almost exclusively for transmission and distribution if aluminum is a "bad conductor".

Where this analogy fails is that unlike balsa wood and airplanes, aluminum is widely used to conduct electricity.

If you stuck with the last part, you'd be correct.

The problem is that the statement that aluminum is a bad conductor is the opposite of semantics, because it's inaccurate. As you correctly said above its "a bad choice as a conductor in home wiring".

todd

Reply to
Todd Fatheree
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Wouldna that sair be a unco mistake, wot?

Reply to
Swingman

"Bad" for home wiring because of termination issues, but good enough for transmission lines.

Reply to
Swingman

Because at that scale, they're using far more material with relatively fewer joints. The benefits increase, the costs are more manageable. Their circuits are also powered almost continuously and a flowing current avoids many of aluminium's problems. It's circuits that are cycled for long off periods that are most prone to the typical faults.

You'll notice that telephone companies, another great user of copper wire, never went for aluminium.

Reply to
Andy Dingley

So what you're saying, without coming out and saying it, is that aluminum is a "good conductor" for the utilities?

I've never said that aluminum was appropriate for all uses. I just disagreed with the blanket statement that aluminum is a "bad conductor". You'll also notice that the telcos are increasingly moving to fiber. Just gotta get that "last mile". ;-)

todd

Reply to
Todd Fatheree

Hi Andy,

Just out of curiousity what is the "Superb ring system".

Pat

Reply to
SawDust (Pat)

You simply CAN'T assume that. You have NO assurance that the person who installed that matched the breaker to the conductors correctly, and, from what you've posted so far, it sounds to me like he did NOT.

Furthermore, you said in your original post that your feed wire is aluminum.

8ga COPPER is rated 40A; aluminum conductors have lower ratings than copper conductors of the same gauge.

The current rating (ampacity) depends on the material, the wire gauge, and the temperature rating of the insulation.

To carry 50A in aluminum, you need either (a) 4ga wire of any conductor temperature rating, or (b) 6ga wire with a conductor temperature of at least

75 deg C. 8ga aluminum is NOT Code-approved, nor is it safe, for carrying 50A regardless of the conductor temperature.

You can't assume that either.

-- Regards, Doug Miller (alphageek at milmac dot com)

Nobody ever left footprints in the sands of time by sitting on his butt. And who wants to leave buttprints in the sands of time?

Reply to
Doug Miller

Reply to
GerryG

No - I was talking about in-house wiring, not utilitites. You're the one claiming that the OP's problems and near house fire couldn't have been caused by the use of aluminium, because 440kV systems manage to use it.

Reply to
Andy Dingley

Ah, yes...I was wondering how long it would take for the qualifications to be made. I've been very clear all along the contexts I've been talking about and have said more than once that aluminum is sub-optimal for home wiring. But, hey, nice try at a misdirection after being painted into a corner. Now that the tactic is just to start making up things I never said, I'll just bow out.

todd

Reply to
Todd Fatheree

Cuz now we're only hearing from the survivors....

Reply to
Australopithecus scobis

Reply to
Andy Dingley

You're right, of course. I guess what I was trying to say was that, trying to evaluate the possible causes of the problem, I look for the most likely events and go from there. If that does not pan out, I examine the less likely events.

You may be correct, there, also, in that the failure of the installer to perform the job correctly coupled with the failure of the municipal inspector to catch the error may be more likely than I expected. I realise they are not necessarily independent probabilities; i.e. neither of them were necessarily doing their job conscientiously.

Thanks for pointing this out!

Unfortunately, I just cannot make out more of the info on the sheathing than the 6 or 8 gauge point. So, I just do not know the temp rating.

Point taken...thanks... CDW

Reply to
Seawulf

In that case, it would be prudent to remove it, and replace it with 6/3 copper with ground - the point being that, given that the wire is aluminum, if it's

8ga it's unsafe, period, and if it's 6ga you're unable to determine whether it's safe or not. OTOH, 6ga copper is safe for 50A regardless of conductor temperature.

-- Regards, Doug Miller (alphageek at milmac dot com)

Nobody ever left footprints in the sands of time by sitting on his butt. And who wants to leave buttprints in the sands of time?

Reply to
Doug Miller

This isn't true Lew. Go down in your breaker panel and look at what comes into it - aluminum. Look at what feeds your sub panel if you have one - aluminum. It's the combination of aluminum and copper in pigtails that caused problems in the 60's, not aluminum wire feeding panels. The OP posted a problem with a branch circuit that was copper. The aluminum feed lines coming into his sub panel hae nothing to do with the copper branch circuits.

-Mike- snipped-for-privacy@alltel.net

Reply to
Mike

Totally different world.

Utilities commonly use Al conductors as service entrance feeders as well as distribution cables; however, that is a totally different application which the utilities address by using specific terminations crimped with tools designed specifically for Al cable.

Take a look at the terminations made by the utility at the weather head of a typical service entrance. (You don't find those terminations at Home Depot)

Attempting to use Al conductor in a clamp type termination found on a typical plug-in c'bkr of a residential load center or the same clamp type termination found on the neutral and ground bus bars for branch circuits is a totally different world.

Cold flow and ultimately melt down are just a matter of time.

Lew

Reply to
Lew Hodgett

True, but only in the sense that *much* more care is required in installation.

Nonsense. Cold flow occurs when a connection is over-tightened. A connection that is not overtorqued will not cold flow. Aluminum conductors, in terminals designed for use with same, are safe enough when tightened to the proper torque specification and no further, and of course when an appropriate anti-oxidant is used.

_Properly_installed_ aluminum wiring is safe. Trouble is, it's a _whole_lot_ more difficult to install aluminum properly, as compared to copper. For starters,

- use only devices, terminals, and connectors rated for use with aluminum

- use anti-oxidant paste everywhere

- use a torque wrench on *every* termination to avoid overtightening (that includes the screws on receptacles and switches)

With copper, you don't have to worry about any of that: copper doesn't cold-flow, any listed device is OK to use with copper, and copper oxide is nearly as good a conductor of electricity as copper itself (aluminum oxide, OTOH, makes a reasonably decent electrical *insulator*).

-- Regards, Doug Miller (alphageek at milmac dot com)

Nobody ever left footprints in the sands of time by sitting on his butt. And who wants to leave buttprints in the sands of time?

Reply to
Doug Miller

Totally different world.

Utilities commonly use Al conductors as service entrance feeders as well as distribution cables; however, that is a totally different application which the utilities address by using specific terminations crimped with

tools designed specifically for Al cable.

Take a look at the terminations made by the utility at the weather head

of a typical service entrance. (You don't find those terminations at Home Depot)

Attempting to use Al conductor in a clamp type termination found on a typical plug-in c'bkr of a residential load center or the same clamp type termination found on the neutral and ground bus bars for branch circuits is a totally different world.

Cold flow and ultimately melt down are just a matter of time.

Lew

So then I said...

Not really different Lew. The meter channel uses crimped lugs like you're talking about, but your service panel uses aluminum feeders that just clamp down in the main and on the buss bar the same way that your copper branch circuits do. The same way that I believe the OP is describing his sub panel to be.

The point the OP made - at least as far as I recall, is that his branch circuites are copper. It's only his feed that is aluminum. That would be essentially what you see in your primary panel. The buss bar is aluminum, so he would not have any problems clamping an aluminum feeder down. It's when you put copper in there that you contend with issues of dissimilar metals and have to use products like no-ox to prevent them.

-Mike-

Reply to
Mike Marlow

I don't know if it has been mentioned but another strike against Al wire in branch circuits is that the wire is very disagreeable about being bent. Al wire will weaken and crack if flexed too often, as can happen while attaching devices (pulling, twisting. folding, stuffing back in the box, etc.)

Reply to
Bruce

Mike, Yes, the subpanel is set up as you describe with Al Feeder and, all copper to the subpanel circuits.

You also say the buss bar is Al. My material recognition is not up to par, so, I really cannot tell. It certainly looks like it could be Al. The grounding bar appears to be the same material as do the hot terminals. The set screws in the neutral and ground buss appear to be the same material, but the set screws in the hot terminals have a color that looks about half way between Al and Brass. BTW, the bracket that connects the grounding buss to the case is the same material as the set screws on the hot terminals.

So, what is it about the construction of this subpanel that allows it to be rated for AL or Cu wire, the Al bus terminals?

Charlie

Reply to
Seawulf

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