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oliver100

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What is the best wiring method for a 100 Amps residential sub-panel (3+1 wires). The wiring path is more than 100 ft and requires several 90 degrees bends.
 
With the price of copper these days I would go with aluminum SER cable. You will need minimum size #1 SER not #2 for 100 amps feeding the subpanel.
 
This thread had been temporarily closed, because it appeared to be an attempt by a Do It Yourself person to obtain "how-to" information.

In an exchange of Private Messages, the Original Poster has provided assurances that this is not the case. The OP stated that he intends only to prepare design drawings and specifications, and will arrange for an electrician to complete the project. Therefore, I am reopening the thread.

I offer an apology to the OP for the inconvenience and the delay.
 
For a residential "sub-panel" I see no reason to not use an aluminum SER cable.

The new aluminum SER cable has a better aluminum alloy then the old aluminum cables and is not supposed to have the same problems as the old stuff.

Chris
 
If the nominal path is through fancy finished walls and other nasty things, you might consider wrapping the place on the exterior as an option if the panel locations were near exterior walls. Its not the usual way people do it, but can save a lot of PITA and inside wreckage sometimes.
 
I would recommend 1/0 Al. SER. Art. 110.14(C)(1)(a) says:

110.14(C) The temperature rating associated with the ampacity of a conductor shall be selected and coordinated so as not to exceed the lowest temperature rating of any connected termination, conductor, or device. Conductors with temperature ratings higher than specified for termination shall be permitted to be used for ampacity adjustment, correction, or both.

(1) ... Unless the equipment is listed and marked otherwise, conductor ampacities used in determining equipment terminations provisions shall be based on Table 310.16 as appropriately modified by 310.15(B)(6).
(( 310.15(B)(6) ... service entrance, service lateral, and feeder conductors that serve as the main power feeder to each dwelling unit...))

(a) Termination provisions of equipment for circuits rated 100 amps or less, or marked for 14 AWG through 1 AWG conductors, shall be used only for the following:
(1) Conductors rated 60 C (140 F)
(2) Conductors with higher temperature ratings, provided the ampacity of
such conductors is determined based on the 60 C (140 F) ampacity
of the conductor size used.
(3) Conductors with higher temperature ratings if the equipment is listed
and identified for use with such conductors.

Make sure your sub panel lugs are listed for 75 C or you MUST use the 60 C chart on 310.16 for 100 Amp feeders or less! 1/0 Al = 100 A
 
Chris said:
The new aluminum SER cable has a better aluminum alloy then the old aluminum cables and is not supposed to have the same problems as the old stuff.
Click to expand...

The aluminum industry said it was fine for wiring back in the 60's and 70's too. Their claims didn't exactly play out the way they said. Give me copper.

:D
 
Make sure your sub panel lugs are listed for 75 C or you MUST use the 60 C chart on 310.16 for 100 Amp feeders or less! 1/0 Al = 100 A
Click to expand...


Although tincan is correct, almost all CB's and panelboards are now equipped with 75 degree C terminations. This leaves you with #1 AL SER. That's if anyone makes it. :wink:
 
I just installed some #2 Al SER (2-2-2-4) recently. Is #1 a weird size? Why wouldn't it be available? I am admittedly fairly ignorant about Al wiring in general since I use copper as much as possible.
 
jeff43222 said:
I just installed some #2 Al SER (2-2-2-4) recently. Is #1 a weird size? Why wouldn't it be available? I am admittedly fairly ignorant about Al wiring in general since I use copper as much as possible.
Click to expand...


#1 AL wouldn't be a weird conductor size, but the supply houses around here don't stock #1 AL SER cable. For the most part they stock three sizes, #2 AL, #2/0 AL and #4/0 AL. This covers the basic 100, 150 and 200 amp services.
 
Larry,
The aluminum industry said it was fine for wiring back in the 60's and 70's too. Their claims didn't exactly play out the way they said. Give me copper.
Click to expand...
We did a number of apartment complexs in the mid-70s with the new alloy aluminum THHN wire and CO/ALR devices. There were no more problems it those jobs than with the ones we did using copper.
Don
 
don_resqcapt19 said:
Larry,
The aluminum industry said it was fine for wiring back in the 60's and 70's too. Their claims didn't exactly play out the way they said. Give me copper.
Click to expand...
We did a number of apartment complexs in the mid-70s with the new alloy aluminum THHN wire and CO/ALR devices. There were no more problems it those jobs than with the ones we did using copper.
Don
Click to expand...

Yeah Don, We have an apartment complex here, that calls us when their maintenance guys are over their head. The problem is not the wire - it's the terminations. Over the years, handyman harry has DIYed it. The last three times I was out there, it was due to burned terminations. Twice, it was the wirenut connection on the water heater. The other was a double backstabbed receptacle.

But, you are right. There is nothing wrong with Aluminum wire. I just don't like it.
 
I have used aluminum wire on various applications for the past 25 years and I have never had a problem with it. Some can speculate about the lack of knowledge it takes for one to terminate aluminum wire correctly and I assure you that I am perfectly qualified to perform this task. Seems to me that the only problems you do have with it comes from the improper preparation of your conductors at the time of termination. I can see why that would discourage one from using this otherwise acceptable product. If it was no good, it would be outlawed
 
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