Dryer cable as sub panel feed?


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Old 11-25-07, 12:15 AM
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Dryer cable as sub panel feed?

Ok heres what I got-

A 200 amp main panel. On that panel I have a 40 amp 240v circuit feeding a dryer outlet. I have a gas dryer and the outlet hasnt been used in quite sometime.

I want to relocate this cable and use it to feed a 100 amp sub panel in my garage. The cable is "Aluminum -B Type SE, #4, Type XHHW, 4 conducter."

The wire will not be run underground nor outside. The total run is about 30ft.

Is this acceptable?
 
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Old 11-25-07, 05:27 AM
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I don't know why an electric dryer would have a 40 amp breaker, it should be 30.

Anyway, a better plan would be to run new wire that is copper.
 
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Old 11-25-07, 08:41 AM
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additionally, if you are actually feeding the panel with a 100 amp breaker, the wire is not big enough.

that wire (based upon the connections involved) would be good for 65 amps.
 
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Old 11-25-07, 09:09 AM
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I appreciate your responses.

The panel will be fused to 40 amps at the main and a 40amp disconnect will be at the new box (if required). I am planning on adding just a few 20amp outlets in the garage..nothing big. Just wondering if the wire/gauge is acceptable under the NEC.

Thanks again.
 
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Old 11-25-07, 09:59 AM
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That cable is suitable for a run to a subpanel, and is legal for a load of 55A or 65A depending upon the temperature rating of the conductor terminations. Protected with the 40A breaker should be just fine, if the conductors fit properly.

The original installation sounds a bit fishy; I would double check at the supply end to make sure that strands were not trimmed from the cable at the breaker.

You can supply a panel suitable for up to 100A with a 40A feeder. If the panel came with 100A main breaker, you can still use this; it will effectively be a switch only, and will not be 'coordinated', meaning that the upstream breaker will trip first. Of course you will only have 40A of capacity. As a design issue, I would change the supply breaker to the largest suitable for the run, simply to keep confusion down.

-Jon
 
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Old 11-25-07, 11:47 AM
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Jon-

Thank you for that excellent response. All my questions have been answered and I appreciate your time. I'll check on that 40 amp breaker and see if its been trimmed. Its good to know that I can use that cable, as rewiring would be a pain in the ass and cost a bit of money. I'll probably leave the sub panel's mains to the 100 amp, as I think its unnecessarily redundant to have a 40 amp breaker on the sub and main panel when they do the same thing. (the 100 amp mains came with the new sub panel)......or take out the 100 amp breaker and just wire the feeder directly to the lugs. I dont know whats legal in the area I live.
 
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Old 11-26-07, 08:43 AM
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Originally Posted by brad1212 View Post
wire the feeder directly to the lugs. I dont know whats legal in the area I live.
Main lugs only subpanels are allowed as long as you are in the same physical building as the main panel.
 
 

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