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Old 02-03-2010, 09:57 AM   #1
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What size conduit to subpanel


I'm going to be installing a subpanel for basement electrical service. I'm thinking of using a 1-1/4" conduit between the main panel and subpanel. The subpanel will be 100 A service with #2 AWG wires running to it.
Is 1-1/4" conduit enough?
Thanks

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Old 02-03-2010, 10:16 AM   #2
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What size conduit to subpanel


Try this link.
http://www.electrician2.com/calculat...alculator.html

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Old 02-03-2010, 10:30 AM   #3
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What size conduit to subpanel


#2 copper ? Why so big ?
You can use #3 copper for a 100a sub
1 1/4" is OK to use, but oversizing is better - I would use 1.5"
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Old 02-03-2010, 11:14 AM   #4
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What size conduit to subpanel


I'm not as familiar with 2 and 3 gauge wires. I read in my wiring book that #2 is rated for 95A. Although, my electrican friend also told me #3 would be good. I guess I'll use #3 with the 1-1/2".
Thanks
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Old 02-03-2010, 01:48 PM   #5
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What size conduit to subpanel


Just to show you where I got my info....

here is a link I found regarding different wire gauges.

http://diyaudioprojects.com/Technica...an-Wire-Gauge/

It says 2 is rated for 94 amps.
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Old 02-03-2010, 01:52 PM   #6
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What size conduit to subpanel


I'm not sure what they are basing that on
I'm going based on NEC code chart 310.16
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Old 02-03-2010, 02:05 PM   #7
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What size conduit to subpanel


Ah, got it. I'm looking at it now on page 70-148.
Thanks for the clarification.
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Old 02-03-2010, 06:44 PM   #8
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What size conduit to subpanel


just curious--does it matter if the conduit is plastic or metal?
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Old 02-03-2010, 06:51 PM   #9
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What size conduit to subpanel


Not sure. I would think metal is preferred, but let someone more experienced answer that one.

One more question regarding this installation:
I will have a 100A breaker installed in the main panel, so I don't need a main breaker in the subpanel, correct? The panel I bought (100A 20 circuit Homeline from HD) comes with a main breaker. Most of the ones come with main breakers. They also have a Siemens 125A panel with 20 spaces for a dollar more without the main breaker...just main lugs. I'm thinking I can just unbolt the main breaker and use the box. Also the Siemens box has a copper bus as opposed to the one that I bought which has aluminum....not sure if it really makes that much difference.
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Old 02-03-2010, 06:52 PM   #10
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What size conduit to subpanel


Quote:
Originally Posted by daddyrabbit View Post
just curious--does it matter if the conduit is plastic or metal?
No should not matter, unless there is some local code that requires metal
I use PVC - grey not the white

I always use a main breaker panel & leave the main breaker in
That way everything can be shut off in the panel at the panel
--excepts for hot lugs
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Old 02-03-2010, 06:55 PM   #11
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What size conduit to subpanel


thanks
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Old 02-03-2010, 07:56 PM   #12
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What size conduit to subpanel


Quote:
Originally Posted by faromic View Post
I'm not as familiar with 2 and 3 gauge wires. I read in my wiring book that #2 is rated for 95A. Although, my electrican friend also told me #3 would be good. I guess I'll use #3 with the 1-1/2".
Thanks
Just bear in mind that 1 1/2" conduit is harder to work with than 1 1/4". But when you pull the wire, you'll feel the difference. The (feeder) wire will just slide in.!
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Old 02-03-2010, 08:18 PM   #13
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What size conduit to subpanel


Actually with (3) #3' & a #6 as a ground you could use 1"
If it is a STRAIGHT run without any bends
Any bends & definetely go to 1.25"
If enough room, longer pull...more bends go to 1.5"
Note you can't have more then 360 degrees of bends without having a pull box
IE (4) 90 elbows

Before you start check out your supply store
Big box stores do not carry much in 1.25" size
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Old 02-03-2010, 10:21 PM   #14
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What size conduit to subpanel


I am going to be installing the subpanel directly next to the main panel. There will only be a 4" piece of conduit (threaded on each end). So I will need to bend the #3's from the bottom of the main panel to the conduit and into the new subpanel. I am limited because I can't move any of the existing breakers because there is not enough lag in the wires. I have an empty space near the bottom of the main panel and will install my 100A breaker there. I will need to bend the #3's to get to the top of the subpanel to connect to the hot, neutral, and ground buses.
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Old 02-03-2010, 10:28 PM   #15
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What size conduit to subpanel


I'd just use the 1.25", gives a little better bending room
Unless you have some 1" or 1.5" around
Too bad you don't know someone with a scrap piece..they are sold in 10' pieces (usually)

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