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Old 02-08-2010, 09:03 AM   #1
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Installing a subpanel


I want to install a subpanel in my brother's garage this weekend. I am almost certain I know the steps involved, but I would like to run my plan down here with a couple questions.

I found this guide that seems pretty good, but the guy admits at the end he isn't an electrician, which is why I wanted to get the general steps here.

I plan to do a 60-amp feed to the sub, this will power a few dedicated 20-amp circuits behind his workbench, that's it for now. I want to leave room for expansion.

Few questions to start off:

1. What brand panel should I get? I am not sure the manufacturer of his main panel, should they be the same? Recommended panel? I was looking at this one.

2. I see panels listed as "16 circuit, 8 space". What does that mean?

3. What size wire do I need to run for 60 amps?

4. Since I will be fishing this wire through walls/floors, do I need to secure it along the way? I know that you are not required to fasten retrofit wires for normal circuits, but what about thick wire for a subpanel?

My basic plan is:

-Run wire from old panel to new panel location
-Connect white to neutral buss
-Connect ground wire to ground buss
-Connect two hot wires to new 60 amp breaker
-With breaker off, snap it into the main panel
-At subpanel...attach neutral and grounds to respective busses
-Attach each hot to a lug
-Install two 20amp breakers, run circuits to new outlets (12awg)
-Turn on 60amp breaker

Anything else I need to know?
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Old 02-08-2010, 09:22 AM   #2
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I use the same Mfg as the main panel
That way the same breakers can be used in both
EXception would be if its an out of date main panel

16 circuits is Max it can handle - using 1/2 space (tandem) breakers
If you needed to use 240v breakers it would only take 4 since it only has 8 spaces & a 240v breaker uses (2) spaces

Attached or detached garage ?
I always use a main breaker panel - I like being able to shut off the panel
What is the distance the wire will run ?
If a long distance wire needs to be up-sized for voltage loss

I (usually) never attach the breaker in the main panel until everything is run in the sub



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Old 02-08-2010, 09:30 AM   #3
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It's an attached garage. Waiting to hear from him about the length. Probably around 75 feet.

I would like a main breaker panel too....it's ok to have two breakers controlling the sub? One in each box?
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Old 02-08-2010, 10:18 AM   #4
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Yes, 2 breakers are OK
The main breaker in the sub many times is a 100a breaker which is OK
I bought a 100a main breaker panel for my pool cabana sub

NEC 310.16 indicates #6 for 60a, voltage drop not a problem at 75'
You could actually use a 70a breaker with #6 as long as the load does not go over 65a
I used a 60a breaker for the same setup - easier to find



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Old 02-08-2010, 10:23 AM   #5
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I guess as long as one of the two breakers is 60, adding a second 100-amp breaker merely provides the convenience of having a shutoff in the subpanel, but doesn't provide any overcurrent protection. Not a bad idea.

What about running the #6 wire? Can I just get 6-3 w/ ground and fish it through the walls just like I would 12/2?

And I'll do all the connections in the sub before installing the breaker in the main.

Thanks.
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Old 02-08-2010, 10:37 AM   #6
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Yes. 6/3 nmb can be run inside the walls just like #12.
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Old 02-08-2010, 10:39 AM   #7
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If you use 6/3NM, you are limited to 55A, but may use a 60A breaker if the anticipated load does not exceed 55A. The 65A rating on #6 only applies if you are using THHN in conduit.
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Old 02-08-2010, 10:40 AM   #8
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Yes Cable can be used.....but its rated at 55a instead of the THWN rating of 65a

You can still use a 60a breaker as long as your calculated load will not exceed 55a



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Old 02-08-2010, 10:41 AM   #9
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I can't imagine the load ever going above 55 amps. Maybe I'll just run #6 wire and use a 50Amp breaker instead of 60, just in case. Any issue with that?

If my limit is 55 with #6 NM-B, then I am only losing 5A of capacity, no big deal.
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Old 02-08-2010, 11:14 AM   #10
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Yes a 50a breaker is fine



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Old 02-08-2010, 11:23 AM   #11
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So all I should need to buy for this...

-Subpanel - safe assumption neutral buss will be already installed?
-Ground Buss Bar
-50 amp breaker for main panel
-100 (or 50) amp breaker for sub panel (unless I use a main lug panel)
-6/3 NM-b with ground
-20-amp breakers for subpanel
-12/2 for new circuits
-GFCIs/outlets for new circuit
-outlet boxes/cover plates

Am I missing something? Seems like this should be doable for about $150, depending on the length of the 6/3.
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Old 02-08-2010, 11:32 AM   #12
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Panels are usually sold with 2 bars so that one can be neutral & one can be a ground in a sub
But in some cases that might not be the case, or the neutral is not isolated from the case

I would buy a main breaker panel
Unless there is a possibility that you may want to use this panel with a generator

50a breaker may be around $16-20, Panel could be 50 or more
A roll of 12-2 is maybe 50 or so; 20a breakers are around $7 each
GFCI's have gone up...maybe $20-30 for (3) in a multi-pak

2 black #6 hots, 1 #6 white, green ground
Haven't bought any #6 in years...75x3=225' could be .80 ft = $180
Just estimates



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Old 02-08-2010, 11:55 AM   #13
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I think the 6-3 nm-b was less than $1.50 a foot when I was at lowe's yesterday.

The 50-amp breakers are $12 or so.

Do they make small (10-space or so) main breaker panels? It seems like main breaker panels are all very large (20+ spaces) so they are expensive. I only need about 8-10 spaces at most. This is why I was going to go witha main lug panel.
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Old 02-08-2010, 11:58 AM   #14
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So much for my pricing on the 6/3 - the wire is $2.32 a foot. I must have been looking at something else.
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Old 02-08-2010, 12:09 PM   #15
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Quote:
Originally Posted by secutanudu View Post
Do they make small (10-space or so) main breaker panels? It seems like main breaker panels are all very large (20+ spaces) so they are expensive. I only need about 8-10 spaces at most. This is why I was going to go witha main lug panel.
Yes, but really, I don't see why you would need/ want one when the subpanel is going in the same building. If you want a local disconnect, you could get another 50 A breaker and a hold down kit. I would just stick with a MLO panel and be done with it.
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