Before I buy my subpanel and feeder wire...

[exactly]

Almost there! Before I run to my local electrical supplier to purchase a subpanel and a feeder wire for my two-car garage woodworking shop:

1. Should I get a main breaker panel instead of a main lug panel?
2. Is 4-3 NM okay (I was originally going to go with 6-3), or should I get #2 aluminum? I do not need 100 amps, but it would be nice to have more than 55.
3. Based on the below, would you get a 22-space panel, or larger? I'm looking at Eaton CH CHP22B100X2, but I could go larger. I'm thinking this will be the first and last garage subpanel install here for the next several decades. Do it once, do it right.
4. Do I...um...need to get any sort of giant wire cutters to work with this thick wire bundle and individual wires?

I decided to ask individual questions in individual threads rather than continue a long thread (it was difficult to get answers, unfortunately), so here are the quick specs:

• 22x22 attached garage in a 1980s home
• 25 - 30' feeder wire runs 17' perpendicular through basement ceiling joists and is never outdoors or exposed to concrete or anything except for the cinder block basement wall when the feeder exits the panel in the 2x4 studded wall
• Garage is for one-person woodworking hobby shop but may in the future support an electric car charger (likely) or a welder (less likely)
• Most likely doing four 120V and three 240V circuits along walls (for flexibility rather than running more than two or three things at once)
• Additionally one or two 120V branch circuits up high for natural gas unit heater and air filtration
• One 240V branch circuit to junction box for future ductless mini split with heat pump
• Walls currently open but will be insulated and drywalled once wiring is in
• I am likely not prepping for car charger or welder at this time
• Lighting on existing 20A garage circuit

Thanks so much!! The support I have received on this forum has been amazing so far. I have learned so much.

 

[pattenp]

I would use at least a 100A 20 space main breaker panel because they are common and relatively cheap. I'd use 2-2-2-4 Al SER, again cheap and good to 90A, but suggest 60A feeding breaker because it's cheap.

 

[mike93lx]

Agree on patten's post. 4/3 Cu will be expensive, especially compared to #2 AL.

You don't need any special tools and can cut the wire with a Sawzall or hacksaw

 

[NUTTSGT]

If buy a matching brand/series breaker box for the sub panel in your shop. It allows the switching of breakers in case one fails at an odd time and its just good practice.


Using a main breaker box, rather than a main lug box, allows you to kill power to the entire box, where you are at and not have to go racing through the house in case of an emergency.

Trust me, you don't want a firefighter walking through your house with wet and dirty fire boots.

 

[exactly]

Thanks for the replies! I found out that 4-3 copper is almost $5 per foot! What’s the amp rating on that anyway? Surely it’s not much more than 6-3, which I believe is 55A but goes on a 60A breaker. 6-3 NM is less than $1.50 / ft.

For 2-2-2-4 SER, which is the same price as 6-3 NM, will I be able to pull that through holes in my joists and up into the main-level wall (2x6 framing)? Do I need to need to worry about the ground not fitting in the ground bar in my existing CH house main panel?

Regarding main breaker panel vs main lug panel, would I leave in the 100A main breaker and put in, say, a 70A at the house main panel? Or do I need to swap out the main breaker in the subpanel? Any chance an inspector would fault me for using this type of setup? Heck, any chance he would fault me for using SER running through joists?

Right now I only need 24A plus a few amps to run air filter, a few amps to run blower fan on small natural gas unit heater (in winter) or 10-15 amps to run AC (in summer), and, long term, 13A to run larger CNC spindle, if I even go that big. Should I even bother with anything other than 6-3 NM?

I may have made a mistake today by purchasing 6-3 and a 24-space main lug panel. It was only $170. I mean...I want a few outlets and circuits. I’m not running a production shop. But I can always repurchase something different if I figure it out this weekend. I don’t mind.

Should I just roll with what I got...or switch to SER and a main breaker panel?

Thanks!!

 

[mike93lx]

You can leave the breaker in the sub a sit is just a means of disconnect. The one in your main is what matters.

There are adapters available if the wire won't fit in the ground bar.

I would do #2 ser, but if you have the 6/3 nm-b, that will work just fine.

You may be able to setup the panel as a backfeed (install a two pole breaker in one of the spots and feed in through that instead of the lugs. Read the label to check that. I would want a means for shutting off the whole thing quickly.

 

[PWilks]

From what I’ve seen in my own research (and asking on this forum), a 100 amp main breaker subpanel is the way to go. It’s price comparison across most manufacturers is only an extra $30 more than main lug (at least from what I’ve seen with squareD) and it gives a means of disconnect.

The 100 amp breaker in your sub panel you can think of as a switch. The overcurrent protection is determined by the breaker feeding it from your main panel (60,70 etc). The one drawback to this is if you trip your main breaker, you have to walk back to the main panel to reset it, as the 60 or 70 will trip before the 100 in the subpanel.