Planning for a subpanel in my garage

[FastEddieG]

Hi all,

Thanks for taking the time to read and possibly offer opinions and advice. We moved into this house about 6 months ago. It's 3 years old and the basement and garage were not modified by the previous owner. Well, in the garage, slightly modified. The garage was drywalled by the builder. The previous owner must have wanted more outlets and had someone run 7 quad boxes and conduit attached to the drywall, tapping into one of the lights in the ceiling. (They doubled up that ceiling light box so that it sticks out of the ceiling and ran conduit out of it to feed the quad boxes on the walls).

I'd like to run a subpanel to the garage. It'll be ~70' run from my main panel which is 200amp. I'm torn between a 50amp and 100amp panel in the garage. Of course, the 100amp requires larger wire which makes me lean towards the 50amp if it will suffice. So what will I be powering off of this subpanel to help you advise me? Here are some initial guesses

• 20 amp (230volt) Existing Hobart 175 welder (used very rarely - once a month) (http://www.hobartwelders.com/om/0900/o944g_hob.pdf)
• 15 amp (110volt) tie in existing quad boxes, removing it from lighting circuit (common devices, radio, power tools) (used frequently - daily)
• 15 amp (110volt) existing craftsman compressor (33 gallon, 6HP, 11.9CFM) (bought it after I got married ~7-9 years ago and know it's not a great one, I plan on buying a good vertical compressor which I want to plan for now) (used every now and then, once a week)

I may split up the quad boxes on 2 diff 15 amp circuits later on. But right now, all of the listed items, including the existing compressor run off of the 15amp lighting circuit. So merely putting the compressor on its own circuit may work, not sure if breaking the quads into 2 circuits is necessary.

Not to confuse, but there is another outlet in the garage on the same lighting circuit that is powering the quad boxes, and it has a refrigerator and sprinkler system control plugged into it. So the subpanel will not need to power these 2 items.

Like I said, future I will be buying a good compressor so I want to plan for it now. I presume I will just swap out the breaker for the "compressor circuit" and run the appropriate wire to the outlet when that happens. Also, I will be putting in some sort of furnace. Whether it's a cheap ventless, or an actual vented furnace, possibly with a fan, so a potential for more electric requirements, although small.

So, knowing what I'll be needing to power, going to an attached garage, and needing to be run in conduit, does a 50 amp panel sound like it will suffice? What size wire is required?

I plan to ask 2 friends that are electricians also, but greatly value your opinions. Thanks in advance!
-Ed

 

[dipper]

I doubt you can find 50amp subpanel. I think for the price, you can get a 100amp load center with breakers for about $100. Since you are pulling wire, it won't be much more to go to 4awg for the 100amp. The welder and the future 220v air compressor are kind of dictating it. You'll have more stuff in the future, don't limit your garage to 50amps when it isn't much more to go to 100.

 

[sberry]

Most panels are 100A rated, since this is attached a main is not needed in the new panel. I like 90 or 100A but 60 is sufficient and easier to install. If I was going to pipe it then I would make for the heavier service, cable I might do the 60.

 

[Falcon67]

The most handy panels are 100A or 125A - those give you plenty of space to break out circuits and upgrade to 220 runs when you need to. If you plan to put in a semi-big 3.5HP 60 gallon type single stage compressor, run #12 to what you have now and that same run will be good for the larger 220V compressor. (your "6HP 110V" is not anywhere near 6HP, more like 1.5 maybe) If you are thinking two stage 80, then go ahead and run #10 now and you won't have to re-do later. I'd even buy and install a dual (220) breaker for the run and just leave one side not connected. #12 run use a 20A, #10 use a 30A. Then when you score a deal on a compressor, you are ready to go LOL.

From your list, 60A is a good run for that.

 

[1Garageman]

I am about ready to put one in my garage also! Hey do we have to get a permit or anything to do this inside are house? Or an inspection or anything?

 

[djd99]

I am about ready to put one in my garage also! Hey do we have to get a permit or anything to do this inside are house? Or an inspection or anything?

It depends on state codes but in michigan a homeowner can do his own work if he pulls a permit. I'm having my neighbor install a cutoff switch after the meter so I can change out my service without any hassle. ie We don't need no stinking permits...

 

[FastEddieG]

Thanks for the replies guys! I meant 60 amp, not 50, thanks for the correction. I never take advice from the big box stores as pure fact, but one of them told me if I get a 100 amp sub panel, I could put a 60 amp breaker on the main panel that feeds it which would limit the subpanel to 60amp. Again, not sure if that is the ideal solution, but seemed like it would work.

And yeah, I know my Craftsman is hardly 6HP, gotta love when marketing guys get the final word

So after reading more websites, your replies and thinking about this more, I think I'll go with a 60 amp subpanel. Next to research what wire and conduit sizes needed

Thanks again,
-Ed

 

[sberry]

but one of them told me if I get a 100 amp sub panel, I could put a 60 amp breaker on the main panel that feeds it which would limit the sub panel to 60amp.

This is true, most panels are 100A anyway, you probably got to work to find one that isn't.

 

[Falcon67]

My 125A 8/16 panel was $26 at McCoys. It's a GE, think the same one is carried at HD and Lowes.

I have a 60A breaker at the house (service entrance) that feeds the overhead run to the shop. Same difference as a 60A breaker in your main panel. I'm careful with an open breaker panel anyway, but it's nice to be able to power off the whole shop panel when you are working in it.

 

[FastEddieG]

Thanks for the all the advice guys. It looks like I'm getting that compressor earlier than I thought. I was fortunate enough to buy the cheapie $160 refurb 2 stage compressor from harbor freight, and it's already shipped.

I'll have:

• 20 amp (230volt) Existing Hobart 175 welder
• 15 amp (110volt) tie in existing quad boxes
• 30 amp (230volt) US General compressor

I'm still trying to decide between 60A and 100A though. The bigger compressor makes me want to allow for more expansion in the future since I'm doing this now. Some of your suggestions resonate with my general way of doing things so I am considering it. Cost will play a big factor though. From what I've been reading, 60A=6AWG and 100A=4AWG. And I also read that the neutral could be a size smaller.

60A = 1" conduit (2) #6 hot, (1) #8 neutral
100A = 1" conduit (2) #4 hot, (1) #6 neutral

So my outstanding questions are:

• Is #4 appropriate for 100A?
• Is 1" conduit appropriate for the 60A and 100A options above?
• Can I truly run a smaller neutral wire, or should it be the same size as the hot?
• Do I need a 4th wire used as ground? If so what size?
• If the welder is rated input at 19.5A @ 230V, a 20A (#12) circuit would be appropriate right? Or is a 30A (#10) required?

Thanks in advance guys,
-Ed

 

[metal1313]

run bigger conduit. ive got 2" feeding my garage and due to a few bends it was a bear to pull 6strand thhn. with one inch i think it might be near impossible. i also have another 3/4line to the garage for stuff like cat-5 cable and a phone line

 

[DJDD]

Your best bet would be to run everything like you're going 100A and put in the 60A breaker. This will allow you to power everything you want right now and add on down the road when you need to without having to rerun everything. Personally I would do 100A and properly redo the extra outlets that the previous owner put in.

Edit: Go ahead and run a 2.5"+ conduit if you're going to do 100A. 4GA wire is not easy to push through conduit if it has any type of turn in it. That being said, WD-40 will be your friend when running everything. Try and run your 4GA and 6GA at the same time, keeping them together with twist ties. Spray them down with WD-40 and you shouldn't have a problem. I'm assuming you will be putting an 8ft. ground rod right outside your garage instead of running a separate ground from the house?

 

[FastEddieG]

Thanks for the replies!! The garage is attached, so from what I was reading I didn't need a grounding rod. I wasn't sure if I could use the EMT conduit as ground or needed a 4th wire.

In my unfinished basement I have the 200A main panel. From there it's a ~45' run almost all the way to the other side of the house, a 90 degree turn to the front of the house followed by a ~25' run and we're in the garage.

I've pulled 3 #10 wires through 1/2" before, and 3 #8 through 3/4". They were challenging, but not impossible. But that was because we had to maximize existing conduit. With all the conduit being put in new, fully exposed, and 2 straight pulls separated by a 90, I don't expect it to be too difficult. But I will take your advice/experience and consider going up to 1 1/2"-2" if I go with #4/100A.

I found a 12/24 100A GE main panel tonight at Lowes for $54, and it includes a few 20A breakers that I could exchange I guess. (I'd prefer to have a main breaker in the garage subpanel). The #4 cable is $1.18/ft. Depending if I can use a diff size neutral or not, I could potentially need 250+ ft (~$300).

If anyone with expertise could chime in on the questions above, I'd greatly appreciate it!

Kind regards,
-Ed

 

[metal1313]

the neutral should be the same size i beleive. i would also check a supply house for the wire, as some will let a full 250ft spool go for less than cut lengths. on mine my 3 wires are 6awg, and 8awg ground. i did not go with a seperate ground just becuase once you get down 3ft in my area its solid rock and clay.

i still think you should go with the largest conduit you can get, even with a pull point at the 90 its gonna be a real pain. for the 90 as well i would use a straight pull box then the 90 right after. trying to bend that wire sharply is nearly impossible. and your gonna want alot more anchor points than you'd think. keep the pipe as rigid as possible and have a partner straighten the wire as you pull, taping it tightly together. i had to do it alone so to help me out i used a few pullies to gain a mechanical advantage, but ive seen pro's actually use a winch

 

[Joel 67]

Can someone clarify the wire gauge needed for 100A? I did not think #4 was adequate, but I am not an expert.

 

[Aceman]

Why conduit and not cable?

I'd run #2 aluminum SER cable, breaker it at 80 amps in the main panel. Most likely install a 125 amp main lug panel to get the most spaces, (12,16,20,24) are usually available and be done with it. Conduit over cable doesn't make sense when garages are attached.

Can someone clarify the wire gauge needed for 100A? I did not think #4 was adequate, but I am not an expert.

If this were feeding the home it could be used to feed a 100 amp panel. But it's not, it's feeding a garage, so a different wire ampacity table must be used, which states:

#4 Romex would be good for 70 amps.

#4 THHN in conduit would be good for 85 amps. If the load was less than 85 amps you could round the breaker size up to 90 amps.

 

[Joel 67]

If this were feeding the home it could be used to feed a 100 amp panel. But it's not, it's feeding a garage, so a different wire ampacity table must be used, which states:

#4 Romex would be good for 70 amps.

#4 THHN in conduit would be good for 85 amps. If the load was less than 85 amps you could round the breaker size up to 90 amps.

Thanks Aceman. So for a full 100A panel you would need to run #2 or #3 THHN correct? Could you even get Romex in a gauge that would support 100A?

Sorry, not trying to hijack the thread, but I think my questions are relevant to the original topic

 

[FastEddieG]

Joel,
By all means! I'd like to know myself.

Thanks for all the info guys, it's greatly appreciated! Not sure if this matters, but just to clarify, my garage is 3 car and attached to my house with a bedroom above it. It's not a detached structure.

So after a lot of thought, and reading your replies and more websites, I'm going to put a Square D 100A 8/16 main breaker panel in the garage. (HOM816M100C) $49.97 at Menards. After I set it up I should have 2-3 slots remaining for future expansion, depending if I give the Modine furnace its own circuit or not.

I'll feed it from my main panel and use 1 1/2"-2" gray PVC. Inside of it will be (3) #4 copper and (1) #8 copper ground. In my main panel, I guess I have to use a 90A breaker. Even the chart at Menards said to use #4 for 100A. I'll verify with our village inspector before I choose. Does that sound like it will work ok?

I haven't researched this yet, but what's the best method to connect larger conduit (EMT or PVC) to the panels? I can't remember there being that big of a knockout, but then again, I never paid attention

Thanks in advance,
-Ed

 

[Daniel Dudley]

I am not an electrician, but I would run a three wire #4 service entry wire from your main panel to the new panel. That is pretty much standard around here now. You are running two hots, a neutral and a ground from the main panel. Whether you run a 100 amp breaker or a 60 totally depends on what your main panel capacity is.

I myself ran #6 wire a few years ago to my garage to a 100 amp service panel. Since then I have upgraded my main panel to 200 amps, and added circuits in the garage. Next I will be replacing the #6 wire, as everything else is ready for the upgrade.

The money I saved on wire a few years ago seems like a waste now.

 

[FastEddieG]

Thanks for taking a few mins to share your opinion. I think what you are saying is similar to my old plan.

I talked with our building inspector on Friday and I had to change my plan to 1.25" EMT (no PVC conduit allowed indoors), and only have to run three (3) #4 copper wires, no "ground." Two of those wires will be hot, while the 3rd will run into the neutral bus which will not be bonded to the subpanel, which will be separated from the ground bus.

I hope to begin on this in the next few weeks when time allows. My big challenge now is finding someone to bend a few of these pipes for me where the prebent 90's won't work.