Garage circuit breaker box advice needed

[Nullifier]

Ok guys I have been slacking on my garage makeover the past few months but I am getting ready to start working on it again. I am going to acquire my electrical supplies soon, and need some advice on picking out a circuit box. My over sized 2 car has a sub box in it mounted over top the water heater. It has is a 4 slot box with (2) 220 breakers in it. No other slots. There is nothing on the box telling me what amp rating is on it, but requardless I want to see about putting in a bigger box there to run more stuff.

Planning the box I need a total of 5 breakers for 220v to run the 2 already in the old box one for my welder and one for a 220v compressor with one open for down the road. Then I want a seperate circuit for lights and one for 110v plugins. I plan to run a plug box every 4' down the side walls of the garage. I do not plan on running a million small power tools at one time, I just hate extension cords. I also want to have 2-3 open circuits for down the road. So knowing it takes 2 slots for a 220v breaker, I put that at a total of 15 spots needed for now and down the road. So I'm probably looking for a 16 slot box.

As for the amperage rating of the circuit box, that is where I am not sure. The miller 185 has an input rating of 30a @ 200v and 26@ 230v I have my water heater to consider, my Flourecents lights, plugins for hand tools, and various 110v bench top poxer tools like small drill press etc. and then the compressor which the one I'm looking at is the Ingersoll ran ss5l5 with a 30 amp draw. So I am thinking a 150 amp box will work for me but am not sure. So electrical gurus what is the consensus. And should the lines running intot he garage already be large enough to handle the need. I am out of my knowledge range here and will have an electrician come out to hook up the box itself. I can run and mount the rest of the electrical tubing and boxes.

So is a 150a 16 slot box going to cut it?

 

[LandCruiserPhil]

Do you plan to refeed the new sub panel? If not what size wire feeds the sub panel now? What equipment do you see running at the same time? The sub panel will be the cheapest part of the up grade if you need to refeed the sub panel.

 

[StumpXJ]

I have a 100 amp 12 slot box that is more than enough for me so far.

Two 20 amp outlet circuits (110v, with about 7 outlets on each circuit)
Two 20 amp lighting circuits (inside flourescents, and outside lighting)
3 30 amp 220volt circuits, welder, car lift, and another welder outlet or future 220 volt air compressor. (have a 110 now)

With the above, I have two extra slots in the box for future expansion.

I guess you are on the right track, but I am wondering why you would need two 220 volt outlets for your water heater? Are they both wired in to the heater?

~James

 

[dnellans]

Most service coming in will be 125A or 200A - I've never run into 150A. Obviously you'll put in what your E company allows you to.

I would say 150A is plenty unless you will have your compressor on all the time and there is a chance it will kick on while you're welding and the water heater is also on. 120 water heaters typically are run on their own 20 amp circuit or larger depending on the size of the heater.

I'd suggest running 4x120x20amp circuits. Do boxes every 4 feet like you're
thinking but put one set at roughly chest level so that it will be above
a workbench surface (however high you like your workbenches). and then another set at traditional bottom placement. run both the upper and lower on separate 20 amp circuits.

I'd put the water heater on its own circuit unless its very very small - big items like chop saws, table saws, big hammer drills, grinders can consume 15+ amps and combined with a water heater will pop circuits.

then finally do an additional circuit for the lights.

If you're pulling new wire, the cost difference between 2/14 and 2/12 isn't much - and 2/12 is the min you should be using to run 20 amp breakers vs 15.

Future proof your garage for the extra $100 bucks, wouldn't you have liked it if the guy before you did?

 

[Root Moose]

I'm not an electrical guru but I do know enough to be dangerous.

You need to decide how large a box you need and then compare that to either the existing wiring that goes to the garage from the house or run new properly routed wire. I'm guessing that the wiring and box for the water tank is enough to run the water heater and nothing else.

When I built my workshop I put in a 70A service from the house (200A at the house, 40A go to the barn already).

I have a 220V compressor, 220V welder, house serving computer equipment and a furnace out there. Plus all the normal overhead fluorescent lighting and electrical outlets.

Sounds like I am "under-amped" but the reality is that it is a hobbyist garage. I'll never be running everything at the same time. The closest might be running the furnace, plasma cutter (if I ever get around to fixing it) and compressor at the same time. If that happens I'll turn the furnace off for a little while. In reality the furnace only ever lights once in a while and normally in the wee hours when it is -20 or similar.

I've never had to "self balance" power to date. If I was going to do it again I might consider going to 100A but then it was already a small fortune in copper to get the wiring out to the work shop already (~70ft).


HTH

 

[Kilroy]

Root Moose is right on target. Circuit boxes are sized according to how much amperage you have available and the most that could be used at the same time. You can get a box with more capacity than your wires. If it is for yourself, it's save as long as your not using everything at once. Problem would be your main breaker may be rated higher than your wires and would not provide protection against shorting. Watching the wires coming to garage start to glow and then fall apart because of melting would not be the worst thing you could see. Starting the garage on fire probably would. If you decide to use a bigger box for more slots, you need to make sure the main breaker is rated properly. You might keep in mind what you have and not have a problem. Someone else coming into your garage wouldn't. If get inspectors involved, they will make sure what you have done is safe, costs you more money to do, and that your taxes will be raised because of the "improvements" your making.

I'm not an electrical guru but I do know enough to be dangerous.

You need to decide how large a box you need and then compare that to either the existing wiring that goes to the garage from the house or run new properly routed wire. I'm guessing that the wiring and box for the water tank is enough to run the water heater and nothing else.

When I built my workshop I put in a 70A service from the house (200A at the house, 40A go to the barn already).

I have a 220V compressor, 220V welder, house serving computer equipment and a furnace out there. Plus all the normal overhead fluorescent lighting and electrical outlets.

Sounds like I am "under-amped" but the reality is that it is a hobbyist garage. I'll never be running everything at the same time. The closest might be running the furnace, plasma cutter (if I ever get around to fixing it) and compressor at the same time. If that happens I'll turn the furnace off for a little while. In reality the furnace only ever lights once in a while and normally in the wee hours when it is -20 or similar.

I've never had to "self balance" power to date. If I was going to do it again I might consider going to 100A but then it was already a small fortune in copper to get the wiring out to the work shop already (~70ft).


HTH

 

[fido]

You said the existing panel is above the water heater. That is a big No No. Panels require 36" space in front for clear access. What size breaker and wire feed that panel? That has to be the starting point. If it is just you using the shop a 100 amp sub feed would get you buy. Though the N.E.C. allow #4 copper conductor to be used for 100 amp feeders in a residencial service I would use #2 copper. Figure this in your budget. I have a feeling you are going to have to run new wires from your main panel to your shop. You'll be much happier if you do anyways. A 16 circuit panel will most likely be large enough. Most panels will allow the use of a twin or waffer breaker, so a 16 circuit panel may actually hold 20 to 24 circuits. Use waffers only after use have exceeded the number of full size breakers. Check your local codes as some areas are stricter than the N.E.C. If you would like to get into more
specifics on this feel free to PM. It's much better to get it done right the first time and be able to enjoy your shop than have it burn down.

 

[Nullifier]

Most service coming in will be 125A or 200A - I've never run into 150A. Obviously you'll put in what your E company allows you to.

I would say 150A is plenty unless you will have your compressor on all the time and there is a chance it will kick on while you're welding and the water heater is also on. 120 water heaters typically are run on their own 20 amp circuit or larger depending on the size of the heater.

I'd suggest running 4x120x20amp circuits. Do boxes every 4 feet like you're
thinking but put one set at roughly chest level so that it will be above
a workbench surface (however high you like your workbenches). and then another set at traditional bottom placement. run both the upper and lower on separate 20 amp circuits.

I'd put the water heater on its own circuit unless its very very small - big items like chop saws, table saws, big hammer drills, grinders can consume 15+ amps and combined with a water heater will pop circuits.

then finally do an additional circuit for the lights.

If you're pulling new wire, the cost difference between 2/14 and 2/12 isn't much - and 2/12 is the min you should be using to run 20 amp breakers vs 15.

Future proof your garage for the extra $100 bucks, wouldn't you have liked it if the guy before you did?

Your suggestions are what I am thinking exactly.
water heater, welder, compressor, lights and plugs will be on their own curcuits this way nothing will be shut down for conflicts of power draw.

I had not thought about running sockets at and low and high placement. I was planning on just running them in a high placement. Something to consider though.

As for wire size I was think 2/12 but am debating on 2/12 or 2/10 for the welder and compressor. both will be with in 15' of the circuit box so it is a short run.

LandCruiserPhil: Do you plan to refeed the new sub panel? If not what size wire feeds the sub panel now? What equipment do you see running at the same time? The sub panel will be the cheapest part of the up grade if you need to refeed the sub panel.

I need to open the panel and see what is coming in. You are probably correct that the wiring is only enough to supply the heater. Maybe I will get lucky and not have to pull from the main panel that would be nice.

 

[bat]

Home owner electricians :Wow1:

 

[soonenough]

As for wire size I was think 2/12 but am debating on 2/12 or 2/10 for the welder and compressor. both will be with in 15' of the circuit box so it is a short run.

I'd consider nothing less than 10-gauge wire for a welding circuit. You said your welder and compressor each draw 30A, and you need 10-gauge minimum for 30 amps. As someone else mentioned, you might as well do it right the first time, so you might consider 40-A circuits if you already know that you'd be maxing out 30-A circuits from day one. IMO there's a big difference in the PITA-factor of wrestling with 8-gauge wire vs. 10-gauge, but running 8-gauge now is a lot easier than doing it 2 years from now.

Also, you might think about putting an outlet or two in the ceiling in case you ever want retractable pull-down extension cords. I'm not a big fan of pull-down air hose reels, but I do like the retractable outlets for some reason.

 

[Antichrist]

I'm fairly certain to meet code your subpanel total rating can't exceed whatever the rating is of the breaker that supplies it.

Check with your electric service, different places have different consumer rules. For instance, my electric coop is required to run power from the pole to the meter for free. So for my garage I put in a 200amp panel and had a buried line run to supply it.

For you welder, the NFPA electrical code allows you to de-rate your supply to a welder depending on the duty cycle of your welder.
I have no idea how you'd wire a 220v welder with 2 conductor wire. At least not properly.

 

[Root Moose]

Also, you might think about putting an outlet or two in the ceiling in case you ever want retractable pull-down extension cords. I'm not a big fan of pull-down air hose reels, but I do like the retractable outlets for some reason.

Also for garage door opener in the future.

On the wire size business...

Certain amperage draws require certain gauge of wire and this changes with distance run as well.

There is a lookup table for this kind of stuff - google is your friend here.

Additionally there are local codes that may (or may not) go beyond this.

You really need to dig into this if you are going to do this correctly.

Also, pick up a book from the Library or Home Depot or whatever. Study it hard.

The way some of the off the cuff numbers are being bantered about wrt wire size and stuff is making me nervous. I expect that is what bat's helpful post is about as well.

 

[Root Moose]

I have no idea how you'd wire a 220v welder with 2 conductor wire. At least not properly.

x2 - see my post above.

 

[bat]

Root Moose you are right I guess I could have been a little bit more helpful and not funny but I do read some things that make me nervous. I think electrical wiring of this type should be left to a electrician and not explained over the internet.

 

[Root Moose]

Tend to agree. I chuckled out loud when I read your post.

That said, it is good to share info so that people can at least have a clue when talking to professional tradesmen. This way they can make "informed" decisions when there is more than one way to approach a problem.

Some people like to ask questions and research to the Nth degree even when they have no intention of doing the work themselves.