Garage Wiring Question

[squeakz28]

Hey everyone. I'm a new member here and am also new to electrical work. I am working on wiring up my unfinished garage and have a few basic questions I hope some of you can help me with. The garage is a 24x30 detached and already has power from the house to a panel in the garage. The breaker in the house for the garage is a double pole 90 amp.

My plan in the garage is to put plug outlets every 4', hang around 12 T12 4 lamp lights, add an 230V outlet for a compressor/welder, add 4 corner led lights outside, 1 led light next to the walk in door and a brighter light between the two big garage doors. My biggest concern and question is, how to split every thing up on the breakers. The way I have planned out right now is to put each wall on a separate 20A breaker, the T12 light on 2 20A breakers and two switches, hopefully all of the outside lights on a 20A breaker and obviously the 230V outlet on a double pole breaker.

I don't have the outside lights picked out, so I don't what kind of amps they will pull just yet. I do know that the T12 lights have 2 ballast each fixture pulling .77 amps each. (The only reason I am going with the T12 lights is because I have around 20 of them that were free, along with 20 or so bulbs.) I also don't have the compressor but I do know which one I will get. It calls for 230V and says it pulls 40A.

Does all of this sound reasonable or would you recommend doing some things different? Thanks in advance and sorry for the long post!

 

[aandpdan]

Don't bother with the T12's, free bulbs or not. Go with T8's or T5's, they are brighter. In a few years when you're replacing bulbs/ballasts you'll kick yourself for doing it twice.

What are your loads beside the compressor?

Instead of wiring each wall, I like to stagger the receptacles on different circuits. That way not everything on the wall is on one breaker.

The lighting on 2 switches is a good idea.

 

[squeakz28]

I would much rather use the T8 over the T12, but due to financial constraints, I'm going to have to use what I have for now. The goal is to slowly replace the T12's with the T8's one at a time. I know it'll be more work in the long run, but I can handle it. While we are on the light topic, is better/easier to swap the ballast and tombstones or just buy a whole new fixture?

As far as loads go, right now the compressor is the real load I'll have in the garage. Maybe a welder one day, but right now it is not a necessity. I have friends and family close by and can take any welding projects to them. I have been thinking about maybe getting into some powder coating in the future. If that ends up panning out, I'll probably have to get a separate meter put on the garage. I know some of those oven pull some higher amps.

That is a good idea on staggering the receptacles. I hadn't thought about it, but I will do that for sure. Thanks.

 

[aandpdan]

Check the cost of the ballast versus a new fixture and there may not be much of a difference.

 

[wyliesdiesels]

How many HP is the compressor? With a 40a FLA, its guaranteed to be over 3hp so it will need to be hardwired!

 

[pattenp]

I think for your use, wiring every other wall outlet on a different circuit is not needed. Unless you are an octopus and can run multiple power tools at once. You will be looking at additional coast for wire to do it. If it's something you want to do, the most economic way would to be to use a multiwire branch circuit (MWBC) to have every other outlet on a different leg.

 

[ACDNate]

FFS people he's got free functioning fixtures. Use them till they burn up and replace them with new ones as you go.

Yall loose your minds over T12 fixtures. Do you guys go into HomeDepot/Lowes and antagonize the staff there for selling T12 fixtures still?

 

[squeakz28]

Wyllie - the compressor is a Quincy 7.5 HP 80 gal unit. I wasn't aware (nor did I think about it) that it would need to be hard wired in. Thanks for the heads up.

Patten - My thought is to only do that on the back wall due to the number of outlets that will be there.

ACDN - Thanks. I would love to be able to put new lights in and not have to worry about them again but it is really hard not use the freebies.

 

[squeakz28]

Another quick question on the electrical. The garage has a sub panel in it from the house. The breaker in the house feeding the garage is a double pole 90. Does that mean that I am limited to a total of 90 amps in the garage or is it more because it is a double pole? This is where my electrical knowledge is limited.

The reason I ask is I may get into doing some powder coating in the future and typically, those ovens pull some higher amps. I'd like to try and turn that into a part time business. If it is going to overload the garage/house, I might have to look at the price of putting a separate meter on the garage. None of this is set in stone yet, but I would like to know what all I could be getting myself into. Thanks.

 

[1Garageman]

squeakz28 Welcome to Garage Journal!
Tennessee is one of my FAVORITE places to vacation!

We need some pictures of your garage/progress on here also!

 

[pattenp]

If the breaker in the house supplying the garage is 90 amps then most likely the feeder wire is sized to handle a max of 90 amps. So 90 amps is the total load you can have. But you should not have your loads maxing out the feed.

 

[squeakz28]

I'll try to put some pics of it up tonight Garageman.

Thanks Pattenp. I was afraid that was going to be the case. If I do get into the powder coating, I'll have to turn the compressor off just to make sure I'm not close to 90. It'll also depend on the oven I get. I know some them can pull up to 50 amps.

 

[ctgoodman]

I would much rather use the T8 over the T12, but due to financial constraints, I'm going to have to use what I have for now. The goal is to slowly replace the T12's with the T8's one at a time. I know it'll be more work in the long run, but I can handle it. While we are on the light topic, is better/easier to swap the ballast and tombstones or just buy a whole new fixture?

I understand totally making do with what you have. It's also good you are planning on the inevitable. Eventually the T12's will be phased out and not convenient to get or cost effective to replace as old stock becomes scarce.

If you can get the ballast at a good price then it is probably worth doing. I recently did this on a rental to 5 fixtures. would have cost me $30+ each to replace. I replace the ballast and tombstones for less than $15 each.

I used a Robertson ballasts. The new one is electronic instead of magnetic, is smaller and runs cooler, doesn't buzz like the old one, starts in a split second in stead of 2 or 3, and are noticeably brighter with the new T8 lamps. The included wiring diagram makes it a easy swap.

Something like this would do you 4 bulb fixture.
http://www.robertsondirect.com/ISS432T8HEMV-A-P16475.aspx

Can be found in a 10 pack on amazon for $110
http://www.amazon.com/dp/B00HS5AQWM/?tag=atomicindus08-20

Then just get some Tombstones if needed.
http://www.amazon.com/dp/B00DZIGJX6/?tag=atomicindus08-20

 

[Falcon67]

In my old shop, I had 14 T-12 two bulb four foot fixtures. I replaced them over time with T8s. I used Lowes shop lights at $17/each. At that time, cheaper than buying ballasts. You're main issue with the T-12s will be in the cold, as they won't hardly light up. You'll have to switch them on and wait a while. Be sure you buy cold or zero start T8 ballasts if you retro fit, then you can flip them on a 40F and see whats going on.

FWIW - Switching the 14 T-12 fixtures for T-8 reduced my measured light circuit current draw by 1/3. With 6500K bulbs it got a lot brighter too.

 

[Charles (in GA)]

No need for new tombstones unless the old ones are bad. Indeed, some will be burned either where the bulbs contact, or where the wires push in, but at least a few will be good. Have a few on hand and go from there. Most tombstones have places for two wires. If the TS has only one wire and it is burned, cut off/remove the wire and use the other contact. These are all push in with a spring locking finger, so they are not the greatest. If you need a bunch, shop online, buying four packs at Home Depot gets expensive.

Charles

 

[ddawg16]

Put your outlets at least 50" above the floor. That way you can lean a 4x8 sheet of plywood against the wall and not block it.

 

[wyliesdiesels]

I'll try to put some pics of it up tonight Garageman.

Thanks Pattenp. I was afraid that was going to be the case. If I do get into the powder coating, I'll have to turn the compressor off just to make sure I'm not close to 90. It'll also depend on the oven I get. I know some them can pull up to 50 amps.

Depends on the oven. While some ovens plug into a 50a circuit, they hardly ever reach anywhere near that. I put a clamp meter on the feeder for my oven one time while baking a pizza and it was pulling 15a!

 

[sands35]

If you are planning on running more equipment like wood working tools, then putting in some 220 plugs would be nice. That allows you to side step the GFCI and TR requirements.

Ovens only draw full amperage when in self clean. (I work for Whirlpool). More often, they are in the 20-30 amp draw range.

 

[squeakz28]

Thanks for all of the info guys. I didn't realize the t12 and t8 used the same tombstones. I've got a bunch of them already.

ctgoodman, thanks for those links. They will come in handy in the future.

I do need to clarify the oven discussion though. I won't be using a regular household oven to do the powder coating. It will one that is built for coating. I'd like get/build one that is around 4'x4'x7'. This would have 3 or 4 3000 watt heating elements in it. From what I have read on them, it will be pulling around 40-50 amps. I apologize for the confusion on that.

I don't see any wood working in my future, but there could be some small welding projects every now and then.

Thanks again for all of the info.

 

[squeakz28]

Here's a couple of pics in its current state. It's a wreck from the wiring and insulation. I'll be glad when I get the insulation wrapped up so I can get it somewhat organized again. I'm gonna wait a month or two before I finish the drywall. Luckily my neighbor has a drywall jack that he is gonna let me borrow for the ceiling.

 

[bob_mp]

A lot of great suggestions here. Some thoughts:

1. Along the lines of what aandpdan suggested, I have 8 120 volt circuits in my garage (44x21) wherein the adjacent outlets are wired to successive circuits (modulo 8). That way if I am working in a particular area with lots of things plugged in, the current draw is distributed over multiple circuits. I use 2 of the circuits exclusively for electronics (digital readouts on lathe/mill and computer). 8 may well be overkill; I don't think 4 or 5 is, particularly if you plan to use a computer, space heater, or a chop saw with an induction motor.

2. Put lights on dedicated circuits. Having the lights go out with a tool running is no fun. Similarly, I suggest having an easy means of turning off the compressor, to preclude it from starting up randomly and tripping the subpanel feed breaker, when you have other high current draws active.

3. I distributed my florescent lights (22, 4' two-lamp fixtures) onto three switched circuits. That way, I can switch between normal, bright, and really bright. I like having this ability. Lights are considered continuous loads and, hence, you can't exceed 80% of the nominal wire ampacity. So for 14 guage wire, you can't put more than 12 amps of lighting on a circuit.

4. Four foot spacing for outlets is great. I would not go any wider than that. I provisioned for even more outlets, though I didn't wire them up initially. Glad I did.

5. I'd consider a 240 outlet near the garage door in case you want to weld something outside of your shop. I'd also consider putting at least one 120V outlet on the outside of your shop. That way, you can have access to power without having to open the doors.


Cheers,
Bob