Author Topic: Adding subpanel to garage shop, need input on power setup  (Read 24677 times)

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Offline hobbes

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Adding subpanel to garage shop, need input on power setup
« on: January 31, 2013, 01:00 AM »
So, I finally broke down and will be getting more adequate power to my garage instead of the makeshift plugs and extension cords coming from the laundry room of the house. I'm going to get a 60 AMP sub-panel into my two-car garage (which rarely houses the cars) and wanted your input on a few things.

So for my 60-amps, I'm planning on 4 x 110v 15-amp outlets and 2 x 220V 20-Amp outlets all along one side of the wall (since most of my power tools will be along this side and the rest of my junk gets stored on the other side of the garage). Question, does it make sense to have all 4 15-amp circuits or should I get two that are 10-amps if my primary use will be for these power tools? Lighting will run off one of these circuits as is a new garage door opener. The two 220v 20-amps are for a future table saw (maybe SawStop 3HP) and the other for a duct collector (possibly the Laguna 2HP one that Paul Marcel recently reviewed). What about the 220v, 20-amp circuits, would I be better off if one was a 30-amp?

Since I wouldn't be running multiple tools at once (save for the dust collector or CT vac and lighting and one of the power tools, this should be good enough, right? To go higher than 60-amp, I'd have to replace my main panel and that's an added cost I don't want to incur at this point. Thoughts and suggestions are welcomed since this isn't scheduled for another couple weeks.

Offline TurnagainD

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Re: Adding subpanel to garage shop, need input on power setup
« Reply #1 on: January 31, 2013, 03:40 AM »
I would think that 60 amps is adequate for most home shops.  You might check about local codes to see if out buildings require more for a sub-panel.  Depending on what panel you use, I would have 6ea. 20 amp, 120V circuits and 2ea. 240V circuits.  The total load may exceed the 60 amp feeder but your load factor is probably 50% unless you have a dedicated circuit for heating or something.  I would also put the lighting on one circuit and leave the others for power tools. 


Offline RussellS

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Re: Adding subpanel to garage shop, need input on power setup
« Reply #2 on: January 31, 2013, 10:32 AM »
I'll tell you how I put a subpanel in my basement.  Main breaker panel in the garage is 100 Amp.  I put in a 60 Amp 240 volt breaker in the main panel.  Ran heavy wire in conduit to the basement.  Not sure of the gauge, but it was heavy copper.  The subpanel in the basement is 100 Amp.  Have eleven 20 Amp 120 volt breakers and two 30 Amp 240 volt breakers in the subpanel.  Separate circuits for the lights on either side of the basement.  Have five or six 120 Volt outlets on each breaker.  The 240 volt breakers only have one outlet on each.  You should use 20 Amp breakers for the 120 volt circuits and 30 Amp breakers for the 240 Volt circuits.  Do not use 15 Amp breakers anywhere.  Use 12 gauge wire for the 120 Volt circuits.  Use 6, 8, or 10 gauge wire for the 240 circuits.  Use a very heavy gauge wire from the main panel to the subpanel.

Offline PaulMarcel

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Re: Adding subpanel to garage shop, need input on power setup
« Reply #3 on: January 31, 2013, 12:41 PM »
When I installed a subpanel in the garage, I ran 4 wires (green, white, redx2) for the circuit that was for my DC.  At the time, I had a 110V DC but knew I'd likely get a 220V DC someday.  Made it easy to convert the distant socket to 220V.

When I laid out the wiring plan for the shop, there's a 110V/220V tool loop, a separate 110/220V DC circuit, and some other 110V@20A circuits.  My garage already had lighting and a garage door opener.

When I say "110V/220V loop" I mean that I send all 4 wires for that loop and break things out as needed.  For example, the SawStop has a 4-wire plug I made that then breaks out the 4 wires into a 220V socket (for the SawStop) and two 110V sockets for the router table and an overhead lamp.  Makes it nice to have just one cord going to the wall from the SawStop.
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Offline Greg Powers

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Re: Adding subpanel to garage shop, need input on power setup
« Reply #4 on: January 31, 2013, 11:07 PM »
This something I need to do in the very near future. As I just ordered a Grizzle 2HP dust cyclone and an 8" jointer. Plus I have a electric car charging station in the garage. So it is time for a sub panel.

Is there a limit on how many sub-panels you can have. I have a 60amp sub panel at the pool equipment and a 90 amp sub panel to the office/theater out back? The main is a 200 amp panel.
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Offline hobbes

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Re: Adding subpanel to garage shop, need input on power setup
« Reply #5 on: January 31, 2013, 11:11 PM »
TurnagainD: Well, I'm hiring an electrician and that's what he said is the max allowed without replacing the main panel which effectively doubles the cost (thus the inclination not to go forth down the "you can never have enough power" route). I'm liking the idea of putting in 20amp circuits instead so will probably do that, thanks. I don't need heating since I'm in So. Calif. and most of the time weather cooperates, if anything I may have some fans running during the Summer.

RussellS: I'm definitely separating the lighting circuit from the rest so that one doesn't impact the other leading to some dangerous situations. I am not sure about the 30 amp though because the electrician guy tells me the outlet is different between a 220v 20-amp outlet vs. a 30-amp outlet (Is this even true?) and I looked at both the SawStop 3HP and Laguna 2HP DC and they both seem to indicate that 20-amp is what is recommended. Will go with the heavy gauge wire if I have my way but depends on what he recommends too I guess.

PaulMarcel: I like the idea of the individual loops, can you come over and wire my house? :) If I showed them the diagram that you made (that I saw on your blog), you think they'll understand what I want from that?

GPowers: I think it is limited by your main and what spaces you have left. So if you have 200 amp at the main, then you start splitting from there and can't or shouldn't get over that limit or at least least be aware that you can't exceed that or something will give. I'm still learning about this too so maybe someone more knowledgeable can give a better answer. For your charging station, doesn't that require a dedicated line just for that?

Offline PaulMarcel

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Re: Adding subpanel to garage shop, need input on power setup
« Reply #6 on: February 01, 2013, 04:12 AM »
If you tell them you want a pair of hots and a neutral at each 220V drop so you can have both, they'll understand.  Old-time dryer drops were done this way; 220V was for the heating elements, 110V for the mechanical timer.  In my case, the drop is done as a "generator" socket; that is, the same socket you'd find on a power generator, say, for an RV.  From there, everything is derived.  If they balk at it, tell them you want the wires there so you can call them back later to re-wire a 220V socket or 110V socket.
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Offline Peter Halle

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Re: Adding subpanel to garage shop, need input on power setup
« Reply #7 on: February 01, 2013, 04:25 AM »
Another thing that you can do is have some of the receptacles wired so that the top half of a duplex receptacle is on a different circuit than the bottom.

Peter

Offline hobbes

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Re: Adding subpanel to garage shop, need input on power setup
« Reply #8 on: February 01, 2013, 07:17 AM »
Another thing that you can do is have some of the receptacles wired so that the top half of a duplex receptacle is on a different circuit than the bottom.

Peter

Thanks Peter, that's a good tip! I'll have to remember that one. the reasoning is so that it doesn't overload it, correct?

Offline Peter Halle

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Re: Adding subpanel to garage shop, need input on power setup
« Reply #9 on: February 01, 2013, 07:28 AM »
Actually my suggestion came as the result of Christmas candles in the windows.  Here it is common to have electric candles in the windows during the holidays.  My wife's father (as well as several of my customers) wired a receptacle by each window in the house in this way so that he could have one (or a few) switches to throw on the way to bed and turn off all the lights.

The reason that this might come in handy in a shop is that in one "box" you would be able to say plug a power hungry tool into the top of the receptacle and another in the bottom and although it would seem that they are overloading the "circuit" there would actually be a circuit for the top and then one for the bottom.

In order to do this you need to break the tab connecting the top and bottom parts.  I will try to find an image and edit this post.

This is similar to what Paul Marcel was talking about, but not quite.  You should of course get guidance from your electrician.

Peter

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« Last Edit: February 01, 2013, 07:54 AM by Peter Halle »

Offline hobbes

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Re: Adding subpanel to garage shop, need input on power setup
« Reply #10 on: February 01, 2013, 07:50 AM »
Peter, I understand what you're saying about separating it. You are putting the top and bottom receptacle on its own switch. No need for the picture, but maybe for others it may be helpful. I remember seeing the instructions on an outlet when I replaced one awhile back showing this. 

Offline Peter Halle

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Re: Adding subpanel to garage shop, need input on power setup
« Reply #11 on: February 01, 2013, 08:13 AM »
I just did a quick search on the internet.  You definitely need to talk and get advice from your electrician.  The codes may be enforced differently in some areas.  It seems to me that you might find a cost savings if it is allowed to use a shared neutral between two circuits and the other requirements are made concerning breakers.

Do not do this without finding out what is permitted in your area and how to do it exactly.

Peter

Offline hobbes

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Re: Adding subpanel to garage shop, need input on power setup
« Reply #12 on: February 01, 2013, 10:10 AM »
As a paying customer, I'll just make the request to the electrician and have him worry about it. He said he's doing everything to code and charging me appropriately for it so I'll take him for his word. :)

Offline Rick Christopherson

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Re: Adding subpanel to garage shop, need input on power setup
« Reply #13 on: February 01, 2013, 02:25 PM »
Overkill is good, but blind overkill without reason is not. You do want a lot of outlet locations, but that doesn't mean you need a lot of circuits. Generally speaking, you can use only 1 high-demand tool at a time. So you won't typically trip any 20 amp circuits. The exception to this would be running an OF2200 and a CT vac (with the router not plugged into the vac). Even then, it will trip the breaker only if you operate the router at maximum load.

For a small garage shop, you could get by with just a single 20 amp circuit, but I would still recommend at least 2, not counting door openers and lights. Your load is actually pretty small. Granted, for a small garage, home-runs to the subpanel aren't that much extra. (For residential wiring, there is no maximum number of outlets on a single circuit.)

You do want to go with overkill on the number of outlets, however. That's not because you will need to plug in so many things, but because some of them will end up being covered or behind something. A duplex receptacle every 3 or 4 feet is plenty of overkill. Some people will put in quad receptacles, but with only a few exceptions, that shouldn't be needed. If you have 2 garage doors, put a quad receptacle between them. A quad receptacle on both sides of a single door would also be handy. You will probably find that these are the most used locations for work both inside and outside the garage. At the workbench area, quad receptacles can be handy, and also closer spacing. Any inside or outside corner should also have extra outlets, as they tend to be more convenient or get loaded with more tools in the corners.

Contrary to the inside of the house, you will be happier having your outlets at 4-feet off the ground (but watch out for being exactly 48 inches, as that would be on a drywall seam). However, for stationary tool locations, the lower outlet placement is desired.

It is perfectly fine to use 15-amp duplex receptacles on 20-amp circuits. The internal parts are actually the same, but they cost less just because they are common. The only time I would recommend using 20-amp receptacles is if you own an older CT vac with the NEMA 5-20 plug. Then you could get rid of the adapter. Otherwise, you will probably never find a tool that uses a NEMA 5-20 plug.

With the exception that Paul-Marcel mentioned for his tablesaw, it is typically not beneficial to run 4-wire circuits for 240-volt receptacle locations. Granted, it doesn't hurt either, but copper is not cheap these days. I will correct him on one point, however (Sorry Paul-Marcel). To convert a previous dedicated 120-volt receptacle to 240-volt, it still only needs 2-wires (plus ground). The only difference is that both wires get connected to a 2-pole breaker in the panel.

For a small garage shop, 20-amp circuits are fine for 240-volt circuits. The only time you need a 30-amp circuit is when you have a 5hp motor. (If you own Grizzly tools, don't read the manual  [tongue]) As for your original question, no, you do not want to use a single 30-amp circuit, because then you are required by code to use 30-amp receptacles. A 20-amp receptacle will accept both NEMA 6-15 or NEMA 6-20 plugs.

The National Electric Code does permit multiple outlets on a single 240-volt circuit, and to-date, I have not found any local amendments that contradict this. I have heard anecdotal stories of people claiming this, but after further research, the stories are found to be untrue. Contrary to popular belief (even among some electricians) the local inspector is not the Authority Having Jurisdiction (AHJ), and he cannot change code on a personal whim. Your State Constitution prohibits this.

With that said, if you are unsure about where your stationary tools will go, then go ahead and put in a couple of outlets per circuit, even if they are just blank junction boxes without expensive receptacles. I do recommend separate circuits for your dust collector, compressor, and tablesaw; but they can have extra junction boxes if you don't know where they will reside. The tablesaw circuit can actually have multiple active receptacles because they wouldn't be used concurrently.

By the way, even though this isn't applicable to you because your electrician would spot it before hand, but some people reading this may benefit from it. Some people may suggest using a 4-wire "Multi-wire Branch Circuit" to serve daisy-chained outlets using 2 circuits and less wire. You can't do this because in a garage, every 120-volt outlet must be GFCI protected, and you can't comply with that unless you use a very expensive 2-pole GFCI circuit breaker, or GFCI outlets at every receptacle location.

I am not a fan of the GFCI mandate, because it was done for political/profit reasons, but it is nevertheless code. The great contradiction in code is that 240-volt garage receptacles don't require GFI protection, but 120-volt receptacles do. I could go on and on, but that would just be a soap-box, so I will spare you from that.

Offline Rick Christopherson

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Re: Adding subpanel to garage shop, need input on power setup
« Reply #14 on: February 01, 2013, 02:42 PM »
I just did a quick search on the internet.  You definitely need to talk and get advice from your electrician.  The codes may be enforced differently in some areas.  It seems to me that you might find a cost savings if it is allowed to use a shared neutral between two circuits and the other requirements are made concerning breakers.

Do not do this without finding out what is permitted in your area and how to do it exactly.

Peter

Oops. Sorry Peter. I just realized that what I wrote above sounds like I was referring to you specifically. I wasn't. It is just a common comment that I see frequently on many forums.

The "shared neutral" is officially called a Multi-Wire Branch Circuit (MWBC), and even though it is common and with little problem, it can't easily be done on GFCI protected circuits. It is a cost-savings where GFCI is not required, but it costs significantly more when GFCI is required.

Also, as I noted above, an inspector is prohibited by law from adding special requirements to Code or local amendments on his own. He can make interpretations, but cannot add requirements. That would be the equivalent of a police officer deciding that on Tuesdays, all red cars have to drive 5 mph below the speed limit. State and Federal Constitutions specifically prohibit any single person from being able to do this.

Offline Peter Halle

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Re: Adding subpanel to garage shop, need input on power setup
« Reply #15 on: February 01, 2013, 03:14 PM »
No problems Rick.  I actually hoped that you would pop into this thread.  I am not an electrician and tried to give an idea but tried to cover my backside with disclaimers.  I had seen references to difficulties with GFCI's but because I don't have a garage didn't realize that implication.

As part of education for all readers of this thread I am going to throw out three questions that I think others might like for you to answer / explain.

1.  When you refer to a 2 pole circuit breaker is that what people who have an electric range, electric clothes drier, or electric hot water see in their panels, or are you talking about what are commonly referred to as split breakers which allow you to have twice as many breakers in one breaker location in the panel box?

2.  When you are referring to a 4 wire circuit are you talking about running 2 hots, 1 neutral, and one ground, or is the ground not counted in the 4 and the actual is 2 hots, 2 neutrals and one ground?

3.  What are the requirements for garages versus a utility building that can't house a car versus an attached addition?


Thanks Rick!

Peter

« Last Edit: February 01, 2013, 06:25 PM by Peter Halle »

Offline AdamM

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Re: Adding subpanel to garage shop, need input on power setup
« Reply #16 on: February 01, 2013, 06:09 PM »
hobbes,  if there's already a single 110v circuit to the garage and you can leave it in, I'd use that for the lights instead of wiring them into the new sub panel.  The further back you can get before splitting out the circuit for the lights, the less the lights will dim when the motors start up on your power tools.

I did my garage this way and I'm really happy with it...but then I happen to be a person that gets really annoyed by the momentary dim lights.
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Offline John Stevens

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Re: Adding subpanel to garage shop, need input on power setup
« Reply #17 on: February 01, 2013, 11:21 PM »
an inspector is prohibited by law from adding special requirements to Code or local amendments on his own. He can make interpretations, but cannot add requirements. That would be the equivalent of a police officer deciding that on Tuesdays, all red cars have to drive 5 mph below the speed limit. State and Federal Constitutions specifically prohibit any single person from being able to do this.

Hi Rick, this is a great point, glad to see you mention it twice.  I don't mean to sound critical, but since you're obviously a guy who likes precision in all things, here's a little more info on the legal basis for your entirely correct conclusion.  There's probably an express or implied statutory prohibition in most states.  The only prohibition in the fed const would be implied under the "due process" clauses of the 5th and 14th amendments.  As for state constitutions, I guess it's conceivable that one or two might have an express constitutional prohibition, but no doubt all have some sort of "due process of law" clause that would impliedly prohibit a code inspector from adding requirements to a code or ordinance.  But ultimately you're correct that a public officer whose office gives him the power to enforce an ordinance, regulation or statute ("law") cannot also enact a law without complying with whatever statutory or constitutional requirements exist for such enactment.  Sometimes constitutions separate the powers of enforcing and enacting law at the local-govt level, but even when that's not the case, every state constitution (and the fed const) requires some sort of public notice to be made when a law is enacted, and none sets the bar as low as "the inspector can spontaneously declare law as needed."

That said, thanks for putting the word out.  I always enjoy seeing Americans remind each other that we're supposed to have governments of laws, not men.

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John
« Last Edit: February 01, 2013, 11:30 PM by John Stevens »
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Offline hobbes

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Re: Adding subpanel to garage shop, need input on power setup
« Reply #18 on: February 02, 2013, 12:36 AM »
hobbes,  if there's already a single 110v circuit to the garage and you can leave it in, I'd use that for the lights instead of wiring them into the new sub panel.  The further back you can get before splitting out the circuit for the lights, the less the lights will dim when the motors start up on your power tools.

I did my garage this way and I'm really happy with it...but then I happen to be a person that gets really annoyed by the momentary dim lights.

AdamM, there is a single 110v circuit but in order to bring in more power they are going to run another wire 3 feet along a pipe above my house to the detached garage (also to a 3 feet pipe above) and in the process of doing this they'll take down the existing wire (which probably didn't have this code requirement when it was put in long ago). I'll just make sure it's on its own circuit and hope that the separate in the circuit is enough not to dim it but if that's they way it's going to be I'll live with it because it'll be a lot better than my current situation.

Rick, thanks for the thorough response...lots of knowledge and lessons passed on to many of us newbies (ok, maybe just me). It always amazes me how much I learn when coming to this forum, even a basic question can lead to so many considerations and paths not considered in the first place and that's very valuable for myself and I hope for others too.

I think what I'm going to do is mock up what I plan to have in my garage (present and future wishful state) and have the Electrician come up with his suggestion and see how closes it mirrors what is suggested here. This will end up being a garage make-over and another reason to really clean up so much junk that's piled up over the past few years. Maybe I'll take some before and after pictures too so you all can see the difference.

Offline hobbes

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Re: Adding subpanel to garage shop, need input on power setup
« Reply #19 on: February 24, 2013, 08:58 PM »
Update on the garage wiring: It's done - finally (the prior two appointments had to be rescheduled because on the day the electrician was supposed to come out it was raining). Now there are two sets of 4 (110V) outlets and one set of 220V outlet, the 220v have their own breaker and the 4 outlets each have a breaker but are repeated several feet down the garage with an extra of couple outlets int he middle of the garage wired to one of the existing breaker. Now I finally have enough outlets not to have to compromise on the use of my tools by constantly plugging things in and out. I should have done this MUCH sooner, but that's a story for another day. Anyhow, very happy with the setup and thanks everyone for your input on what makes the most sense!

Re: Adding subpanel to garage shop, need input on power setup
« Reply #20 on: February 25, 2013, 04:44 PM »
Time to make some sawdust!


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