220 for the garage?

[eyekode]

I am planning to run 220 to my garage and had a couple q's.

I have half of a 2 car garage for my hobbies ~22x10.

Right now it is woefully underpowered with a single 15amp circuit.

I anticipate the need for 2 220v tools running at once. One is a dust collector and the other is a tool (table saw, band saw etc).

I have 200amp service run to my house (Apex). The outside breaker box serves 3 AC units, the stove and sends 90 amps to another breaker box in my garage. The outside box is full except that I use a gas stove so the 40amps is unused. But adding up all the circuit breakers yields > 200amps. Anyone know how far you are allowed to push this? I.e. if I wanted to run 60amps to the garage would this additional 20 amps be a problem for code?

The garage box is fully used too except for a 30amp 220v circuit for the dryer. But I use gas dryer too.

My plan is to re-use the 40amp circuit for my stove and wire a new breaker box in my garage. The stove sits against the garage wall so I plan on reusing the 8 AWG run of wire from the outside box to the garage. I don't plan on using they dryer circuit.

Looking at lowes the minimum I see is 70 amp breaker boxes. Are there any code issues with running a 40 amp circuit to a 70 amp box? I only plan on installing 1 20 amp 220 circuit and 2 20 amp 110 circuits. I guess 1 220v circuit is cutting it pretty close for a DC + a tool. Both would have to be max 2ph...

The wiring plan is to install a junction box where the plug for my stove currently is. Then wire from the box up the wall to a breaker box in the garage. From the breaker box I will run EMT to the ceiling and from there around half of the perimeter of my garage. Where I need outlets I will put a junction box and drop the cable down into the wall and install outlets a little over counter level.

I plan on adding 2-3 220v outlets and at least 4 110v outlets.

I do plan on pulling a permit for the work and I will have a friend help who has done a fair amount of wiring.

Any feedback on my plans?

Thanks!!!

 

[eyekode]

Hrm... maybe I am being silly. I just added up the breakers in the garage panel and it is 180 amps. It is only being fed by a 90amp breaker in the main panel outside. If it is allowable to have 2x the amperage in the subpanel then I should be fine doing 2@ 20 amp 220's and 2@ 20amp 110's fed off a 40 amp breaker in the main panel.

I know this does not mean I can pull 60 amps off of the garage panel but the highest load I anticipate is 2 3hp machines running at the same time (total 26 amps?) (and it will take me years before it is anything more than 2 2 ph machines ).

 

[PeteQuad]

Hi, I am only a beginner at wiring and do not want to provide too much advice for fear of causing danager, and I'm sure others with much more experience will happen by. But I do know that adding up the number of breakers in your box has nothing to do with the amp rating of your main breaker. The main breaker prevents you from pulling more than 200amps at once - running actual machines that use that much. You could have 20 40amp circuit breakers in your box and it wouldn't matter - once the total usage went above 200amps your main would trip. Of course you'd be hard pressed to fit all that 8 gauge wire into your box .

For example, in that mythical scenario, and in simplest terms, each circuit could actually be pulling up to almost 10 amps before it tripped the main, or you could be maxing out 5 of those and not using the others.

The circuit breakers are simply matched to the wire gauge to protect you from over heating and causing a fire.

 

[BumoutBob]

Nobody wants to jump in on this thread so let me start.

If I understand things correctly you have the old dryer 220V line and the stove 220V line. The general problem being to get these lines in the garage where you can connect to them. First of I would say, talk to a local electrician to keep you safe and up to code. With a 40A service it seems enough to run the 2 ---2HP machines. What I don't like is the splice box at the stove that then runs to the garage. See if there's any way to run new wire direct to the new box. In addition, I don't quite understand the old dryer 220V line. You could pull that breaker and wire two 115V circuits from that box to several places around the garage. OR!! use that 220V line for one of the 220V machines. Note that a 220V circuit requires only 12 gage wire, just like the 115V circuit. The 12 gage wire is a 20A wire, and the voltage doesn't matter.

The general idea of attaching a branch box to the stove or dryer line works very well--I've done it myself. The 40A circuit should be able to run the whole shop for awhile as long as observe the general rule of turning on one tool at a time( for instance first the saw then the dust collector)---you might blow a breaker if you try to turn on a 15A cut off saw with them on. You seem to indicate you wouldn't be doing that.
This is one of those design problems that needs a site visit to really understand it. My $.02 RS

 

[PeteQuad]

By the way, I put a 30amp subpanel in my garage and have no issues running my 2HP dust collector and 3HP jointer at the same time as my lights and other incidentals. Actually today I had a full sized refrigerator running off that panel also.

If you can put in a seperate subpanel in your garage, it is an ideal situation.

 

[eyekode]

What I don't like is the splice box at the stove that then runs to the garage. See if there's any way to run new wire direct to the new box.

Thanks for the response. This is the part I don't particularly like as well. It is simple because it means I don't have to run large gauge wire from the outside box to the garage. But it means that if (when?) I sell this place I probably have to come up with another solution...

I guess in the long run it is better to just bite the bullet and run a new feed from the main breaker. And the best temporary solution is probably to cannibalize the dryer circuit that is already in the garage.

 

[eyekode]

By the way, I put a 30amp subpanel in my garage and have no issues running my 2HP dust collector and 3HP jointer at the same time as my lights and other incidentals. Actually today I had a full sized refrigerator running off that panel also.

If you can put in a seperate subpanel in your garage, it is an ideal situation.

Thanks for the data point Pete. This makes the existing idle 30 amp breaker seem more appealing.

 

[eyekode]

By the way here is a quick sketchup model of my garage:

You can see I only currently have 3 outlets (on a 15am circuit ). Also note the EMT running from the new panel. The idea is to run it along the ceiling and drop the feeds into the wall to avoid having to make so many holes in the drywall and cutting holes in all the studs. Also this should allow for some flexibility if I need/want to add another drop.

 

[mkepke]

No problem to have the sum of your breakers exceed your service. The calculation is based on expected usage patterns, not the sum of circuits.

Also no problem to use a panel with a capacity much higher than you intend to wire. In fact, I'd recommend nothing SMALLER than a 100A subpanel. You want lots of extra spaces for circuits and 100A is about the sweet-spot for price (check out the package prices at the big boxes).

I don't understand your situation with the stove, but if your outside panel does not have a main breaker, then code says you can have a max of six separate circuits. If you already have 6 circuits, I'd consider either replacing the panel with one with a main breaker (thus freeing you from the 6 circuit rule) or repurposing the stove's slot for a 60A feed to a subpanel in the garage.

BTW, you "need" more than 1 240 circuit - figure a minimum of two for a DC + a tablesaw. It's easier to add two or more at once than go back and dot it again.

FWIW, I started out with typical set of hobby 120v tools. They're almost all 240V now: saw, jointer, planer, sander, dc, bandsaw, material handling tables..ok, that last one is a little unusual. :wwink: But never more than two machines at once: dc + <other tool>.

-Mark

 

[eyekode]

No problem to have the sum of your breakers exceed your service. The calculation is based on expected usage patterns, not the sum of circuits.

Also no problem to use a panel with a capacity much higher than you intend to wire. In fact, I'd recommend nothing SMALLER than a 100A subpanel. You want lots of extra spaces for circuits and 100A is about the sweet-spot for price (check out the package prices at the big boxes).

I don't understand your situation with the stove, but if your outside panel does not have a main breaker, then code says you can have a max of six separate circuits. If you already have 6 circuits, I'd consider either replacing the panel with one with a main breaker (thus freeing you from the 6 circuit rule) or repurposing the stove's slot for a 60A feed to a subpanel in the garage.

BTW, you "need" more than 1 240 circuit - figure a minimum of two for a DC + a tablesaw. It's easier to add two or more at once than go back and dot it again.

FWIW, I started out with typical set of hobby 120v tools. They're almost all 240V now: saw, jointer, planer, sander, dc, bandsaw, material handling tables..ok, that last one is a little unusual. :wwink: But never more than two machines at once: dc + <other tool>.

-Mark

Outside box does not have a main breaker. I don't yet understand how you are supposed to work on a box without a main breaker... But I will figure this out before I open it up .

I think I will be ok with 6 2 post breakers in the outside panel. I have 3 AC units, stove, existing sub panel in garage, and... one mystery breaker. I should be able to use either the stove or the mystery breaker. I also received a PM on the subject that clarifies my "stove situation". I was trying to avoid running huge cables (AWG 6) by reusing the existing unused cable run to my stove. But this is in vain because aparently sub panels need at least 60a by code.

 

[Glennbear]

When I wired my shop, I installed a 100amp subpanel fed from my 200amp house service. As Mark said, adding up the breaker ratings in the subpanel is really meaningless since you will never be using all the ampacity at once. I too would recommend a 100amp subpanel package from the BORG, the package price is quite reasonable. The feed for the subpanel should be protected with the proper size breaker at both the panel where you start the feed and in the subpanel itself. You do not want to have to run back to the main panel every time you want to shut off power to shop circuits. I highly recommend "Wiring a House" by Rex Cauldwell published by Taunton Press. Cauldwell is a practicing electrician in NC and not a desk jockey like the authors of some of the other DIY electrical books. :wsmile:

 

[JackLeg]

When I wired my shop, I installed a 100amp subpanel fed from my 200amp house service. As Mark said, adding up the breaker ratings in the subpanel is really meaningless since you will never be using all the ampacity at once. I too would recommend a 100amp subpanel package from the BORG, the package price is quite reasonable. The feed for the subpanel should be protected with the proper size breaker at both the panel where you start the feed and in the subpanel itself. You do not want to have to run back to the main panel every time you want to shut off power to shop circuits. I highly recommend "Wiring a House" by Rex Cauldwell published by Taunton Press. Cauldwell is a practicing electrician in NC and not a desk jockey like the authors of some of the other DIY electrical books. :wsmile:

I agree with Glenn. Put in the sub panel, you won't regret it. :icon_thum

 

[DaveD]

You asked.....Outside box does not have a main breaker. I don't yet understand how you are supposed to work on a box without a main breaker... But I will figure this out before I open it up :smile:.

Not to be a wise butt but the answer is 'carefully'. Its a matter of 'snapping in a breaker just like in any other panel. BTDT but you have to know your limits. In my case it was a 60A welder feed I added. Messing around in a hot panel does make you think about safety a little more.

Or you can pull the meter head, but then you have cut the meter head seal and the local electric company doesn't like to find meter heads with the seal broken. Have your electrician friend do that part (install the breaker and hook it up).

 

[jjstillwell]

I'd like to continue to recommend adding the sub-panel (w/ main) and confirm the notion that breaker panels (sub or otherwise) and the sizes of breakers and wires as required by code are primarily for safety purposes. Power companies are more interested in, well, power. Generally speaking, they like for non-commercial customers to stay below 5-hp equipment and away from 3-phase equipment. Once that is ruled out, even within code you could have a 400A service if desired. More specific to your needs, you could have a 100 amp subpanel on a 200-amp main panel and its a non issue for ampacity as long as the wire / breaker size is acceptable wrt to the each panel and circuit. BTW, adding a 220V subpanel becomes more complicated wrt code in regards to bonding and grounding, but is still the best way to grow and adapt a shop.

I would also like to point out that I have seen a few run the correct size wire...with the wrong number of wires such as 12/2 vs 12/3 :BangHeadBack to bonding and grounding req'tablesaw).

My last comment is in regards to pulling the permit. Inspector's expectations vary greatly from place to place regardless of code. The first shop I every built, the electrical inspector made me re-wire many receptacles because I only had 5" of slack wire instead of 6" in several boxes and it was clearly "stated in the code" :kamahlitu!
It is absolutely worth the effort when you get the permit to ask if the inspector can come by and review your plans, even before the rough-in inspection. This allows you to avoid any of the inspector's personal pet peaves, not to mention when / if you move there will be nothing to worry about from a home inspection and you can almost guarantee a swift final inspection!!

I could go for days on this, but if you are permitting this work the inspector (after being safe) can be the most important ingredient when a resident vs a non-licensed electrician pulls a permit.

Remember, luck and electricity don't care about each other! Safety first. :eusa_naug

 

[eyekode]

Thanks for the response Stillwell.

I am convinced to run a new subpanel . And I understand that the rules are for safety. But it seems for safety there should be some max breaker amperage allowed in a panel. Especially in my case where the main panel doesn't have a main breaker. Isn't there a rule to protect from fire from pulling too much current through the main panel?

So for example right now my main panel has:
90a - existing subpanel powering most of the receptacles etc
30a - heat pump air handler and emergency heat (this was my previously mentioned "mystery breaker")
25a - heat pump condenser
25a - second floor AC
30a - first floor AC
40a - stove (unused)

This is over 200a. Very improbable that I could actually draw this much at a given time. But what if I swap the 40a breaker for a 90a breaker for a new subpanel. At some point isn't this a safety concern?

Thanks!
Salem

 

[eyekode]

You asked.....Outside box does not have a main breaker. I don't yet understand how you are supposed to work on a box without a main breaker... But I will figure this out before I open it up :smile:.

Not to be a wise butt but the answer is 'carefully'. Its a matter of 'snapping in a breaker just like in any other panel. BTDT but you have to know your limits. In my case it was a 60A welder feed I added. Messing around in a hot panel does make you think about safety a little more.

Or you can pull the meter head, but then you have cut the meter head seal and the local electric company doesn't like to find meter heads with the seal broken. Have your electrician friend do that part (install the breaker and hook it up).

Thanks for the info. Oddly enough my meter head does not have a seal! I had my 3rd floor finished which entailed some work in the outside panel (adding a heat pump) and I guess they never put it back?!

 

[Glennbear]

Thanks for the response Stillwell.

I am convinced to run a new subpanel . And I understand that the rules are for safety. But it seems for safety there should be some max breaker amperage allowed in a panel. Especially in my case where the main panel doesn't have a main breaker. Isn't there a rule to protect from fire from pulling too much current through the main panel?

So for example right now my main panel has:
90a - existing subpanel powering most of the receptacles etc
30a - heat pump air handler and emergency heat (this was my previously mentioned "mystery breaker")
25a - heat pump condenser
25a - second floor AC
30a - first floor AC
40a - stove (unused)

This is over 200a. Very improbable that I could actually draw this much at a given time. But what if I swap the 40a breaker for a 90a breaker for a new subpanel. At some point isn't this a safety concern?

Thanks!
Salem

IMHO there would not be a safety issue as long as the WIRE you use for the subpanel feed is sized to match the breaker protecting it. If you put in a 100amp subpanel and breaker the wire must be rated for 100 amps. The whole purpose of a breaker is to trip before you draw enough amps to cause the wiring to overheat. :wsmile:

 

[PeteQuad]

Take a look at my first post again. The breakers within a box have nothing to do with the main breaker in a box.

You could have a 100 amp box (100amp main breaker) with 10 90amp breakers in it. It does not matter. You will never be able to pull more electricity than the box can handle, since it will switch off if you ever reach 100amps. That's the point of the main breaker.

Having 10 90amp circuit breakers in the box says nothing about how much electricity you are actually pulling. It just means that individually they will not switch off until they reach 90amps. The total cannot exceed 100amps.

The important thing is to match the thickness of the wire to the circuit breaker rating.

 

[eyekode]

Take a look at my first post again. The breakers within a box have nothing to do with the main breaker in a box.

Pete,
I understand this. The panel cannot pull more than the breaker it is connected to. And as you said as long as the gauge of the wire can handle the breaker all is well.

But the panel that is fed from the street does not have a main breaker. It has the meeter and 6 double pole slots. What protects this panel? What protects the feed coming from the street?

Thanks!
Salem

 

[Dudelive]

Pete,
I understand this. The panel cannot pull more than the breaker it is connected to. And as you said as long as the gauge of the wire can handle the breaker all is well.

But the panel that is fed from the street does not have a main breaker. It has the meeter and 6 double pole slots. What protects this panel? What protects the feed coming from the street?

Thanks!
Salem

I am missing something here, you stated that there are only 6 double pole slots which mean they all are 220v where is the 110 volts breakers at that are used in the home.

As long as the wire size is correct, install a 100 amp breaker in the main panel and wire it to a sub panel as stated and leave all other circuits alone. You may have to remove the stove breaker and use larger wire for the sub, but be sure to remove the stove receptacle to avoid confusion later. That way it will be as though all along it has had a sub panel and there would be no questions at all in later selling the home.

Your situation is easier than you think, mine is or was ALL screw in fuses for everything lights and all. I came of of the main panel where there was a pull disconnect in the panel and went to a sub panel mounted right beside it and now use ONLY the main panel for lights and feeding the sub the same as you can do.

Just DON'T forget the GROUNDING of the sub panel as mentioned.

Work safe and smart and take your time....be careful.