Garage wiring guidance needed

[sickboi55]

My wife and I are in the process of buying our first home. I have big plans for the 2 1/2 car garage. I plan to have the following in use in the near future.
-7.5HP compressor
-220v plasma cutter
-220v lathe
-220v welder
in addition to other 110v power tools and lights. The main panel is 150 amp and I want to add a 100 amp panel to the garage. The load on the main panel is lowered due to the use of gas for the range and dryer.
I think it will be rare that any two tools will be used simultaneously with the exception of the compressor and plasma cutter.
So I am looking at 2 50 amp 220v breakers, one dedicated for the compressor and the other for the remaining 220v tools. I want to have plenty of light as well.
So my questions are...
-is a 150 amp main panel enough?
-will i have any issue with multiple high draw circuits combined with all of the outlets on one breaker and all of the lights on one breaker.
-if my compressor is running and the lights are on am I going to have an issue when i turn on my table saw? what about the same situation but with the plasma cutter instead of the saw. Situations like that are what I am trying to get my head around.
I work with wiring in the NAVY on aircraft, so electricity is not new to me but i have never done any home wiring.

 

[DC73]

Could you clarify some things? Where is the 150 main panel and what does it currently feed? Is it the main panel for the house and you are wanting to add an additional 100 A panel for the garage? How do you plan to get power to the new 100 A panel? Is the garage detached? What size wire feeds the existing 150 A panel? These answers will make it easier for some of the electrical gurus on the site to help.

Once you sort out the how, if you have room in the panel, I'd split the lights between two circuits and I'd split the outlets between two circuits.

As an example of what you might be getting into, my in progress workshop will be getting a 100A panel. I couldn't feed it from my existing house panel (200A) because the wire to the existing panel couldn't handle the additional load. It turned out that it's going to be less expensive and less trouble to bring another service from the alley for the shop.

Good luck.

DC

 

[justsam]

Don't know where you are at so I have to begin by assuming NEC is applicable.

I do not see an issue with your high level plan of feeding a 100 AMP circuit. You may want to check if your home panel can have a 100 Amp, for some the max is 90. Is HVAC on a heat pump, gas/ electric?

You mention multiple outlets on a 240 volt run. This is not NEC compliant. Each must have it's own circuit. The compressor and I suspect the lathe will need to be hardwired and use no outlet. Receptacles, (outlets) carry a HP rating and most readily available have a max of 3HP. Receptacle (outlet) is OK for welder and plasma cutter, and perhaps lathe if under 3HP, but again, no daisy chain, must be separate circuit.

I see no issue with logical multiple devices on at the same time, and as stated above the 240VAC ones will each have their own breaker.

 

[sickboi55]

The main panel is in a cabinet in the kitchen. The garage is just off of the kitchen, attached to the home. The home is located in Jacksonville, Fl. I havent actually seen the house so I am unsure of the feeders going into the main panel. To feed the sub panel my plan was to feed through the attic. I planned on hardwiring the compressor but everything else would have a plug. The plan is also to have 2 50 amp 220v breakers, one dedicated to the compressor and the other for other 220 tools.

HVAC is the only large load on the main panel as everything else is gas.

 

[justsam]

Since garage is attached, you are not required to have a subpanel and if room in your existing box you could just use it and have individual runs to the garage. Look at cost and it may well be cheaper to establish the subpanel.

Again, if you want to be NEC compliant, you may NOT have multiple 240 receptacles on a single circuit. Will it work, of course it will but not compliant.

If you wind up with more than six breaker handles in your garage sub, it will need to have a main disconnect too.

 

[sickboi55]

To be clear I only plan on having 1 220 outlet and 1 220 hardwired. The outlet will be so i can hook up 1 tool at a time. For the sub panel, if it has more than 6 breakers, are you saying I will need to install a master breaker for that panel, or a disconnect switch before the panel.

 

[Norcal]

#1
Again, if you want to be NEC compliant, you may NOT have multiple 240 receptacles on a single circuit. Will it work, of course it will but not compliant.
#2
If you wind up with more than six breaker handles in your garage sub, it will need to have a main disconnect too.

Care to cite a NEC article? And for the 2nd one that is not the case for a attached garage or shop, it's desirable, but not required to have a main like it would be in a detached structure.

 

[alfredeneuman]

Care to cite a NEC article? And for the 2nd one that is not the case for a attached garage or shop, it's desirable, but not required to have a main like it would be in a detached structure.

Justsam can't cite the NEC article because there isn't one ...... but Norcal already knows this.

The NEC allows multiple 240 receptacles of any amp rating on a single circuit.
The IEC allows multiple 240 receptacles up to 20 amp rating on a single circuit.

 

[sickboi55]

So back to the roots of the problem, if the feeder for my 150amp panel is adequately sized to the 150 panel, can adding a 100 amp panel be done safely? I don't want my house to burn down if I have 8 4ft florescent lights running, while using a table saw and the compressor kicks on.

Should I add specific outlets for power tools off of the sub panel ? The ones currently in the garage are on a 15 amp breaker.

 

[pattenp]

Yes you can safely add a 100A sub-panel off the 150A main panel provided the 150A main panel shows that it can take a 100A breaker. Look at the listing label in the 150A panel to see what the max size breaker it can take. Also it's best to make any 120V outlets to be on a 20A circuit and to add 240V outlets specific to the equipment to be powered from the sub-panel.

 

[Norcal]

Yes you can safely add a 100A sub-panel off the 150A main panel provided the 150A main panel shows that it can take a 100A breaker. Look at the listing label in the 150A panel to see what the max size breaker it can take. Also it's best to make any 120V outlets to be 20A and to add 240V outlets specific to the equipment to be powered from the sub-panel.

There is no legitimate reason for 20A receptacles, if anything needs a 20A plug because of the load it should be on it's own circuit. My shop has 20A but I had them, to spend extra money for 20A receptacles is wasting money that could be spent elsewhere, 15A duplex receptacles on a 20A circuit is fine.

 

[DC73]

So back to the roots of the problem, if the feeder for my 150amp panel is adequately sized to the 150 panel, can adding a 100 amp panel be done safely?

As pattenp said, it can be done safely if you can put a 100A breaker in the 150A panel. You'll be protected but it doesn't automatically mean it will work well. More than likely it will work, but if your house is a power hog and you're working in the garage, you could start tripping the main breaker.

It's best to add up the requirements of everything in the house and garage that you think could possibly be running at the same time. If the total amps required is less than 150 amps and the total garage amps required is less than the 100 amps, it'll work. But, I'd factor in a 20% safety factor just to be sure.

DC

 

[pattenp]

There is no legitimate reason for 20A receptacles, if anything needs a 20A plug because of the load it should be on it's own circuit. My shop has 20A but I had them, to spend extra money for 20A receptacles is wasting money that could be spent elsewhere, 15A duplex receptacles on a 20A circuit is fine.

Oh... I didn't mean actual 20A rated outlets. I was meaning to say 20A circuits for the outlets. Yes the 15A rated outlets are fine on a 20A circuit. Thanks, I reworded my post.



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[sberry]

With taking the electric appliances off in the house it will be adequate and then some.

 

[Onewolf]

With taking the electric appliances off in the house it will be adequate and then some.

As someone else suggested, I think the total house load needs to be calculated. HVAC, water heater(s), pool pumps, etc.