Determine Electric service size for work shop

[ch47dpilot]

I'm building a work shop and planning on 200amp service but not sure if that's enough. I plan to have a welder (50A), compressor (50A) and plasma cutter (50A). All could be on at same time possibly. Then there would be the normal lights, fans ect you'd be using in a shop and possibly a window size AC unit in a small office area. What's the best way to determine if I need 200A service or need to go up to something bigger.

 

[rhunt]

I,ve never heard anyone complain they put too large a service in. Bob

 

[ctrider]

The NEC has very specific ways to determine this for you. Each piece of equipment usually goes by the nameplate rating for amperage, some which can be de-rated. There are also guidelines for lighting and receptacles. How big is your shop? A 200amp service will provide a lot.

 

[ch47dpilot]

Shop will be 40x70 but will also have 2 25x40 areas. 1 garage for cars other will divided. Storage and wood working shop . Total building 40x120

 

[thepumpguysc]

I JUST HAD the electric co. out to my shop, 24x32 to give me an estimate on running 200 amp service..
They had to come from the nearest transformer, down my property line, put in a pole. face all the trees,[100 yards of pine trees], run the wire, put in another pole at my building..1750ft of wire. $4500.00
BEST BET is to call your provider & get them to come out & let THEM TELL YOU what you CAN HAVE..
I brought up the notion of getting 3phase.. He shot me down QUICK.. NO 3PH available out here..

 

[EddieWalker]

While this isn't going to be 100% accurate, the theory is pretty close. If you have 200 amps available, you will never use all of that power at the same time. Your power usage, or demand, is based on what you will be using at the same time. If you are welding and using 50 amps, then your other power tools will not be operating, so it doesn't matter what they need. If your air compressor is running, you might also have some other power tools going at the same time, but rarely more then just one. Even if you have helpers, you split up your outlets and the power tools are all on different breakers so you never overload and trip one of them. Your lights are on one or two breakers separate from your outlets. They don't use much, so usually a 15 amp breaker is more then enough for lights. 20 amp for power tools and bigger for special tools, like a welder. 200 amps is plenty. 100 amps is more then needed in most cases, so you are already double what you will ever need.

 

[fried1765]

While this isn't going to be 100% accurate, the theory is pretty close. If you have 200 amps available, you will never use all of that power at the same time. Your power usage, or demand, is based on what you will be using at the same time. If you are welding and using 50 amps, then your other power tools will not be operating, so it doesn't matter what they need. If your air compressor is running, you might also have some other power tools going at the same time, but rarely more then just one. Even if you have helpers, you split up your outlets and the power tools are all on different breakers so you never overload and trip one of them. Your lights are on one or two breakers separate from your outlets. They don't use much, so usually a 15 amp breaker is more then enough for lights. 20 amp for power tools and bigger for special tools, like a welder. 200 amps is plenty. 100 amps is more then needed in most cases, so you are already double what you will ever need.

Exactly correct !!!!

 

[oosik]

When I built my house I tried to decide how much power I needed. Ended up with 400 amp service. 200 to the house - 200 to the outbuildings. The only heavy use in the outbuildings is my Miller welder. Otherwise its just powertools of all types and sizes which I have never had more than one on at a time.

The other reason I didn't go to more power was - $$$$$$$$$. The utility boxes made a gigantic jump in cost and the power utility had a significant jump in cost per KW hour also. The next jump would have been 800 amp service.

 

[Deere Dude]

While this isn't going to be 100% accurate, the theory is pretty close. If you have 200 amps available, you will never use all of that power at the same time. Your power usage, or demand, is based on what you will be using at the same time. If you are welding and using 50 amps, then your other power tools will not be operating, so it doesn't matter what they need. If your air compressor is running, you might also have some other power tools going at the same time, but rarely more then just one. Even if you have helpers, you split up your outlets and the power tools are all on different breakers so you never overload and trip one of them. Your lights are on one or two breakers separate from your outlets. They don't use much, so usually a 15 amp breaker is more then enough for lights. 20 amp for power tools and bigger for special tools, like a welder. 200 amps is plenty. 100 amps is more then needed in most cases, so you are already double what you will ever need.

I agree. The only time you will max it out is if you had a 3-4 people working with you in a commercial type setting and using high usage tools like a couple welders at the same time as the compressor is running, and 200 amp will still be enough. If that would be the case anyway, have one take a breather for a minute.

 

[texasranger556]

I ran 100 amps to my attached garage. The highest instantaneous load is if I have the heater running (5-6 kw toaster style), beer fridge running, plasma cutter maxed out (powermax 45), and the 5 HP air compressor kicks on while cutting. I haven't tripped the main yet doing that, so with double the power you should be good.

Multiple cnc machines running at the same time as a cnc plasma table, that would be one of the few cases I could think of needing more than 200 amps, but that's pretty rare in a home shop.