Determine Electric service size for work shop

[thepumpguysc]

Even the guy from the ELECTR. Co. asked me WHY I wanted 200amp out to the shop..
He said 100 is PLENTY.. I told him I'll be running a big air compressor, lites, grinders, possibly a 2ton a/c unit..??
he said 100 will be fine.. but spec the equipment out FIRST.. just look on the machines that WILL BE RUNNING.. all the info is on the tag..
& don't forget to take into consideration THE STARTING AMP DRAW.. it takes more amps to "start" an a/c unit than it does to "run" one..
SAME w/ air compressor..
& he said I could always use a portable transformer to run a specific piece of equipment..

 

[oosik]

Thirty six years - 200 amp service to the out buildings has NEVER let me down. And it doesn't cost any more that 100 amp service.

 

[ultrarunner]

40 x 120 is the shop size of my dreams...

There is one near here with a 150 amp service and natural gas.

He has never had any problems with the service being too small and it was calculated to minimize voltage drop...

Put in Gas for two ceiling mounted furnaces... might get used a few days each year in winter... weather is mild here.

If you are going with electric heat... bigger is always better for sizing your service.

 

[muddstopper]

I have a 250amp ac/dc welder stick/tig welder, A 5hp 220v lathe, a 175amp mig, A Miller spectrum plasma, Two drill presses and a air compressor. I have a 60amp fuse box. I have blown the 60amp fuses when trying to tig aluminum at the 250amp setting on the welder, and the air compressor kick on at the same time, but that is seldom. I have also blown the 30amp fuses while running the drill press and the compressor kicks on. But every light and plugend in the shop is on one screw in glass fuse. I need to rewire my shop and add more breakers, just havent got around to it. At anyrate, I seldom tig at 250 amps. What I am saying is if I had a 100amp panel and have a couple of other breakers in the box. I doubt I would ever trip another breaker or blow another fuse. The feed for my shop comes out of my 200amp house panel and is on a 100amp breaker. Never have tripped it, and its on a long run, over 100ft. Even knowing I dont need a bigger breaker box than 100amp, if I ever get around to redoing the panel, I would still probably go with a 200amp panel. Simply because it would probably have more breaker spaces and I could split up the load a little more.

 

[Fallon]

I upgraded from 60@ of wire & 100@ of breakers (whoever had my house/barn before I bought it wasn't smart & cut corners) to 125@ service when I put solar on the barn.

One key thing to remember... How many machines can you run at once? Heater, compressor, plasma & lights is about the biggest draw I can come up with, despite having a lot more tools there. A 2nd person working in the shop could change that equation though.

I tend to believe 100-125@ of service will take care of the most ambitious home gamer unless there is a lot of electrical heat or something/someone else involved.

 

[flingwing1969]

A 200 amp service provides you two 200 amp legs so in reality, you can run 200 amps at 220 vac or 400 amps at 110 vac or a combination of the two. Technically, a 100 amp panel can provide 200 amps of service to only 110 vac appliances or, for example, 50 amps of service to a welder and 100 amps of service to lights and plugs at 110 vac.

Just keep it to at or under 200 amps of breakers/demand on each side of the box.

 

[mikester]

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.

Check with your local electrical utility - especially if you rent or they supply the transformer. Around my neck of the woods the utility has higher standby/loss charges the larger service you have. 400-600A is/can be considered commercial and you pay a commercial rate for your electrical connection.

 

[sandman2234]

I purchased a house with a detached garage. Two story 30x30 with a 60 amp panel, but no main breaker. I wanted to cut the power at the main, so I started looking for the disconnect. Tracked it down, the nearest breaker would be on the pole when I popped the incoming service breaker.(YIKES) So I started looking for a solution (quick!!) I have a Miller welder that max draw is 105 amps, so I figured tapping off of the 150 amp service in the house might not be a great idea. I finally asked a friend if he knew anything about electricity, and he said I needed to talk to "Pete". Who is Pete??? Pete was the guy that I walked by in the first room playing video games as I would make my way back to talk to my friend. Turns out, Pete was a journeyman electrician and he pulled the permits, did the work which included completely rewiring the bottom floor because code had changed since I had it installed 3 months before. All I had to do was get a separate address for the garage (don't allow multiple service drops to same address). Anyway, I got 200 amp service to run my welder and complete shop, and the upstairs also. Have never had any problems, never popped a breaker, and still appreciate "Pete" for his help. Pete knew that I was low on cash after just buying the place as is from an estate and spending a small fortune getting things fixed. He went with the Square D boxes outside and some 40 slot Squre D boxes I already owned on the inside and when it was time to settle the bill, would only take $300. It was great having someone to take care of me when I needed it. Hated that he moved on.
David from jax

 

[PILOON]

I have a lathe, 220 amp welder, table saw with 2 hp, drill press, and just about every power tool made.
My shop has a 60 amp sub panel and I only once blew a breaker and that was when my welder switch dead shorted from old age.
Blew the breaker and stunk up the shop but that was all. Reset and good to go.
So all being said 100 amps is adequate for sure.
Oh, but my compressor draws only 15 amps and that is at start up.
Oh yes, I also heat with a 4000 watt construction type heater.
Granted when I weld I only occasionally use very high or even max amperage and if so that's outside in warm weather when no heater is needed.

For 200 amps you would need to have multiple users and at that be commercial in nature.

More important keep all lighting separate from tool outlets/circuits.
Use 12 gauge/20 amp circuits for tools and then also limit the number of outlets per circuit* and perhaps criss cross the circuits. OK a bit more wire but cheap in the long run.
*perhaps one circuit per wall and locate the outlets at about workbench height.

 

[ultrarunner]

At the ranch there is a 200 amp service/home/shop/barn and at the far end of the property is another 200 amp service dedicated for the tree operation... each is separately metered and only one address for the property.

It must vary depending on jurisdiction.