New building, new electrical, no experience

[NBN]

My 30x40x14 is being finished up this week and I will be working on flooring and electrical next to make the space usable. With the electrical, I want to be sure that I am not going to be starving for power once I'm in the building, I know someone that put themselves into that situation and it was quite inconvenient and probably dangerous.
Here's what I have or expect to have in the shop...
LED shop lights
several exterior lights
AC/heat
80 gallon compressor
MIG and TIG welders
Lift
Assorted cutting and drilling tools
Assorted grinders and buffers
lathe
mill

Can I realistically expect a 200 amp service to handle my needs or can I even drop to 100 amps? I've been told that a 400 amp is what I will actually need, but feel that is way overkill as that is what I've seen at a business feeding 2 large shops and 3 houses.

 

[jkeyser14]

Your most likely simultaneous loads are:

• AC/Heat could be 30-50A
• Air Compressor 30A
• Tig Welder 30-100A (machine dependent)
• Lights 10A

I would say 150A is the minimum I would go with for what you plan if you don't want to juggle turning stuff on and off constantly, but even that might not be enough. 200A should be a pretty safe setup though.

 

[Terry D]

What kind of electric heat. Mini split/heat pump or conventional electric furnace. If a furnace, how many KW

 

[NBN]

What kind of electric heat. Mini split/heat pump or conventional electric furnace. If a furnace, how many KW

good question

 

[klassenl]

Are you a 1 man shop or is it a business.

In a 1 man shop usually there isn't much running at the same time. Heat, compressor, and welder would be the most likely concurrent running loads. Would this trip a 100a breaker? -->> obvious answer is it depends on the load.

From personal experience I would say 100a is good 99 days out of 100 or better. I have seen places with pitiful electric systems with no problems. I have also seen overkill jobs that make you wonder if the contractor was taking advantage of the customer.

 

[rburke65]

I would think 100amp. feed will be plenty!

 

[nadogail]

Add me to the 100 should be plenty group.

All advice you take from me is guaranteed to be worth exactly what you have paid me for it.

Good luck on your project.

 

[Manganos]

I don’t like “should be enough”. Go with the 200 amp

 

[Stuart in MN]

I think these days 200 amps is the 'standard' service size from most electric utilities, and should be more than adequate for your purposes.

 

[u2slow]

Are you applying for a new service for the power company? Or sub-feeding off the house? The former can result in sticker-shock as a second service is often charged at commercial rates. The latter usually limits you to a portion of the main service size (i.e. 125A max subfeed off a 200A main; depends somewhat on your equipment and arranagement.)

Compressor tank size is a useless spec for electrical sizing. 7.5hp tends to be a problem on a 100A feed with other loads. OTOH, 3-3.7HP leaves lots of headroom. 5hp is a popular size.

I now have 90A to my shop, but got by with 40A fine - incl. 3hp compressor and 120/240V welder. I started with only 20A in the beginning. I don't need to think about AC or heat until after I find funds for insulation or interior sheathing. Glad I didn't pre-wire generously or buy new bigger equipment... or I'd be even further behind.

 

[NBN]

Are you applying for a new service for the power company? Or sub-feeding off the house? The former can result in sticker-shock as a second service is often charged at commercial rates. The latter usually limits you to a portion of the main service size (i.e. 125A max subfeed off a 200A main; depends somewhat on your equipment and arranagement.)

Compressor tank size is a useless spec for electrical sizing. 7.5hp tends to be a problem on a 100A feed with other loads. OTOH, 3-3.7HP leaves lots of headroom. 5hp is a popular size.

I now have 90A to my shop, but got by with 40A fine - incl. 3hp compressor and 120/240V welder. I started with only 20A in the beginning. I don't need to think about AC or heat until after I find funds for insulation or interior sheathing. Glad I didn't pre-wire generously or buy new bigger equipment... or I'd be even further behind.

For what electrical supplies are going for now, it would have been cheaper then.

Regardless, I know I wont be running 3 welders, the bandsaw the lathe and the mill simultaneously. I'm just looking at leaving myself some headroom so as not to overheat or pop anything.

 

[b-boy]

I think 100A would be fine.

 

[bad_idea]

One more vote for 100 amps. Except I would us MHF at 90 amps (that's what I did and it has been plenty, much cheaper than running any other type of wire). Again, it depends on the tools you are using. My stick and mig welder both do fine on a 240v 30 amp breaker, look at the actual amps drawn by YOUR machines (not just the plug type). A true 5hp air compressor will handle most any home garage's needs and a 240v 30 amp breaker will handle that too. Aren't too many tools that draw more than that. You won't be using multiple tools at once, you only have so many sets of hands.

 

[u2slow]

For what electrical supplies are going for now, it would have been cheaper then.

I already have 90% of the supplies.

If I'd wired my shop in advance - before knowing where things we're going to end up - it would take twice as many supplies.

 

[TRWham]

For what electrical supplies are going for now, it would have been cheaper then.

Regardless, I know I wont be running 3 welders, the bandsaw the lathe and the mill simultaneously. I'm just looking at leaving myself some headroom so as not to overheat or pop anything.

You really need to start with a list of the specific equipment you are likely to have and how it will be used. If you already have some of this stuff, then you know what it needs. For items not yet in your inventory, do you have a good sense of what items you will acquire? The HVAC is a real wildcard as it will likely be your single biggest load and will run much of the time so I'd nail that down first and build up from there.

 

[dcg9381]

Can I realistically expect a 200 amp service to handle my needs or can I even drop to 100 amps? I've been told that a 400 amp is what I will actually need, but feel that is way overkill as that is what I've seen at a business feeding 2 large shops and 3 houses.

Here's what I have or expect to have in the shop...
LED shop lights
several exterior lights
AC/heat
80 gallon compressor
MIG and TIG welders
Lift
Assorted cutting and drilling tools
Assorted grinders and buffers
lathe
mill

I'm Tejas too. I have a 60x40x16. It has 2 x 2 ton ductless systems, full kitchen, high bay LEDs, a hot tub, and several 50A RV connections. I don't have a large compressor,I do have a mig... Lots of cutting and grinding tools. I have 3 sub-panels on the shop. I feed it with 90A and have never had issues with power. I've run both ACs, the hot tub, a 2-AC 40' 5th wheel and a MIG all at the same time - no problem.

I'd be absolutely shocked if you needed more than 100A. 90A is the "sweet point" in terms of pulling cable (cost per foot of wire). One thing you can do is drop in 2" conduit (you'll likely need conduit in Tejas anyway). If I'm wrong about power, pulling a new main can be done.

My "main" service is 320A. That feeds the house, the shop, and an accessory dwelling unit. I'd run the same setup on a 200A main.

Of all your items, your compressor and HVAC (possible) are the big ones. Unless you're running a commercial shop with multiple people, I think 90A will be fine.

The only place I can see trouble is if you have to run electrical resistive heat (IE "emergency heat") on a heat pump, but with a 1200 sqft shop in Texas, I think you're fine.