What Amp Service Do I Need

[powerhound]

I'm gathering info and materials before I start my shop and power has to start on the first of the list so, what will I need? I will be powering
40 x 40 shop
220 air compressor
220 welders (mig/tig/stick) which can be unplugged until needed
assorted grinders, drill press power tools etc...
deep freeze

Would 200 amp be good or overkill? I'm sure my electrician will have his thoughts, just good to have a second opinion

 

[wellpoison]

if you have a 200 amp service to your house i would do a 100 amp sub. you will never run out of power with 100 amp. also you dont need to unplug the welder when not in use it will not draw any amperage when not in use. i would run atleast 6-8 220v locations so that if you decide to remodel you can move your welder/comp any where.

 

[cj7365]

I have a 100 amp sub panel, I DO NOT ave a 220v compressor just a 110v but have a 220 welder, plasma cutter drill press etc the basics, Lighting consist of 8 4ft 3bulb T8 flourencse lights, I have had no problem, its only my son and I in the shop so not more than one thing is running all the time, well, I usually have a tumbler running cleaning brass

 

[OldmanB]

I did similar to this ,20 years ago. My house has 200 amp service, we took 100 amps off to my shop, and run 2-220 volts welders, 52 amp plasma, 220 volts compressor, 14" chop saw, and much more, never had a problem, but never run everything at once either.
Brian

 

[Full Throttle]

do yourself a favor and run a new 200 amp service to your shop now. Ierther upgrade house meter to 400 service and sub 200 to shop, or just run a new separate 200 to shop. think of future HVAC etc. 100 amp sub is ok for 1 car or 2 car shop but not a 40x40 building. my 2 pennies worth.

 

[930dreamer]

I would plan for the future on the panel.

 

[larry_g]

Electric heat is usually the deciding factor between the 100a and the 200a service. A one man shop can do with 100a in most cases as you usually only run one machine at a time. Got helpers and multiple machines running then go with the larger.

lg
no neat sig line

 

[Speedy Petey]

100A is PLENTY.

Be wary of adding a separate service to the shop. Things like the meter/supply fee and higher rates can make this long term cost prohibitive.

 

[powerhound]

I'm a one man operation. The most that would happen would be the welder, compressor and freezer running at the same time if the stars aligned just right.

 

[vartz04]

100 amps
30 ish for each the compressor and welder
15 amps freezer
15 amps lights (high side)

youve still got 40 amps left over for hvac stuff, and whatever else (radio tv ect)

if it comes down to it just flip the switch on the compressor before you start welding.

 

[sberry]

Yes, 100 is adequate here, you will never see a peak of more than 60A. If it was mine it would be fed from the house if possible, just that much less equipment and service to deal with. Unless you already have everything electric up the azz a garage is barely a demand factor.

 

[Falcon67]

I tested my old shop - ran 5000w heater, air compressor (3.5 hp 240v), drill press, 9x20 lathe, grinder, small belt sander, 240V 1HP mill, 16 two bulb 4' lights. Barely made 50A.

 

[powerhound]

I tested my old shop - ran 5000w heater, air compressor (3.5 hp 240v), drill press, 9x20 lathe, grinder, small belt sander, 240V 1HP mill, 16 two bulb 4' lights. Barely made 50A.

Well, that solves that Thanks

 

[Speedy Petey]

100 amps
30 ish for each the compressor and welder
15 amps freezer
15 amps lights (high side)

youve still got 40 amps left over for hvac stuff, and whatever else (radio tv ect)

This is SO not how it works.

100A @ 240V is 24,000 watts

A 30A circuit @ 240V will provide 7,200 watts.
A 15A circuit @ 120V will provide 1,800 watts.

At full load, which will NEVER be seen BTW:
7200
1800
1800
10,800 load

24000
10800
13200 watts unused, or roughly 55A @ 240V.


Even then, this is NOT how load calculations are done. Adding up breaker sizes is a completely meaningless number.

 

[vartz04]

I understand that is not how it works, I wasn't going to go through a multitude of electrical calcs to show this guy that it isn't an issue because it is no where even close to overloading a 100 amp service.

 

[Full Throttle]

I understand that is not how it works, I wasn't going to go through a multitude of electrical calcs to show this guy that it isn't an issue because it is no where even close to overloading a 100 amp service.

So we use a wrong example to teach a fellow. I like that.

I will stick by putting in 200 amps, one never knows what the future will hold. Easier and cheaper to do now than later.

 

[dipper]

I will stick by putting in 200 amps, one never knows what the future will hold. Easier and cheaper to do now than later.

Probably not gonna be a savings if his house is already a 200A feed and he can be pretty sure that he will never need more than 100A. As been shown, 100A out to a shop is a lot of power with a lot of headroom even with the air compressors, welders, lifts, saws, plasma cutters etc etc. Most times these are our home shops that have one or two users at once.

 

[jvitez]

Shouldn't a load calc for a shop be grade school math, ie really easy? I always thought so. School me if I'm wrong please.

1. Figure out what possible things you would be using all at the same time, welders, compressor, lights, plug in heaters, permanent electric heat, whatever you think.

2. Add up the wattage, not amperage, of all the above.

3. Divide #2 by 240.

4. Install a cable that supports an amperage higher than #3, and use the proper breaker for this cable.

Anything else I'm missing?

 

[Stuntmonkey]

I honestly can't be bothered correcting several people in this thread in regards to load calculations, but I would recommend switching your house to 400 and running a sub panel of 200A.

If you can afford to do this now it will save you a whole lot of headaches in the future. Trust me, I do this for a living.

If you can't afford it, sub 100A and live with it, I can't tell you with certainty that you won't see peak without being there.

Also - running separate 200a panel will be quite a bit more costly, hence the suggestion for a sub.

 

[pattenp]

Oh really... there's noway you're going to get away with that comment. Where's the beef?

I honestly can't be bothered correcting several people in this thread in regards to load calculations, but I would recommend switching your house to 400 and running a sub panel of 200A.

If you can afford to do this now it will save you a whole lot of headaches in the future. Trust me, I do this for a living.

If you can't afford it, sub 100A and live with it, I can't tell you with certainty that you won't see peak without being there.

Also - running separate 200a panel will be quite a bit more costly, hence the suggestion for a sub.

 

[powerhound]

No worries guys, just thought I would ask. Like has been mentioned before, I'm a one man show and unless my wife and my son take up hobbies that involve multiple users at once, I should be okay. First things first, figuring out what I have for service in place to the house.

 

[Dick in Wisconsin]

My shop will be 1,000sf. I don't have all the stuff many of you have. I maintain my race car. I might get a welder, plasma cutter, and lathe ... they likely won't be running all the time.

So I'm thinking about putting a 100amp subpanel in the shop coming from the 200amp existing service that I have. I think I might put in a cable big enough for 200amp to the shop in case for some bizarre reason I want to upgrade ... but with 1,000sf, I find it unlikely.

How does the sub-panel service work? Will there be a huge 100amp breaker in my 200amp main panel and a huge wire running out to the shop to the 100amp sub-panel?

Thanks everyone for all help and advice. I learn something new every night!

 

[Speedy Petey]

The main breaker will not be huge. A 100A main is roughly the same size as a typical two-pole breaker.
If you run 200A rated cable you'll have to get creative with terminating it. 4/0 or 2/0 will not fit under any 100A breaker that I know of. You'll need to splice it to smaller wire to make the connections to the breakers.

IMO a 100A feeder is more than enough for a one man shop. You'll simply NEVER be using two (or more) tools large enough at the same time to even come close to tripping a 100A circuit.

 

[pattenp]

Short answer... Yes.

View media item 16967

My shop will be 1,000sf. I don't have all the stuff many of you have. I maintain my race car. I might get a welder, plasma cutter, and lathe ... they likely won't be running all the time.

So I'm thinking about putting a 100amp subpanel in the shop coming from the 200amp existing service that I have. I think I might put in a cable big enough for 200amp to the shop in case for some bizarre reason I want to upgrade ... but with 1,000sf, I find it unlikely.

How does the sub-panel service work? Will there be a huge 100amp breaker in my 200amp main panel and a huge wire running out to the shop to the 100amp sub-panel?

Thanks everyone for all help and advice. I learn something new every night!

 

[slip knot]

I've only got a 70 amp feeder to my shop sub panel and haven't had any electrical issues. I have ran my compressor and a plasma cutter for extended periods without any problems. But I use gas heat for the bitter cold south Texas winters.

 

[jbberns]

The reason most houses put in a 200 amp service in is for panel space. Doing a load calc. most houses don't touch 200 amps.

 

[Dick in Wisconsin]

Short answer... Yes.

Thanks!

 

[mm08822]

Based upon your description of the limited expected simultaneous loads, 100a is more than plenty. I suggest you put your $ into a 30 or 36 full space 100a panel and consider upsizing the wire (one size) just in case you ever did get close to 100a to cover voltage drop. Not to start a whole new thread frenzy, but how far is this sub-panel from main panel?
You can also run a reduced nuetral if using conduit and individual conductors - price it out both ways - reel price vs. per foot price. Ground only needs to be #8. If metal conduit, ground wire is optional, but most like to pull one anyway.

BTW - Most service "upgrades" in homes typically only need more branch circuit space in the panel and rarely require additional ampacity. Big mis-conception, some of its marketing hype.

 

[6768rogues]

if you have a 200 amp service to your house i would do a 100 amp sub. you will never run out of power with 100 amp. also you dont need to unplug the welder when not in use it will not draw any amperage when not in use. i would run atleast 6-8 220v locations so that if you decide to remodel you can move your welder/comp any where.

That is exactly what I did with mine 20 years ago. I have a 220 compressor, air conditioning unit and lift, among many other electrical tools. I never have a problem. The thing to ask yourself is how many things will you run concurrently.

 

[Falcon67]

I'll add my layout for reference. I was lucky - the utility came out to re-seat the meter base and put in ground rods for the house when we bought it. The house was built in 2001 and whoever wired it "forgot" to ground the place. We bought it as a re-po in 2010 and that was the first thing I spotted. Anyway, I asked the engineer about a feed for the shop. He pulls a Square D 100A 6 slot out of the truck and says I'll just put that right here and you can hook up to it when you get there. So I got a 100A drop from the meter base for a smile and a handshake. From there, I ran 2-2-2-4 AL to the shop. I put a 70A breaker in the Square D box on the house. It was in stock at HD, cheap and would handle #2 AL. I could go 90A, but it was a special order. The shop end is a 100A Square D Homeline 20 slot with a 100A main. I was eying the 24 slot, but this box was on sale. I bought the 70A breaker, box, 120' of cable and some conduit and still got out of the store under $300. I ended up cutting maybe 20' off the run total when done. I can shut the place down from either end if necessary and the house box is marked in case the fire dept has to do emergency work. I figure if I can trip a 70A breaker, I'm really doing something or there is a dead short somewhere.

 

[toyotadriver]

As mentioned, 200 amp is overkill. 100 amps will be more that enough.

 

[tomshep]

I just went through this.

I have 225 at the house.

My shop is 40x36.

I was looking at 100-125 amp boxes and they were pricey. I couldn't help looking at this 200 amp box with a main breaker, one 220 breaker and four 110 breakers for less than an empty 100 amp box.

I decided to put a 125 in my home box to run to the garage.

I now have a 200 amp main (clearly marked) disconnect IN THE GARAGE which I really like for safety and had 5 breakers for my compressor and outlets on each wall. I saved money over the smaller box and have a lot of room to grow.

It may be overkill BUT it was cheaper than going smaller and I have a lot of extra space in the box.

Tom

 

[Shocker]

My shop is 24x32 and I run it off of an 18v Lithium Ion battery.

 

[hughfree]

I am in the process of extending my 20x20 detached to 32x20. Decided to pay someone else to do the job turnkey. Pricing from my GC included pulling a 100 amp feed from my house panel to a 100 amp sub-panel in the garage. I was on a jobsite talking with an electrical sub doing work for me shortly after receiving pricing from my GC. He suggested that I contact my local utility about pulling a dedicated feed from the transformer. He mentioned that in some areas the utility will pull the dedicated feed for "next to nothing". I am glad that I talked with him! I had my GC call the local utility. He met with one of their engineers and for approximately $600.00 they will install a buried 200 amp feed running approximately 250 feet from transformer to my shop. This price includes the meter. The deduct for running the 100 amp sub-circuit from my home panel to my shop was $570.00. A dedicated 200 amp service for net add of $30.00....this decision was a "no brainer" for me! In my opinion it is worth talking with your local utility before making a decision.

 

[cj7jeep81]

I am in the process of extending my 20x20 detached to 32x20. Decided to pay someone else to do the job turnkey. Pricing from my GC included pulling a 100 amp feed from my house panel to a 100 amp sub-panel in the garage. I was on a jobsite talking with an electrical sub doing work for me shortly after receiving pricing from my GC. He suggested that I contact my local utility about pulling a dedicated feed from the transformer. He mentioned that in some areas the utility will pull the dedicated feed for "next to nothing". I am glad that I talked with him! I had my GC call the local utility. He met with one of their engineers and for approximately $600.00 they will install a buried 200 amp feed running approximately 250 feet from transformer to my shop. This price includes the meter. The deduct for running the 100 amp sub-circuit from my home panel to my shop was $570.00. A dedicated 200 amp service for net add of $30.00....this decision was a "no brainer" for me! In my opinion it is worth talking with your local utility before making a decision.

does your electric company charge you a seperate monthly fee for that second metere? I know here they do, and if you have to pay an extra $20 or $30 a month to have that meter, that will end up costing you quite a bit more in the long run.

 

[Falcon67]

What he said - check the fine print with the utility. My co-op charges $30 min/mth for every meter. AEP Texas' rate tariff allows for them to charge commercial rates on the 2nd meter at an address. On my old shop, they did the drop no charge. By the time I got the 3rd bill, I ran power from the house panel and had them pull the drop. The savings paid for the extra wire, panel, etc in less than 8 months. You might find your "net loss" growing pretty quick.

 

[digdug18]

Funny, I feel like I went overboard with mine now, lol.

I upgraded to a 400amp electric service in the house, and a 200amp service in the shop.

I have one mini split already powered by the shop service, and wanted plenty of room for a 2nd, as well as 2 lines for 220 equipment, one being a welder, another being a electric cooking stove for shop use.

I also wanted enough room to run more lights in my house basement, as well as the garage. Possibly the addition of converting the house to solar in the future as well.

Bottom line though, electrician gave me the option, he was doing a bunch of stuff. The panel we had was an original from the 50's and we were told by about 10 different people that the main breaker was of a kind that sometimes had issues, well better safe then sorry. So we had only 3 open spaces in the box we had, with a 200 amp service, electrician wanted to install a 300amp service, run sub panel to garage, run generator panel and outside generator hookup. He said he'd charge me the same rate for the 400amp service, the box for the 400amp has about 40 extra slots in it, more then I will ever need, but I'm of the do it once mind set....

But I think I went overboard, lol.

 

[pattenp]

Don't know where you priced the 100/125A main breaker boxes, but around here the 200A main breaker boxes cost a fair amount more.

I just went through this.

I have 225 at the house.

My shop is 40x36.

I was looking at 100-125 amp boxes and they were pricey. I couldn't help looking at this 200 amp box with a main breaker, one 220 breaker and four 110 breakers for less than an empty 100 amp box.

I decided to put a 125 in my home box to run to the garage.

I now have a 200 amp main (clearly marked) disconnect IN THE GARAGE which I really like for safety and had 5 breakers for my compressor and outlets on each wall. I saved money over the smaller box and have a lot of room to grow.

It may be overkill BUT it was cheaper than going smaller and I have a lot of extra space in the box.

Tom

 

[Speedy Petey]

Yeah, something does not sound right.
100A panels pricey??? I don't think so.

I bet he was looking at something like a 100A 32 space QO MB panel and a 200A BR value pack.
Apples and oranges.