Garage/Shop electrical service sizing

Fabrik8

Fabrik8

Overcomplicator
Joined
May 27, 2015
Location
Huntersville
This is a spinoff of my garage thread, but wanted to keep this focused and maybe easier to find for other people asking the same questions.

I need to talk to an electrician about the specifics of how the garage and house would be wired together, and those fun things too. I think the main feed to the house runs right where the (detached) garage is going to go, so that will have to get moved or something like that.

I'm trying to figure out what my electrical needs actually are, so I can ask the right questions while sorting out electrical quotes and figure out what how to get from pointA to pointB.

For my 900-1200sqft garage/shop, I am likely going to have (for planning purposes):
  1. Garage door opener (1.5-2A 120V consumption)
  2. Outlets (couple of circuits, at least one 20A)
  3. Mini-split system (probably 30A 230V breaker, max)
  4. Welder (don't have one yet)
  5. Compressor (don't have one yet; most likely 5HP so 30A or 40A breaker)
  6. 2-post lift (20A or 25A 230V breaker)
  7. Lights
  8. Maybe a 4-post lift later (future dreams)
I'm open to suggestions on the welder outlet rating. Might be doing some hot rod stuff and general fun, but won't be building buggies or doing heavy fab most likely.

IF I get a 4-post in the future, I assume I can share the breaker with the 2-post because they are never going to be operated at the same time?

What am I forgetting for loads/circuits?

Kinda sucks that a lot of things only give breaker ratings and not actual current draw (or even motor HP), so load calcs aren't easily possible. I'm no electrician, but I know better than to sum up the branch circuit breakers to get the main breaker sizing.
 
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Yes, 200 amp. It’s pretty standard and affordable, not really any more expensive than a smaller service. Wire size may be a little more but most everything else is comparable in price.
 
200 amp, no question. Assuming you are under 100' or so. Four conductor 4/0 MHF (mobile home feeder) is a 200 amp cable, is for direct burial (or conduit) and runs $3-ish a foot. Panel boxes aren't too expensive. For a shop, go big on the panel, I put in a 54 space 200 amp panel. You'll eat up a lot of space with 220 breakers...each 220 outlet should be served by it's own breaker.

At my distance, turned out to be about 460' of wire, settled on 125amp due to calculated voltage loss. That's on 4/0 MHF. Bigger than that gets expensive fast. I almost always work alone, so there can't be but so much running at one time anyway. Worse case max load for me is a few lights, the welder running and then the air compressor kicking on at the same time. My old shop was on a 60 amp subpanel, and I never popped the breaker or burned it down.
 
The house has a 200A meter, and a 200A main breaker, so I'll probably have to do one of the 320A meters (400A intermittent) if I do a 200A garage service. Sounds easy enough though. I had to research what the heck was bigger than the standard 200A residential meter.
I may have to move the meter anyway, and I'm not sure what size conductor is coming off the pole, but we'll see how that works out. The garage will only be 10 feet from the house, and maybe 30 feet from existing house service to where I imagine the garage service will be (on the side, where I can't see it from the street).

200A it is.

Does anyone know if I can move the meter to the garage, and then put one panel on the garage and one on the house? I'm guessing that would be hitting the "easy button" if the meter needs to be changed and the feed from the pole needs to be re-routed to get it out from under the garage slab. The garage is closer to the pole, etc.

kaiser715 said:
and you forgot one on your list

9. Kegerator
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See, that's why I make these posts. I get forgetful sometimes. :beer:
 
I've got a separate 200 amp service in my shop with its own meter and all. There's a flat fee like $25 or 30 even if I used no electricity but that's never happened. Bill is usually 40 to 70 a month but I have seen 150 to 160 a few times due to leaving the heat pump running for paint curing for example.

South River EMC ran the new underground feed from the transformer box, conveniently in my front yard and on the same property line as the shop for free back in 04 but I believe the policy has changed now.

Even if you feed it off the house as a sub panel still put in a 200 amp box just for the space. Every 240 circuit has to be on a separate breaker, no sharing, although I cheated and tied two 50 a outlets together for my welder, one at the back by the benches and one by the bay doors so I can use my extension cord to reach anywhere in the shop or on the pad outside.

With a big sub panel or panel you can run extra breakers to split up the 120 wall outlets, mine alternate on breakers (left outlet on one right on another in a dual gang box every so often) I can have drop lights, drills or whatever plugged in at the same time and no worries of tripping. I got this idea from the shop behind my grandmas house I used to work in. All the outlets on one wall were on the same breaker, if I was grinding something with a drop light on and a buddy made a tack with a 120 welder we'd have to trip the breaker. I've got 6 120 breakers, 2 for each wall with no bay doors, and one 120 breaker for outlets between the bay doors. Extra outlets over the bench because I hate swapping cords.

One dedicated breaker for lights, and another for the shop fridge, one for outside lights.

Air compressor, welder, window AC/elect heat strip combo and lift all have their own 240 breakers, and 2 240 breakers for the heat pump (30 for AC, 60 for heat strips).

The shop is a metal pole barn and the insulation is crappy so if it's very hot I run both the heat pump and window AC to get it cool. Same in winter I'll fire up both heat pump w/strips and electric strips in window AC to get it comfortable. Then cut off the window unit once comfortable. I don't run them if I'm not out there because it may only be on the weekend, no sense heating or cooling all week. I used to use the window AC only and propane space heat but it's cheaper for me by 100 dollars or so a month after I put in the free used 2 ton heat pump I got by trading some wiring harness labor out.

For a one man hobby shop without the crazy heat or ac setup I've got you'd probably be good with a 60 to 80 amp breaker feeding off the house if you figure the load calcs.
 
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Or two because your over thinking stuff and you intend to have all sorts of expansion dreams.
And yep I trenched cable enough for both.

The electrician didn't flinch....he likes money as much as the next guy. He said I could run a small campground. Wish it was: "what are you thinking?"
 
I have 60 amps feeding my 28x36 shop from the house panel. I have a large 220v welder, 30amp 220v air compressor, a heat pump, and a fridge and all your other normal 110 stuff. My shop sees a lot of heavy use and in the 12 years I have lived here I think I have tripped my 60 amp breaker twice. I think a 80-100 amp service would be plenty for a home hobby style shop unless you were planning on installing a bunch of big equipment.
 
Fabrik8 said:
The house has a 200A meter, and a 200A main breaker, so I'll probably have to do one of the 320A meters (400A intermittent) if I do a 200A garage service. Sounds easy enough though. I had to research what the heck was bigger than the standard 200A residential meter.
I may have to move the meter anyway, and I'm not sure what size conductor is coming off the pole, but we'll see how that works out. The garage will only be 10 feet from the house, and maybe 30 feet from existing house service to where I imagine the garage service will be (on the side, where I can't see it from the street).

200A it is.

Does anyone know if I can move the meter to the garage, and then put one panel on the garage and one on the house? I'm guessing that would be hitting the "easy button" if the meter needs to be changed and the feed from the pole needs to be re-routed to get it out from under the garage slab. The garage is closer to the pole, etc.



See, that's why I make these posts. I get forgetful sometimes. :beer:
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Place a 400 amp meter main combo on house and run a 200 amp service from that to the new shop. That will eliminate the extra monthly meter fees from the power company. That’s the way I setup my house and shop when I built. Just helped a buddy run his new shop off of his service from his house with zero issues running everything you said you would be running and then some.
 
obullfish said:
Place a 400 amp meter main combo on house and run a 200 amp service from that to the new shop. That will eliminate the extra monthly meter fees from the power company. That’s the way I setup my house and shop when I built. Just helped a buddy run his new shop off of his service from his house with zero issues running everything you said you would be running and then some.
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That sounds like the way to go, that should be way more continuous rating than I'll ever need while doing things by myself. If I'm welding at night with the HVAC on, and the compressor turns on, that's going to be about the highest it will ever be.

I'm also wondering whether I can move the single meter location from the house to the garage, because that might be easier than trying to stretch the cabling from the pole to the meter. I don't know if there is going to be enough cable length to re-route so it isn't running under the garage footings. So that would be meter on garage, one 200A panel on garage, then run from meter to the other 200A panel on house. Any insight on that?

I suppose it's not a problem to re-run longer cables from the pole, depending on who is paying for that (hopefully not me). Or I can move the meter down the wall of the house closer to the pole, and maybe move the house panel inside while I'm at it. I'm assuming they're already big enough, and don't need to be re-run with a larger size, etc.

It makes sense that wherever the cabling ran from the pole to the house, that is the exact spot where the garage would fit without a major compromise somewhere else, so the cables would have to move. :mad:
 
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More than likely the current feeder is not big enough to handle a 400 amp service. You should be able to place new meter main combo on shop and tie into a sub panel on the house from it with no issues. One thing to consider is you will have to have a C.O. on the shop before they will place a meter to have permanent power at the house.
 
obullfish said:
More than likely the current feeder is not big enough to handle a 400 amp service. You should be able to place new meter main combo on shop and tie into a sub panel on the house from it with no issues.
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So you're saying I likely need new cabling from the transformer? If that's the case, the meter can go anywhere.
 
Everybody keeps throwing around the terms 200amp and 400amp service. At what voltage?

I have a 50 KVA transformer feeding both my houses and shop. Each has its own meter. The power company (Duke) has ran all 3 for free. There's a ~$20 monthly fee on the shop, and ~$10 on each house. I was gonna run the shop off of the house, but 200ft of wire capable of running a 10hp compressor or lathe was gonna take a few years to break even, and then the house would probably dim every time I hit a big load.
 
Fabrik8 said:
So you're saying I likely need new cabling from the transformer? If that's the case, the meter can go anywhere.
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That’s something that your power provider will have to look at and determine. More than likely they didn’t oversize the wire that would handle the new demand. If it were my house I’d replace what I had on the house with a 400 amp meter main combo then a sub panel in the shop fed from house panel.
 
jeepinmatt said:
Everybody keeps throwing around the terms 200amp and 400amp service. At what voltage?

I have a 50 KVA transformer feeding both my houses and shop. Each has its own meter. The power company (Duke) has ran all 3 for free. There's a ~$20 monthly fee on the shop, and ~$10 on each house. I was gonna run the shop off of the house, but 200ft of wire capable of running a 10hp compressor or lathe was gonna take a few years to break even, and then the house would probably dim every time I hit a big load.
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240 volts
 
jeepinmatt said:
Everybody keeps throwing around the terms 200amp and 400amp service. At what voltage?

I have a 50 KVA transformer feeding both my houses and shop. Each has its own meter. The power company (Duke) has ran all 3 for free. There's a ~$20 monthly fee on the shop, and ~$10 on each house. I was gonna run the shop off of the house, but 200ft of wire capable of running a 10hp compressor or lathe was gonna take a few years to break even, and then the house would probably dim every time I hit a big load.
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I'm getting an electrician in the mix to sort some of this out.

obullfish said:
That’s something that your power provider will have to look at and determine. More than likely they didn’t oversize the wire that would handle the new demand. If it were my house I’d replace what I had on the house with a 400 amp meter main combo then a sub panel in the shop fed from house panel.
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Ah, makes sense now.
 
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I think putting 400amp at the house and 200 amp at the shop is what I’m going to do. I think you could take your 200amp panel and use it in the shop and feed it from your new 400 amp service.

around me, the utility provider wants their transformer within 200’ of the 400amp service. And, unlike a 200amp service where you provide the meter base, etc, our utility provider supplies it for the 400 amp service.

I suggest you call their engineering group to work out the details.
 
rockcity said:
I think putting 400amp at the house and 200 amp at the shop is what I’m going to do. I think you could take your 200amp panel and use it in the shop and feed it from your new 400 amp service.

around me, the utility provider wants their transformer within 200’ of the 400amp service. And, unlike a 200amp service where you provide the meter base, etc, our utility provider supplies it for the 400 amp service.

I suggest you call their engineering group to work out the details.
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That's what I did. I have 2 200 amp panels in my storage room and had them bias as many heavy user breakers to my A panel. I should have plenty of juice left on B panel for a 200a feed to my future shop. I also buried a dummy water line and a 2" conduit half way across my yard. I didnt want to tear up my driveway and concrete or have to trench clear around d the house in the future :lol:
 
rockcity said:
I think putting 400amp at the house and 200 amp at the shop is what I’m going to do. I think you could take your 200amp panel and use it in the shop and feed it from your new 400 amp service.

around me, the utility provider wants their transformer within 200’ of the 400amp service. And, unlike a 200amp service where you provide the meter base, etc, our utility provider supplies it for the 400 amp service.

I suggest you call their engineering group to work out the details.
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Will do. I'm about 180 feet plus pole height, so I'm right at 200 feet probably.


Also, my neighbor who just built a fence in the power line easement with no access gate is going to be pissed. :D
 
awheelterd said:
That's what I did. I have 2 200 amp panels in my storage room and had them bias as many heavy user breakers to my A panel. I should have plenty of juice left on B panel for a 200a feed to my future shop. I also buried a dummy water line and a 2" conduit half way across my yard. I didnt want to tear up my driveway and concrete or have to trench clear around d the house in the future :lol:
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Directional boring is cheap....

Based on a situation a friend finds himself in I've sworn off to giving advice online in public.
But look into "tap rule" I think it may simplify your plans.

Note I don't do resi nor will I work in Mecklenburg county under any circumstances so you may have different rules.

I know a very good electrician in the area that does however
 
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