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200amps to the house - 100amps to the shop... Will it work?

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Forum topic by SuperCubber posted 01-30-2019 02:51 AM 1528 views 0 times favorited 39 replies Add to Favorites Watch
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SuperCubber

1078 posts in 2680 days


01-30-2019 02:51 AM

Hi all,

My wife and I are just getting ready to break ground on a new house. It will include a basement, where I will have a shop (yay!). I have some questions regarding electrical.

- The house is 3500 sqft.
- Basement will be about 1500 sqft, including shop.
- Shop will be set up with a dust collector on 240v, a compressor on 240v, an air cleaner on 240v, and several 120v power tools. Obviously, they won’t be running at the same time. I will most likely have the air cleaner, dust collector and another power tool running all at the same time.

Our current plan is to have 200amp service to the house, other a 100amp sub panel for the shop and 2 minisplits (the rest of the basement will be on the main panel). I’m pretty confident that the sub panel will be enough to meet my needs, but I’m a little concerned about whether or not the 200amp service to the house is enough, while I’m also using the shop.

My builder says it’s plenty, and when I think about the load on the house, that seems to make sense, but I’d like to get some feedback if any of you are in a similar situation.

Thanks for your time.

-- Joe | Spartanburg, SC | "To give anything less than your best is to sacrafice the gift." - Steve Prefontaine


39 replies so far

View Aj2's profile

Aj2

2285 posts in 2193 days


#1 posted 01-30-2019 03:17 AM

It should be fine. The real question is the wire size of the service line drop. How close are you to the transformer how many neighbors do you share the transformer with. Your machines will run fine it’s the surge when you startup 5hp or bigger.
You don’t want to dim the lights in the house every time you start a machine. Big bandsaws and compressors are the worst.
It’s not the end of the world to have a soft service but can be annoying.
This has been my experience here on the west coast.
Good luck

-- Aj

View Mainboom's profile

Mainboom

90 posts in 153 days


#2 posted 01-30-2019 03:20 AM

I have 100 amp to by house and have sub in my shop with 240c. think you will be fine if the builder does not know what your wanting id tell him or fire him lol

-- CRANE OPERATORS START EARLY because iron workers need their heros ready when they wake up

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JAAune

1864 posts in 2712 days


#3 posted 01-30-2019 03:39 AM

Only way to know for sure is to do a load calculation or have the electrician do it. Figure out the maximum amps you’ll draw from the shop at any given time and add that to the amp draw of the house to make sure you’re not pushing over 200 amps.

In your your shop, it’s possible the lights, dust collector, air filter, air compressor and the largest power tool you own will run simultaneously at some point in time.

But chances are, you’ll be fine unless your house is full of energy-sucking devices.

-- See my work at http://remmertstudios.com and http://altaredesign.com

View CaptainKlutz's profile

CaptainKlutz

1394 posts in 1890 days


#4 posted 01-30-2019 06:19 AM

+1 need load calculations run by electrician

Amperage required for typical house depends heavily on appliances with large continuous current draw.
Eliminate the heavy hitters from your home design and you can live with 50A service, especially due to environmental elimination of incandescent lighting.

List of electric devices that suck electric power:
- Electric hot water heaters
- Electric heat
- Heat pump (especially skip those with electric emergency backup heaters)
- Double stacked kitchen ovens
- Separate electric cook top and oven (doubles Kitchen demand calculation .vs. standard 50A single unit range)
- infrared rotisserie oven
- Electric pizza oven
- Electric wood smoker
- Air Conditioning
- Swimming pool and/or hot tub
- Outdoor misting pump systems
- Landscape lighting

It’s easy to go overboard when designing a new home. Once built/owned 3400 sqft house with 250A service that had many of bells/whistles listed above. I had (2) 48 slot panels completely full of breakers. The load calculations of house/appliances limited the garage shop sub panel to 50A. Fewer kitchen toys or less outdoor demand, and shop could have 100A panel.

Best way to ensure you have enough power for work shop in residential area with normal 200/250A service limitation due shared transformers, is to use petroleum for any heating, and keep kitchen appliances to bare minimum.

Best Luck.

-- I'm an engineer not a woodworker, but I can randomly find useful tools and furniture inside a pile of lumber!

View Fred Hargis's profile

Fred Hargis

5552 posts in 2889 days


#5 posted 01-30-2019 11:46 AM

My last three houses (including this one) had detached shops, and a 200 amp main panel with a 100 amp sub in the shop. You would need some really big loads to exceed that capacity. You can be ultra safe by having the loads calculated, but it would take some big stuff to exceed the 200 amps.

-- Our village hasn't lost it's idiot, he was elected to congress.

View GrantA's profile

GrantA

1512 posts in 1803 days


#6 posted 01-30-2019 01:09 PM

If you’re building and it’s an option, go ahead and get more from the start. You’ll only pay for what you use on a monthly basis. I built abut 7 years ago, had a 400a service put in, I have the meter base feeding 2 200a sub panels, one feeds the house and the other feeds my shop. I ran a 150a service to the shop because that’s plenty (40a is for my well which is by the shop). You start adding up things like compressors, refrigerators, freezers, it can get tight quick. I have a full size fridge/freezer in the shop and a 5hp air compressor. One my 5hp DC is finished being built I can pretty well figure with the well if all of that cycled at once which is possible there’s 130a right there. Add 1 power tool under a load and there’s my whole 150a. Not sustained but needed for a minute.
Oh and a window unit AC pretty much stays running. I’ll eventually put in a mini split but the struggle is real!

View Oldschoolguy's profile

Oldschoolguy

62 posts in 232 days


#7 posted 01-30-2019 01:26 PM

If it were me, I’d have the shop wired at 200 also. In today’s world it is better to have to much than not enough….ya never know. Just my 2 cents.

View BlueRidgeDog's profile

BlueRidgeDog

485 posts in 175 days


#8 posted 01-30-2019 01:40 PM

Your electrician should give you a workup sheet that shows how he calculated the recommendation. It is impossible to guess if it will work as we don’t know what type of heat you have, what type of hot water heater, the size of your air conditioner or heat pump etc.

“if” you have gas heat and gas hot water, then yea you are good. For a one man shop, you will only run one item at at time, plus dust collection and air compression. As such my shop is three 20 amp 220 circuits (tools, dust, air) and two 20 amp 110 circuits (lights and outlets). If you have electric hot water, electric stove, a heat pump and two mini-splits AND a shop of 220v tools…then the numbers would likely push you to 400a service….but don’t know as we don’t know what you have.

I have a 15 SEER heat pump with electric backup, an electric hot water heater and an electric oven/range and live well with my 200 amp service BUT I am the only one in the house, so nobody is cooking when I am in the shop. The tools are not big draws except on start (my saw will pull 12 amps at turn on and then idle at 9…most other tools are similar).

View Brawler's profile

Brawler

34 posts in 226 days


#9 posted 01-30-2019 01:51 PM

I upgraded my service in my last house. Just for giggles I put a current probe on each leg of the service panel. I then proceeded to turn on just about everything I could see including oven, stove, and dryer. One leg had 22 amps and the other had 19 amps. My guess is you won’t even come close to 100 amps in your shop unless it is a production shop with several employees and electric heat.

-- Daniel

View CaptainKlutz's profile

CaptainKlutz

1394 posts in 1890 days


#10 posted 01-30-2019 02:05 PM


My last three houses (including this one) had detached shops, and a 200 amp main panel with a 100 amp sub in the shop. You would need some really big loads to exceed that capacity. You can be ultra safe by having the loads calculated, but it would take some big stuff to exceed the 200 amps.

- Fred Hargis

Load calc is always required IMHO.

Funny, my last 3 houses had 200 or 250 service with attached 3-4 car shop space, and provided max of 50-80A for sub panel in work shop after running load calculations?
Guess a lot depends on where home is located, size of home, and number of people living in it.

Here in Arizona, stressing 200A service is easy on larger home with big family.
Typical new build 3500-3800 sq ft home will have (3) 2.5 HP HVAC systems (~45A), 7-9 HP of combined motors on pool/spa/misting (~50A), and kitchen average demand load of 60A. The represents 155A continuous service requirement without laundry, baths, lighting, or anything special added.

As I posted before: If have full compliment outdoor toys, and gourmet kitchen, can have issues.

Another challenge lately is electric cars are popular here in AZ. Adding 50A Tesla super charger to garage can be almost impossible with ONLY 200A service in larger home, as the demand calc requires 125% load rating. That is another big load I missed in earlier list. :(

as always, YMMV
Cheers!

-- I'm an engineer not a woodworker, but I can randomly find useful tools and furniture inside a pile of lumber!

View SuperCubber's profile

SuperCubber

1078 posts in 2680 days


#11 posted 01-30-2019 02:37 PM

Wow, thanks for all the quick replies.

I apologize for not giving more info. I should have been more patient. I was trying to get the post in before my flight departed. Thanks for your patience.

The heat, range and hot water will be gas. We will have double ovens, but that’s about it for fancy toys in the kitchen. We will have an in-ground pool. I estimate the mini-splits will cost me about 25 or so amps from the sub panel, which leaves me with plenty to power the shop.

I don’t see any 5hp tools in my future, though I’d prefer not to limit myself. The compressor is 3.7 and my dust collector will probably be in the 2-3hp range. All of my other tools are below 2hp.

The electric car comment has me thinking though. We don’t have any immediate plans to get one, but it’s plausible that we may venture down that path as time passes in this house.

Thanks again for all the input!

-- Joe | Spartanburg, SC | "To give anything less than your best is to sacrafice the gift." - Steve Prefontaine

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firefighterontheside

20312 posts in 2252 days


#12 posted 01-30-2019 02:44 PM

I have a 400 amp service to the house, but only a 200 amp panel. It didn’t cost anything for the power company to give me that. This way in the future I can expand and have the power needed. 200 sounds small for a big house, but as said, if you don’t have electric heat or hot water and all led lighting it will probably be fine.

-- Bill M. "People change, walnut doesn't" by Gene.

View Woodmaster1's profile

Woodmaster1

1173 posts in 2983 days


#13 posted 01-30-2019 03:50 PM

I have a separate 200amp service for my detached garage and 150 for my house. The city lets me have two separate meters with a minimum charge for the second meter but I have never not used more electricity than the minimum.

View bmerrill's profile

bmerrill

50 posts in 469 days


#14 posted 01-30-2019 04:46 PM

Load calculations With a structure that large, you will want 2-200 amp panels for the breaker spaces for the residence no necessary for the load. 100 amp for the shop would be fine.

Have you considered a whole house backup generator? These are becoming popular. If so, discuss with your electrician so it can be rewired for install at a later date. The generator doesn’t have to serve the whole house, but the electrician can set up the panels where all of the essential circuits are in one panel for service by the generator/transfer switch and the non-essential in the other.

-- "Do. Or do not. There is no try". Yoda

View clin's profile

clin

1035 posts in 1392 days


#15 posted 01-30-2019 10:52 PM

Another vote for a proper load calculation.

100 Amps sounds like plenty for the shop, but you mention 2 mini-splits. Are these two separate mini-splits each running a single head, or are each of these each a multi-zone running something like 4-5 head each?

Obviously the larger units require more power, though mini-splits are amazingly efficient.

As an aside on this new home, if you are looking at using mini-splits for the whole house, that’s a great idea. I have a 3,600 sq-ft home that came with two 5 ton combo units and it sucks. The house really only needs about 3 tons. And in a large house, even with two units (zones), you just can’t get the whole house comfortable at one time.

So it’s horribly inefficient (expensive to run) because 2-3X oversized and doesn’t really keep the house comfortable because different rooms need different amounts of heating or cooling based on the time of day. A single thermostat or two in my case just can’t regulate the temperature throughout a 3,600 sq-ft home.

Bottom line, I will be going to all mini-splits when my units die. I can’t justify replacing them at this point, but when they crap out, I won’t be replacing them.

-- Clin

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