[OP]
Member
I'm slowly progressing on the shop;I've finally decided to power the shop with sub-panel off the house panel.
Shop electric:
(1) 15 amp lighting circuit;
(1) 15 amp HVAC - minisplit
(2) 15 amp recptl. circuit
This building is small; won't have any major woodworking tools- those go in another building.
My question is what to use for the sub-panel? I found 70amp load center and a 60amp main lug and a 70amp main lug at Home Depot- use one of these or is there something better?
thanks
Member
There are local codes that define what you are trying to do. If you really want to know the right answer, ask your local inspector. They are usually very accommodating and helpful. I'm not trying to be flippant. Decades of working in electrical construction have taught me this is the right approach. You'll sleep better.
Contributor
I put in a 12 slot Square D. Don't remember the amperage rating. I feed it off a 50 amp breaker in my main box. Since I work in the shop by myself, I generally only have one tool running, plus my dust collector. It seems that over time, I am gravitating to 240 volt tools and each one takes two slots. I did get a 240V breaker that also includes two 20 amp 120V circuits, which helped me with the number of slots available.
Mike
[I have a solar system and they fed the solar into my sub panel, so that takes two slots, also. All passed by the local inspector. So with the solar, I have 10 "available" slots, 5 of which are 120V (but with the double breakers, they don't really take 5 slots).]
Last edited by Mike Henderson; 01-06-2015 at 7:59 PM.
Go into the world and do well. But more importantly, go into the world and do good.
Contributor
I wouldn't put anything less than 95-100amp service in. I put a 40amp service in the garage and found that a 100 amp was the way I should have started. A few bucks more runs Saw,dust collector, heater,radio,lights,chargers,compressor,etc It doesn't take long to find the use or 100amp service.....
As Julie said, there are codes that define how this should be done. Doing it yourself and doing it wrong can be a serious mistake. It is best to get professional help. Inspectors are good sources. You can also get quotes from electrical contractors if you tell them what you are trying to do they can tell you what it will cost to get it done. Your insurance may have problems if you do it yourself and have problems later, such as fire or someone gets hurt. Fixing a bad electrical job after the walls are in place is much more costly than getting it done right the first time.
Lee Schierer
USNA '71
Go Navy!
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[OP]
Member
Here is what I'm working toward-
Running a new 200amp to the house (60amp now); two sub panels, (1) 100amp to large
workshop with table saw , etc
and one subpanel to the small shop I'm asking about. All this will
be inspected. The building inspector and PoCo engineer have already met with me.
Before I approach the elec inspector, I'd like to have a idea
of how I would run the electric
and then get his yea or nay.
Member
Everyone likes overkill, but as the voice of moderation I've got a bunch of big tools (3HP cabinet saw, 3HP planer, 2HP bandsaw, 1.5HP dust collector, etc.) and a bunch of outlets/lights/etc. all powered off a subpanel fed by a 40A feeder line. Haven't tripped it in 9 years.
Also, you may find it cheaper to buy main breaker panels instead of main lug panels. I got a 100A main breaker panel and a bunch of breakers (in sizes I specified) as part of a standard "house panel bundle" at the electrical supplier. Might not make sense for the smaller building, but might be worth considering for the larger shop.
Member
I agree that a 40-50A subpanel should be plenty for the limited number of loads that the OP is talking about. One of the 60A or 70A subpanels from HD should be fine. That is the upper limit for current, not the minimum.
One thing I would suggest is to run 240V even if you are only using 120V lines at the moment. It is only one extra wire and you may want it in the future. I would upsize the 120V receptacles to 20A and split them to different phases of the 240V lines.
And make sure your mini-split can do both heating and cooling. I think some of them are AC only. It should only be a few more dollars to get one that does both.
Steve
Contributor
Commercial electrician got on to me thursday for running 30amp breaker on a hotel heating/cooling unit in garage . I only use the heater but the 30amp breaker gets warm. used 10 guage wire and should have been heavier. Its not hard to underwire based on price..
Better to go bigger than just enough.....
Member
Why go bigger than necessary? Bigger wire is heavier, stiffer, and more expensive. There are already safety factors built into the code.Originally Posted by jack duren
Planning for future expansion is different...that can make sense if you're pretty confident that you'll need more capacity in the not-too-distant future.
Just curious, what's the heating portion of that unit rated at? If it's 30A or less then I'd say you're fine, though to be safe you might want to physically disable the cooling portion so you can't turn it on accidently.
Member
If it's rated for over 30A, you have to wire it at the rated amperage. Never choose wire based on price! Running only the heater doesn't mean you can wire it for a lesser amperage (if that's what you did). If it's wired correctly and the unit isn't faulty, the breaker shouldn't be getting warm. This commercial electrician agrees with your commercial electrician. You wired it wrong.
You're questioning the electrician? Why? I'm sure he's seen the unit and knows exactly what he's talking about.
That heat/cool commercial unit is only designed to run either heat or cool. Disabling one or the other, especially when you don't know what you're doing, is unnecessary and foolish.
I'll never understand why anyone would come to a woodworkers forum to get electrical advice on installations. Or plumbing advice or HVAC advice either. I've seen all kinds of bad electrical advice given here and much of it seems to have been followed. I could write a book on all the bad wiring jobs I've fixed over the years. Just because it works doesn't mean it's properly installed.
This will probably fall on deaf ears, but if you don't know how to properly install electrical, call someone who does. There's a lot more to it than meets the eye.
Moderator
You might want to check your local building code. I believe most electrical codes will call for 20 amp circuits in a shop. Whether or not you plan to use any "heavy" equipment or not, the next guy might.
Member
You're right, I was not envisioning the sort of unit that runs a heat pump forwards or backwards using the same components. My bad.
As for why people might go to a woodworker's forum to get electrical advice...I suspect it's because many people here have gone through the same process. A residential electrician may not be able to tell you what you might want in a shop space. (Or maybe they could, but that would depend on the electrician.) And some people might want to make sure they're not being ripped off by an electrician. Or they're scoping out the job to see if it's within their capabilities or if they need to hire a pro.
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