# Woodshop Electrical Requirements - Concurrently running tools



## cathode (May 18, 2014)

I'm currently planning out a new woodshop that will be approximately 14ft x 28ft. It's attached to the house, but due to the distance from the house's load center, I think it will be preferable to install a new small subpanel.

With that, I'm trying to size the feeder for the sub. I realize it doesn't make sense to consider ALL the tools that will be in the shop, only the ones that are running at the same time. The absolute most I can think of, which factors in future upgrades to my existing tools, would be:

*Lights: 120V, 120W x 8 fixtures = 8A
Dust Collector: 240v, 3-5HP = 10-16A
Tool in use: 240v, 3-5HP = 10-16A
Air compressor: 240V, 5HP = 16A
Electric heat: 240V, 2500W x 2 heaters = 21A*

I added in the air compressor because it could kick on during operation of anything else.

This gives me a total running load of 77A. Because breakers need to be sized so that the full load does not exceed 80% of the rated amps, I would need to go up to a 100A feeder. If I ditched the heaters off the shop subpanel or used gas heaters I could likely get away with a lot less.

Am I missing anything? I'm also unsure as to whether 5HP is a reasonable allowance for an air compressor in a woodshop. I could see an auto-body or machine shop needing a lot of air for running hungry tools but I imagine I might be fine with a 2HP compressor realistically.


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## bbasiaga (Dec 8, 2012)

Seems like you are on the right track. I don't know how much air you plan to use, but I've got a 20gal 110V from one of the big box stores. I only charge it up when I'm going to use it, and I can nail a lot before it has to kick back on. If you are going to blow a lot, or use it for spraying, you'll want the biggest one you can get. I spray with a separate HVLP system, so not a concern with me. I also don't use an air powered grinder or anything. Is this a production shop or a hobby shop?

If you've got a way to go to gas heaters easily it will cost you more up front, but save you a ton of operating cost. I'd highly recommend it.

Brian


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## rwe2156 (May 7, 2014)

First, I am not an electrician I know enough to be dangerous BUT I've done quite a bit of wiring in my life and so far, nothing has burned down.

Second, I STRONGLY urge you to consult an electrician before you do anything.

I don't think you can calculate the load that way. You'll never draw that many amps with all the machines running. Correct me if I'm wrong, but amperage rating on motors is usually FLA (full load amps). The only machine that would come close is a compressor (when running).

I ran my entire shop on a 60A feed that was a 1200 sf shop with a 5HP compressor, 240V arc welder, 2/3HP, 2/2HP machines and a dust collector plus about 20 8' T12 lights. Never had a problem at all. I would suggest a portable 2HP compressor that way you have flexibility to move it around.

I think a 60A service should work. You can use split breakers for 120 if you need more room in the box. You can put all your 240V machines in one circuit. The compressor and DC should be on dedicated circuits. Lights and outlets on separate circuits.

5HP compressor is WAY too big for a ww'ing shop. I have a 5HP 80gal compressor in my mechanic shop that feeds the airlines in my ww'ing shop. It is a beast and pulls ALOT of juice when its running.

Similarly, a 5HP tablesaw is totally unnecessary expense for the average ww'er. They are applicable to a commercial shop with power feeders.

Also for a shop that size a 5HP DC would also be overkill IMO.

Bottom line: I think your overestimating what it will take to run your shop.

*Once again, PLEASE consult an electrician.* I learned by experience you can hire a young man to moonlight a job and get lots of freebies, too like wire. They can also buy the materials far cheaper than you can. The savings on the wire and conduit alone will offset the labor expense quite a bit.

Also, I recommend running all your circuits in conduit or armorflex. The lighting is much easier to wire and you will be able to change/add/extend circuits or add outlets and switches very easily.


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## cathode (May 18, 2014)

Thanks for the input. I did consult an electrician (me). I currently have a Husky 30gal air compressor with I think a 1.5HP or 2HP motor, i have the HF 2HP dust collector, and I realize that tools don't draw their FLA all the time but when they do is usually when it's most inconvenient…

I'll look into gas heaters though, although the ceilings may not be tall enough (12ft sloping down to 8.5ft) to hang a gas heater.


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## Rob_s (Sep 12, 2016)

I'm finding, personally, compressed air to be much less of a requirement in today's shops due to the availability of 18v cordless replacements for many of the tools. I went with a California Air Tools 11v 10 gallon because of this and am pretty happy so far. So you might not need a massive compressor either.


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## cathode (May 18, 2014)

Rob - agree 100%. I don't even own a corded drill, and the only reason right now I would think of buying one is if I needed it to mix things, e.g. drywall mud or thinset.

That being said, I really like with air-powered drills is that the air typically blows out of the bottom of the handle so clearing the dust from around a hole you just drilled takes half a second at most.


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## MrUnix (May 18, 2012)

> I'm finding, personally, compressed air to be much less of a requirement in today's shops due to the availability of 18v cordless replacements for many of the tools.
> - Rob_s


Do you do any finish spraying or media blasting? I don't use air powered tools often, but I do spray a lot of stuff and couldn't do most of it without a decent sized compressor. Ditto for media blasting. If all I were using it for was to blow chips off the workbench or fill up pneumatic tires, then a smaller one would certainly work, although it does limit what you can do with it in the future should the need arise.

Cheers,
Brad


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## splintergroup (Jan 20, 2015)

I agree with Unix, I have a 60 gallon 6HP and it'll run constantly when I'm spraying or when I'm flushing the irrigation system 8^)

My sub panel is 60A, never had any issues, but my DC (2HP) is never run when I'm running my compressor. Typically I'll fire it up at the start of the day then shut it off. Plenty of air for the general stuff but that extra oomph pays off when needed.

If you really want airflow, a two stage will fit the bill, but that's when things get pricey.

Dropping the electric heat would be the first thing I'd do. Electric heat is high dollar, especially if you have gas available (assuming the cost of the swap is reasonable).


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## JBrow (Nov 18, 2015)

William Shelley,

By my way of thinking, the most difficult part of the upgrade is running the feeder cable. Replacing an undersized load center can also be a difficult chore. While your load calculations may be spot on, having additional and perhaps never needed capacity can save from having to re-do rather difficult tasks later on should you guess wrong. Having the ability to upgrade electric service later on could be as simple as doing nothing or swapping out an undersized breaker. If the additional capacity is never needed, I guess it is a waste of a few dollars. But that is balanced considerable cost of re-doing the electric to get the added capacity should it be needed.


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## OSB (Dec 16, 2016)

You probably won't leave the compressor on 24/7, I suggest you leave it off when you know you are going to use your dust collector and a high current tool.

LED lights would not need a kilowatt.

Insulation will work out cheaper than electric heat pretty quick.

If you ever see yourself needing a phase converter for some big boy toys, you might want to budget for more power but if you have your woodworking habit under control, you could try to get by with less than you have planned probably.


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## runswithscissors (Nov 8, 2012)

When I was doing my shop, I looked at 60 amp panels. The guy in the hardware store (a real one, not a BORG) pointed out that a 100 amp panel would actually cost less, and would give me the capacity to expand if needed. I heeded his advice, and have not regretted it.


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## wapakfred (Jul 29, 2011)

Ditto everything above: the 100 amp isn't going to cost that much more than anything smaller, start with it and don't look back even if you think it's overkill. Keep the cpmpressor switched off, unless it's in use. Here's why: a sudden failure like a burst hose could happen when you're not in the shop and start it running. It will keep running and could catch fire is it overheats…at the very least it could use a lot of juice if it runs for a long time. Lastly, if at all possible, choose a heat source other than electric. You may find you need to keep the shop heated to above freezing all the time (to protect some finishes, glue, and whatever) and electric heat will challenge your will to do so.


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## rwe2156 (May 7, 2014)

William if you're an electrician you should know you don't size a service panel for everything on at full load all the time. I'll bet if you check your main panel and add up the breakers it exceeds the main breaker amperage.

I've had 3 service panels installed by electricians over the last 10 years I've asked them about the load aspect. They all told me you the same thing: you size a panel more by the # of circuits you need than the amp draw.

As you know, the key is dedicated circuits for compressors, DC, etc. You should be able to run your entire shop on a 60A subpanel. I did for years with no problems, and that included a 5HP beast of a compressor.


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## OggieOglethorpe (Aug 15, 2012)

I think your DC circuit is too small if you really plan to go over 3HP.

I have a 3HP JDS cyclone, and it's on a 30A circuit. Startup current is in the 80A range for a few seconds, then it ramps down to about 18A and stays there. I know this because I had a bunch of issues with remote controls back when I installed the unit, and we did a bunch of real world measurements to determine actual needs.

You can also keep in mind that machines like planers, jointers, and saws when up to steady speed and running no-load, use far less power than under load. I have a SawStop 3HP ICS and DJ-20 running on the same 20A circuit  (I know, virtual electricians… ;^)) and often leave both running as I go back and forth ripping and edge jointing in my one man shop with no issues at all.


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## LittleShaver (Sep 14, 2016)

Go big. Leave yourself room for expansion and a possible second user. Who knows what your future needs will be.


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## cathode (May 18, 2014)

Lots of good points here. There's a significant price jump after 60A, for example the feeder breaker in my main panel costs $9 for a 60A, 2-pole, or $35 for a 70A, 2-pole. Wire gauge is also a factor.

I typically oversize the wires on branch circuits that are running a lot, or have really high inrush current demands. For instance, I ran 8awg for a 30A, 240v feed to my rack of computer server equipment because it runs 24/7 and draws in excess of 3500w with everything on.

The air compressor and possibly dust collector should be the only tools that actually start under load, I think I will oversize the wires for these circuits.

I might stick with electric heat just because the cheapest gas heater I can find starts at almost $400, and that doesn't include the cost of getting the gas plumbed into the shop. I have access to tons and tons of 4" and 5" thick polyurethane isocyanate insulation surplus from my workplace, it's R-7 per inch so 2×6 walls with that much insulation should maintain temperature pretty well even with like a small portable electric heater (for now).


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## cathode (May 18, 2014)

Another big draw might be my homemade 19" bandsaw project. Currently I have a 1hp motor on it but I think that's going to be woefully underpowered for resawing 12-18". I plan to bump that up to a 5hp or possibly a 7.5hp 3PH motor with a VFD to turn single phase into 3 phase.


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## JBrow (Nov 18, 2015)

William Shelley,

I looked at the equipment in my shop and conclude that the load estimates your proposed are probably too modest in some cases and excessive in other cases. The power requirements of equipment in my shop are summarized below and hopefully can be helpful as you try to nail down your power requirements.

MOTORS
For your purposes dividing 745 watts (1 hp) by the voltage seems to understate the Full Load Amperage of motors. Checking the motor plates in my shop I found that the following

5hp, 240v motor requires a Full Load Amperage of 22 amps
3hp, 240v motor requires a Full Load Amperage of 13 amps
1hp, 115/230v motor requires 11/5.5 amps

LIGHTING
As OSB stated, shop lighting requires a modest amount of power if LED lighting is used. I recently picked up a 4', 4500 lumen LED strip light at Walmart. The package states the lamp requires 40 watts. If you illuminate the workshop to yield 35 lumens/square foot, three lights are needed requiring 120 watts of power. A 120v/15 amp circuit could power up to 36 of these lamps (probably equivalent to daylight brightness on Mercury).

As aside, after hanging this Walmart light I am skeptical that it is outputting 4500 lumens, although it does pump out a lot of light. Also a shop illuminated at 35 lumens per square foot should be very bright.

ELECTRIC HEAT
The CeramicCircuit Infrared Radiant Heater, model 945CL, is a 240v 1000 watt heater and draws 4.2amps. I have three in my 450 sf shop and these draw a total of 12.6 amps and output a total of about 10,000 btus.


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## rwe2156 (May 7, 2014)

Good points, Jbrow.

William, what could you possibly be doing with a bandsaw that needs a 7.5HP motor????? Maybe you need a sawmill?

No doubt 1HP on a 19" bandsaw is underpowered (NOW we're talking FLA ;-). My 19" bandsaw is 2HP & does just fine resawing 11" hard maple. BTW the blade is a big factor on power req's.

Aha - just saw your signature that explains a lot :-D


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## OggieOglethorpe (Aug 15, 2012)

One more thing on compressors…

I don't spray with compressed air, because I have a 4 stage HVLP system. Since I don't use air for much else besides inflating, nailing, and dusting, I've had the same small portable compressor for 20+ years. If I were doing it over, I'd still buy the HVLP, as it's portable and I'm not tied to the shop, and it's always clean, dry air. The small compressor is also portable.

I have 18v impact drivers and rotary cutters / grinders, electric sanders, etc… Every time over the last 2 decades where I've tried to convince myself I needed a big compressor, I've ended up passing on it. Even now, as that unit starts to die, it's hard for me to justify something beyond another $99 6 gallon home center replacement.


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## PaulHWood (Mar 26, 2012)

No heater and lights are on another breaker, and I have a 60 amp subpanel which works just fine with the same calculations you have, tool, dc, and potential for compressor to kick on


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## cathode (May 18, 2014)

> Good points, Jbrow.
> 
> William, what could you possibly be doing with a bandsaw that needs a 7.5HP motor????? Maybe you need a sawmill?
> 
> ...


My saw isn't done yet but I plan on running the blade quite a bit faster than a typical small shop bandsaw. Something in the range of 6000-8000 SFM.

Putting VFDs on tools and setting them up with a 1-3 second ramp-up should help reduce inrush current needs, I would imagine.



> One more thing on compressors…
> 
> I don t spray with compressed air, because I have a 4 stage HVLP system. Since I don t use air for much else besides inflating, nailing, and dusting, I ve had the same small portable compressor for 20+ years. If I were doing it over, I d still buy the HVLP, as it s portable and I m not tied to the shop, and it s always clean, dry air. The small compressor is also portable.
> 
> ...


My 30 gallon cycles frequently if I'm using my framing nailer for home improvement stuff or for assembling outdoor things e.g. raised beds


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## stevepeterson (Dec 17, 2009)

> I don t think you can calculate the load that way. You ll never draw that many amps with all the machines running. Correct me if I m wrong, but amperage rating on motors is usually FLA (full load amps). The only machine that would come close is a compressor (when running).
> 
> I ran my entire shop on a 60A feed that was a 1200 sf shop with a 5HP compressor, 240V arc welder, 2/3HP, 2/2HP machines and a dust collector plus about 20 8 T12 lights. Never had a problem at all. I would suggest a portable 2HP compressor that way you have flexibility to move it around.
> 
> I think a 60A service should work. You can use split breakers for 120 if you need more room in the box. You can put all your 240V machines in one circuit. The compressor and DC should be on dedicated circuits. Lights and outlets on separate circuits.


I agree with rwe. 60A can power a lot of tools. I ran my 300sf shop with a 50A breaker. My heating load was smaller than yours. My shop had a 5HP dust collector and a 5HP tablesaw, but no compressor. The key is to start the dust collector and let it come up to speed before turning on the tablesaw. An autostart dust collector might be too much.

The biggest things in the original power list are the heater and the air compressor. Maybe you could turn off one of the heaters when the dust collector is running. In fact, running the dust collector will be adding 1000-2000W of heat into the room as long as you don't vent outdoors. The air compressor could also be downsized if needed. Also, half of the lights could be put on the other circuit so the total draw would only be 4A at 220V.

Sure, you could upsize the feed to 100A if the cost differential is not too great. I think you could get by on 60A though.


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## cathode (May 18, 2014)

An update: I'm pretty sure at this point that I'm going to be purchasing a Baileigh JP-1686 jointer/planer hybrid which has a 5.5HP 3-phase motor. Therefore, to supply 3ph to the motor, I will need a Variable Frequency Drive rated for approximately 200% of the HP of the motor (I'll probably just buy a 10 or 15hp VFD), and the NEC dictates that a supply for a VFD needs to be sized to 125% of the rated input of the VFD regardless of what it's powering. A 10HP (7.5kW) VFD typically draws 33-35A so therefore the minimum breaker size for that circuit would be 50A.


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## klassenl (Feb 13, 2011)

Just for reference: my shop has run on a 30A breaker for a number of years now. The biggest thing I have is a heater it draws 21 amps. With the heater going, the lights and one tool at a time I have never had problems. The wire that my new shop is fed with is rated at 70 or 80 amps I was just too cheap to buy a new breaker.


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