which is better 120 or 240

[Dana Miller]

I'm facing a decision along these lines right now. I just received all my Dad's old workworking equipment and am setting up shop in the third bay of my garage. The stinking cheap builder only put one outlet in the WHOLE garage. Luckily, the breaker box is in the garage and has about

15 slots still unused.

The first step is to check the motors for current/power requirements and multi-voltage capability. Here is what I found for 120/240V

DC : 15A/7.5 TC : 12A RAS: 11A/5.5A DP : 11A/5.5A

Throw in a shopvac, assorted routers, and other hand tools, maybe some lighting, and sundry stuff and you quickly see that power management is a problem.

The DC won't spool up to full speed before kicking out the 15A breaker on its circuit. I've NEVER actually managed to get to run yet. Nevermind running it WITH comething making sawdust. When you consider that the DC works equally hard wheather or not I'm cutting at the moment, and its fan load keeps it close to its rated power for its entire run, that circuit is a candidate for considerable I^2*R heating. Considering that the DC also starts under load, it has the worst life.

Starting the TS or RAS causes a considerable ammount of dimming of the halogen light on the same circuit. Starting puts a motor in its max current condition. Now having the line not sag so badly would help with starting performance and reduce the chance of tripping the whole circuit.

This is what I'm planning on.

1 240V 20A circuit w/2 outlets. One dedicated to the DC. 3 120V 20A circuits with just 2 duplex outlets per circuit. 1 120V 20A circuit for lighting. I hate looking for the blown breaker in the dark.

While selecting the electical hardware at Menards (what color of BORG is that?) I noticed a considerable range in the price and quality of duplex outlets. I chose the commertial grade outlets over the residential grade. The low end outlets get as cheap as $.39. The ones I got were about $2.39. The commertial outlets are supposed to withstand more plug-in cycles than residential. There were industrial grade outlets for about $6.00. If my commertial outlets don't pass muster, I'll go with the industrial.

Here are some advantages I see in configuring some of my heavy loads for

220V.

1). No TWO heavy 220 loads will overload the 220 circuit.

2). Offload the 120 circuits so combined loads are unlikely to cause problems. 3). Reduce the number of running (non stall) breaker trips. The motor's thermal protection should keep you from overloading the motor. Tripping the breaker in the middle of a cut is a bummer. 4). having some 240V outlets already wired allows me to bring in new machinery without worry about their power needs.

I consider the DC the hardest working motor I have. It works an hour for each minute the TS, RAS, Drill Press, or any other tool works. Getting it onto a low current circuit can only help avoid low voltage issues.

How many outlets do you place on a circuit? What current are your workshop circuits? How many circuits?

[Charlie Self]

Dana Miller asks:

I think NEC is still 8 on a circuit. I wouldn't place more than 6. My workshop circuits are 120 volt 20 amp (15 amp for the 3 lighting circuits), and 240 volt

30 amp for the rest. IIRC, I've got 6 or 7 20 amp, 3 15 amp and 5 220.

Charlie Self "It is not strange... to mistake change for progress." Millard Fillmore

[LRod]

Rex Cauldwell's book (Taunton Press; don't have the exact title in front of me) quoting the NEC says there is no limit in residential work. There is a limit in commercial work.

- - LRod

Master Woodbutcher and seasoned termite

Shamelessly whoring my website since 1999

[Pop Rivet]

IMO, you've done a good job of planning for the most part. May I add the following (inline) opinions?

+++ You don't mention wire gauge, but for best contol of voltage drop, 10 and 12 gauge stranded is your best bet. Stranded has more surface area and the wires can dissipate heat easier, especially on very hot days or heavy loads. Stranded also provides lower IE drops. ... I chose the commertial grade outlets over the residential

...

+++ IMO, ckts should be such that if TWO 220 machines are on the same ckt, they should be two that will NOT be used simultaneously. For best motor protection and performance, , and assuming brkr box to outlet runs of abt 50 ft max, total current draw of all machinery that could run simultaneously on a ckt should not exceed 1/2 the breaker rating. If they can run simultaneously, they'll also eventually be started in quick succession, so that deserves some thought too. If possible, and it often isn't, each piece of equipment wants its own ckt.

+++ Same as above for 220 ckts. Depending on how the runs work out, you can often cross-share lighting with equipmen t on theses. You could, say, share the TS lighting with your lathe power run and vice-versa. That way you have lighting on multiple ckts and blowing one breaker doesn't kill lights at the machine that blew it, meaning lights can stay on. I have two switches going into my garage; both for lighting. So, even if I blow a lighting ckt, there is still light.

+++ "Should" being the key word here. It will be pretty much true as long as the normal current draw is not approaching breaker-trip. If that's the case, it's very easy to pop the breaker on simple even momentary overloads. Thus the rating of twice the breaker rating to the equipment draw. Tripping

+++ In my own shop, I have one ckt per machine for 4 machines, and the rest I have calculated so that max draw is less than 3/4 of the breaker rating plus normal expected current draw is less than half. Other than the obvious, the vacuum also gets its own ckt. That actually runs a lot of machinery - when you count beam lights, battery chargers, radio, speaker drivers, couple of flourescent lights, etc. one ckt can go quite a ways. I have it set so that all the easy-to-forget stuff is completely disabled by one of the three switches at the entrance to my shop. The noisy stuff, well that's harder to forget to turn off :-).

Also consider whether you might move something. Say, you want to rip and then cut a 50 ft piece of wood, will your TS be able to do it without being moved? Or do you maybe need another outlet for it in case you have to move it just out of reach of the intended outlet? That's my condition here. I also have a garage stall but sometimes it just isn't big enough in one dimension. And no, I don't cut 50 ft beams! ;-]

I ain't no expert, but it does work out well for me.

Pop

[Tom Bergman]

Before I get into what I have, for you since it sounds like you haven't run circuits yet I'd recommend you run all 20A circuits instead of 15A. Some of the tools push the 15s too hard as you've noticed.

All my 240 stationary tools are on dedicated circuits (the jointer & planer share one, but I only have one plugged in at a time). The plus of this is you can match the breaker to the motor, not a Code issue, but Grizzly recommended it - could save a motor. I used 10 ga wire on all these for two reasons: 1) wasn't sure where the TS would end up, the biggest load, and 2) there was enough wire in the box (100') to run all 3 circuits... Now if I need to move the TS, I can switch breakers around and I'm good to go.

My air compressor is on a dedicated 20A/120V circuit. I have 2 other

20A/120V circuits for duplexes running around the shop. I guess there's maybe 5 per circuit (to lazy to go count). It's a one man shop - not like I'm going to have 5 tools up and running on a single circuit. Normally the DC is running and one tool - regardless of tool it's on a separate circuit so no problems.

My shop is about 65 feet, as the wire is routed so to speak, from the main panel. I used a 50A feed to a subpanel in the shop to reduce total wire runs. This sub feeds all the tools. The lights are on their own circuit from the main panel so I don't lose lights if I pop the feed for the sub, which has never happened. I also have a $15 emergency light in case we have a blackout mid-cut.

[Tim Douglass]

When you look at the answers you've gotten here you can see that there are a lot of ways to skin the proverbial cat (which begs the question of what you are going to do with a cat skin). Your layout is similar to mine. I have 3 20A 120V circuits, each with about 6 duplex receptacles. It means I have so many receptacles that I can reach one from anywhere along my 25' long workspace without taking a step. The number of receptacles doesn't matter with regard to load because I only run one thing at a time, not counting light draw things like work lights, fans or radios.

I put in 2 240V circuits 1 20A dedicated for a DC (which I don't have yet) because the DC is the only major motor that will run while another major motor is running. That circuit has only one outlet on it. The other is a 20A circuit with 4 outlets on it, one for my TS, RAS, the future jointer and possibly planer. Because only one will run at a time I'm not worried about having them all on the same circuit. My lights are on two separate 15A circuits, which is really overkill, but I do that sometimes.

The only things I wish I had done semi-dedicated wiring for are a bandsaw and a drill press, neither of which I have now, but intend to add at some point. Those will both probably 120V tools and shouldn't draw enough to be problems on the existing circuits.

All the 120V stuff is wired with #12 wire, all the 240V with #10. The sub-panel is a 90A, so I think I'm pretty well covered.

Tim Douglass

[Andy Dingley]

240 - I don't know how you 'mericans even keep the light bulbs working on that piddly little 110V stuff.

Mind you, these new metric volts are smaller anyway.

[Lew Hodgett]

As far as the builder is concerned, that's all you paid for.

As far as a distribution design is concerned, let me offer the following:

2P-60A c'bkrs and below are all the same price.

Wire is CHEAP, especially if you standardize one size.

Buy 500 ft spools of wire where possible.

Run as many 240 VAC as you can, dedicated circuits are preferred.

I'd standardize on #10 AWG with a 30A c'bkr where possible.

You'll need #8 for decent size air compressor, say 5 HP.

Remember the only job of the c'bkr is to protect the insulation on the wire, NOT THE LOAD.

If the load burns up, you should of had an overload relay in the circuit.

Use #12 AWG for all 120 VAC circuits backed up by 1P-20A c'bkrs.

I have purposely not addressed the subject of wiring devices (plugs, receptacles, etc).

They are a subject of a separate post.

Have fun in your shop.

If you feel in any way obligated, my fee at one time for a design like this would have been about $1,500.

Enjoy the freebie.

[John Paquay]

A good start.

It's really only a big problem if you don't consider the number of these circuits you'll be using at the same time. Ideally, all large machines and motors should be on their own circuits. In reality, you could put all the stuff you listed on a single 30A 240V cct (and run it all simultaneously), but that doesn't mean that's the best way to go.

It's drawing 15A on a 15A 120v cct, and it's probably drawing 18A on startup. Poof!

You've only used six of your fifteen spare spaces so far, so feel free to grab a couple more while you still can.

I'd give the DC its own 20A 240V cct. It's the only big motor you're likely to use at the same time as another, and you're likely to do that most of the time. You could probably run it just fine on a 120V

20A cct, but it will be happier wired for 240V.

I'd put the lighting on two circuits if possible. It makes things much more safe and flexible down the road, and good lighting can be a huge current draw. It really depends upon how large an area you have and what kind of work you'll be doing, but its damned hard to overestimate shop lighting needs.

Good Choice.

There you go.

NEC does not *specifically* limit the number of general use (which is what most of them will be) receptacles you can place on a 120v cct. It does say that you have to figure 180VA per receptacle for these, so theoretically, 15Ax120V/180VA = 10 receptacles. On a 20A cct, you could theoretically go to 13 receptacles. Either is more than common sense would generally dictate. It's best to group your ccts logically and geographically, and leave yourself some overhead (about 60% of capacity is a nice, reasonable number to shoot for). NEC does require that you use the actual V*A numbers for other than general use receptacles (for example, a refrigerator or air conditioner). It doesn't say you can't combine these loads (and of course you can), but where possible, you are to use the actual loads for these types of items.

Don't even consider 15A 120V ccts, except possibly for lighting -- use

20A instead. The difference in the cost of the breakers and devices is negligible, and you only need to go from #14 to #12 wire to use 20A 120V circuits. There is an NEC option for figuring receptacles and circuits based on square footage (I've forgotten what the exact numbers are for the moment), but logic will probably tell you that you need more than that in a shop, anyway. In a shop, I want receptacles placed no more than 6-8' apart.

You should also keep in mind that per NEC, all 120V receptacles in a garage or similar outbuilding must be GFCI protected, and if your shop is in or attached to your garage, that means your shop must be so protected as well (at least that's how our state and local code officials interpret things).

Hope some of that is helpful.

John

John Paquay [e-mail]

"Building Your Own Kitchen Cabinets"

Glory and Passion No Longer in Fashion The Hero Breaks His Blade. -- Kansas, The Pinnacle, 1975

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[Robert Boucher]

There are 130 volt light bulbs. When used at 120 volts, they provide longer life, but less output (lumens).

[Edwin Pawlowski]

Look at statistics. Many people go through their lives using only one receptical in the garage. The builder is not going to install (pay for) something that many people will never use. The original owners of my house had none in the detached garage.

The builder is not going to be able to anticipate your needs either, as very few homes have a shop as extensive as you will require. So, look at the big advantage you have. The shop can be wired to meet your needs with your design. At least you have plenty of empty slots so you can have many circuits for your tools. Most of us would envy your position. Ed