Prompted by suggestions that a shop needs convenient power, I created a (pdf) SU view of my proposed outlet configuration (for one wall), and also a corresponding wiring model:
Bill
BTW, I think I will feel better if I use 120v duplex outlets that are **GFCI protected** in addition to GFCI CB's.
Sorry, you won't get that "simple nod" from me.
Keep it simple. Rather than wiring your 120V outlets to opposite sides of the
240V circuits, keep them separate: run 120V circuits for your 120V outlets, and 240V circuits for your 240V outlets. It's easier to wire, gives you more flexibility in the placement of your 120V outlets, and -- most important -- doesn't limit your 240V circuits to the same 20A as your 120V circuits.Note that you need only two-conductor cable, not three, for the 240V circuits once you've put the 120V outlets on 120V circuits.
You should install _at least_ twice as many 120V outlets as you think you need. I'm kicking myself for having installed only three 240V outlets in my
16x20 shop, but I do have enough 120V outlets (fourteen duplex receptacles).I have found it particularly useful to have a ceiling-mounted 120V outlet with a drop cord on a retractor. It worked so well in the shop that I put another one in the garage, plugged into the other half of the duplex receptacle that powers the garage door opener.
The air compressor could be on the same circuit as either the table saw or the dust collector, since it's unlikely that you'd ever be using it at the same time as either of the others.
Run a minimum of 10ga wire, maybe even 8ga, to your 240V outlets. Using 12ga wire unnecessarily constrains you to a future of small air compressors and table saws. If you ever upgrade to a more powerful compressor or saw, you'll have to rewire. Easier to just put in heavier wire at the outset.
Why? There's no point at all in having both.
I'm going to agree with Doug and Mike both. Motor loads have some high start up currents and your asking for nuisance trips. Don't be stingy with the breakers and circuits. The retractable drop from the ceiling as recommended I've found really useful.
Mike M
The top of my workbench overhangs the support frame by about 5 inches. I put a 120V duplex every 2.5 feet or so along the frame under the overhang, facing out into the shop.
This keeps the top of the workbench clear of cords running from the back wall (as pictured in your "garage" sketch) when using sanders, heat guns, etc.
I'm sure you already know that the lights should be on their own circuit so that no tools can take them out and plunge you into darkness.
The last is just silly...
I'd (more or less) agree w/ the other posters...
Agree on separating the 120V on own circuits and moving up to 30A/10ga over 20A/12ga for at least a couple of the circuits (and if do any, might as well do all).
Slight disagreement w/ at least one suggestion...30A @240V is enough for any reasonably efficient 5-horse single-phase motor and given that going to >30A outlets raises compatibility and cost significantly, I don't see any need/justification for more than that for anything other than a dedicated welder circuit or somesuch. Presuming, of course, that the distances are reasonable so that voltage drops are 5% or less and this is a typical home shop, not commercial or a behemoth thing...
Agree that the "never enough" for 120V and the overhead are certainly also truisms as well as the admonition for lights to not be on work outlets.
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Never combine two motor loads on one circuit. The simultaneous starting current will typically take out the breaker when you least want it to.
Two motors on any breaker / circuit is a big no-no and will also not protect your equipment from any locked-rotor current. This is when the equipment jams or shorts out and the circuit breaker is sized wrong for that piece of equipment (big enough to carry the two motors), does not trip and your motor windings go up in smoke. Bigger repair bill and possible fire hazard.
Proper motor protection circuits found in industry typically have two levels of protection, one for the large starting current and one for the typical loaded running current. Anything lasting longer than the two situations, at that current level, will trip out the breaker / circuit interupter.
In home usage only one level of current protection is typically afforded with a simple breaker. Don't defeat it by combining two motor devices. The Electrical Inspector would advise against you doing this, if he catches it or you ask.
I'd (more or less) agree w/ the other posters...
Agree on separating the 120V on own circuits and moving up to 30A/10ga over 20A/12ga for at least a couple of the circuits (and if do any, might as well do all).
Slight disagreement w/ at least one suggestion...30A @240V is enough for any reasonably efficient 5-horse single-phase motor and given that going to >30A outlets raises compatibility and cost significantly, I don't see any need/justification for more than that for anything other than a dedicated welder circuit or somesuch. Presuming, of course, that the distances are reasonable so that voltage drops are 5% or less and this is a typical home shop, not commercial or a behemoth thing...
Agree that the "never enough" for 120V and the overhead are certainly also truisms as well as the admonition for lights to not be on work outlets.
All my 120v shop outlets are quad boxes, with the left outlets on a separate breaker than the right ones. I run 12/3 to them and use a ganged breaker so you never have a half-live box.
I've found a ceiling mounted 240v outlet to be *very* handy. It's not a locking outlet; if you trip over the cord you want it to just pull out.
I have two sets of lights - the regular basement lights, and extra shop lights. One tripped breaker is not enough to plunge the shop into darkness.
All my shop-specific circuits are off a shop-specific panel, which I can disconnect at the main panel for safety if needed.
Nonsense.
Only if you turn both of them on at the same moment -- a rather rare occurrence in a one-man home workshop, I'd say.
More nonsense.
You have a serious misunderstanding of the purpose of overcurrent protective devices. Circuit breakers are there to protect the branch circuit wiring,
*not* the loads that are plugged into the receptacles on that circuit. If a particular load needs some specific level of overcurrent protection, that is achieved by fusing that load.We're talking about a one-man home workshop here, not an industrial installation.
One-man home workshop, remember? How often will two tools be operated simultaneously?
Nonsense. How often do you turn two motors on at the same time? How often do you *use* two motors at the same time (unless one of them is the dust collector)?
There is _absolutely nothing wrong_ with the OP putting his table saw and air compressor on the same circuit, or his drill press and jointer. They will
*never* be in use at the same time -- and even if they are, it's not likely to be a problem unless they're switched on simultaneously. Now you tell me how often that's going to happen. One-man home workshop, remember?
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What he said... :)
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From your nonsense comments I see you must operate your compressor with a manual on/off switch. Imagine you recommending a person operating a table saw to have it stall in the middle of a cut because they forgot to turn off the air compressor. You give dangerous advice here.
I don't now what you kind of air compressor you operate but real compressors have a pressure sensor on the tank to keep the pressure within a range set by the operator.
As far as overcurrent protection, you have no idea. Don't even try to convince me of anything in that regard.
I was trying to display some common sense and adherance to most electrical safety codes. You could try reading yours.
Nonsense.
Only if you turn both of them on at the same moment -- a rather rare occurrence in a one-man home workshop, I'd say.
More nonsense.
You have a serious misunderstanding of the purpose of overcurrent protective devices. Circuit breakers are there to protect the branch circuit wiring,
*not* the loads that are plugged into the receptacles on that circuit. If a particular load needs some specific level of overcurrent protection, that is achieved by fusing that load.We're talking about a one-man home workshop here, not an industrial installation.
One-man home workshop, remember? How often will two tools be operated simultaneously?
Nonsense. How often do you turn two motors on at the same time? How often do you *use* two motors at the same time (unless one of them is the dust collector)?
There is _absolutely nothing wrong_ with the OP putting his table saw and air compressor on the same circuit, or his drill press and jointer. They will
*never* be in use at the same time -- and even if they are, it's not likely to be a problem unless they're switched on simultaneously. Now you tell me how often that's going to happen. One-man home workshop, remember?--- news://freenews.netfront.net/ - complaints: snipped-for-privacy@netfront.net ---
While I agree with you, just to play devil's advocate, I usually run my
2HP dust collector (240v) simultaneously with a 3HP tables saw, planer or bandsaw. That said, all my 240v tools are on dedicated circuits.I do have the 240V shop heater (Dayton, ceiling mount) on the same 240 circuit as the shaper, simply because I don't use the shaper that often (and I ran out of slots in the subpanel).
Compressors are a strange beast, since they may start at anytime the pressure switch hits some threshold (yet again, I've got mine on a dedicated 120v/20A breaker).
scott
No matter how many you put in there never seems to be enough or one in quite the right place.
I have a row of outlets running down the centre of the ceiling in my garage/workshop.
OK, I'll give you that one. The rest of your post was complete nonsense.
Point out exactly what errors you imagine I made in that regard. Hint: you are completely clueless if you think that branch circuit overcurrent protection has anything to do with protecting the loads that are plugged into that circuit.
Had you actually managed to do so, it would have been its initial appearance in your posts.
I'm quite familiar with mine; much more so, apparently, than you are with yours or any others. Here's a link to mine; perhaps you'd be good enough to point out where it prohibits putting two motors on the same circuit.
Don't presume to lecture me on residential electrical installations. You have no idea.
Ayup ...
Ayup!!
BTW, you're getting mellow in your old age, Doug! :)
As are mine.
I run mine on a 120v non-dedicated circuit that, being in a garage "shop" on residential property, is required by local code to be GFCI protected, but I've never had any trouble with the setup at all. The 20A circuit is shared with a small fan, some undercounter fluorescent lighting, battery charger, and the occasional shop vac.
One of the good things about a dedicated circuit is that it's exempt from GFCI protection requirements in most locales where they are required in "garages" (which is most of them in the US).
Thanks, Swing, I've been working on that actually...
IIRC if you use a NEMA L5-20P on that circuit, the GFCI isn't required. That was the approach I took (since I'm also in the garage).
scott
Do keep in mind that Josepi is posting from the UK, where the code may differ.
scott
I bought a "shop specific" panel already. I've already considered that the lighting should be on separate circuits. I'm glad I bought a bigger panel than I thought I needed at the time (I bought the 24 pole one Lew advised).
Thank all of you for helping me to learn more about these matters!
I am surely not an expert and don't pretend to be one here. I have a couple of follow-up questions.
I think that the "worst" part of this whole operation may be drilling vertically up into the attic where there are already so many wires coming out of the main panel--and it's neer impossible to view from the attic because it is so close to the eave. I suspect I'll be "fishing" with a coathanger, stapling 8 feet along the attic framing and then going down into the wall. I think that my own standards are higher than those who have worked in the attic before...I've started wrapping plastic conduit around some of the small wires passing through.
I hope I'm not the only one who has learning something from this thread. Thanks!
Bill
Your point is well-taken. Unfortunatey, I'm not fully comitted on where the tools are going to be (I may decide I want the DC closer to the door to improve the sound-level). Dedicated 240v lines seems to maximize flexability, which seems appropriate. Thanks for making me think!
Bill
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