Fixin' up the electrical ckts in the shop...

[milanuk]

Hello,

Well, it's starting to get a bit nippy here so I'm kind of shifting to indoors mode, and plan to start fixing things up a bit in my shop. Right now the issue at hand is getting a decent number of receptacles around the walls as I insulate, cover (drywall) and paint everything. Right now I've got I think 3 total in a 11x22 room, and I was looking at adding more so I have 4 down each 'long' wall, and 3 on one short wall (the other is a set of double doors to the outside). One of the walls is shared w/ a larger shop room (~20x30' or so), w/ not many more outlets there either. I need to have at least one (absolute minimum), or preferably at least two 240v outlets. One for large power tools like tablesaws, bandsaws, jointer, drill press, etc. that *can* be wired for 240v, so that someday I will be able to maybe get that 3HP cabinet saw and 8" jointer I'm lusting after...

Meanwhile, back in reality, what I'm wondering is this: I had originally intended to run 12/2 120v/20A circuits to the various places, like one for the small shop (big power tools), one for the main shop (air compressor, hand drills, grinder), and one for the outer areas (covered storage, etc.) and then run dedicated 12/2 to the places I figured I needed the 240v circuits. Then in conversation w/ a fellow the other day (fairly successful contractor/shirt-tail relative) about his shop, he mentioned he ran two circuits to all his outlet boxes and combined them when he needed 240v at a given point.

I understand the concepts and concerns behind using 12/3 to each box to make a 3-wire circuit for the 120v outlets. Unless I'm mistaken what this fellow was referring to was using the two hot wires to power each one-half a normal 120v duplex receptacle, and then using the two hots (black and red) for the 240v outlets, thus allowing him to pull *one* cable from outlet box to outlet box, and if the shop layout changes, the 240v outlets can be moved accordingly. Am I missing something here (other than which wire white/ground gets used on the 240v outlet... I'll have to go look that one up)? *P.S. fwiw I'm not intending to replace all the circuits w/ one, just whether it's ok to use both legs of a 3-wire outlet circuit to power 240v outlets as well as 120v outlets*

Assuming that for whatever reasons I were to stick w/ the idea of dedicated 240v outlets, my other question is this: Is there a limit to the number of outlets per circuit? I remember hearing that you are limited to one 240v outlet per circuit. The reason I mentioned two circuits above is that I figured a Dust Collector and a cabinet saw (looking ahead to the future here) coming on at roughly the same time might overload the breaker. But that is likely the only combination that would be running at the same time; the DC and one other large stationary power tool.

Ok, well, enough babbling for now. Please let me know if I'm on the right track here or completely off in left field.

Thanks,

Monte

[Cody Colston]

Monte,

When I wired my shop, I put a 120v, 20a outlet every 4 ft. along the wall, total of 6 separate circuits. In addition, I placed a 220v outlet where I knew I wanted one...Air Conditioner, (future) Dust Collector.

To remain somewhat flexible and to make it easier on me when I upgrade my tools, I used 10-3 wire on some of the individual 120v circuits.

That way, I need merely change the breaker in my sub-panel and the outlet receptacle to convert to 220v. I need not pull wire.

Cody

[ol]

Nostalgia ain't what it used to be.

[/ol]

[milanuk]

Cody,

That's part of the problem right now... I don't know for absolute sure where I'm going to want some things in the future. The Air Conditioner is probably going to get stuck in the only window availabe, but it's also a 120v unit. I have a fair idea where to put an 240v outlet or two for use of things like tablesaw and jointer out in the middle area, and I guess a 240v outlet in a couple corners for stuff like a drill press and bandsaw would be nice as well. The ceiling in the smaller shop currently destined to be the woodworking shop/ reloading room slants from 7' to 9', and there is no way to get above it to snake wires, so I might have to get inventive as far as a couple sections of smurf tube and a couple access panels to make things a bit easier to move around and rearrange down the road.

Just checking on this: am I limited to just one 240v outlet on a 240v circuit, or is it like the 120v outlets, as long as you don't exceed the load rating (80% capacity or whatever) of the circuit)?

Thanks,

Monte

[Cody Colston]

Monte,

I would think that a 240v circuit was like a 120v - you could have as many outlets as you wanted as long as the amperage load didn't exceed the CB rating or wire rating.

But, I'm in over my head already and electrical is not an area I feel comfortable or am qualified to give advice. That stuff can be dangerous if done incorrectly.

So, be patient and perhaps Sonny or Lou or one of the electrical gurus will be along to give you the straight skinny on your questions.

Sorry I couldn't help.

Cody

[ol]

Nostalgia ain't what it used to be.

[/ol]

[TDHofstetter]

Monte, according to the NEC there is no maximum number of receptacles which can be fed by a single circuit provided the circuit is not overloaded by the equipment drawing current through that circuit... 120VAC or 240VAC. Feel free to add more if you like - there should be absolutely no safety concern with adding more.

Keep in mind, should you use your two hots to provide power to 240VAC equipment, that any 120VAC load you simultaneously place on either of the hots in that same circuit COULD push you over the edge and pop the breaker. That means that if your DC is running and you plug a 15A handheld circular saw into that same run of wire (and start using it), you stand a good chance of crossin' the line. Were I you, I'd keep anything that may run continuously (like a DC) or start unexpectedly (like an air compressor or air conditioner) on its own sweet circuit all by its lonesome. Anything else, things you cannot be expected to use at the same time (like a table saw and a jointer) is fair game... they can play perfectly happily on the same strands of copper - and can be 120VAC / 240VAC mixed any ol' way you need 'em to be.

-- Tim --

Lesson: An aptitude adjustment.

[milanuk]

Tim,

Thanks for the info. I've been digging thru the various electrical reference books that I have (unfortunately most are based on the '96 code) and had basically came to the conclusion that I'm not really limited on how many outlets I can put on a circuit. I'm sure I heard/read a limit somewhere, but I'm reasonably convinced its *not* an NEC limitation. I also read quite a bit about the 3-wire circuits, and I'm kind of riding the fence on whether these would be worth the potential trouble down the road if I (or somebody) else went to replace an outlet w/o remembering/realizing what was involved. That the outlets would be fed by a two pole breaker should be a big tip-off, but...

I guess the one thing that bugs me still, is that no matter where I've looked, I've not seen anything resembling an example of a 3-wire circuit w/ both 120 and 240 outlets on it. Dunno if it's because it's not entirely legal, or just that most people get their 240 to their outlets in a different manner.

For right now, I'm really leaning towards just completely separating the 120 and 240v circuits. 12/2 is cheap, and it's not that big a deal running wire (now). I can predict reasonably close to where I'm likely to need 240 in the future, based on what I have and what I want to buy, but its the unanticipated stuff I'm trying to stay one step ahead of ;) Not likely!

A separate outlet for the air conditioner and air compressor seem like a good idea on the surface, but may take a little doing to work out so I don't have an outlet tied up doing nothing. Guess I could always use the same outlet for the air conditioner and the electric heater; not likely to run them at the same time and that'd keep the outlet from being idle. Biggest issue w/ the air compressor is figuring out some way to keep everybody else in the family from unplugging it and using that outlet for their extension cords! Well, I guess w/ more outlets available, that might draw to a close.

As an aside, for sub-panels in the 60-100A range, how many breakers are commonly available? I looked briefly in Lowes one day, and it seemed like most of the ones they were selling only had 4 breakers, which is pretty much where I'm at now: It's kind of difficult to sub-divide all these circuits ideally on such a limited # of breakers. I'd kind of like to have a general clue what to expect before I wander into someplace more specialized than the local big box stores asking questions.

Thanks for the info and food for thought, fellows.

Monte

[paulh]

Panels are available in a zillion different sizes and configurations, but 8 and 12 breaker 100A panels are commonly available.

I got an 8 breaker (that's 8 full size) 100A panel from the big orange place.

paulh

[TDHofstetter]

Yeah, eight's a good target. Too many and you'll never (sensibly) use 'em all. Four's a little skimpy on the other hand - especially if you've got dedicated circuits tying up some of 'em.

Monte - how about hardwiring that air presser? You could use BX (armored) cable, and put a blank plate on the box.

-- Tim --

Lesson: An aptitude adjustment.

[milanuk]

eh... I think I'll leave the compressor mobile and on 110v... At least for now. I've got some home projects that it may be real handy to have some pneumatic tools for, and it's about 65yds to the house. Way too far to drag a hose. Now if I ever get a pancake model, I might change my mind. But I'll also be putting the compressor up on a stand of some sort (horizontal tank 20gallon model) so I can get to the darn drain valve a bit easier if I do that ;)

Thanks

Monte

[randall]

>Monte, according to the NEC there is no maximum number of
>receptacles which can be fed by a single circuit provided
>the circuit is not overloaded by the equipment drawing
>current through that circuit... 120VAC or 240VAC. Feel free
>to add more if you like - there should be absolutely no
>safety concern with adding more.

Yeah, I don't see where there is a problem with the NUMBER of outlets on a circuit, the whole shebang is controlled by the breaker anyway, on a 20A circuit you could have 100 outlets or 1 outlet, you are still only able to ever run 20 total amps thru that circuit, that means you could plug in a 20 amp space heater or 96 25 watt lamps, whichever you prefer :)

One last thing to remember is the code does specify things like having an outlet on EVERY wall wider than 24," and then if the wall is longer than something like 12 feet, I think they want outlets no further on that wall than 12' apart at least in residential. So I would take that as having a minimum of 4 outlets in a room.

I would pickup a couple of electrical wiring books for some guidelines, they come in handy.