220 VAC Wiring/Plug Question

[rich]

Hi, All,

Very soon, I will be ordering a table saw, jointer, and maybe a planer. Santa was VERY GOOD!!! All will run on 220. My shop has 220 at the box, at least 2 circuits. The previous owner ran a welder and huge compressor, so the amps are there.

I did some wiring 25 years ago, but am a little rusty. I think I want junction boxes every 6-8 feet or so around the shop, so I can plug in things or move them to a different location. Is there a standard plug, like a dryer or oven plug that I should use? Does it matter for my shop? I understand I will want to keep the plug to equipment distance as short as possible, but would like the ability to plug the saw in on one wall, then maybe later on the other wall for a different job, or for whatever reason.

Should I run separate conduit for the 220? I have 110 boxes every six feet at chest hight currently, and it might be possible to snake additional wire down the same conduit, and add a 2nd junction box for the 220???

Thank you all for your help and suggestions.

Regards,

Rich.....

[ATP*]

If you have the required space in the conduit mixing the two is OK. For the receptacles I think I would match the plug on the largest (most amperage) piece of 220 equipment that you have.

[nospam_coloradotrout]

I used 20a 220 receptacles. It's very similar to the 120v flavor, but one of the blades is horizontal rather than vertical. I believe it uses the same faceplate, and plugs are pretty cheap. For 20A 220V it's fine. The 30a or greater have those giant plugs, but for converting shop tools to 220, 20A is sufficient. Realize all 120V tools will run at 1/2 the amps on 220. You don't need 8ga wire and

30A plugs. I used 12ga 2-conducter (plus grd) wire, and 12ga cords (bought long extension cords and cut it to size.. cheaper than buying wire in bulk). I think most 1-1.5hp tools are wired with about 14ga stranded.. I could have just used that. But I went ahead and rewird with about 15-20' of 12ga stranded. I did this on my TS and Jt. I just used the existing wire on my DC. I'm still running my BS and DP at 120v.

Maybe an electrician can chime in here.. but I did some homework, and simple 220V at 20A and below is pretty simple. I would not mix 120 and 220 in the same box.. but that's just me. Code might allow it.. I just don't know.. but it seemed simpler for me to keep them seperate.

[Markem]

1/2" conduit unlikely, but possible with some grease (wire pulling grease) two hot wires 12 gauge and one 10 gauge for neutral 30 amp 220 volt, three 10 gauge will not fit. plus the two at least 14 gauge wire for a 15 amp 120 volt, 12 gauge for 20 amp. Fitting wires to tightly in the conduit can cause problems beyond just pulling them. I would pull the current wires out and pull the whole new set both 120 and 220 it is just easier. Reuse the original wire.

Mark (sixoneeight) = 618

[Josh]

Amperage generally isn't a problem when running shop tools at 220V. The current is half what it would be at 110V, so 20 amps is usually more than sufficient.

Likewise, having a long power cord on your tools is usually less of an issue at 220V. Power (in watts) dissipated in the cord = I^2*R, where I is current (in amps) and R is the resistance of the cord (in ohms). Since current is half at 220V, the power dissipated in the cord is 1/4 what it would be at 110V. Thus, you can have a cord four times as long as you could at 110V. And even then the cord wouldn't get as hot because the power would be dissipated over a greater length.

I'd put a pair of standard 20 amp 220V outlets every 10 or 15 feet, fed with 12/3 (plus ground) wire. Since your tools won't need a neutral connection, you could also get away with 12/2 wire, but for the small extra cost of the 3-conductor wire, it could potentially save you or a future owner of your house some confusion and danger, since you'd have to use the white (normally neutral) wire as hot.

[Charles Krug]

I've never seen where it was "legal" but my Practical view is that I wouldn't do it even if it were allowed.

Even up to 60A (ovens) or higher is pretty straightforward. You decide what ampacity you need by the nameplate of the device (required to be accurate), choose your wire gauge based on your tolerence for voltage drop, choose your conduit fill by looking it up in a table OR calculation.

Nothing about it is especially Difficult, but it Does require attention to detail.

Always work to your comfort level and call an electrician if any part of the job makes you UNcomfortable, preferably before starting it.

My comfort level is, "If I can kill power and the source panel has capacity. (space and ampacity) for the given job." YMMV and work within your comfort level.

[Scott Lurndal]

It's not a problem to mix 220v and 120v current carrying conductors in a raceway (read: conduit), as the potential to ground for any single conductor is 120v.

It is an NEC violation to mix 600v(for example) and 120/220 in the same raceway, for obvious reasons.

scott

[DJ Delorie]

It might be that all the conductors in a given box have to be on the same breaker, though. Ask your local inspector to make sure.

[gfretwell]

Where did you hear that? It is certainly not an NEC rule.

[peterh5322]

NEMA 6-15P for 240 volts, 15 amps.

NEMA 6-20P for 240 volts, 20 amps.

If your machines came with a molded corset, they most likely conformed to those configurations.

Use 12 AWG wire for these, and install a NEMA 6-20R, which will accept both the NEMA 6-15P and NEMA 6-20P.

Other configurations are available for 30, 40 and 50 amp loads.

[Mike Marlow]

It might not be.

[peterh5322]

It's called a multiwire branch circuit, and it's allowed.

It's allowed primarily because in any box there is never more than 120 line-to-ground, even though there is 240 line-to-line.

The CB which protects a multiwire branch circuit must be a "common trip" type, so should a 120 side blow, the other 120 side and the 240 blow simultaneously.

Essentially, you wire your boxes as 120/240, using 12/3+G; you tap into

120 alternating black (L) and white (N) then red (L) and white (N), and so on, from box to box, and if you want 240 in a box then you tap into black (L1) and red (L2). Wire G as usual.

[DJ Delorie]

I didn't hear it, I was just guessing. My guess was based on the safety factor - if you shut off a breaker to work in a box, it would be dangerous if there were other live wires in the box. If each box had exactly one breaker, shutting off one wire in that box shuts off all the wires in that box.

My inspector's attitude is 100% health and safety - if it's safe, he'll pass it, if it's not, he won't. It made it easy to guess what would pass.

[DJ Delorie]

For those who don't know, the 20 amp outlet will accept a 15 amp plug, much like the 20 amp 120 VAC outlets.

[Mike Marlow]

I'll bet his attitude is more like, "if it's up to code, he'll pass it".

[dnoyeB]

How will you get 220V without having 110v? 220 basically uses the 110 circuitry anyway. Not saying its legal. But from the point of view of not mixing voltages it wouldnt make sense. From the point of view of not mixing breakers it would.

While what you say is loosely true, your wires are actually sized to your circuitbreaker or larger. Never smaller. Your CB will be based on the current you wish to provide and how much is available.

Only difficult part is getting shocked. Outside of that, screwing down bolts and running wire through tube is not too tough.

true. Consider if you want a permit as well.

[DJ Delorie]

Well, he told me what his attitude was when we first met, and his actions backed it up. But, if you know something about my inspector that I don't, please, let us all know about it.

For example, we were using a type of insulation he was unfamiliar with it. Code said it was OK, but he also took a bit of it home to see how it reacted to fire, just in case.

Since our town and state use the national code, I could probably argue with him about anything that wasn't strictly code, but I'm not that stupid. He was acting in my best interests, and it was obviously so, and I was happy about it.

[Mike Marlow]

Getting shocked - difficult??? Heck - ain't nothing difficult about getting shocked.

[alexy]

That's the way I have my shop wired. In fact, I found fixtures that have one 240 and one 120 outlet. I put one of these and one dual 120 outlet in each box, with the 120 outlet in the 240 fixture on one side of the circuit, and the 120 fixture on the other side.

But I haven't seen the "common trip" discussion, just assuming that was how it worked. How can I tell if that is what I have?

[Mike Marlow]

I'd bet a small sum of money, with no knowledge of your inspector that what he really means is that if it meets code it's fine. Are you saying he rejects wiring that is up to code because it does not meet his definition of safety? Or perhaps even that he accepts things that are not up to code because in his opinion they are somehow safe? I would like to believe he does not view himself as above NEC and decides for himself what is safe. I believe he probably relies on NEC.

And... I'll bet he passed it right? What did his "test" prove? Not to be insulting, but this kind of inspector sounds like he is just entertaining himself with his tests. He surely does not really believe that he is going to somehow dismiss the findings of UL or any other industry certification with his home grown tests, does he? My bet - no, he's going to defer to NEC.

If you're happy, then that's all that matters. You're wired to code and you can't do any better than that, and you like what your inspector says. Don't see how that suggests that he doesn't defer to NEC though.