Why 240V over 120V?

[Bulkley]

The one area where I would want 240v, if I could, is for heat. An outlet that would take one of those 240v box heaters would be really nice.

[LCHIEN]

quote:Originally posted by RagerXS

Loring, why would you convert the windings to 240V in your example? What benefit is there from doing that?

~ Fred

My example was if there were existing 240 outlets, I would convert the nearby equipment with motors that could run either 120V or 240V to 240V.

One reason is that each 240V circuit used frees up two 120V circuits for other things (e.g. there are usually not enough).

The other reason is that its easy to do, you just change some jumpers in the inlet to the motor. Its also easy to change back should you desire to do so.

[monte]

So far I've really had no need for 240V in my shop except for my 7HP stationary air compressor. That's the only thing that needs it.

[RagerXS]

Well I had hoped I'd find compelling reasons to run some of my circuits as 240V, but really the only thing I've learned is that if I ever get something with a 3 HP motor (or larger) I'll want it.

Should I make any special provisions to make upgrading a circuit easier? Such as running 12-3 for a couple of them instead of 12-2?

~ Fred

[gjat]

Rager,
Sure, why not? It may be even best to run 1 circuit as 10-3 to make sure you have plenty of ampacity (30 to 35 depending on type of insulation and installation). It's way cheaper to run oversized awg and # of conductors if your working on it anyways than doing it later. If you aren't upgrading anything, it's pointless to do it unless you need it.

[LarryG]

quote:Originally posted by RagerXS

Should I make any special provisions to make upgrading a circuit easier? Such as running 12-3 for a couple of them instead of 12-2?

Does the NEC now require a neutral for ALL 240V circuits? I thought it was only for appliances that have 120V lights and timers and so forth. For shop machines with only a motor, you need a hot, neutral, and ground for 120V operation and two hots and a ground for 240V operation ... so 12/2 (or 10/2) would work now for 120V and could be converted to 240V later.

[stewchi]

Larry you are correct you only need a neutral for the 120 portion of the appliance on a 240 circuit. However when talking about using romex it is more common to use 12-3 than 12-2 generally because of the color codes on the conductors. If you don’t need a neutral and you use 12-2 that has a black and white, NEC REQUIRES that you re-label the white conductor with tape or paint preferably red, yellow, orange or brown. (can’t use grey, white or green). There are more color distinction in industrial settings were you have more varieties of voltage and 3 phase. But for residential white and grey are always neutral, green is always ground and thats about it.

[LarryG]

Okay, I now better understand the question about pulling 12/3. And I do know about the relabeling requirement. I guess what I was trying to say is that for someone who seriously doubts they'll ever need 240V, or does not anticipate that need, pulling 12/2 everywhere doesn't mean they've painted themselves into a corner if it turns out they do, in fact, need a 240V circuit someday.

[waterpro]

I am thinking of running a new line to the garage. The problem is that the breaker box is completely full (it is an older box though with a lot of wasted space. I've done routine electrical work around the house (ie put in new outlets, wired new light fixtures, etc..) but have never had to really touch the breaker box except to turn off the electricity. How hard would it be to replace the box? Also assuming I ran all the wire myself how much do you guys think it would cost an electrician to replace the box if it is too big of a job for me. Assuming I purchase the box myself along with the new breakers?

[RagerXS]

Waterpro, your question will be better answered in its own thread where message surfers will see it. That said, this is a big job for the minimally experienced DIY person, and I expect about a half day's work from an electrician meaning not at all inexpensive. I would only go this route if you marry it to a nice upgrade, which in turn may require a larger feed line from the pole... It adds up quickly.

What I would recommend is finding out whether or not your box will accept half-sized breakers, and then replace a few existing breakers with those to free up room for a new circuit or two. Sounds like you would only need two half sized breakers to make room for one new circuit, unless you need 240V in the new sub panel. Also note that circuit panels have a limit on the number of individual circuits that they can be wired for, which is usually equal to the number of single pole standard with breakers that fit. And that means for each double pole breaker you have (240V) that takes up two spots for one circuit, you can then split one spot with 2 half sized breakers.

~ Fred

[sacherjj]

I had planned on putting in 2 240V outlets before I close up the side of the wall in garage with insulation and sheet rock. My main usages would be for a 5hp motor to use in dust collection, and a future tool. (Most likely a welder.) I'm fine with all the wiring and was pretty much ready to proceed, except for the GFCI break discussion for 240V. This is in a garage, so the three 120V circuits I installed are all GFCI'ed, except for the single outlet plug for the freezer. When I was reading code re: 240 V circuits, it indicated that they were exempt from GFCI. Is this the case? If not, I'm guessing the GFCI breaker for a 240V 30 A circuit is going to make me rethink my economics.

[BobSch]

A friend of mine suggested running 12/3 to everything and splitting the outlets so the top and bottom are fed off opposite sides. This also makes it easy to switch to 240 later.

[gjat]

BobSch, ignore your friend. It is a very unsafe practice to split-phase a single 120v device. You would trip 1 breaker and still have the potential to have a live circuit. Run 1 circuit at 240v and provide a 240v outlet. You can branch out of that in the future if needed, but it's wasteful and dangerous to run the extra conductors/circuits to all your devices.

[stewchi]

Bob the difficulty you would have is that if all of your outlets are on the same circuit you would have to convert all of them to 240.

You can split them the way your fried described in what’s called a multi-circuit were you have 2 hots sharing a single neutral. For this to work the hots have to be on different legs. Its fairly common in many application to run a single 12-3 and run 2 circuits off of it. Electrically is makes a lot of since because you will see less return current. Since the hots are on different legs of 180 deg out of phase with each other the return currents from either leg will cancel each other out. That is why it has to be on opposite legs, if it is on the same leg the return currents could be additive and you could end up with 25 amps on a neutral that might burn up.
The down side of doing this is you may have 2 circuits in a box and may not realize that when you switched of one breaker you did not shut off everything in the box.
The other down side is if it’s not properly labeled and things get moved around in your box you could create a fire hazard. Say you replace a couple breakers with the space saver and plug both hots 0f the multi-circuit into each of the inputs of the space saver breaker. In this case you just created a fire hazard, that space saver may have 2 circuit breakers built in, but they are both on the same leg so you could have dangerous current on the neutral.

Now if you want to switch a multicircuit to 240 you will have to switch all of the receptacles on that circuit to 240. You cannot have a single circuit that has both 120 receptacles and 240 receptacles. Breakers are design for one or the other but not both at the same time. This could also create a serous fire hazard.

[BobSch]

I thought it sounded too good to be true.