Is it possible to combine two AC power circuits to double current? (limited household current problem)

I'm in a situation where I need around 20-24 amps continous of 110V (for a milling electric motor), but my strongest circuit in my breaker box is 20 amps. I have 3 15 amps and 2 20 amps. Is it possible to have the AC circuits in parallel somehow to be able to safely (relativly) use the combined currents? What hardware would I need? Am I concerned with the ac cycles being off in some way?

Any other ideas?

Reply to
mjp.metals
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I am addressing only the technical aspects of your question. Nothing I say should be taken as a recommendation that you do this rather than getting your electrical service changed to suit your needs in a conventional, code-conformant manner.

It would be possible to design something that would do what you wish safely. It would have to have relays (or equivalent) to be sure that unplugged male plugs did not have exposed line voltage on them, either before starting paralelled operation or in the event a plug was pulled out during operation. Such a system would not be simple to build and would likely cost more than having a electrician come in and do it conventionally. The relay controller would likely require some electronics. And the available power would not necessarily be a simple sum of what is available from each socket unless even more cost and complexity was added to the custom gizmo. It is likely that the currents taken would not be well related to the breaker trip points due to differing wire run lengths, socket resistance, and breaker resistance.

I have not seen such a device for sale. I suspect this is because of the cost issue I mention above.

You'd better be. With no offense intended, I must say that question leads me to believe you should not be devising such a device and calling an electrician is your best bet.

A generator? It would have other uses and probably be cheaper if your time is worth much.

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--Larry Brasfield
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Reply to
Larry Brasfield

question leads me to believe you should not be devising such a device and calling an electrician is your best bet. <

True, I have no practical knowledge of power AC systems, that is why I am asking the question. I am sorry if that leads you to believe I have no business this matter.

Upgrading the circuits is not what I am asking about, I know about this option. Circumstances make this approach better for me. Also this is indoors, so a generator would not work either.

Despite all you posted, I still don't have an answer... from what I know from books and school, I don't know what kind of circuits and devices you would need to (assuming you could) combine two ac sources to form one source with (minus losses) twice the power. So any help on this would be great.

Reply to
mjp.metals

Perhaps you would take less offense if I expand on that. Given your unfamiliarity with the electrical issues, you are extremely unlikely to be able to design a safe device for doing what you want. If you go ahead anyway, you or somebody you care about could be electrocuted. If you have to hire that expertise, the whole design and build job will cost more than that electrician.

If safety is not an issue, just wire some plugs together, taking care to wire hot to hot, neutral to neutral, and be sure not to plug them into any oppositely phased outlets. This is a very dangerous solution, which I would not use myself if I had your problem.

The generator would not have to be indoors.

You need relays that are well enough protected from over-current to not get welded closed and a control circuit to operate the relays according to the criteria that I stated in my earlier post. If that is not an answer, then you appear to be looking for a complete design. Most likely, to get one you will have to pay money, and more than you would pay to take the solution you already know of.

Good luck getting a more satisfactory answer.

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--Larry Brasfield
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Reply to
Larry Brasfield

Get a big DC to AC converter. ($189 here:

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Power it off of a 12V auto battery, which you keep charged with a trickle charger off of the AC you have. If you need more time, add batteries.

It's not going to power the milling motor all day, but it'll work for a while, and recharge overnight.

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Regards,
   Robert Monsen
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Reply to
Robert Monsen

breaker

Am

Hi. Many electrical motors are made to be wired for either 120VAC or

240VAC service. If you're not interested in hiring someone to upgrade your service, it may be easier to look at the motor and see if you can rewire it. If the motor requires 20-24A @ 120VAC, it will only require 10-12A @ 240VAC if it is a motor of that type. Then, if you have 240VAC @ 15A or 20A service available in your work area, you can just plug it in.

I had to do this once for a motor I needed to run in a basement. They happened to have a 240VAC outlet available at their electric dryer, so there was no problem.

DO NOT put AC circuits in parallel. It's not a good idea, even if you don't accidentally short phases.

As has been mentioned in several other responses, if you don't know what you're doing with line voltage, let someone else who does give you a hand.

Good luck Chris

Reply to
Chris

In many breaker panels, alternate breakers are fed from power from opposite sides of the 220 volt input. Paralleling two breakers that are not fed from the same side of the line will result in possible destruction of one of both breakers. You also do not get proportional current sharing when two breakers are paralleled, so you do not get the combined ratings as the effective trip point. Besides, any wiring that is presently protected by either breaker is no longer protected for the same trip current by the parallel combination.

I think you need to try to find a 30 amp breaker to replace one of the ones now in the panel (preferable a spare) and wire your load to that, following the electrical code for wiring size and practice. If your place burns down after this, you had better hope that your insurance company does not find out you have been doing such wiring, or they will probably disallow your claim, regardless of whether your work was involved in the fire. All that assumes you have not electrocuted yourself before that.

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John Popelish
Reply to
John Popelish

After all the responses I will give in to sanity and NOT try to parallel the AC circuit (not that I would have tried it before knowing it was safe)

As for the the battery idea, that seems like something I may try. The url your pointing to I think is wrong though, (I will need an inverter, not a ac-dv converter)

The only thing that concerns me is the safety of using car batteries inside (they need a well ventilated area I think, and there is always some danger of rupture) since I live in an apartment. And also finding batteries that can stand that much abuse.

So far I what I find is this that may do the trick:

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Qustions is now, what the heck is modified sine wave? (Just how modified is it?) A true sine out is probably too much to ask for at this power I guess.

Reply to
mjp.metals

First, have you tried running it on a 20? Its not a good idea to put two

Reply to
Henry Kolesnik

Are the apostrophes in the wrong place?

Lets tear up some walls and pull wire, without any knowledge of proper codes. It's like your recent suggestion to replace the fuse box to add grounding. "Just yank it out! remember where the wires go!" Who needs electricians? (Bzzzap!) Perhaps you are a member of the Burridge school of electrocution theory: "Nobody ever dies of electrocution, they just move into another reality where they didn't actually die, they only came close..."

Why exactly is it a stupid idea? Is it dangerous? Expensive? What's the problem? Educate me. 30A inverters are relatively cheap, as are auto batteries. Seems far safer than trying to merge two circuits. Hell, you don't even know how often or for how long he is using the thing. If he uses it once a month, seems like a waste of money to have his circuits upgraded and his wiring replaced.

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Regards,
   Robert Monsen
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Reply to
Robert Monsen

All in all, taking into account the warnings from others (and me !!), it would very likely be the most economical to have another breaker installed, most certainly the safest. The other option of the dual volt motor could be your saving if you have it.

-- Regards ..... Rheilly Phoull

Reply to
Rheilly Phoull

There have been a lot of interesting replies to this question, and I am glad to see that you are accepting those that steer you in the direction of caution. I've got some questions that, if the answers are right, might get you going safely and easily.

You say you have three 15A and two 20A circuit breakers. That's not a lot, what environment are you in? It doesn't sound like a typical residence. Are you in a separately wired shop or garage? If so, and if you have to rewire, the job could be a lot easier than in a typical house.

You've already decided to not try to parallel two circuits. Good. Now, if you are confident enough in your ability to not poke around with your fingers in places where they might get burned, take the cover off your CB panel and look at the wires. In my house, I have a 20-amp breaker that is dedicated to the kitchen range. Since I have a gas range, that connection doesn't require much power, and is probably why the breaker is only a 20, instead of a 40 or 50.

The wiring, however, is big (three conductor, 8 awg), so if I ever installed an electric range, I could put in a bigger breaker, and Bob's your uncle. If you have a similarly wired circuit, you could do that - replace the breaker *and* the outlet (there are particular plug configurations for different voltage and amperage capabilities).

Failing that, you'll have to rewire one of your circuits. If you are talking about a shed or a garage, it might be a really easy job. If it's a long run through a house, I'd consider the professional help. Finally, if you have 220V capability, find out if you can run your motor on 220 and put in a 220V circuit breaker. You could have a pro do that last job, too; it shouldn't cost that much.

-- Al Brennan

Reply to
Kitchen Man

You can use a 220 volt circuit if your motor is set up for it. By going with

220 you cut your amps >
Reply to
Beeper

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