Theoretical Idea

No theoretical reason, other than 240V is not 230V. Also, you could get inductive heating and choke on the circuits you use, due to the unbalanced load situation you will cause in each of the two circuits.

For safety's sake, have a 2 pole breaker and 240 volt receptacle installed.

Mitch Thompson

Panel Schedule software for use with AutoCAD

Mitch

I *wasn't* going to do it!

Can you explain why there would be inductive heating (I guess I'm unclear as to what induction and choke are). I don't see why the circuits would be unbalanced. I sorta checked out of physics somewhere between DC electricity and AC and thermionic valves and electronics!!

Cheers

Den

| I have a some European (i.e. 230V) kit that is frequency independant. In my | house (120V) I have the usual split-phase arrangement (i.e . +/- 120V off | the pole, some circuits fed with -120V and neutral, some with +120V and | neutral, net effect is 120V where it's needed). I don't have any 240V | outlets (i.e. -120V and +120V). If I wanted to run this kit is there any | theoretical reason why I shouldn't wire it to each of two hots on separate | 120V circuits (obviously making sure one is +120V and one is -120V). What | about practical reasons?

If you attach a 240 volt device between the two opposite 120 volt hot lines which are wired on separately protected circuits, you have a hazard if one of those circuits is opened due to some fault. It can happen just because you might switch off one of the circuits. The problem is that your device is now a crossover between the opposite 120 volt lines. That puts the device in series with everything on the opened circuit operating in parallel. This combination now gets 120 volts divided up some way depending on the effective resistance of each device. Some devices can be damaged with low voltage. And the open circuit will still have voltage on it, creating a hazard if you or someone else tries to work on that circuit.

240 volt devices must be either connected as the only device on the circuit if there is a possibility of a single pole being opened (such as with fuses as the protection), or must be connected to a 2-pole circuit breaker which will open both poles should either is overloaded or faults.

Alternatively, you could use a 120 volt to 240 volt (or 230 volt) step up transformer. If one of the wires on the 230 volt device is connected to the chassis (often done with older equipment), you must ensure it connects to the wire that is grounded. American 240 volt circuits cannot provide that, but you could do it that way with the transformer to match what is found in Europe.

Hmm

I hadn't thought of that angle ... it's obvious when you state it clearly as you have done.

I'm going to be using a step up transformer ... it's just I wondered if it could be done this way ... I wasn't going to actually do it as it would clearly be (at best) bad practice ... and as you have demonstrated dangerous.

Thx

D

Doable, if you use the 2 hot circuits from a split-plug circuit (i.e., protected by 2 ganged circuit breakers).

I've been using this approach for the last 17 years for a counter top mixer/blender (Kenwood Chef) that is rated as 240 V. It worked just fine using the voltage range of 208 (from an apartment split-plug feed) to 240 V (from an detached house split-plug feed). 230 rated is really 230 +10/-6% (or is it +6/-10%?), so if you use the above approach, you should be OK.

Very often laundry rooms have 240 volts to run driers and they use both legs.

Two things come to mind:

The 240V circuit you will be creating may form a loop enclosing a significant area since the two conductors are not adjacent. If the load current is significant you will create a magnetic field which will induce currents in other circuits or objects.

I'm not familiar with European codes, but this device might be designed with the assumption that its neutral is grounded rather than floating around at 120V.

| Very often laundry rooms have 240 volts to run driers and they use both | legs.

And they use the neutral, too.

Sometimes. Sometimes not. I believe my laundry room is a three wire connection (I know my last house was, and I didn't buy a new cord). All would be well if the appliance manufacturers didn't cheat with 110V components. Even as is, it's not a big deal (but not pure either).

On Thu, 22 Apr 2004 22:16:52 -0400 KR Williams wrote: | In article , phil-news- | snipped-for-privacy@ipal.net says... |> On Thu, 22 Apr 2004 16:35:12 GMT bushbadee wrote: |> |> | Very often laundry rooms have 240 volts to run driers and they use both |> | legs. |> |> And they use the neutral, too. | | Sometimes. Sometimes not. I believe my laundry room is a three | wire connection (I know my last house was, and I didn't buy a new | cord). All would be well if the appliance manufacturers didn't | cheat with 110V components. Even as is, it's not a big deal (but | not pure either).

I have not seen a dryer that does not use the neutral. What I am told is that the heating elements are connected between the 2 hot wires, but the motor, which is not that big, is connected between 1 hot wire and neutral. I guess that is the "cheat". Maybe motors for 120 volts are cheaper due to mass market in them (technologically, there wouldn't be any difference).

Now it would make more sense to me to just go ahead and hook the motor to

240 volts, too. I'd rather have that. The question is, how much would I be willing to pay extra for that, to have a possibly non-stock motor used, and also to have the control circuits on 240 volts, to eliminate the neutral wire entirely. Not much point in it.

But I'd still rather have an electrical system that didn't use neutral, and no appliances depended on it. It would still have ground, and the secondary transformer winding would still be grounded at the most central point to have the least voltage to ground. For single phase that would be the center tap as is common in North America, and for three phase it would be the center wire of a WYE (or star) secondary. Then to make things more universally compatible, both single phase and three phase would have the same voltage between hot wires. If it were me picking that voltage, I'd go a bit higher with 300. That would mean 150 volts to ground on single phase and 173.2 volts to ground on three phase. But the only voltage used would be 300. Back when all these things were decided, though, they didn't know how to make things as safe (e.g. separate ground wire), nor how to make sure no one used the ground wire as a current conductor (GFCI), had all these bulb sockets with metal base as one of the conductors, and didn't want to use

2 pole switches. And we can't change today because of so much installed base of distribution and usage. Well, we still could stop using the neutral on 240 volts and maybe adopt 240Y/139.

A GFCI is not intended to prevent the use of a ground wire as a current conductor. It is intended to protect you, by interrupting the circuit if there is an imbalance (of about

5 mA or more) in current flow on the hot vs the neutral wires. The idea is that a short in something you are holding runs current through your body to ground, which could kill you. It is specifically allowed by the NEC to be used where no ground wire exists - thus can't be intended to be used to make sure no one uses the ground wire as a current conductor. See 406.3 (D) (3) in the 2002 code.

No, the "cheat is that there is a ground (no neutral) and the

120V motor uses the return through the *ground* (it's wired to the case). AIUI, the later codes require the fourth wire (neutral), like they do with kitchen ranges.

Given the volume of widgets sold, I can't see it costing a dime extra. There is no way anyone is going to use a drier on 120V (well my MIL tried for a while, but that's another scary story).

I don't see the point. Very few appliances need the higher voltage and the ones that do should have a separate circuit designed for the higher load. I don't see the need for a 240V circuit to power my bed lamp, alarm clock, cell-phone charger (the only things normally on my bedroom circuit). Ok, there is a

1/2 ton AC on there for a couple of weeks in the summer too (were I wiring the house it would have its own circuit - wire's cheap). Big deal.

Too complicated. Why bother. I rather like things the way they are. It's simple, cheap, and easily expandable (for values of easy approximating the ease of opening a wall ;).

On Fri, 23 Apr 2004 20:57:26 GMT snipped-for-privacy@bellatlantic.net wrote: | | | snipped-for-privacy@ipal.net wrote: | | | | |> Back when all these things were decided, though, they didn't know how to |> make things as safe (e.g. separate ground wire), nor how to make sure no |> one used the ground wire as a current conductor (GFCI), | | A GFCI is not intended to prevent the use of a ground wire as | a current conductor. It is intended to protect you, by | interrupting the circuit if there is an imbalance (of about | 5 mA or more) in current flow on the hot vs the neutral wires. | The idea is that a short in something you are holding runs | current through your body to ground, which could kill you.

But the technology of GFCI could do that, regardless of what its intended use is today. My point was that back before GFCI, it would have been difficult to prevent people hooking circuit up via the ground wire, have things been configures as no neutral with ground wire.

| It is specifically allowed by the NEC to be used where no | ground wire exists - thus can't be intended to be used to | make sure no one uses the ground wire as a current conductor. | See 406.3 (D) (3) in the 2002 code.

I'm not talking about how it is intended to be used, but rather, how it could have been used with a different kind of power feed configuration, had that been chosen. I'm sure had my idea been adopted way back when, NEC codes would be different in a lot of areas today.

On Fri, 23 Apr 2004 22:29:40 -0400 KR Williams wrote: | In article , phil-news- | snipped-for-privacy@ipal.net says... |> On Thu, 22 Apr 2004 22:16:52 -0400 KR Williams wrote: |> | In article , phil-news- |> | snipped-for-privacy@ipal.net says... |> |> On Thu, 22 Apr 2004 16:35:12 GMT bushbadee wrote: |> |> |> |> | Very often laundry rooms have 240 volts to run driers and they use both |> |> | legs. |> |> |> |> And they use the neutral, too. |> | |> | Sometimes. Sometimes not. I believe my laundry room is a three |> | wire connection (I know my last house was, and I didn't buy a new |> | cord). All would be well if the appliance manufacturers didn't |> | cheat with 110V components. Even as is, it's not a big deal (but |> | not pure either). |> |> I have not seen a dryer that does not use the neutral. What I am told is |> that the heating elements are connected between the 2 hot wires, but the |> motor, which is not that big, is connected between 1 hot wire and neutral. |> I guess that is the "cheat". Maybe motors for 120 volts are cheaper due |> to mass market in them (technologically, there wouldn't be any difference). | | No, the "cheat is that there is a ground (no neutral) and the | 120V motor uses the return through the *ground* (it's wired to | the case). AIUI, the later codes require the fourth wire | (neutral), like they do with kitchen ranges.

Are you sure of that? I've seen these wired up, and they put the white wire on the neutral bus, not the ground bus.

Are you talking about a NEMA 6-30R or a NEMA 10-30R? I'm talking about the 10-30R.

|> Now it would make more sense to me to just go ahead and hook the motor to |> 240 volts, too. I'd rather have that. The question is, how much would I |> be willing to pay extra for that, to have a possibly non-stock motor used, |> and also to have the control circuits on 240 volts, to eliminate the neutral |> wire entirely. Not much point in it. | | Given the volume of widgets sold, I can't see it costing a dime | extra. There is no way anyone is going to use a drier on 120V | (well my MIL tried for a while, but that's another scary story).

I never suggested going with pure 120 volts. That would require 60 amps that way. Instead, what I am suggesting is to use only 240 volts, instead of a mix of 240 volts for heating elements and 120 volts for motor and control sorcuits.

|> |> But I'd still rather have an electrical system that didn't use neutral, and |> no appliances depended on it. It would still have ground, and the secondary |> transformer winding would still be grounded at the most central point to |> have the least voltage to ground. For single phase that would be the center |> tap as is common in North America, and for three phase it would be the center |> wire of a WYE (or star) secondary. | | I don't see the point. Very few appliances need the higher | voltage and the ones that do should have a separate circuit | designed for the higher load. I don't see the need for a 240V | circuit to power my bed lamp, alarm clock, cell-phone charger | (the only things normally on my bedroom circuit). Ok, there is a | 1/2 ton AC on there for a couple of weeks in the summer too (were | I wiring the house it would have its own circuit - wire's cheap). | Big deal.

Almost nothing needs a particular voltage. The need is for some amount of power (real or reactive as the case may be). For things as small as a bed lamp, alarm clock, or cell-phone charger, 240 volts offers virtually no advantage.

My suggestion for no neutral as a power configuration is more about getting things on a singular standard voltage, and doing so in a well balanced way, with a minimal ground potential. It's not that things like bed lamp, alarm clock, or cell-phone charger need 240 volts, but rather, if they an everything else used 240 volts, then the wiring would be simpler, and the ground potential would still only be 120 volts (139 volts for three phase). In Europe, the 230 volt standard is between line and neutral/ground. So the ground potential is the full amount.

Eliminating the neutral leaves only one voltage, the line to line voltage. Making the voltage higher means less current and even less I^2*R losses in the wiring.

|> Then to make things more universally |> compatible, both single phase and three phase would have the same voltage |> between hot wires. If it were me picking that voltage, I'd go a bit higher |> with 300. That would mean 150 volts to ground on single phase and 173.2 |> volts to ground on three phase. But the only voltage used would be 300. |> Back when all these things were decided, though, they didn't know how to |> make things as safe (e.g. separate ground wire), nor how to make sure no |> one used the ground wire as a current conductor (GFCI), had all these bulb |> sockets with metal base as one of the conductors, and didn't want to use |> 2 pole switches. And we can't change today because of so much installed |> base of distribution and usage. Well, we still could stop using the neutral |> on 240 volts and maybe adopt 240Y/139. | | Too complicated. Why bother. I rather like things the way they | are. It's simple, cheap, and easily expandable (for values of | easy approximating the ease of opening a wall ;).

Perhaps only because you are already accustomed to it? Obviously we are not changing things. But if you had only know of a system like I suggest, would you think making a change to add a neutral wire and allow things to be run at half the normal system voltage be allowed, and have a different value for three phase circuits?

Could be. They are the same lug in the entrance panel. I guess you can call it a neutral, since it is carrying current. ;-) It's bonded to the case though. ...as my MIL found out.

Not sure. I've only seen the thing twice (when I bought it and when I moved).

I didn't say you did. My point was that a 240V motor, given the volume of driers sold, shouldn't be any more expensive than a

120V motor. I have no clue why they use a 120V motor. Seems pretty stupid to me, but there must be a reason.

Sure, my point is that most rooms have nothing in them that takes any significant power, so 120V is good enough. Kitchens, perhaps.

I don't see many appliances in the home that need higher power than can be delivered now at 120V. AC units, sure, but they usually have dedicated circuits. I have a small window unit, but it works fine off 120V too.

Sure, but I don't see this as a significant issue in a residential dwelling.

The advantage of the system as it stands is that I can use 120V for small things and glue two together for the biggies. That's about as simple as it gets.

(All kinds of stuff snipped)

So they can use the same motor for gas dryers, which are often used when 240 is unavailable..............

I think there is a more likely reason. Some older electric clothes dryers, near the rear terminal cover, were labeled for connection to classical

120/240V circuits, but alternately 120V-only hookups. [Er, appliance's two ungrounded terminals were strapped.] Of course, the "4500W" heater element is reduced to ~1100W, but it still works?sort of.

?s falke

| Could be. They are the same lug in the entrance panel. I guess | you can call it a neutral, since it is carrying current. ;-) It's | bonded to the case though. ...as my MIL found out.

An entrance panel might do that. But there should be separate neutral and ground bus bars, just connected together in the entrance panel and kept separate in subpanels.

|> Are you talking about a NEMA 6-30R or a NEMA 10-30R? I'm talking about |> the 10-30R. | | Not sure. I've only seen the thing twice (when I bought it and | when I moved).

Grab this file and view the dimensions:

| I didn't say you did. My point was that a 240V motor, given the | volume of driers sold, shouldn't be any more expensive than a | 120V motor. I have no clue why they use a 120V motor. Seems | pretty stupid to me, but there must be a reason.

A motor can be made cheaper if it's windings are at a fixed voltage and there is no option to rewire to a higher voltage, as would be the case if the windings were paired with 4 leads each. Since instead of a versatile motor, you have to make separate ones for each voltage. Given the massive market scale for 120 volt versions (for whatever reason, but perhaps due to it being used for other appliances, too), the 240 volt version will cost more because of the higher cost to inventory compared to sales volume. Even if a single voltage motor over a dual voltage one saves only $0.25, manufacturers will do such things.

|> Almost nothing needs a particular voltage. The need is for some |> amount of power (real or reactive as the case may be). For things |> as small as a bed lamp, alarm clock, or cell-phone charger, 240 |> volts offers virtually no advantage. | | Sure, my point is that most rooms have nothing in them that takes | any significant power, so 120V is good enough. Kitchens, | perhaps.

I'll still be putting a 6-20R or two in most rooms of my future house. The major room that won't have them is the bathroom (even though hair driers pull a power level that really should use 240 volts). I have seen countertop microwave ovens that use 240 volts, but never a hair dryer. Usually they are wired on a dedicated circuit, and for the planned one, it will get one. All the 6-20R's in the kitchen will be GFCI protected at the subpanel adjacent to the kitchen, as will the

5-20R's. Both will have 120 volts to ground, which is the biggest risk in a kitchen or other wet area.

|> My suggestion for no neutral as a power configuration is more about |> getting things on a singular standard voltage, and doing so in a |> well balanced way, with a minimal ground potential. It's not that |> things like bed lamp, alarm clock, or cell-phone charger need 240 |> volts, but rather, if they an everything else used 240 volts, then |> the wiring would be simpler, and the ground potential would still |> only be 120 volts (139 volts for three phase). In Europe, the 230 |> volt standard is between line and neutral/ground. So the ground |> potential is the full amount. | | I don't see many appliances in the home that need higher power | than can be delivered now at 120V. AC units, sure, but they | usually have dedicated circuits. I have a small window unit, but | it works fine off 120V too.

Sure, many things available that use 240 volts can also use 120 volts. But I prefer to use them at 240 volts regardless. The only things that I would be using at 120 volts are those that do not have any 240 volt versions (which is most things).

|> Eliminating the neutral leaves only one voltage, the line to line |> voltage. Making the voltage higher means less current and even less |> I^2*R losses in the wiring. | | Sure, but I don't see this as a significant issue in a | residential dwelling.

We see things differently.

| The advantage of the system as it stands is that I can use 120V | for small things and glue two together for the biggies. That's | about as simple as it gets.

But if the system had always been just 240 volt, would you really have thought "Gee, if only I could have a current carrying conductor back to the grounded center tap, I could run things on 120 volts, even though I would now have double the current and no less risk of ground shock".

BTW, shared neutral wiring effectively gets you the same benefit of less current for a given total (and balanced) load. Two 60 watt lights with one on each pole of a shared neutral 3-wire circuit will draw a total of

0.5 amps, the same as a 120 watt 240 volt light would. But to get that advantage you also have to have the risk of a shared neutral circuit. But that is a viable option with a 2-pole circuit breaker that ensures both poles are cut off if either overloads. But I don't plan to do any shared neutrals.

| "BFoelsch" wrote... |> > I didn't say you did. My point was that a 240V motor, given the |> > volume of driers sold, shouldn't be any more expensive than a |> > 120V motor. I have no clue why they use a 120V motor. Seems |> > pretty stupid to me, but there must be a reason. |>

|> So they can use the same motor for gas dryers, which are often used when 240 |> is unavailable.............. | | I think there is a more likely reason. Some older electric clothes dryers, | near the rear terminal cover, were labeled for connection to classical | 120/240V circuits, but alternately 120V-only hookups. [Er, appliance's two | ungrounded terminals were strapped.] Of course, the "4500W" heater element is | reduced to ~1100W, but it still works?sort of.

That depends on how it is wired. If the heater consists of two separate

2250 watt elements, each of which has 1 wire on the neutral, and each of the other two wires are on the two hot wires, then wiring it with both hot prongs on the same side of 120 would get the full 4500 watts. The catch is it would raw 37.5 amps through the neutral, necessitating the connection being rated for 50 amps. But with 240 (opposite phases) then it would only draw 18.75 amps, usable on a 30 amp circuit.