US system is not as inefficient as I once thought

Well, it would physically work. As you say, the plastic can withstand the voltage gradient and the spacing is not much different.

But in the US there are different orientations of the blades and pins for different service. 120V-20A and 30A are different than the common outlet.

240V the blades are turned 90 from that of a 120 outlet. This is to help prevent some layman from plugging equipment rated for one voltage into an outlet wired for another.

I suppose if you wanted you could wire your whole house with 480V welder outlet plugs/sockets and just wire 120/240 to them. But it wouldn't meet local code and you'd have to fix it before you could sell the house ;-) And each time you bought a new coffee pot or desk lamp, you'd have to cut the existing plug off and wire on one of your own.

daestrom

I'm not sure I know what you mean by general power circuits but I just went down into my basement and audited my main panel. The main breaker is 150 amps/2 pole and it supplies 24 single pole breakers and

2 two pole breakers (single pole breakers ganged together). The single pole units are split evenly 12 and 12 between 20 amp and 15 amp ratings. The double pole units are each 40 amps for the range (stove) and the central air conditioning. I believe my furnace just uses 120v. There's room for two more breakers in the panel.

The house is 16 years old and is typical for this area(Ohio) of the USA.

ARM

Electrically it will work just fine. However, we *don't* want people plugging in their 120V thingies into 240V outlets.

There exist NEMA 6-15R and 6-20R outlets for 15A and 20A 240V circuits, respectively. They look very similar to the standard 5-15R outlet, except they accept plugs with both blades horizontal, not vertical. (A 6-20P plug has one blade vertical, and it fits into a 6-20R outlet not a 6-15 outlet. A 6-15P plug fits in either)

I'm not sure if a 6-20R is available in a duplex outlet (6-15R is).

Historical aside: Many older places in the US have *old* outlets that accept both vertical and horizontal plug blades and look like they would accept all of 5-20P, 6-15P and 6-20P if you cut the ground pin off (there is no ground on them) What were they for, 240V? DC? Were items available with 2 prong horizontal blades? I've never seen one.

Also, at work here are a handful of oddball duplex outlets with one each

5-15R and 6-15R. Not sure if they are one circuit or two.

Excuse me, but 800 Watts is "power hungry" enough for me! I would peg 600 watts at the point where 240 makes a LOT more sense than 120 volts. In fact, were I planning a new home with a mess and audio/visual stuff at the minimum I would run three wires for the duplex 120 volt outlets to "share" the load.

Oh, of course, complete re-wiring would be out of the question BUT when near routine projects that kitchen upgrading occur, it would make a lot of sense for the dishwasher, toaster, ice box, and microwave to run on 240.

I do believe that "they" might start making higher grade appliances in 240 volts. Folks don't shoehorn in top of the line appliances: they are for true upgrade of the entire kitchen or first class new construction.

You have missed the BIG point that all that is necessary is to run three wires rather than two so serve the kitchen. Some outlets would be 120 and some would be 240. With three wires in each box it would be possible even to have both 120 and 240 at the same duplex outlet.

When your old 120 volt toaster gives up the ghost, you replace the split 120 volt duplex outlet with a 120/240 volt duplex. The new toaster will work faster and the cord will not get a warm!

More like a combination of both in the case of air conditioners. A window air conditioner that used over 3 kw back in the '70s would use something like 1.5 kw today. Since 2.4 kw is all that a standard 120 volt circuit can carry, a threshold has been crossed and the 240 volt circuit is no longer necessary for most window units.

I want one if those. Instead of popping a bag of popcorn in two minutes, I could burn it to a crisp in one. :-)

I'm sure that a 2.4 kw model could be made available here in the US that runs off of 120 volts as long as it used it's own dedicated circuit.

Robert

I wouldn't be too sure about that. If one outlet is only good for 2400 watts as you mentioned, it would be pretty hard to get a microwave anywhere close to that. They are more efficient than stove-top cooking, but they still aren't really efficient.

daestrom

Andrew never told us if the 2.65 kw is the input power through the power cord or the output power from the magnetron. Maybe he can clear this up.

Robert

When you look at the duty cycle it becomes clear that the cost of rewiring far outweighs any I2R saving you might get. Since Europeans use smaller wire in their 10a 240v circuits I imagine it is really a wash. The US may spend more on copper but I doubt we lose that much as heat. As I pointed out, during the months you are paying for heat, it is really not saving you much.

Input power. The magetron output power is 900W and the oven also has a grill, convection, and fanned heating elements. You can operate most combinations of elements together except microwave and fanned heating elements.

I think there is one EU country which uses 10A final circuits to socket outlets, but much more common are 16A, 20A and 30A/32A.

In the UK, 16A and 20A would be wired using 2.5mm^2, and 30A/32A using

6mm^2 or (more commonly) a 2.5mm^2 ring circuit. For particularly long cable runs, or cable runs through thermal insulation or higher than normal ambient temperatures, conductor size is increased. I'm pretty sure Ireland is exactly the same (their wiring regs originally based on the UK's), but I don't know the conductor sizes used in other EU countries. Sorry, someone else will have to convert these to AWG ;-)

This is actually a pretty silly discussion, the fact is we ain't changing. If anything, as other posters have said, we are actually making more 120v stuff where it might have been 240 in a less energy efficient model. Modern homes have an excess of capacity and wire in the wall now so I2R is not that big an issue. Older homes that have shaky wiring would be the last ones to make any change, much less one that required a big capital investment with meager immediate return. You can't even get these people to install a few extra circuits to remove orange cords going from room to room.

Of course you will have the perceived safety issue too. As soon as you say 240 volts, people here jump back and say that is too dangerous. (even though the voltage to ground is exactly the same).

Thanks. Using that system would not reduce the number of available circuits - the breakers would be single pole - so that part of my original answer was wrong.

Thanks! In the UK, are you required to use 2 pole breakers? In other systems with 2 hots, I would assume the use of 2 pole breakers is mandatory, but I don't know.

Nope, haven't missed that. That point was not raised in what I replied to. Again, we are talking different things. I was responding based on total conversion to 240 - NO 120 volt outlets. That's a 2 wire (plus ground) system. You have to check the context of the posts!

(Now I am replying with the mixed 120/240 concept in mind) Not in the kitchen, where your toaster example (below) would apply. Receptacles serving counter tops must be GFCI per code. You can't split a GFCI duplex receptacle. Further - when your toaster dies and you buy the replacement 240 unit and then replace the 120 volt GFCI with a 240 volt GFCI, using the third wire which was formerly not used, then you won't be able to plug your 120 volt coffee maker (or anything else that is 120) into the new receptacle.

Now, if you use a standard duplex receptacle, and the GFCI is at the panel instead, you would need 2 GFCI's - one for teh 120 volt circuit, and one for the 240 volt circuit. No current carrying conductors can be shared in that scenario - so you would have to wire the box with FOUR counductors (plus ground), not three. AND - there is no such thing as a duplex receptacle for both 240 and 120.

There is no practical way to convert - and there is no reasonable benefit to doing so. Appliances designed for 120 volts work very well on 120 volt circuits. If they don't, either there is a defect in the appliance, or a defect in the circuit.

Look at some numbers: assume a 1200 watt toaster. It draws 10 amps at 120v or 5 amps at 240v. Say it is plugged in to a receptacle which is wired to the panel with a 50 foot run of #12 Romex. The resistance in the wire is .2 ohms, per tabel 9 in the NEC. The power lost (I^R) in the Romex at 10 amps is 20 watts. At 5 amps, the power lost in the wire is 5 watts. I pay 13.5 cents per kwh, most people pay less. I would need to run the 240 toaster for 66.66+ hours to save one kilowatt - that's 13.5 cents on my electric bill. If I could buy a replacement receptacle for say $2.00. I would have to run the new 240V toaster for 987.65+ hours to recoup the cost of the receptacle. I still have to recoup the cost of the extra breaker and the difference in cost between the 2 wire and the 3 wire romex - and that's if you do it without GFCI's. If you include GFI's in the equation, as required by code and for safety, the cost becomes (relatively) astronomical. You more than double the wire cost, as you'll need to install 2 runs from the panel to the box. 240 volt GFI breakers cost around $50,

120v GFI breakers around $35. You are looking at close to 100 dollars to wire up the receptacle for your toaster the way you specified, at the time the house was built. You would have to run your 240 volt toaster for 49372.5 hours to recoup the cost. Thats a LOT of toast!

John,

I posted some numbers in a reply to another of your posts in this thread. I used your example of a toaster and assumed 1200 watts. The reply I made demonstrates that, for the specific example you posted, there was a large cost/benefits ratio (which means it was not a good idea) to going to 240 volts by simply replacing a receptacle. I would have to run the toaster for over 66 hours to save $2.00 on my electric bill at 13.5 cents/kwh.

Can you post some numbers to support the idea that 240 makes a LOT more sense than 120 at 600 watts?

No, as we don't have 2 hots.

Thanks for the info Alan!

150 amps is a pretty big system for a house!. With our 240V service over here, most places would be 60 amps max. - meaning that the circuit breaker panels are physically smaller and all of the breakers are single pole (unless you have a 2-phase stove like we do).

This saves a fortune in the cost of new switchboards - 6 single pole breakers and one RCD will do an entire house! Must be *half* the cost of yours at least..

Cameron:-)