(Another) Wiring Question

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Two 20A circuits, yes -- but he'd be just fine with one 30A circuit. [...]

Maybe he can, maybe he can't -- see my other posts in this thread discussing the voltage at which the heaters are rated vs. the voltage in the OP's house. He said the installation instructions say to use a 220V circuit -- suggesting that the rated output of the heaters may be based on an input of 220V. But it's likely that his actual supply is 240V, and at the higher voltage the heaters would draw enough current that he can't put both of them on a single 20A circuit. Two 20A circuits would be fine regardless, as would one 30A.
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Doug Miller (alphageek at milmac dot com)
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On Sat, 09 Dec 2006 03:38:22 GMT, snipped-for-privacy@milmac.com (Doug Miller) wrote:

I am still not sure I follow your explanation. It is true that there are more than one application for 220V 240V and even 208V, but is it not true that all homes are designed to be 220 nominal?
I am not sure how buying anything for a home would be designed for anything else?
The op says 220V and I am sure that he got that from the box. Why would a home owner assume they had more than 2 choices?
I am also not sure why you would be able to go to a 30A circuit. While it is true that using a 30A circuit would be more than adequate, I am unsure that is it permitted by the code. (I hope someone can cite the section)
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No, not really -- utility supplies have been 240V for quite a while now.

The point is simply that if the heaters are rated for so many watts at 220V, when installed on the 240V supply that the OP almost certainly has, they will draw more current -- enough more that they cannot both be used on the same 20A circuit. If their rated output of so many watts was rated at 240V, then they can both be used on the same 20A circuit.

Why would it not be permitted? The breaker is there to protect the *wire*, not what's attached to it. Look: you probably have an electric can opener in your kitchen. It's plugged into a 20A circuit, even though it's about a 1amp device. So what?
As a matter of fact, if the rated output of the OP's heaters was determined at 220V instead of 240V, and he puts them both on a single 240V circuit, the Code *requires* that circuit to be 30A *minimum*.
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On Dec 10, 10:58 am, snipped-for-privacy@milmac.com (Doug Miller) wrote:

I admit I don't know, but I would think instead of going to #10 and a 30A circuit you would be required to run 2 seperate 20A circuits if the total load exceded 16A.
I would also assume that you would take the the only two choices you would have. Either the equipment would be 110 or 220. Why would they sell something that was not the common voltage for the home?
Taking 240V instead of 220V the current would be less and not more. This would be 14.6A
I do understand that if you use somethign designed for 220V and it is infact 240V the current would be more, but can't see that being the case something designed for a home.
I wish the OP woud chime in and give any more information he could give on the heaters, like maybe the Full Load Amps.
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Why? Is there some reason you think it would not be acceptable to attach a 16A load to a 30A circuit?

Residential electrical supply in the US and Canada hasn't been 110/220 for many years -- it's 120/240 and has been for a long, long time. Doesn't stop people from referring to it as 110 and 220, obviously, but that's not what it is.
My point was this: the OP referred to installation instructions that said (according to his post) to connect the equipment to a 220V circuit. Maybe that was just a mistake on the part of the OP and the instructions really said 240V, or maybe they really said 220V like he said -- and if *that* is the case, that the manufacturer really said 220 and not 240, it's quite possible that the rated output of the heaters is based on their output at 220, and not at the 240 that the OP certainly has in his house. And the distinction is important because if these heaters were rated at 240V, then they can both go on the same 20A circuit -- but if they were rated at 220V they cannot.

Wrong.
Take the case of a resistance heater that emits 2000 watts at 220V. It draws 2000 watts / 220 volts = 9.09 amps. Now calculate the resistance: 220 volts / 9.09 amps = 24.2 ohms.
Note that the resistance is a physical property of the heating element, that does not change no matter what voltage is applied to it.
Now push 240V across that same 24.2 ohm resistance.
240 volts / 24.2 ohms = 9.92 amps.
A similar calculation applies to the 1500 watt heater.

Isn't that exactly the opposite of what you said in the previous paragraph?

Maybe you're right -- but assuming that, without proof, could be dangerous. Which is why I cautioned the OP to check the rating plate to see whether the heaters were rated at 220V or 240V.

Simply knowing what voltage they're rated at is sufficient.
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Doug Miller (alphageek at milmac dot com)
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On Dec 10, 9:00 pm, snipped-for-privacy@milmac.com (Doug Miller) wrote:

Like I have said, I don't know for sure, but I have it in my head that if you can limit the load to 15A or 20A then you should.

My assumption for using 240V was that the OP had made the same mistake we all do in referring to 110-220 and 120-240 interchangeably. If this was the case, then the load would be 14.6A. Maybe I didn't say that too clearly, but that would be my observation. I am sure he got the wattage right, and I would think that he couldn't buy a heater for the home if it was truly rated for 220V.
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You seem to be confusing "load" with "capacity". In any event, there is *no* reason why you could not connect a 16A load to a 30A circuit. [snip]

I would think that, too -- but when talking about electricity, assumptions can be deadly dangerous if they prove to be incorrect. The only reason I raised the issue is that the mention of installing the heater on a "220V circuit" raises the possibility that the devices may have been rated at 220V instead of 240V, and hence the possibility that they may draw more current than anticipated when operated at the higher voltage.
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wrote:

If you need to fish two wires, fish a rope or wire or strong string, like nylon, and use it to fish each of the two electric wires. You can use a snake to fish the string. The string only has to be twice as long as the distance you are fishing it, so you can pull the string back and forth and not lose the end at either end. And you can sometimes fish in stages like an inch worm.

So don't waste it. Give it to someone who needs it. Give it to a friend or a store that sells the stuff.
I damaged my bathroom sink years ago -- by letting water sit in it for days or weeks, under a sponge iirc. I thought that a porcelain sink could hold water for months or years, but maybe my steel and enamel sink isn't the same as porcelain. So insteaad of going to a good plumbing supply store, I bought a replacement at a big box store that is meant to mount on top of the counter instead of underneath, like the original. Last night I found one that one of my neighbors has thrown away, and it is a perfect match, and it's in perfect condition.**
So I'm going to give away the sink I had bought. The store that I bought the sink from is out of business, 8 years ago, Hechingers, so I'm going to find a plumbing supply store and give it to them. I was going to buy a new sink from them, that actually fit, and maybe try and get some money off for giving them the sink I bought, but now I'll just give it to them.
**Even the faucets, and the drain pipe and stopper control rod beneath the sink I found are in perfect condition. And shiny clean. The faucets are just like mine, so they and the sink are almost certainly original, which means 27 years old. I don't know how anyone could be so clean. And there aren't many people here anymore who were here even 15 years, so it must have been two families in a row who were clean.
Even then, have any of you ever polished the metal strip behind the drain which raises and lowers the stopper, or even the drain pipe? I didn't think one was supposed to clean those parts.
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