(Another) Wiring Question

I need to install baseboard electric heating units in two rooms I'm refurbishing. One will need a 48" 2000 watt unit; the other a 36" 1500 watt unit.

The instructions in each box say that I will need to use a 220v circuit with "amperage according to local code".

Both rooms are next to each other and I'm wondering if instead of fishing two wires, I can go with one 10/2 30amp circuit and have both units branching off the main line. What might be the minimum wiring and amp circuit? What would be safest? What's the most amperage I can get out of a 10/2 line?

Related question: I've got tons of 12/3 wiring with ground laying around unused. Can I turn this into, say, 10/2 by simply clamping the black and red wires together at the panel and at the end point and then painting the red wire with black marker pen to indicate power? I hate to waste wire with the cost of copper these days.

Reply to
46erjoe
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Nope

Reply to
avid_hiker

220, or 240? It makes a difference. If the heater is rated 2000 watts at 220V, it will produce almost 2400W at 240V -- which is almost certainly the voltage that you actually have in your house. And never mind the installation instructions. Look at the rating plate on the heater.

You'd have to talk to a local electrical inspector to find out what your local code is.

Under the National Electrical Code, 10/2 is limited to 30A overcurrent protection (breaker or fuse), and continuous loads (such as electric resistance heating) are limited to 80% of the overcurrent rating -- which would be 24A for a 30A breaker. 24A at 240V is 5760 watts; your heaters total

3500, so one 10/2 30A circuit will be just fine.

NO. First off, that's a Code violation: connecting conductors in parallel is not permitted. Second, even if that was allowed, that would take care of only

*one* of the two conductors in the circuit anyway. What about the other one? It would still be 12ga. And don't even think about doubling up the white and bare wires -- you could wind up making the case of the heater live.

However, if the heaters are rated 2000 and 1500 W at 240V, you don't need a

30A circuit anyway, and you can use 12ga wire: 20A * 240V * 80% = 3840 W, which is adequate for the heaters you have.

OTOH, if they're rated 2000 and 1500 W at 220V, and you run them on 240V, then you will need a 30A circuit, because the heaters will produce almost 20% more power: 2380 and 1785 watts respectively, for a total of 4165 watts -- too much for a continuous load on a 20A circuit.

This is why I asked above if they're rated at 220V or 240V. It does matter.

That would be unnecessary -- red is assumed to be power anyway -- but as noted above, it's a Code violation, and it's not safe.

It's come down quite a bit since June. It's still more than double what it was two years ago, but I saw 250' of 12/2 NM at Home Depot last week for $67... and just a few months ago, it was over $100.

Reply to
Doug Miller

Well I can't think of a violation if you would cut the black or red wire at each end, or cap it, but not use it in any part of the circuit. I am not sure about that however. Of course you would not have 10/2 you would have

12/2.

Best bet is to find someone with extra 10/2 and work out a trade.

Reply to
Joseph Meehan

Unless you're only serving one device,

2 12-AWG wires 240V apart at 20Amps will deliver more watts to the other end than one 10-AWG wire at 120V and 30Amps.

And the 12-AWG will probably even fit on the screw-terminals.

Reply to
Goedjn

Yes, and that might in and of itself be a violation, as I explained in an earlier post -- he might *need* a 30A circuit.

Reply to
Doug Miller

So what's your point here? The OP has 240V heaters. The notion of a 120V 30A circuit was never being discussed.

Reply to
Doug Miller

Basic Electricity 101: current flows in a circuit, and needs to return back to the source (in this case let's call it a breaker box) along a 10 gauge wire as well. Thus, by "clamping" red and black together you get a heavier conductor only in one direction (from the breaker box to the load) but still have a light conductor in the return path. You would need to start with 12/4 and "clamp" 2 pairs together to do what you want.

Smarty

Reply to
Smarty

Right so far...

But that's a violation of the National Electrical Code.

Reply to
Doug Miller
061208 1139 - 46erjoe posted:

If the heaters are not too far from the panel, say more than 50 feet of wire, you can use the 12 gauge wire, using just one circuit for both heaters.

2000/220 = 9.1 Amps 1500/220 = 6.8 Amps 9.1 + 6.8 = 15.9 Amps

Derating the 20 gauge wire to 80% would be 16 Amps.

Don't even think about paralleling the wiring. If the voltage drop is severe, then consider running two of the 3-wire cables -- one for each heater.

Reply to
indago

You need to know the Full Load Amps. If you have the specs for the heaters it should be listed. If it is less than 16A then you can use one 20A circuit with number 12 wire.

If it is more than 16A, I think you are required to use 2 circuits.

No, but you can use 12/3 without connecting the white to anything. (cap it. don't cut it)

Reply to
Terry

Not so fast. If the heaters are rated at 220V as he stated (not 240V) but his service is actually 240V (as is very likely), the currents will be almost 20% higher (10.8 and 8.1 amps, respectively) for a total of 18.9 amps, requiring a

30A circuit because...

You mean 12 gauge / 20 amp, of course.

Reply to
Doug Miller

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.
Reply to
Doug Miller

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.

Reply to
mm
061208 2234 - Doug Miller posted:

Ooops! Yes...

Maybe he should check his line voltage to be sure...

Reply to
indago

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)

Reply to
Terry

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*.
Reply to
Doug Miller

utility supplies have been 240V for quite a while now.

that if the heaters are rated for so many watts at 220V,

*wire*, not

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.

Reply to
Terry

Think about what you are saying, Doug. A 2000 watt resistance heater stays a 2000 watt heater no matter what the voltage applied. Same for the 1500 watt heater. The resistance stays the same. Only the amps and volts are variables. The higher the volts, the lower the amps. Indago's calc was correct, as he figured it on the (worst case) lower voltage. One 20 amp circuit is sufficient for both baseboard heaters.

Reply to
volts500

If it's a pure resistance element, then no, that's not true. The

*RESISTANCE* stays constant; watts and amps increase with volts. V=IR and all that. Of course I know we're talking about AC circuits here so that will only be an approximation, but you get the general idea.

nate

Reply to
Nate Nagel

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