240V wiring question

I have a couple of in wall heater/fan units that were originally wired to run at 120V/15A. They are Cadet Register Plus Mulitwatt units, so they can also run at 240V. After doing some reading, I thought that it might be better to have them run on 240V, so I was thinking of rewiring them.
In my reading, as I understand, the only thing I would need to do, I THINK, is to change the neutral in the circuit to a hot breaker, and leave the ground the same. The wiring instructions on the device does not state any differences in wiring, so I am assuming that the device handles either voltage the same. Also, right now I have the hot (black) passing through the thermostat (separate). Would I need to change this? I would think it would work the same (it is rated for 240V-not that it will be sensing anything different-would it?).
Also, would it just be two bridged 15A breakers?
thx
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T-stat should be OK You need a double pole 15A breaker for these units. But I would like to ask if they are running fine at 120V now, why change it? You are not gaining much by switching to 220. Plus you'll use up an extra breaker slot in your panel for the double pole breaker, which can be a problem if your panel is full already.
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Clincher here is the fan isnt made to run off of 220v.........
Anyone mentioned "Magic Smoke" lately ???
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SVL




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Not to mention the fact that a 1500 watt heater at 110v = 8.0667 ohms and will draw 13.63636 amps........
Connecting the same ohms heating element up to 220v will produce a whopping 5999.99752 watts while drawing 27.2727 amps from the supply circuit.
IOW: Best to just forget the notion entirely.
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SVL




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PrecisionMachinisT wrote:

He's a bit mistaken about the voltage ratings of his unit, obviously.
At least he mangaged to find out that he was about to do something really stupid before he actually did it. And they wonder why we so often recommend a professional....
Hey OP, http://www.cadetco.com/show_product.php?prodid 01 Where is that 120/240 volt unit that you have?
Richard Perry
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Yeah, pretty much a disaster that was just waiting to occur.
Sorry man.....but I just couldn't resist......still I'm glad that he at least had the forethought to ask.......
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PrecisionMachinisT wrote:

    Well, I had asked about 240V, not 220V (NOTE the title of my thread?) I may be a little confused about the issue, but not about the voltage of my unit. I just had read a whole section on -240V- wall heaters in the book "Wiring A House" by Rex Cauldwell. He talks about the advantage of 240V vs 120V (it is 1/2 the current draw (page 220)).
    And then there is my Cadet Register Plus MultiWatt manual (models RMC 151 and RMC 162). On the front page of the manual,one of the "Feeatures and Benefits" is Multi-Watt: Determined At Installation: 120V or 240 V, running at eitehr 1500W or 1600W, respectively (at the top end).
    NOW my understanding of wiring for 240V is not expansive, since... I never have done it. But my understanding is this: The white functions as a "HOT" in the circuit, and there is no neutral return. The current flows back through the hot legs of the circuit.
    I guess I am not clear on what the guy below is talking about 240V being a European Voltage. Is the book I bought, which talks extensively about 120 vs 240V, and 240V dryers, heaters, water heaters, etc. completely worng? I am pretty sure it is made for USA use, since...it is written in English, published in USA, and sold in places like Home Depot.
    Now my understanding of European Voltage is that IT is 220V (maybe 230V now?)
    Clearly seome person(s) in this thread don't know what they are talking about. It MAY be me, but perhaps not...
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A lot of times 110 and 120 as well as 220 and 240 are interchanged. Since the voltage at any given electrical panel is not the same, I don't sweat it. As long as the unit works at 60 Hz you know it will work in the US.
As for the power determined at installation, I assume it means that you can either wire the 110/120 style plug to the 110/120 terminal or you could attach a 220/240 style plug onto the 220/240 terminal?
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It's the _same_ wattage (twice the voltage/half the amps) so it costs the same to run, so there is almost NEVER any advantage to converting an existing 120V heater to 240V.


Right, but you have to rewire the heaters so it doesn't let too much current through. The manuals _should_ show you how to rewire them.

He's confused (and wrong), don't worry about that bit.
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Chris Lewis, Una confibula non set est
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....LOL...
Now don't you start into getting all persnickity with me young man !!!
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yes I see it is not either voltage. It had been a while since installation, and looking at the manual it gave me the intitial impression that it could be wired either way. It does separate the models in one sentence in the manual, noting that one model is 240V and one is 120V. I don't generally like manuals that address more than one product at a time.
i appreciate the input, and especially your super condescending attitude.
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chester wrote:

As long as you caught your error....that's what matters eh?
hvacrmedic
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Stop: If you literally mean 240V, that's European voltage, not US and the wriing/attachment is different! IF it was a NA voltage, it'd be rated at 220V. They are FAR from the same, and no way it can run off either voltage without either a wiring change at the heater or a switch setting change if so equipped. You'll ruin it and have a good flame for a few seconds or minutes.
Pop

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If it's possible, there will be a wiring diagram on the device showing how to do it. If there is and you understand it, and feel comfortable doing the work, then certainly.
At the breaker end, you'll need a two-pole breaker, wired the same as you'd wire a dryer or a HW heater, depending on whether it requires two or three wires.
Study a "how to." If you understand it and feel comfortable doing the work . . .
Electrical work is not, in general, difficult, but it requires careful attention to detail.
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Actually, NA voltages _are_ 240V (and 120V). The reason why they mention 220V (and 110V), is because it is permitted by code to fall that low due to resistance in the feed by the time it hits the device.
There is some electronics that automatically sense 120V vs 240V, BUT NOT resistive heaters.
To switch to 240V, he'd have to rewire the panel end (to dual breakers) and the heater end (to 240V).
If it _really_ is convertible between 120V and 240V, there'll probably be two resistive heating elements. For 120V, you wire them in parallel, for 240V you wire them in series.
if it really is convertible, there'll be a wiring diagram _IN_ the heaters showing you how to change them.
But, there's no significant advantage to switching them from 120V to 240V.
--
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