Using a single pole RLV430 honeywell thermostat I need to wire a 240 volt heater. In my box I have 2 live and 2 neutral wires. The thermostat has 2 wires.

http://www.homedepot.ca/wcsstore/Hom...8044b91564.pdf

So, your confused? Pretend the thermostat is a switch with 2 poles. Wire it that way. It can switch 120 or 240.

It able to derive power for operation because of the low resistance of the heating element when off. It can then store this energy to use when the heater is on.

A 240 heater doesn't use neutrals, however in say a 10-2 with ground, the whites are the other hot leg, not a neutral. One black/white pair is the feed from the breaker. The other goes to the heater. Connecting the whites together and each black to a terminal on the thermostat will work. Connect all the bare wire and any green ones together and to any green screws in the boxes and housings. If the whites are hot wires, they should be marked with black tape at each end.

Using a single pole thermostat leaves all the wiring and heating element hot even when not on. A double pole thermostat leaves everything from it on, dead when off.

Thanks for both those responses. Just to clarify for anyone else reading this one. In Canada at least, you can use a single pole thermostat for a 240V heater. You wire one of the hot wires into the thermostat as usual, then tie the other hot to the remaining non-hot wire in the box.

Stas, thanks for that clarification, I thought that a single pole stat was allowed to control a 240 volt heater in Canada.

In the USA, that is not allowed, a 2 pole stat is needed, for thhe reason Labman explained.

Kiss, I need to ask about,


What derives power for what? What stores energy?

None of your statement makes any sense.

Let's take a simple circuit. A 120 V power source, and(The parallel combination of a 5 W light bulb and a switch) and a 1200 W heating element all wired in series.

If the switch is off, the 5 W light is on because the heating element resistance of 10 ohms is completing the circuit. So, in the analogy, when the thermostat is not calling for heat, we are powering the thermostat (the 5 W light bulb). Hence the term power stealing.

When the switch is on, the light bulb is off. We lost power. Not good. Well, maybe not exactly, we might have less than a volt available because of the drop across the semiconductor.

Now suppose that when the switch is off, in the above analogy we collect that energy in a capacitor, namely a supercapacitor with a value of a few FARADS. This then can provide power for the stat while the switch is closed. When a solid state device is used like a Triac, only a little energy is required at the zero crossing to keep it on.

It may not be the only way, but it's a way.

Aside: There are some new electronics devices that are being introduced that can generate an infinitetesimal amount of energy from mechanical motion and vibration. These will be used to power sensors with the same energy that they are measuring.

As forum expert, sometimes it is more quick to delete questionable posts rather than respond to them. Just click on the little box in the upper right corner of each of Kiss' plus this one. Then go to just under the last post and select delete under moderation. Select soft delete. Click Go, and the thread is cleaned up. If anybody complains, you have a record of what you deleted. So far, all my deletes in Dogs have stuck.

I hope the OP didn't see the first answer and go away convinced he wouldn't get any good help here.

labman:

I suppose you think I'm full of Sh**. Take a look at this article from Electronic Design Magazine.

Electronic Design Welcome

And:

Electronic interface for power stealing circuit - Patent 6490174

And 1.5 Farad caps for battery backup applications

http://www.panasonic.com/industrial/...ABC0000CE4.pdf

Keep in Simple Stupid:

The Guy is asking a simple question, not wanting a degree in electronics. Just answer his question.