Hot Water Heater Wiring

How can a 240 volt hot water heater run with 2 hot wires and no neutral?
Where's the return path??
Reply to
tarin
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050330 1800 - tarin posted:
The return path is the other hot wire; no neutral involved.
Reply to
indago
If the 2 hot wires are fed from different phases they sort of have a voltage between them, most of the time. So the current flows out of one hot wire and returns via the other, and vice versa a bit later.
(There will be times when there is no voltage between them - which is a good time to switch the heater on or off as it will reduce wear and tear on the switch and not send spikes onto the supply rails. As it can be tricky doing this by hand, buying a zero crossing point controller is a more practical way of doing this.)
If the two hot wires are fed from the same phase then the voltage difference between them will be pretty tiny and the water will take a long time to heat. Particularly if Summer has passed and the days are getting colder rather than warmer. But it should result in lower bills and nice bracing showers in the morning, to set you up for the day...
(Another advantage in doing this is that it changes even the cheapest Walmart switch into something as effective as the very best and expensive zero crossing point controller.)
Was there a particular reason for asking, or have you got lots of spare neutral wire that you need a use for?
Reply to
Palindr☻me
I just connected mine and thought it a bit unusual. I guess by understanding of how electricity flows is somewhat limited. And yes, I do have an unused neutral. The bare ground at least had a grounding screw to attach to.
What is a Zero Crossing Point Controller? Where do I find one and how and where is it connected.
Reply to
tarin
"They Sort of Have a Voltage between them, most of the time"?
"... The voltage difference will be pretty tiny"?
Is this a new standard of precision in the world of Electrical Engineering?
Beachcomber
Reply to
Beachcomber
I only like sunflowers if they are bonded to the neutral in the subpanel.
Reply to
tarin
At 240v, all the electrons spew out into the water and make it hot. The elements have a sharp curve in them and the + and - electrons meet at the center of the curve and jump off. Some folks will tell you that the wire is its own return path, and talk about AC changing polarity and stuff, but that's crap. Those electrons jump off, I've seen them.
Do you like sunflowers?
Reply to
Steve Cothran
I was taught to always use the lowest precision actually required to provide the required solution - anything more was over-engineering.
Whilst a more precise definition of the instantaneous values of the voltages referred to above, and how they vary with time, is essential to solving many problems - it isn't when the problem is simply where the current goes and why it is important not to use two "hots" from the same phase..
Once one starts approximating to actual values ( eg stating there will be no voltage between wires connected to the same "hot" line) - there will be someone who will say -- but oh yes there will be .....
Reply to
Palindr☻me
I don't know what the accepted practice in your country is for what to do with an unused neutral - so cannot advise you on this, sorry.
As to zero crossing point controllers - you can google this but basically this is how they work:
Electricty is supplied as alternating current - the voltage on one wire is sometimes higher than the return wire and sometimes lower, so the current alternates in direction between the two wires. As the voltage difference changes smoothly from one extreme to the other, at some point it is actually zero. Now, if you want to switch the power to the load on or off - arranging the switch to happen at or near that zero point can be a good idea.
So a zero crossing point controller does that with electronics - When you switch it on, it waits for the next zero point and switches approximately then. When you switch it off, it waits for the next zero point before switching off.
Usually the command to switch on and off is done by further electronics - eg combined with a temperature sensor, so as to keep a heater temperature constant.
The switch may be operating every few seconds or even many times a second in order to keep the element temperature as constant as required.
It does have limitations - it can't be used to control the temperature of something really really tiny, such as the filament of a lamp bulb - because the light would flicker too much. The time waiting for the next "on" command would be too long when set to "dim".
They are ideal for continuous flow electrical water heaters and small water tanks with high wattage elements.
Where you find one is, I would imagine, where-ever you buy electrical heating system components from. We have things called plumber's merchants in the UK.
How you connect it is simple - at least in the UK. It comes with two terminals labelled supply and two labelled load, plus an earth wire. You connect it between the isolating switch and the load. The one I use with my hot water tank came with a sensor with an adhesive ring and a tool for removing a plug of insulation so it could be stuck on the copper tank.
Reply to
Palindr☻me
I totally agree, two hot conductors from the same phase is as nothing (0~VAC) to a 220AC appliance., like tapping one 110AC conductor with 2 different wires at 2 seperate points on the same conductor (No Potential Difference)No current will flow, only if grounded., you'd, the appliance would probably need a transformer with a neutral tap to step it up.
In 220 ac motors & appliances (ergo heaters) the difference in phase conductors compliment each others voltage in a sine wave proportional to the sum of it's parts., a single phase has no potential difference or voltage but to ground, neutral or a different phase.
a heating element expends the potentially different electrons in making heat, never returning to the source, or as colorfully described they fall off and bounce around Hot inside the tank heating up the water.
Placing a two circuit (0r 220~AC) timer/switch on it is helpful curbing costs & easy to install.
=AEoy
Reply to
Roy Q.T.
ha ha ha, i think tarin set u up!!!
Reply to
sandman
Why not just say that the power varies as the square of the voltage divided by the resistance. That is the mathematical relationship and it clearly expresses the advantage of a higher voltage to your audience of readers.
The language that an engineer uses indicates the depth of understanding of the subject and allows s/he to communicate effectively with other engineers. The language of engineering or science is precise, elegant, mathematical, and has a logical structure.
I don't know where you went to engineering school, but I was taught that when working with standard electrical engineering projects, the level of precision should be taken to 3 significant figures. (More might be required for a precision scientific experiment.)
Call me biased if you like, but I don't think that most women, in general, have the slightest understanding of electricity.
Beachcomber
Reply to
Beachcomber
Thanks for your reply - good to see that your knowledge of science and engineering is matched by your knowledge of women.
Reply to
Palindr☻me

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