Electronic switch for water heater?

Question

An electric water heater can heat the water when it's convenient. It just needs some kind of electronic switch to decide when it's convenient. That switch can control the water heater's 240V outlet.

For example, if you have 100 amp electric service, and the water heater uses 22 amps, you could program the electronic switch to keep the water heater turned off whenever the electric usage of the rest of the house was more than 78 amps. That might only be a few minutes per day, then the water heater could heat the water for the next few hours, as needed.

My question is how to buy that electronic switch. What brand and model is the best for the money? How easy is it to set it up and program it, etc.?

Answer 1

About $70 - $90 for a basic residential timer. Any brand that's UL listed should be as good as the other. My old house had a Square D brand timer. My mothers house has an Intec brand. The water heater in my new house requires that no such device be installed.  

Answer 2

A clock or timer will not do what you want because they will operate at a specific time.

What you describecan be done with the right current sensors on the service but it is not terribly practicle. First you would need to establish a high shut off limit and a lower turn on limit or what you describle will not work. If the water heater is running at 22 amps and the load jumps to 80 amps, then your circuit will turn off the heater and the current will fall to 58 amps and your circuit will turn on the heater and then sense 80 amps and turn off the heater and so on.

Additional Info

Don't get bent out of shape about turning off the heater. A 100 amp service is fine for a house as long as you do not use electric heating which needs a 200 amp service. Keep in mind that the 100 amp service is at 240 volts or 24 kilowatts. The heater, stove and dryer are the only 240 volt appliances in most homes.

Answer 3

It's called an electric timer. We use this brand and you can set it to turn on and off at different times of the day. Any large home repair store should carry them.

As far as programing? there a cinch. Loosen the thumb s***w; slide trip key to desired time and re tighten s***w.

The wiring is straight forward.  

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Answer 4

they sell clocks for this reason around $65.00! Because you have a 100 amp service does not mean that you will even come close to that rating. 78 amps of current is a lot of juice, like four dryers all at the same time. What do you have in this house that pulls that much current all at same time. You can put a smaller element in the heater 3500 watts=14.58 amps.

it will not take four or five hours to heat water! If you are using that kind of amp draw you must have a big bill! Yes they sell devices like that  and they cost big money.

Answer 5

I think your suggested set up would require a program-able controller, with an output controlling the heating element contactor and an analog input card; wired to read the amps on your feeder from an amp clamp donut. This would be expensive beyond what your trying to accomplish. You'd be better off with a timer like other people have suggested.

Answer 6

This doesn't make sense to me.

Don't you want hot water when you need it?

Check with your power company, they may have a program where they control power to your water heater during peak periods in exchange for lower rates.

They will advise you of what would be needed to do this.

Answer 7

Check out the web site below. These paragon timers are used in schools and other building where hot water is not needed all the time.

They last a long time and work really well. All you do is connect the power to the heater into this timer and then connect the heater to the timer. Set it to come on around 5 pm and shut down around 10 pm then turn on around 6 am and shut down again at 8 am. It will pay for itself in energy savings.