Water Heater On/Off switch

I have a vacation condo I would like to put a zwave On/off toggle or paddle switch to control the electric water heater. The idea would also be to combine it with a zwave water valve so when someone turns on the water heater it also turns on the water valve. Any suggestions on what product I can us as an on/off switch?

Aeon Labs ZW078-A Heavy Duty Appliance Switch

GE 12726 40 Amp Indoor/Outdoor Contactor

Intermatic CA3750 Multi-Volt 120-277VAC Contactor Module

Edit: Re-reading your post, I realize what you have in mind. You could use a Linear/GoControl WT00Z-1 Accessory Switch(a one button scene controller) to simultaneously activate/deactivate your contactor from above and your Z-Wave water valve.

Just a word of caution… The Intermatic CA3750 is discontinued - and for good reason. You can still find them from various sellers (old “new” stock). After any power failure, the CA3750 forgets its zwave association. You literally have to pair it again with the controller - something you obviously cannot do remotely.

I ended up replacing mine with these three things from Amazon:

240v Contactor (uses 1-leg to ground for 120V coil) $9
Linear dry contact z-wave relay $35
Small NEMA enclosure for the above $18

So for about $65, you have a reliable, simple, and solidly built z-wave ‘switch’ for your water heater. Then you can use any remote to trigger the z-wave relay. I put one of these on my WH and 240V well pump at my vacation home. There is a very slight hum from the contactor coil. I think it pulls less than 4 watts when it’s on. They’ve run flawlessly. The Intermatic is going to the dump.

The end goal is to have an on off switch so people who are there can just flip it on and I can control it from home in the event someone forgets to turn it off.

Here is a link on how to do this. you can add any Zwave switch to power the relay.

Have recently installed a ZW078 controlling my 5.5KW water heater. Using UI7 on a Veralite controller. Works like a charm, also reporting the temperature (of the switch).

My issue is with the energy reporting. I “see” the instantaneous consumption on the device page but would like to to know which application I should use to monitor usage… The “default” ERGY does not appear to work correctly …


I found a terrific device to turn a GAS water heater ON and Off.

I don’t like the idea of being able to turn on my heater if the water to the house is off. Makes me uneasy.


This and your favorite appliance module and you are all set.

I like being able to turn it off, but I still don’t like being able to turn the water ON when I am not there to see if there are any leaks.


That’s a very cool device! Currently I can turn my drain and water off and on remotely, but the water heater has been the item that forces me to go to the basement every time I visit my cabin. This could end that trip outside at night!

I don’t see much information on how to use this device. 2 questions for me:

  1. how do you set the hot temperature point?
  2. can you manually operate it if the power is out?

I think I saw some mention of #2 being possible in the reviews on the company’s web site.

thanks again for posting this.

I have 2 Intermatic CA3750 and never had a problem loosing associations during a power failure. One is a rental unit over 1000 miles away and the other in a rental unit beside me.
One is switching 120v and the other is switching 240v. Had them for 3 years now, no issues.

Following up on my own questions on the gas water heater timer: it defaults to what they think is about 130 F, but it is adjustable. And their solution for a power outage is to disconnect it. They say it is really easy. I may give this unit a try.

Now back to the original topic - sorry for the diversion.