Monitoring and controlling a hot water in a vacation home

(Cham) #1

Hi everyone,

I’m new to the community and pretty new to Smartthings in general. I’ve been using Smarthings to monitor my home for a while now, but this is the first time I’m attempting a more major “control” project.

I have a vacation home in a cold weather environment, so it’s pretty expensive to keep a hot water tank on all week, even though we are usually only there on weekends.

I was thinking that it would be cool to use something like the “it’s too cold” app to cycle the power to the hot water heather/tank based on a Multisensor’s temperature reading (to keep the tank from freezing).

My problem is that I’m no electrician, and I have no idea what a safe way to switch the power to the tank on and off would be, or if a SmartThings device can be set to fail to “on” (in case I lose my internet connection). I think Failing to ON would be important because we usually have power, but often the internet will cut in and out, which my temperature sensor to prevent freezing won’t work.

Can anyone recommend a switch (or is it a relay?) that I could have an electrician install? The specs off the side of my tank are:

Cap: 270 Litres
240/208 VAC 1-PH (whatever that means)
Watts Upper/SUP: 4500/3380
Lower/INF: 4500/3380
Total: 4500/3380

For those that know brands of hot water tanks, it’s a Rheem Professional 615.

If I can find a switch that works, any thoughts/recommendations on the temperature monitoring and “fail to on” idea?



Would introducing a water shut-off valve help in this project? What if you had the ability to shut off the water at the main or even at the hot water heater?

This one is kind of expensive but take a look:

Some cheaper ones are coming to market soon.

(Convinced ST will never be unbroken…) #3

I use an Intermatic CA3750 to control my water heater, but it does not default to anything. As with anything with SmartThings, if it goes offline, you lose control.

So if internet is an issue, would recommend hooking up something with local control outside of SmartThings (possibly Vera or Universal Devices).

(Cham) #4

Thanks Tyler and Scottinpollock!

I hadn’t considered a water shutoff valve, but that would minimize the risk in the event of a power loss. I’ll definitely investigate further, as even a “dumb” shutoff valve would really give me some piece of mind.

The Intermatic CA3750 looks like it could do the trick for the basic on/off. Have you been using it for a while scottinpollock? Any tips or recommendations?

Thanks for your help guys!

(Convinced ST will never be unbroken…) #5

I have been using it without issue for a couple of months now. It replaced a GE analog timer so install was just replacing the box and wiring the same load an line to the screw terminals. I guess the only tip I can offer is that this is a discontinued model. That’s one reason you can get it so cheap. It has limited range when compared to the newer Z-Wave stuff so plan on having other devices between it and the hub if there is any appreciable distance or obstacles.

Although Intermatic has discontinued their entire InTouch line, they provide a ten year warranty on these devices, and they’re not going anywhere as a company so I thought the purchase a wise decision. Don’t wait too long though. Don’t know just how many of them are left in the wild.

(Cham) #6

Great point, on both range and availability. Thanks!

(John Rucker) #7

Here is a link to a ZigBee controlled 30amp relay that can control large AC loads like a pool pump or hot water heater. It may require a custom device type to be written in SmartThings.

Now for the off-line solution (No Internet connection) The ZigBee spec has the ability to bind devices together so they communicate directly to each other without the need for a coordinator. We now need to find a ZigBee based temperature device that can send an on/off command based on a temperature setting. What device are you using is it ZigBee or Z-Wave based? If it is ZigBee do you know if it supports End-Device-Bind?

(Cham) #8

At this point, I’m still planning. I don’t have a temperature device as yet. My initial thought was really just to use a smartsense multi to measure the ambient room temperature, based on the assumption that if the room is above freezing, the tank will be above freezing.

If I were to purchase a separate temperature sensor, I would think that it should replace the current tank’s sensor. I’m keen to give that a go, but it’s well beyond what I know how to do.

Sounds like I should focus my efforts on a ZigBee based temperature sensor if that will allow direct offline communication.

Have you worked with one that you would recommend? Ideally, it would work with the Intermatic CA3750, as that is almost half the cost of the Smartenit product.

I guess the final question would be; how hard is it to write a custom device type? I’m new to this, so haven’t tried anything along those lines yet.

(Convinced ST will never be unbroken…) #9

CA3750 is Z-wave…

(John Rucker) #10

Cham, I was thinking about this over the weekend and I hate to say it but I’m not sure a wireless solution is the way to go here. If you read the usage polices of most of the Home Automation devices they state to not use them in situations where they may cause property damage. In your case a frozen water tank or a frozen water line can cause a ton of damage to your home. It may be best to have some type of fail safe thermostat directly wired to your hot water heater. You can still turn it off and on with a ZigBee switch but don’t count on the ZigBee switch to keep it from freezing. Chances are if your hot water heater is gong to freeze your pipes are also going to freeze so it may be best to just keep your house heather running but turned way down say 40 degrees or so to protect all your pipes.

(Edward Pope) #11

Or he could do a hot water on demand system. You would still need to monitor the situation around the pipes. I fo agree with John here. If you need to use a Water Tank, it is better to turn it down vs. off.

(Cham) #12

Thanks for your thoughts @JohnR & @theedpope. I’ve been thinking along the same lines. In fact, if the tank were easily accessible, I probably would just turn it down by hand!

I am less concerned about the pipes, as I actually do keep the heat on inside. It’s just that my hot water tank is located in an unheated crawlspace (making it that much less energy efficient).

I’ll look in to some replacement (zigbee or z-wave) thermostats for the hot water tank. I’ve never heard of such a thing, but someone must make them.

@JohnR, I think you are right about an on-demand system being the way to go. It will probably be what I go with ultimately, but it’s a fairly new tank, so I’m trying to hold off on the upgrade for the time being.