Arduino pool heater and other


I would like to try and replace my solar pool heating unit before forking out $300 for a new one and thought about using an arduino to do the job.

The solar heater I had checked the temperature of the roof and pool.
If the solar temperature was greater than the pool temperature and the pool temperature was lower than the set temperature it would turn on untill it reached the set temperature.

If roof didn't get hot enough it would run the pump for about 10minutes(great for winter use to keep the pool pump alive)

I am wondering if it would be possible to do this with an arduino?

I have gathered a few things I think might help with actually doing this project, can you point me in the right direction or say if its even possible?

Is there anything else I might need?

I also might add a light to the arduino that I can turn on with a web app? or do I need a special arduino board for wifi?


I would probably use a solid state switch optically isolated to switch your pump .

There maybe issues with how you measure the pool temperature , you need to take appropriate electrical safety measures .

Good project !

I would probably use a solid state switch optically isolated to switch your pump .

There maybe issues with how you measure the pool temperature , you need to take appropriate electrical safety measures .

Good project !

Would you use a solid state relay if the pump only requires 240v 4.3amp?

Is it better in general to use a SSR because of how long they can last?

Those cheap made-in-China relays are almost certainly overrated, keep that in mind. 4.3A is a pretty serious current.

SSRs are great for their longevity and quiet switching, but they do produce heat - which of course gets worse with increasing current. For that kind of currents it may be a good idea to look for a zero crossing switching type, in order to lessen the strain of the switching.

For measuring the temperature: those DS18B20 probes should do the job just fine, and as long as you keep your Arduino properly isolated from the mains power there should be no way for the high voltage to reach the water.

The hardest part may be the distance of the probes from your control board: you're talking about a water heater on the roof, and a pool, and a pump - three items that are probably at quite some distance from one another. Long wires may pick up a lot of noise, which can result in poor readings.


I have controlled my solar pool heater (and a lot of other stuff..) with Arduino for 4 years. (New pool last 2 years).

DS18B20 "Waterproof Type" like this work fine over 100 feet+

CAT5 cable is good for extending them See more info here:
scroll down to "long wires"..

A good optically isolated Solid State Relay like these would be good to control the pump.:

I measure input and output temperature of the solar panels to decide if it's worth the gain to run the pump. Problem is you can't tell from the temperatures with no flow. So I run the pump for 5 minutes and THEN check the differential IN/OUT. Only try this from 9AM to 6 PM. Recheck every hour.

With Arduino, you get to decide how this all works, and test stuff.

Make sure your Arduino ground is connected to building ground.

You can start with manual control of the pump/relay, then time it, then do temperature measurements and decision-making. "StepWise Refinement".. And save each version of your code so you can go back to "What Was Working Last"..

I also do the Chlorine dosage twice a day. Great for when you go away for a while.. Here's my pump and on the far upper right the small peristaltic pump for Chlorine. Keeps the chlorine at 3 to 5 ppm and never smells like chlorine when swimming.

Let us know how it goes...

I think you know that this is a good project and even a good beginner project.

caution is always advised when working around mains power 120VAC or 220 VAC.

I would suggest you look into an alumium double gang weatherrproof box for the relay.
they are pretty small
you might need to screw to the side of the box becuase the back has a huge boss for a back conduit connection.

assuming you will be putting this in a covered area, you only need to keep out the spiders.
if you want to put this in the exposed weather, then get a second waterproof box for the rest of the stuff.

I too would put my vote for the DS18B20 for temperature sensing. close to 0.1 deg F. resolution.

as for the Web enabled part, that would mean the use of something like an ESP8266 and that you have WiFi within range.

as for the SSR, they are usually over rated. by a lot.
also, they have a range of current and also a type of power

if it says 5 amps to 25 amps, it probably is good for 5 amps to 12.5 amps.

if it says 220 VAC, you are fine. Last time I got some there was no universal AC/DC versions. they were either AC or DC.
but they all took a low voltage input signal.
this looks just like the one Terry posted. you can see the lettering a bit better.
the output is AC and good for between 24VAC and 380 VAC
and even though the amp rating is 25 amps. you would be well served to not use more than 80% of that.

google pulled this pic from YourDuino
seems they have all the parts we have been discussing.
and although I have no affiliation with them whatsoever, I do believe the guy that runs that is an active member on the Arduino Forums.