Custom hydronic heating controller

[compman723]

Hi,

I was wondering if you have any updates on how your project is working?

Great work so ffar!

[opiesche]

Originally Posted by compman723

Hi,

I was wondering if you have any updates on how your project is working?

Great work so ffar!

Thanks! I'm still at it - the pump arrived and is installed next to the manifold, and I've also got a relay to switch it with. On the software side, things are slowly progressing - I've got it running in a loop, measuring, calculating and predicting when to turn on/off the pump. For the last week, I've had it running and pretending when to switch the pump, just to see how well the math worked, leaving it running overnight, tweaking the parameters the next day, and repeat. It's working pretty well now, and can also estimate the lag (between turning on the pump and the temperature rising) and heat retainment (time between turning off the pump and temps dropping) based on prior measurements, and takes that estimate into consideration for pump switching.

Today, I cleaned up the code a little, but it's still a ways off from what I'd call maintainable. Give me a couple of days and I hope to make it publicly accessible

Work has been busy lately, so aside from that I haven't gotten much done. the web interface still needs a bunch of work (saving of the configured parameters in a way that the controller can then read and use them, and better ways of adjusting target temperature and viewing the sensor and calculated data) I hope to get some help on once the code is out there

[opiesche]

Hi all,

Back with an update. The water heater is installed, after a long and difficult series of unfortunate events (see my second to last blog post), and the Raspberry Pi controller is now happily measuring temperatures and switching the pump.

Adventures in home improvement: Controller and manifold

The whole wiring job was really easy (of course I've got to do a little bit of cleanup and water proofing to make sure nothing ever goes wrong), and once the controller was hooked up to the sensors and the pump via a relay, everything worked on the first try.

I'm currently tweaking the water temperature and flow rate to see how that affects heat output, as it's not nearly as much as I'd hoped (although enough to keep the house comfortable). I hope to have some time tonight to push the source code for the controller software to github.

[opiesche]

Finally:

https://github.com/opiesche/Prometheus

The code is anything but pretty, and much of it is still hardcoded (such as the sensor IDs and GPIO pins the sensors and relay are hooked up to). It's working though, so if anyone cares to take a gander, please do so

The web interface is also still rudimentary (and still contains some unmodified elements from the template I used), but it does plot temperatures and pump-on times, shows current pump status and estimates for lag, retainment and time to target temperature, and allows for the target temperature to be set.

I haven't had much time to work on it lately (travel for work got in the way , but I'll update the repository as soon as I've got the next set of changes ready.

[AC_Hacker]

Originally Posted by opiesche

The code is anything but pretty, and much of it is still hardcoded...

So, regarding the floor, etc., is there anything that you'd do different were you to begin again?

-AC

BTW, I've had other time demands, but I am reading materials from your links regarding crawlspage insulation. Thanks!

[opiesche]

Very good question. I'd mostly do small things we learnt during the process from the beginning to make the job easier. If I wanted to summarize,

-cutting the OSB substrate at an angle at the tubing turns so that the tubing doesn't pop out as easily when running it

-spray down a little spray adhesive before putting down the underlayment so it doesn't slide around when putting the flooring down on top

-I'd definitely tackle crawlspace/underfloor insulation first, as I now realize how much of the heat I'm losing downwards.

-What I would think about changing about the heating system is possibly use smaller spacing between the tube runs to help the alternating warmer and cooler spots on the floor and increase the output, but that may very well be alleviated with the crawlspace insulation.

-Use Sharkbite PEX connectors wherever possible, as the crimp fittings can be a pain to get water tight

In terms of the installation process, I think the fact that my dad and I did almost 1000 square feet in 10 days including ripping out carpet, installing the heating system, installing the hardwood floors, and cleanup, shows that it worked pretty well. I don't think I'd use a prefabricated floor panel system over the strip cut OSB, because that would actually make it more difficult in many places to route the tubing through tight spots and around hallway corners. Some of the routing where multiple runs from different rooms come together would have been really tricky to make fit with prefabricated panels.

As for the hardwood floors, I stand by saying that strand woven bamboo is the way to go. It's ecologically friendly, not too pricey, and despite the fact that we're hard on floors (e.g. big dogs and a bunch of various construction and renovation work *after* the floors were put in) we don't have more than a few surface coat scratches that are hardly visible. This stuff is tough.

[Daox]

I think you are the first to mention crimp pex fittings leaking. What kind of type of crimps did you use?

I've personally never had a problem and others seem to love them. On the other hand, I've had a problem (one) with the sharkbite type fittings not sealing properly when I move my washing machine and had to run new plumbing.

[AC_Hacker]

Originally Posted by opiesche

-Use Sharkbite PEX connectors wherever possible, as the crimp fittings can be a pain to get water tight

I can't speak for Sharkbite, but I also had trouble with the standard crimping rings when I was re-doing my plumbing.

I found that the Cinch/Pinch rings worked wonders... no more leaks... not a single one.

Also, the tool required was cheaper, and smaller which allowed me to get into tight spaces more easily.

The rings are somewhat more expensive, but the ease of use and leak-free joints made all the difference.

Also, due to my own inattention, a ring had to be removed and replaced, and these rings are much easier to remove without damaging the PEX than the usual copper crimp rings. There may be a special tool for the job, but I just used some sharp, sturdy dikes and cut through the 'pinch' with ease.

Best,

-AC

[opiesche]

Interesting. I was using standard copper crimp rings and had a really hard time getting the connections to the water heater tight on some of the thread-to-PEX connectors. For some reason a few of those just didn't want to seal. One of the connections to the pump had a similar issue. Took me three or four tries to get them sealed.

[Daox]

I've also used the pex 'cinch' rings AC Hacker has posted with great success. Haven't had one leak with them yet. I haven't done a TON with them... but they've been very handy for the reasons AC Hacker stated.