EvoHome, OpenTherm and Remeha

[MindBender]

I am so glad I bought (most of my) EveHome setup at the business where I also bought the boiler, and with whom I have a service contract on the boiler.

My boiler is a 2006 Remeha Quinta 28c boiler, not that old. Is has been properly maintained every year since I have had it installed and it never gave me any problems with the original Celcia 20 thermostat that came with it. My experiments with a self-developed HomeSeer plugin controlling the Celcia 20 through the Remeha Gateway did unfortunately confuse the Celcia a couple of years ago: Even with the gateway removed, it regularly spontaneously jumped to 35 degrees. So I tossed the Celcia 20, replaced it with an iSense and that again has worked well for the past couple of years.

However, with the EvoHome OpenTherm boiler controller installed, the boiler regularly reports errors. In this error mode, the mode display and the temperature display on the boiler blink alternately and no heat or warm water are available. The numbers shown don't seem to be error codes, but merely the last mode and temperature from before the error occurred. All I can find on the internet is somebody writing this is a firmware error on a forum. Power-cycling the boiler doesn't cure the problem. Pressing the reset button does, but not permanently: It may come back the next day, or a couple of days later, but it will come back. Coming home in a cold house is not pleasant, especially not after having invested €1200 in a thermostat.

My boiler supplier has sent and engineer, who called Remeha and according to Remeha the burner controller in my boiler may have compatibility problems. Later burner controllers for this boiler don't have those. I consider that a defect: It's not doing something it is supposed to do.

Later my boiler supplier called Remeha again, and then they said there's only one version of burner controller for my boiler. More recent boilers have a different burner controller, but don't fit my boiler. The newer burner controllers have a feature called Smart Power, allowing to power more demanding thermostats and that should be able to deal with my OpenTherm boiler controller. He also called Honeywell for the whole past week, but they don't answer the phone (!) and don't call back on voicemail messages.

I find that a bit hard to believe: I don't think the EvoHome OpenTherm boiler controller draws that much power: Radiator valve controllers have much the same hardware, plug a motor, and they last 2 years on a battery. Plus: Smart Power is an OpenTherm 3.0 feature. If OpenTherm 3.0 is required, I thing Honeywell should have put that requirement on the box.

Now the supplier has proposed to use an EveHome on/off boiler controller on my setup, but I think that's a huge downgrade, both in performance and in efficiency, so we're in a bit of a stand off here.

Does anybody know more about OpenTherm compatibility problems with the EvoHome system? I have a fully equipped electronics workshop and I'm pretty sure I can measure power drops and/or power de boiler controller externally, but I doubt if that will help. Does anybody know more about OpenThem power supplies?

[MindBender]

According to a Honeywell specialist, replying to inquiries from my dealer, EvoHome should work normally on a standard OpenTherm boiler. He explicitly confirmed no SmartPower is required, that the OpenTherm boiler interface is designed for low power consumption and that it should work with a Remeha Quinta boiler.

The Remeha specialist, also replying to inquiries from my dealer, didn't get much further than the suggestions to check the wiring and to put back the iSense thermostat to see if that cures the problem; Trial & error, unfortunately. The errors indicated by the boiler, imho the starting point for diagnosis, were ignored.

To make sure the code displayed are really error codes, and not just the last mode and water temperature before the error occured, I instructed my familiy to write down the codes before they reset the boiler. The code reported the most by far is 0-18. Other codes we regularly see are 6-18, 7-18, 0-22 and 6-22. If anybody knows anything about these codes, please post!

[emmeesse68]

Don't know much of those codes but I'm facing a bit of resistance from Honeywell to support my OpenTherm setup. I live in Italy.

To make a long story short, I had problems buying an R8810 OpenTherm adapter since some dealers said it was not compatible with the EvoHome, even if it's explicitly mentioned in the installation manual.
When I reported communication issues to the dealer I bought the R8810 from, they wrote to Honeywell and in reply they said there would be no easy support because the R8810 is not marketed in Italy - that's a plain lie, since it is on their official price list.
So everyone is advising me to switch to an on-off boiler relay. Not an option for me either.

A thing I'm doing to try getting more insight is to use an OpenTherm Gateway (search this forum, you'll find a lot about it). I bought a kit and built it myself, for fun more than other things, now it's sitting between my Ferroli BlueHelix Pro 32c and "the evil R8810", patiently recording logs and adjusting some communication issues. If the problem for you is the smartpower only, IMHO this device could do something for you, because it really decouples boiler and thermostat, providing separate interfaces for both. Just a thought, anyway.

Cheers

M

[r_255]

Dont know if you have a outside temp sensor?
But I was reading the other evo topic again, and i came across this text from Digit....

I've had some problems with Evohome Evotouch in the beginning too. My central heating kept on pumping heat into our house
Only after I disconnected the outside temp sensor, the Evotouch was able to take control of my Remeha Calenta.

Hope your problem gets fixed!

[MindBender]

Today the Remeha specialist revealed that the Quinta internal controller is a Honeywell OEM part. That suggests at least some compatibility with Honeywell's EvoHome system...

The error codes seem to have some logic too: the number on the water temperature display turns out to be an error code. The number on the mode display is the mode in the boiler was in when the error occurred and not very useful in this case because the errors seem to occur is any mode. Mostly in mode 0, but nearly all other modi have been observed.

Error 18 is some sort of overheating error, indicating that the return water is too warm, of warmer than the water supplied by the boiler. Interestingly, error 22 is unknown to Remeha.

The Remeha specialist consulted his colleagues internally and he suggested to install a bypass valve: when the boiler is still beating and all the radiator valves are closed, the flow is obstructed and overheating may occur. Now we do have a bypass installed, but it may be stuck, broken or just adjusted for a too high pressure. So I took his advice to open one radiator permanently and in a couple of days we'll know if that cures the problem.

[emmeesse68]

This thing of the EvoHome not talking to itself is something I'm observing quite often. Luckily my boiler has an embedded bypass (that unfortunately makes a hell of a noise), I still don't have TRVs, just two zone valves, so I can't leave a radiator open as a bypass - until my zoning kits attive, at least.
Anyway, the annoying behaviour of the EvoHome looks similar: calling for heat from the boiler when all radiators or zone valves are closed. That suggests a programming error on Honeywell's part.
And it's not a compatibility issue with the boiler (I opened my Ferroli BlueHelix Pro 32c and noticed the Honeywell logo on more than half the parts inside), in my opinion it's a plain programming error: a trivial check on the controller, to see if a radiator/zone valve at least is open, BEFORE firing the boiler... et-voilà.

Obviously, since users are rarely listened to... the hope Honeywell vould even acknowledge such an issue to exist will stay a hope, in Italy at least.

Cheers

M

[MindBender]

Perhaps a bug, or perhaps a shortcoming. We know the radiator valves and touch controller only communicate every 4 minutes. So for a period of at most 4 minutes, all radiators may be closed without the controller knowing this and acting upon it. And 4 minutes is probably long enough for the boiler to overheat when the water flow is obstructed. As far as I know, the EvoHome system does require a bypass to be installed. And I don't really know if a built-in bypass will do the trick. A bypass is usually installed at the end of the chain, as far away from the boiler as possible. The Remeha Quinta boiler requires a bypass at least 60cm away from the boiler, leaving a minimum circuit of 120cm in case the bypass is active, but more is better.

Since Friday evening, I have permanently opened the radiator in my downstairs hallway by removing the valve controller. It's the smallest radiator we have in the system, but our hallway is now really warm. It's a bit early to mean anything, but we didn't have any error codes since.

I wonder what a sensible setting for the bypass would be. It needs to be tight enough to force water through the radiators, without creating a shortcut. But it needs to be light enough for the water pump to open it in case all radiator valves are closed. We have currently set it to 0.3bar, which didn't seem too high at the time, but I don't have any specifications on the pump inside the boiler.

[emmeesse68]

In my case, as I observe, a built-in bypass won't avoid overheating. My boiler would just stop and wait for a while to lower ecessive temperatures. But communication intervals for the radiator valves are no twhat I mean when I say EvoHome doesn't talk to itself. In my case I have two zone valves driven by two BDR91, and an OpenTherm R8810 to drive my boiler. Well, sometimes valves do open without the boiler being fired at all (pointless), and some other time, both valves are shut while boiler is firing (resulting in instant overheating and my boiler pausing). I observed situations in which my house was cooling down well below the intended setpoint, both zone valves were open, but the EvoHome "forgot" to call for heat. I resisted the temptation to manually fire the boiler because I wanted to see how long it would last and at some point the boiler actually started, but it has been nearly ONE HOUR (not 4 minutes) after valves were opened.
And in the opposite case (boiler firing with both valves shut) as well, I observed much more than 4 minutes insistence by my EvoHome controller to ask for heat before opening a valve or shutting the boiler.
Before setting up the R8810,my boiler was connected to zone valve's switches (in on/off mode). That way it could not fail (boiler wasn't driven by the EvoHome but directly by zones), but since I'd like to switch from zone valves to radiator valves, I bought the R8810 and since then I'm doubting abot having a faulty unit. I ordered some HR92 to fit radiators of one of my zones, when they arrive I could use the BDR91 taken off of that zone to replace the R8810 (losing OpenTherm functionality) just to check wether the EvoHome would behave the same in on/off mode, or if it's my R8810 that misses some beats. Either case, the reseller I bought my EvoHome from said Honeywell doesn't market OpenTherm in Italy (strange, since I bought my R8810 there, and it's in the official listing), that makes me think there is some issue they know about but don't want to officially acknowledge, expecially when EvoHome is set up by the homeowner and not a professional (Honeywell-authorized and trained) installer.

About your hallway radiator, could you try leaving it half-open? You would obtain a reduction of the excessive warmth and there would still be an open path to water (as a narrower bypass) to prevent overheating your boiler...

[MindBender]

Honestly, I don't see the behavior you're discribing. When ik works her, it works pretty well. The system is capable of finding thermal equilibrium with the boiler running at a constant power setting. And the radiator valve seem to find balance too, where I expected them to fully open and close intermittently. I'm rather impressed with how it works. Perhaps something else is wrong with your system, or perhaps you have an older firmware version.

I just found out that my bypass was set higher than I thought is was: it was at a generous 0.42bar. So tonight I screwed it back to 0.3bar and closed the radiator in the hallway. And at 23:00, when the heating shuts down, it had to reset the boiler again.

So now it's at 0.2bar, but I have little hope this will cure the problem. Perhaps the bypass is just broken.

[nickhend86]

Hello,

Is your problem solved? What specific code does the boiler give? Have you checked your pump?

[MindBender]

Is your problem solved?

No; It still persists. However, when keeping one radiator open for for just a bit, keeps the symptom away.

What specific code does the boiler give?

Errors are reported by alternately blinking mode and temperature indicators. When reporting an error, the mode indicator shows the mode the boiler was in when the error occurred and the temperature indicator shows the error number. In my case the mode varied and the error number was either 18 or 22.

Error code 18 means t1 (supply) temperature too high. Error code 22 didn't appear in Remeha's list. They seem to use a Honeywell controller and apparently they didn't bother to ask Honeywell.

Have you checked your pump?

It's integrated in the boiler and I wouldn't know how, without fitter two pressure gauges. And the boiler is under service contract, so I'd rather not fiddle with it too much.

[nickhend86]

I think either the burner controller has passed away, or your flow is too low. Could be the pump. I don't know your service contract, perhaps you could let someone check it out.

If your watertemperature rises too fast, the boiler should go in block mode and display code b 2.5. It stays locked for 10 minutes and should reset itself after that.

[ErikD]

@mindbender ... did you check fok.nl forum? There is quite some discussion ongoing on using Evohome and the problems you may encounter. I found it quite informative. The forum is in Dutch. See http://forum.fok.nl/topic/2195698 (there are 9 parts discussing Evohome)