Tracking down random boiler demand with Evohome

[erik]

You actually said "If you're heating up a room, you'll see Evohome continue'ing to request heat from the boiler every 10 minutes, even after set point has been reached." That is simply saying we expect it to fire up every ten minutes. My knowledge of English is that it cannot mean anything else.

1: Yes, that's what I said and I stand by it. However, that does clearly not mean the same thing as saying it's asking for heat REGARDLESS of setpoint and actual temperature. It's saying it's asking for heat SPECIFICALLY within a certain temperature-range related to the setpoint after reaching this setpoint. So yes, you can expect it to fire every 10 minutes, specifically after reaching the setpoint and not having reached 0.7 degrees over setpoint or more. And no, you can not expect it to fire every 10 minutes in the middle of the night when all zones are set to 5 degrees. My knowledge of English says these are 2 completely different things.

2: that comment was made AFTER top brake's comment, so he couldn't even have been reply'ing to that

[HenGus]

Interesting to see how Google supports Nest:

https://nest.com/support/article/Nest-Learning-Thermostat-software-update-history

[Wally©]

Well... To me it is definitely a showstopper if this system causes unnecessary wear and tear on my boiler...strongly decreasing its life expectancy... I feel that the purported savings just flew out the window...

[orange]

Interesting to see how Google supports Nest:

https://nest.com/support/article/Nes...update-history

if Nest became 'multi-zone' then you know it would be a be a better option that evohome. I know people who have it installed and the software backend is so much better. Whatever Honeywell may suggest - this stuff is not rocket science.

Honeywell should just concentrate on the hardware and open up the software side for someone else to take care of.

[erik]

@top brake: I know you don't want to continue trouble shooting me, but I'm very curious about just 1 thing: does any of the ideas you have involve Honeywell having to fix the firmware, or are they all based on the assumption that Evohome is perfect and that it must be the user who did something wrong?

[G4RHL]

1: Yes, that's what I said and I stand by it. However, that does clearly not mean the same thing as saying it's asking for heat REGARDLESS of setpoint and actual temperature. It's saying it's asking for heat SPECIFICALLY within a certain temperature-range related to the setpoint after reaching this setpoint. So yes, you can expect it to fire every 10 minutes, specifically after reaching the setpoint and not having reached 0.7 degrees over setpoint or more. And no, you can not expect it to fire every 10 minutes in the middle of the night when all zones are set to 5 degrees. My knowledge of English says these are 2 completely different things.

2: that comment was made AFTER top brake's comment, so he couldn't even have been reply'ing to that

Blame it on my advancing years and lack of detailed knowledge behind the system but am not following the points you raise. You say we should expect the boiler to fire every 10 minutes "specifically after reaching the setpoint and not having reached 0.7 degrees over setpoint or more" Then you say we cannot expect it to fire every 10 minutes when all zones are set to 5 degrees. The two points don't marry. If all zones are set to 5 degrees and the temperature drop causes the boiler to fire then surely that in time will trigger the boiler every 10 minutes as you say? In my case it does not.

I woke up in the early hours last night and noticed my boiler had fired up. There is only one room set to 5C and I knew it would be that radiator that had fired the boiler. Other rooms are set to 14C during the night. The outside temperature had dropped to 1c and the relevant room set to 5c is a conservatory. As I was awake I checked all and waited to monitor what was happening. When the conservatory TRV reached 5.5C the boiler shut off leaving a pump over run for a short time. Other rooms were showing their temperatures had dropped to close to the 14C setting, some dead on that some at 14.5 but were not firing the boiler. I stayed awake for awhile to listen to what was happening. Despite rooms being close to the setting I was not hearing the boiler firing up every 10 minutes. The system all worked as I expected it to.

The conservatory is being replaced today so I removed the TRV and shut the radiator down. I noticed other rooms had dropped to close to 14 - 14.5 in fact. One dropped below it and the boiler was triggered as I expected. Then it all shut down. That was at 1:30 a.m. By 2:00 a.m the boiler was not being triggered at all and at 05:00 a.m. when I got up all was quiet.

To me the system is working as it should but I suspect I have not fully understood the point you have raised. I have never had such a well controlled balanced heat throughout the house and when demanded. The only adjustment I need to make is to bring into use the separate thermostat for the lounge for I fear the temperature adjustment is affected by the proximity of a settee to one radiator and its TRV and I think I will be better advised to use a separate thermostat elsewhere in the room for that.

[erik]

I was assuming the temperature in a house never reaches 5 degrees or lower. This assumption was wrong for your situation, sorry about that.

But are you saying that setpoint was 5 and when it stopped heating it was already 5.5? That's a pretty big overshoot already. And it could even mean the actual temperature was 5.6 or 5.7. So 0.7 above setpoint. So it stops firing the boiler. Pretty much in line with my theory in that case.

This whole point I'm raising is easier to see when using Evohome in thermostat-modus (no radiator valves). Because in thermostat modus, it doesn't stop firing the boiler untill 1.5 degrees above setpoint. This is much more obvious than 'just' 0.7 degrees.

However, the 10 year old and cheap Honeywell Round on/off is able to keep room temperature within margins of 0.1 degrees. So I'm not going to be content with a 0.7 margin for a brand new 1000 euro system.

[emmeesse68]

By the way, I haven't even mentioned the fact that Evotouch is actually lie'ing about the measured temperature. It's always displaying it as if it's closer to set point than it actually is. For example: setpoint is 17. Measured temperature is 17.4. Evotouch will show 17 instead of 17.5. This makes it even harder to notice when it's not doing its job properly. And funny thing is, when you change setpoint to 18, it will instantly switch the displayed measured temperature to 17.5. Switching setpoint to 17 again, and suddenly it displays a measurement of 17 again. I would very much like to be able to see the true measurement on the display, instead of whatever Evotouch decides to display.

Noticed that already, but I just forgot to mention here because I was trying to look into all the other (bigger) issues like EvoHome calling for heat with all zones shut. That would waste energy (not much, but it's too much if the system purpose is to save energy) and would surely increase boiler wear n tear.

By the way erik, you mentioned earlier that you can read the actual measurements EvoHome performs... how do you achieve that?

[erik]

I received temperature logs of my system from my support contact at Honeywell.

[G4RHL]

It was reading 5.5 when I looked at it and at that time the boiler was off but the pump on.

I have never had the boiler come on when all valves are shut.

I do at times have the pump running on for a little while but that is normal. Indeed what puzzles me is I have heard the pump come on but the boiler not to fire up. Almost as if the system wants some heat but somewhere it thinks there may be sufficient in the system to pump around. I would not have thought that possible as if the pump is told to come on by an HR92 then the boiler would fire unless the boiler was too hot and its own thermostat had shut it down but that does not apply to a scenario where no heat is called for.

Today I had the pump being switched on and no heat at all but that was because the power throughout the house was switched off for a few minutes whilst plugs were isolated in the conservatory. It transpired that switching power back on must have caused a surge of sorts that triggered the automatic cut off on the boiler. Once ascertained all was fine. Indeed it shows that when all power is off and later restored the system remembers everything and is back up to normal quickly.

However as for precise temperatures I have never expected the HR92s to be showing a spot on accurate reading of temperature and am more than happy with something that is close to what it is without being that exact. If one wants the HR92s to show a more accurate figure you can programme in compensation allowances from its settings. The important aspect for me is the temperature of the room itself at normal sitting level, not four inches off the floor. Plus such is the human body that 21C for example can feel warm or cool or just right dependant on so many other aspects, including indeed one's mood. I have used independent thermostats to check the accuracy and initially it seemed the HR92s were way off in one or two rooms compared to a thermostat at desk height but then in time there was a closer accuracy. At present I am sitting in my lounge. The HR92 is set to 21C. It reads 21.00, a separate thermostat some distance away reads 21.5, this has remained like this without the boiler on for the past 10 minutes. Just as I type this I heard the valve adjust and the boiler has come on but I suspect it is my hall radiator that has called for heat. I am happy with this level of accuracy. You learn to live with what is comfortable and adjust to that. Evohome enables this. Far better than the old thermostat in the hall set to 21 but other rooms either too hot or too cold. I am sure any manufacturer can be spot on with accuracy for temperature but that does not mean human beings will always be comfortable. 21C can feel right, too hot or cold depending on many things including a human's own core temperature. The level of accuracy with Evohome seems to me to be perfectly acceptable.

[erik]

Well, my Evohome in the living room turns the heating on for 2-3 hours untill it reaches 0.7 above setpoint and then goes off for 2-3 hours untill it drops close to setpoint. When using it in thermostat-modus (nog radiator valves), it even goes up to 1.5 above setpoint and then lets it cool down to setpoint, wich easily means 4 hours of no heat. In no way is this even close to comfortable or acceptable. It's not smart heating at all. Especially since an old fashioned cheap thermostat from the same brand is able to perform 10x better.

There's many factors involved, so milleage may vary across different users in different user cases. By lots of monitoring and experimenting I've been able to pin point quiete exactly under what circumstances the problem I'm having occurs. If these circumstances don't occur in someones user case, then they won't have any problem. That's fine. Be happy But it doesn't mean it's doing a good job for everyone.

The accuracy of the reading by HR92 is not an issue in my case. Besides trying the HR92 and HR80 as temperature sensors, I've also tried the Evotouch controller as a sensor, on a pretty good spot in the room. And I've also used a Honeywell Round Wireless as a temperature sensor, located on exactly the same spot as the old Honeywell Round On/Off, wich performs fine. The reading is not the issue. It's the heating behavior.

If you would like to do an experiment, try the following. Put all your zones to 5 degrees, or totally off, if possible. Turn 1 zone to 1 degree above current temperature. Then monitor the behavior of the BDR91 relay and the room temperature for a while. When does the BDR91 stop going ON every 10 minutes? When setpoint is reached? Or when setpoint + at least 0.5 has been reached? Also, when does the BDR91 start coming on again?

[G4RHL]

Thanks, will run the test - when wife is out, she feels the cold!

[Rameses]

Hi

@Erik - your case is still open with Honeywell and we have your system being modeled in the labs. We have taken the data and findings from our site visit and are using this to evaluate your comments.

@Erik / @Orange / @G4RHL / @Wally and others, you have demonstrated a desire to know more about the controls and how the system works in a more detailed way. Therefore we are constructing a proper response to your appetite to know more.

Nothing in the system is random, whatever is done is done for good reason, and ultimately we are aiming to give a deeper insight, for those who want it. More information shortly.

[top brake]

Hi

@Erik - your case is still open with Honeywell and we have your system being modeled in the labs. We have taken the data and findings from our site visit and are using this to evaluate your comments.

@Erik / @Orange / @G4RHL / @Wally and others, you have demonstrated a desire to know more about the controls and how the system works in a more detailed way. Therefore we are constructing a proper response to your appetite to know more.

Nothing in the system is random, whatever is done is done for good reason, and ultimately we are aiming to give a deeper insight, for those who want it. More information shortly.

where is the 'like' button on this forum

[orange]

Great news Rameses - I think the more documentation that is out there for evohome the better.