Evohome - large temperature overshoots

[f1arp72]

I know that I have had the controller beside my bed and spent all night checking it.

And that's where mine is right now. I wake up at 3am and look at it just to see how cold my house is getting !!!! I think I'm going crazy.

[f1arp72]

Quick question on your rooms that didn't reach temperature. Are the radiators of the right size such that they can heat the rooms up to that temperature ?

I'm sure they are. Before Evohome was installed, my house was pretty much static at 21 downstairs in all rooms (except conservatory due to obvious heat loss). That's one of the reasons I bought it so I could heat the conservatory without the rest of the house. Problems is, with the erratic temperatures, I'm beginning to think about the saying "if it ain't broke, don't fix it". Mine wasn't broken, but I'm beginning to feel like it is now.

[erik]

If you search around you'll find a Python script that reports the temps (as reported by your HR92s or whatever else you have as a sensor in the zone) every five minutes.

I got a temperature logger so I didn't have to watch the temperature myself anymore. Put it right next to whatever sensor Evohome was using (either the Round Wireless, the HR92 or the Evotouch). Nifty little device that records temperature every 10 minutes and allows me to make a graph of it on the PC later. I would leave the setpoint on 1 certain temperature all night (no influences of sun or doors opening/closing or devices causing heat) and see how it performed.

It's important to use an independant temperature sensor if you want to check the precision of the temperature regulation. The temperatures that Evohome shows on the screen and in the app are biased towards the setpoint. For example: if HR92 reads 17.4 and setpoint is 18, Evohome will report 18. If HR92 reads 17.6 and setpoint is 17, Evohome will report 17. Same thing happens when using an external sensor (round wireless for example) by the way, or when using the Evotouch itself.

[paulockenden]

I guess, ultimately, an HR92 is attached to a radiator and hot pipework, so will be affected (to a certain extent) by them.

Also, against a wall, and a few inches above the ground probably isn't the optimum place to measure a room temp. So I'm surprised the HR92 makes as good a job as it seems to. But for some rooms you're going to need to use the 'offset' facility to get a normalised room temp, and for really awkward rooms you might even need an external sensor (DT92 or whatever). Probably worth doing that, before you give up (or go insane!)

[G4RHL]

I guess, ultimately, an HR92 is attached to a radiator and hot pipework, so will be affected (to a certain extent) by them.

Also, against a wall, and a few inches above the ground probably isn't the optimum place to measure a room temp. So I'm surprised the HR92 makes as good a job as it seems to. But for some rooms you're going to need to use the 'offset' facility to get a normalised room temp, and for really awkward rooms you might even need an external sensor (DT92 or whatever). Probably worth doing that, before you give up (or go insane!)

I understand the Hr92 is designed to allow for its location and reads the temperature rising from the floor level. Generally I find it slightly lower than a free standing thermometer at waist height. Having optimisation off has certainly reduced the constant cycling of the boiler for me.

[erik]

So if that's the problem, it would need a revised version of this logic to fix the problem. Wich would probably require a firmware update on the controller probably?

[paulockenden]

Have those with overshoot problems tried turning the boiler thermostat down a bit? I suspect an an Evohome controlled system doesn't need the full-blast of heat that suits conventional on/off controls.

P.

[erik]

1: tuned down from 90 to 60.

2: other thermostats work fine with the same boiler (even when not tuned down).

3: 'Evohome controlled' isn't really that different than conventional on/off control for me. Evohome, in my case is on/off as well (non modulating) and my conventional thermostat uses TPI as well. Only difference would be zoning. But with the conventional controls, I manually close the valves in the un-used rooms, so no difference there either.

[Rameses]

@f1arp72 - I have DM'd you

[mikey8156]

I have had Evohome for 4 years, I had overshoot problems, at first I thought something was wrong, turned down boiler temperature, half turned down the inlet radiator valve. Finally I realised that the system was learning, can take a few days. If the overshoot is unacceptable, for instance 2 degrees over shoot, just reduce the set point by that amount until the fuzzy logic has learned.

[G4RHL]

For me optimisation never worked, certainly for switching on. Adjusting off time was better. But after many weeks it never learned it did not need to come on as early as it chose. I found it just as comfortable and of course more economical having the heating come on at the chosen time.

[mikey8156]

It takes about 2 weeks for Evohome to learn the heating up time.

[G4RHL]

It takes about 2 weeks for Evohome to learn the heating up time.

So I understand. I left it for over 4 weeks and there was no change.

[erik]

I've tried it for 2 years and it never learned.

By the way: in the same house, location, boiler, same everyhing, an old skool dirt cheap simple thermostat learns in under 1 day (and uses TPI as well, so is just as efficient).

[guyank]

Did you ever find a resolution to this? I have a similar problem in one zone, the lounge. When I get up in the monring, it's set to 15C still and not to 20C until 90 minutes later. However, Optimum Start doesn't indicate on for that zone on the controller and the temperature has already risen to 20C (from about 17c overnight) with the radiators very hot. It reaches 21.5C (indicated on the controller, not a different thermometer) before it starts to cool down. The HR92s are able to fully shut as at other times of day the radiators are cold when others in the house are hot. It's been installed for 2 weeks now and every other zone seems to have learnt but this one.