Evohome woes

[graham.gibson]

Hi,

Not sure yet if it's fully sorted or not. Tonight I selected 'heating off' around 9pm with all zones around 20-21 degrees (which I think lowers the set point of all zones to 5 degrees?) and was pleased to note that the heating BDR91 went off about 9:04 and didn't come back on until I deselected heating off around 11pm. Initially a good sign. I'll need to do some more testing - it's too cold in Aberdeen at the moment to leave the heating off all night :-)

Thanks for all the suggestions.

Regards,
Graham

[graham.gibson]

Forgot to mention - Paul - I don't think your idea is bonkers at all and will give this a try if I experience any more BDR91 issues.

[DBMandrake]

Do you have "Failsafe" enabled in the System settings ?

[graham.gibson]

Hi, I don't have that setting available - I'm using one BDR91 as a heating valve relay and the other as a hot water valve relay as per the S plan configuration - I think you only get that setting when you have a BDR91 configured as a boiler relay.

[theasman]

Graham did you find a solution? I'm still having the same symptoms.

[graham.gibson]

Hi,

Well, I switched the heating off (via the button on the controller) overnight a couple of days ago (which I think lowers all the zones to 5 degrees) and the BRD91 stayed off all night (it took about half an hour before it went off - not sure why - but then it stayed off until I switched it on again.

What I need to try next is just lowering the temperature of all zones (maybe to something like 8 degrees) without switching the heating off to see if the BDR91 also stays off in that case.

I'll let you know how I get on.

What sort of scenarios are you seeing the BDR91 keep coming on and off?

Regards,
Graham

[paulockenden]

Another thought that crossed by mind - it IS possible to get genuine boiler firing when all of the temps on the controller look like they are up to heat.

It's when you have multi-TRV zones, and the zones are set to 'multi room'. Only the temp of the first one is reported for the zone on the controller (and via the apps/api). But in multi room mode each of the radiators can call for heat.

So, let's say you have two rooms in one zone. Bother have the same size radiator, but one is a small room and heats up quickly while the other is a big room and takes much longer. Let's also assume that the small room is the first HR92 bound.

The small room will heat up, and the zone will to all intents and purposes appear to be up to temperature, but the big room might still be calling for heat.

I realise this won't explain all of the problems that people are reporting, but it might be the reason for some of them.

P.

[graham.gibson]

Last night I set the target for all zones to 10 degrees and the BDR91 stayed off all night, so I'm hoping the problem may be solved for me now. I did wonder if multi-room might be an issue as I have a multi-room zone and I'd read a comment on another thread somewhere about this possibly causing an issue. I've got the sensor for that zone in the largest, coldest room. I'll continue to do some more monitoring and report back.

[DBMandrake]

I did wonder if multi-room might be an issue as I have a multi-room zone and I'd read a comment on another thread somewhere about this possibly causing an issue. I've got the sensor for that zone in the largest, coldest room.

I think you misunderstand multi-room zone mode. There is no one "sensor" for the zone, every HR92 uses its own internal temperature sensor to control its own radiator, but as Paul points out only the temperature of the "first" HR92 is reported back to the controller, yet all HR92's can independently call for heat if their own internal temperature sensor demands it.

I would also point out (although it's been mentioned across the various threads) that the Evohome system will still fire the boiler (but at a reduced duty cycle with a BDR91 or at a lower flow temp with an OpenTherm bridge) even when the zones are all "up to temperature" or even slightly above - up to a degree or so. A zone does not just suddenly stop calling for heat altogether because the target temperature is met, there is a proportional band on either side of the target. Only if it is about 1 degree or so over would it stop calling for heat entirely.

[paulockenden]

yet all HR92's can independently call for heat if their own internal temperature sensor demands it.

ONLY in multi-room mode zones. In 'normal' mode it's just the main sensor in the zone (be it a room stat or the first bound HR92) that can call for heat.

P.