Evohome - poor temperature regulation

[roydonaldson]

- Seems to be regular when the zone is coming on. Lasts for about half an hour at least (though I've not monitored it thoroughly). Does it all the time.
- Not creating it in any way.
- I'm saying overshoot to mean, temp is set to 19 on EvoHome controller, reading of temp in zone on EvoHome is showing 21.5.
- All other zones in house now, bar 1, are HR92s.
- HR92 has been in place now about 2 weeks. I had thought it would settle down.

One thing that is different in my config is that it is non-standard. I have S Plan Plus. I have the downstairs zone to control downstairs zone valve, upstairs zone controls upstairs zone valve. All other zones are radiators and there is *no* boiler relay configured (just about to get that sorted, but I need a plumber to do some pipework for me).

However, was working perfectly with the old HR80 there. PM me if you'd prefer to talk offline.

[Rameses]

- Seems to be regular when the zone is coming on. Lasts for about half an hour at least (though I've not monitored it thoroughly). Does it all the time.
- Not creating it in any way.
- I'm saying overshoot to mean, temp is set to 19 on EvoHome controller, reading of temp in zone on EvoHome is showing 21.5.
- All other zones in house now, bar 1, are HR92s.
- HR92 has been in place now about 2 weeks. I had thought it would settle down.

One thing that is different in my config is that it is non-standard. I have S Plan Plus. I have the downstairs zone to control downstairs zone valve, upstairs zone controls upstairs zone valve. All other zones are radiators and there is *no* boiler relay configured (just about to get that sorted, but I need a plumber to do some pipework for me).

However, was working perfectly with the old HR80 there. PM me if you'd prefer to talk offline.

Appreciate that as this thread is getting long but a few more Q's which may help other forum members

- Have you put the HR80 back on? and problem goes away?
- By creating I meant how were you issuing the command for heat - so in this case sounds like your normal schedule - if so what was the point before if you can recall?
- just to confirm its this zone that has the prob ? or all zones with Hr92?

Thanks for patience in answering

[erik]

An overshoot as large as 1.5 is something I've only consistently seen during a year of extensive testing when using thermostat-modus (no hr92's/hr80's). Also, I haven't seen a real difference between HR80/HR92 behavior. So my guess would be that some other factor is playing a role in your case, Roy. The challenge is to find out what it is. Wrong binding? Still learning?

Rameses, not trying to be negative, really. In my opinion, it's really not good practice to be too sure of a product being perfect. It might make you miss actual real problems. A product might perform excellent in certain situations but perform poorly in different situations. For example, the 1.5 overshoot in thermostat modus only happens if a heating system is able to eventually raise temperature by 1.5 degrees with just 1 minute of heat per 10 minutes. This does not apply to all systems/houses. In certain houses, the 1 minute of heat per 10 minutes might keep the temperature spot on perfectly, or maybe it won't be enough and even cause the temperature to drop, making the system having to change to 2 minutes of heat per 10 minutes, to maintain temperature. Anyway, they won't get an overshoot. There's so many factors playing a role, there's not a single rating agency that will have tested them all. You've got hard data saying it works as it should, but some people have hard data saying it doesn't work as it should. Is it not possible for both to be right?

I'm happy to see that you're saying that you want to understand what other factors could be playing a role for Roy and not instantly dismissing the problem. I'm sure it's appreciated by Roy and certainly by me.

[roydonaldson]

- Haven't had time to do swap over with HR80 or HR92 to test as of yet.
- Yes, just normal schedule. Point before is 16. Todays schedule is: 12:00, 16 15:30, 20 20:00, 15 22:30, 10
- Seems to be particularly this one I've noticed. I've not been watching closely. I think the kitchen slightly does this, but this is 3 HR92's in 2 rooms set as multi-room.

[Rameses]

- Haven't had time to do swap over with HR80 or HR92 to test as of yet.
- Yes, just normal schedule. Point before is 16. Todays schedule is: 12:00, 16 15:30, 20 20:00, 15 22:30, 10
- Seems to be particularly this one I've noticed. I've not been watching closely. I think the kitchen slightly does this, but this is 3 HR92's in 2 rooms set as multi-room.

Let me mail you - as I have some more Q's

Had the same overshoot observations - ironically kitchen utility was one, but I dont worry as the poor Hr92 has a bugger of a time trying to learn as one week we close the door, then next we dont . So obviously the air flow was way different.

The other time I had an overshoot was the orientation of the HR92 - found out one of my boys had moved it around so it was facing more near the rad - this didnt help.

[Rameses]

An overshoot as large as 1.5 is something I've only consistently seen during a year of extensive testing when using thermostat-modus (no hr92's/hr80's). Also, I haven't seen a real difference between HR80/HR92 behavior. So my guess would be that some other factor is playing a role in your case, Roy. The challenge is to find out what it is. Wrong binding? Still learning?

Rameses, not trying to be negative, really. In my opinion, it's really not good practice to be too sure of a product being perfect. It might make you miss actual real problems. A product might perform excellent in certain situations but perform poorly in different situations. For example, the 1.5 overshoot in thermostat modus only happens if a heating system is able to eventually raise temperature by 1.5 degrees with just 1 minute of heat per 10 minutes. This does not apply to all systems/houses. In certain houses, the 1 minute of heat per 10 minutes might keep the temperature spot on perfectly, or maybe it won't be enough and even cause the temperature to drop, making the system having to change to 2 minutes of heat per 10 minutes, to maintain temperature. Anyway, they won't get an overshoot. There's so many factors playing a role, there's not a single rating agency that will have tested them all. You've got hard data saying it works as it should, but some people have hard data saying it doesn't work as it should. Is it not possible for both to be right?

I'm happy to see that you're saying that you want to understand what other factors could be playing a role for Roy and not instantly dismissing the problem. I'm sure it's appreciated by Roy and certainly by me.

Thanks erik appreciated.

As for hard data - etc you are right not everything can be tested and it depends on constants and variables. We test and rate as much as we can - the hard live data (some of it is your's) is demonstrating a good level of control, hence our confidence. But if we can work together in the forums to enable people, how to identify the other factors (and reasons) then we can all benefit - hence reason I am now giving insight into personal experiences.

End of the day I and the family feel ok (we never had this level of control before so hey!) - but appreciate others need to explore that comfort value further. Hence the anecdotes.

[roydonaldson]

- Haven't had time to do swap over with HR80 or HR92 to test as of yet.
- Yes, just normal schedule. Point before is 16. Todays schedule is: 12:00, 16 15:30, 20 20:00, 15 22:30, 10
- Seems to be particularly this one I've noticed. I've not been watching closely. I think the kitchen slightly does this, but this is 3 HR92's in 2 rooms set as multi-room.

[roydonaldson]

Just created a brand new zone, added a out of box HR92 to it, copied the schedule over and swapped it in.

[G4RHL]

It seems perfect conditions create perfect results. Today I went out and forgot to turn off my custom action which puts 3 zones at 21c. My wife went out later. I came in about 2 hours after my wife had left. Nobody else in the house. Every zone was reading 21c, thermostats the same. Nobody in moving around, emitting body heat, air changes, opening doors, cooking etc. Not a good test but it indicates in a perfect world the system works perfectly. Humans don't though!

[erik]

G4RHL, sadly that doesn't work in my case. I've been testing while being out of the house whole day, perfect conditions, and saw very much sub-perfect results.

But with the old wired Honeywell Round I'm seeing very good results. So I know that Honeywell CAN work very well in my home. I just wish it had zoning

[roydonaldson]

I should add that all my other zones are bang on temperature wise.

[G4RHL]

G4RHL, sadly that doesn't work in my case. I've been testing while being out of the house whole day, perfect conditions, and saw very much sub-perfect results.

But with the old wired Honeywell Round I'm seeing very good results. So I know that Honeywell CAN work very well in my home. I just wish it had zoning

That is telling me it is something about the heating installation in your house and perhaps the structure that is different causing the system to struggle. I would not know where to start with that one. You have probably already done it but perhaps a detailed survey from a heating engineer as to the best overall installation to suit your property, if you were starting from scratch, would lead to an answer.

[top brake]

- Seems to be regular when the zone is coming on. Lasts for about half an hour at least (though I've not monitored it thoroughly). Does it all the time.
- Not creating it in any way.
- I'm saying overshoot to mean, temp is set to 19 on EvoHome controller, reading of temp in zone on EvoHome is showing 21.5.
- All other zones in house now, bar 1, are HR92s.
- HR92 has been in place now about 2 weeks. I had thought it would settle down.

One thing that is different in my config is that it is non-standard. I have S Plan Plus. I have the downstairs zone to control downstairs zone valve, upstairs zone controls upstairs zone valve. All other zones are radiators and there is *no* boiler relay configured (just about to get that sorted, but I need a plumber to do some pipework for me).

However, was working perfectly with the old HR80 there. PM me if you'd prefer to talk offline.

How have you configured your BDR91s for S Plan Plus? What did you do regarding binding the hot water?
Thanks

[erik]

That is telling me it is something about the heating installation in your house and perhaps the structure that is different causing the system to struggle. I would not know where to start with that one. You have probably already done it but perhaps a detailed survey from a heating engineer as to the best overall installation to suit your property, if you were starting from scratch, would lead to an answer.

Just to be clear: it works just fine with other thermostats. And my property is pretty standard. Also, Honeywell employees who visited concluded there should be no reason for the system not to work in my house.

The big difference between other thermostats and Evohome seems to be that Evohome seems to want to turn the boiler on once every 10 minutes, no matter what, except untill very far above setpoint. Other thermostats (including other Honeywell thermostats) stop turning on the boiler much earlier. It's like Evohome doesn't expect it to be possible for temperature to rise with just 1 minute of heat per 10 minutes and hasn't accomodated for this into their controls. But this behavior is actually pretty common, especially when just heating 1 room (zoning) in a somewhat insulated home.

I know you're not always seeing this in your house and might find it strange or hard to believe, but other users are seeing this as well. Your house heats so quickly, it's often already more than 0.5 above setpoint within 20 minutes, so very hard to even analyze the 10 minute cycle behavior there. It only gets 2 cycles in those 20 minutes.

PS: I will create my own thread about my case soon. So I can stop 'polluting' other threads with it.

[top brake]

Not being one to start flames, but I changed the HR80 in my family room for a new HR92. This is direct on a Honeywell fitting (so no adapter). It now consistently overshoots by about 1.5C. The old HR80 used to keep it bang on. I'm not seeing this in any other zone, so wondering if there is some bug in there somewhere that is causing this. I have a spare HR92 and will create a new zone, add the HR92 to it, copy the schedule over to it and put it in.

Roy.

Always one to state the obvious but did you rotate the black wheel fully anti-clockwise before attaching the HR92 to the coupling?

Sounds like the radiator isn't closing off properly, perhaps the HR80 had full stroke/torque applied?