Evohome continually bringing boiler on for one minute then off for 10 minutes

[colin_]

Hi

When the zones are near temperature (if far away it keeps boiler fully on instead) it seems that the Evohome is bringing the boiler on for 1 minute in every 10 (as some of the zones are reporting not at 0% even though the system is reporting that it is at temperature).

I believe (though not sure) that the control system is doing this to keep push some heat into the radiators so it keeps at temperature rather than dropping far and having to put boiler on full blast (TPI function), however it seems to be continually doing this. This means that it the equivalent of bringing the boiler on for 6 minutes every hour and so for 20 hour same as if boiler had been on full blast for 2 hours.

The issue I have is that the minute on is not enough for the water the boiler (Bosch Greenstar 8000 Life) pushes around to get to more than 36 degrees and so the radiators calling for the heat do not get more than slightly warm (could never get above the 36 degrees but in reality much less). I could set the min on time for longer (max is 5 minute) but this then means that the boiler will be on for half an hour every hour) and 5 minutes still will not produce much heat (it takes around 10 minutes to go from 36-70 degrees), all that I would achieve is the boiler on for 10 hours every 20 hours!

Resideo (Honeywell) say it is "learning" but so far never seems to bring it on longer than a minute unless temperature difference is around 1.5 degrees lower.

Does anyone have an Evohome and know whether this is normal operation on their system (and whether it really does learn) or anyone have any suggestions/experience as to why I seem to be having issues (at the moment I regret changing my simplistic 3 zone controller that just brings it fully on when drops 0.5 degrees below set point).

Thanks
Colin

 

[EvilDrPorkChop]

Hi

When the zones are near temperature (if far away it keeps boiler fully on instead) it seems that the Evohome is bringing the boiler on for 1 minute in every 10 (as some of the zones are reporting not at 0% even though the system is reporting that it is at temperature).

I believe (though not sure) that the control system is doing this to keep push some heat into the radiators so it keeps at temperature rather than dropping far and having to put boiler on full blast (TPI function), however it seems to be continually doing this. This means that it the equivalent of bringing the boiler on for 6 minutes every hour and so for 20 hour same as if boiler had been on full blast for 2 hours.

The issue I have is that the minute on is not enough for the water the boiler (Bosch Greenstar 8000 Life) pushes around to get to more than 36 degrees and so the radiators calling for the heat do not get more than slightly warm (could never get above the 36 degrees but in reality much less). I could set the min on time for longer (max is 5 minute) but this then means that the boiler will be on for half an hour every hour) and 5 minutes still will not produce much heat (it takes around 10 minutes to go from 36-70 degrees), all that I would achieve is the boiler on for 10 hours every 20 hours!

Resideo (Honeywell) say it is "learning" but so far never seems to bring it on longer than a minute unless temperature difference is around 1.5 degrees lower.

Does anyone have an Evohome and know whether this is normal operation on their system (and whether it really does learn) or anyone have any suggestions/experience as to why I seem to be having issues (at the moment I regret changing my simplistic 3 zone controller that just brings it fully on when drops 0.5 degrees below set point).

Thanks
Colin

It is normal, however I have set mine to 2 minutes rather than 1. How long has the system been installed? It takes 3/4 weeks to fully learn the system, and tbh it does it's own thing. I've told customers to just leave it in this initial period and allow it configure itself. After this you can then start tweaking settings. Do you know which software version you are running?

What's you system configuration?

 

[John.g]

Colin seems to say that even with the boiler firing continuously for 10 minutes that "it takes around 10 minutes to go from 36-70 degrees", can you think of any reason for this?.

 

[EvilDrPorkChop]

Colin seems to say that even with the boiler firing continuously for 10 minutes that "it takes around 10 minutes to go from 36-70 degrees", can you think of any reason for this?.

His boiler has a 1:10 modulation range, I can only imagine that it's modulating accordingly to the system demand.

The only other issue is that it could be return through the automatic bypass too quickly when the TRVs are on a low demand. Hence why I prefer a manual bypass. For me i'd set the auto bypass on the highest setting.

 

[John.g]

A bit of a puzzle alright though as one would think that it should reach its target temp of 70C even if it then exceed it.

 

[colin_]

Hi

Sorry for the late replies but been somewhat tied up this weekend.

As far as I can tell the system is OK when it has over 1 degree to heat up, it will bring the boiler on 100% and things will get warm.

The issue is when it is near set point as I think it is trying to maintain some low temperature in the radiator and it brings the boiler on for 1 minute and then off for 9 minutes.

I have noticed that my new Worcester boiler will by itself take around 5-10 minutes to warm from 30 - 70 degrees even if radiators are fully open (it modulates low and starts ramping up over time).

This means that in the 1 minute on/ 9 minutes off mode that the boiler does not raise the water to much over 36 degrees and coupled with the fact that the HR92 valves are near closed, the radiator stays coolish. It thus never exceeds the desired set temperature and so is always in the cycling on/off mode (unless hot day and sun warms up the rooms). It is worse in the fact that when it does this and goes to the off part I can hear water gurgling in the system from one of the radiators (I am still trying to bleed all the air out of the system 2 weeks later) that is in the bedroom which makes it hard to fall to sleep.

Even if I set it to 2 minutes on (8 minutes off) it does not change much as it is still ramping slowly up (36 degrees is the most I have ever had in this 2 minute on/ 9 minutes off mode. I could set it to 5 minutes by I suspect that will not help much and just mean that the boiler is on for 12 hours a day!

The automatic bypass is on 0.4 and is not getting warm (initially it was set to 0.15 for some reason), I will set it higher as a test (I sometimes hear a "clunk" after the boiler has stopped)

The system has been in for around 3 weeks and according to Resideo it should have learned by now (I am not sure as it had been warm until recently and so HR92s off). Unless it does learn then I cannot see it being useful as the boiler is on for 6 min x 24 => 2.5 hours without foing anything useful (initial readings show it on target to use approx 25% more gas than any other year for this month). So far worst decision I have made for heating control.

I have 12 zones in use and some of them are set for single room with multiple HR92 units. I have noticed for the sinlge room multi HR92 that when the controller says that the value % is say 20% that when some heat eventually gets in it is just one radiator so I presume that the others are fully closed and only one of them thinks it needs heat.

The software is the latest one as Honeywell pushed it for the installer when they tried to ascertain why it is not working correctly.

Does anyone know how the HR92s are used by Honeywell

1. The system tells them the temperature and they decide how far to open. If this is the case I cannot see how it could learn.
2. The system tells them the heat and how far to open. This way the system could learn but then I would have thought that all the HR92s bound as a single room zone would then open that far and they do not (as only one gets slightly warmer and different radiators in that zone do it).

Any information/ suggestions would be most welcome.

Thank you
Colin

 

[colin_]

It is normal, however I have set mine to 2 minutes rather than 1. How long has the system been installed? It takes 3/4 weeks to fully learn the system, and tbh it does it's own thing. I've told customers to just leave it in this initial period and allow it configure itself. After this you can then start tweaking settings. Do you know which software version you are running?

What's you system configuration?

Hi

If set for 2 minutes does that means that twice as much gas will be used (on for 12 minutes every hour => 4.8 hours as opposed to 2.4 if one minute - as in this mode mine never seems to get out of it unless the littel sun we have heats up the room a little)

When yours is in that mode, do the radiators get hot or just stay luke warm (mine never get hot when it is in that mode as the boiler takes up to 5 minutes to get from around 30 degrees to 50 degrees as it modulates up).

Thanks
Colin

 

[EvilDrPorkChop]

I think you're getting confused. It won't run 2 minutes every hour unless it needs to.

My radiators never get hot once the system is up to temperature as the system just learns and keeps topping the system up. In winter I leave mine on all day at set points and unless I boost a zone the radiators are generally luke warm.

If you've only just started using the system for heating then it won't have learnt enough over the past 3 weeks. I'd say you need a good 4 weeks in full heating use to give it the ability to calibrate itself correctly.

The main panel tells the HR92s what to do and what % to open close.

In terms of the radiator in the room you're saying it's warm enough. Is it near the set point, and if you boost it up to say 23oc does the radiator get hot then?

Honestly the biggest problem I usually find is people watching/messing with it too much in the early days. You need to let it do it's own thing.

 

[colin_]

I think you're getting confused. It won't run 2 minutes every hour unless it needs to.

My radiators never get hot once the system is up to temperature as the system just learns and keeps topping the system up. In winter I leave mine on all day at set points and unless I boost a zone the radiators are generally luke warm.

If you've only just started using the system for heating then it won't have learnt enough over the past 3 weeks. I'd say you need a good 4 weeks in full heating use to give it the ability to calibrate itself correctly.

The main panel tells the HR92s what to do and what % to open close.

In terms of the radiator in the room you're saying it's warm enough. Is it near the set point, and if you boost it up to say 23oc does the radiator get hot then?

Honestly the biggest problem I usually find is people watching/messing with it too much in the early days. You need to let it do it's own thing.

Hi

Many thanks for the reply.

I think my concern at the moment is that when the boiler is in this mode and is on then the radiator in one of the rooms demanding heat appear to not be warming up at all, indeed it appears as cold as the ones that are not demanding heat.

I have looked at the boiler display when it is heating for the minute and it has raised the temperature from say 30 degrees to 32 degrees which does not seem to be much. I have noticed that, even when zones are 100% on and valves fully open, the Worcester boiler will take around 10 minutes to go from 30 degrees to 70 degrees heat (it starts low and as time goes on you can hear the boiler working harder as it modulates up), now this may be normal but in this case I was wondering if the lack of heat and valves near closed was causing an issue. It may be that increasing the on time to 2 minutes (so we have 2 minutes on, 8 minutes off) may be helpful with this boiler but I am trying not to change anything whilst it is learning (as well as being on twice as long may use twice as much gas)

I asked Resideo about the learning and they said it should have learnt after 2/3 weeks even if the heating not required. Now I cannot see how this can be the case as the valves would always be at 0% and nothing to learn, hence I presume I have to wait the 4 weeks from now (as the weather being colder means the valves will be moving).

I have one room where it is not up to the desired temperature, the Evohome does its 1 minute/9 minute cycle but it never gets to the set temperature on the Evohome display (it was still cycling 1/9 10 hours later and that room was the only one not getting up to temperature, this appeared worse as it was happening at night and I still have water gushing noises that are being heard as air slowly bled out over last week and counting). The HR92 has been changed in that room and the stroke is set to 1 (setting to 1 was recommended by Resideo and seems to help in the other rooms). If the temperature is set to say 1.5 degree above what is required then it will get hot (and wireless realy to boiler will read 100%) but it never quite reaches the set temperature (usally 0.5 degrees below) and the radiator will go cold. I am hoping from what you say that the Evohome will eventually tell it to open more and/or bring the boiler on for longer than the 1 minute in every 10.

You mention that the main panel says what % to close the HR92 actuator, in the single room with multiple HR92s I have noticed that even though it says a % (and all the HR92 units read the same valve position) that only (usually) one of them (in the cylcing mode) is slightly warm. I presume that even though they all say the same, they are saying what the Evohome globally thinks for that zone and this is normal operation.

I will let it think for 4 weeks and if all is well I will also update here in case anyone else has the same issues. If it has notlearnt by then I am unsure of what to do next.

Thanks
Colin

 

[John.g]

"I have noticed that my new Worcester boiler will by itself take around 5-10 minutes to warm from 30 - 70 degrees even if radiators are fully open (it modulates low and starts ramping up over time)."

I think this is also part of your problem, any of the few gas boilers that I have seen will get the boiler flow temp up to SP in a minute or two except from a completely cold start, this doesn't mean that the rads will though which is correct in the Evohome case?.
I read up a bit about the system and it seems to me that the HR92s do the PI learning and tell the controller what to do and in some cases can even control themselves like a true TRV?.