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

[John.g]

That definitely makes sense.

 

[colin_]

No boiler will do that you should be able to change the perimeters of evo to adjust this

Hi

I adjusted the evo to keep on for 2 minutes but all that happens is it gets to ~40 degrees before tunring it off (nowhere near the 70 degrees set on the boiler).

Near the end of the 2 minutes you can hear the tone of the boiler change as it starts to modulate up, ust in time for the Evohome to tell it to stop.

Not sure I want to go longer than 2 minutes as gas usage will go up rather than the heat.

There appaears to be a parameter 5-A3 "Minimum boiler output (heating and DHW)" whose default is 10% (and max is 50%). I will be asking the installers (who did the boiler and Evohome) whether this needs to be set higher (perphaps 20-25% or higher?) so the boiler does not modulate so low at the start (especially as the Evohome will be in control)

Thanks
Colin

 

[ShaunCorbs]

Need to go longer else you will knacker your boiler as there designed to run longer

 

[colin_]

Need to go longer else you will knacker your boiler as there designed to run longer

The default of the Evohome is 1 minute on time (max is 5 minutes) when it is in the cycling mode (6 timers per hour).

I rang Worcester technical several days agao and he said the boiler would be happy doing it!

The boiler has the Worcester 12 year warranty so hopefully all should be well on that score.

When set for 2 minutes it only gets to 46 degrees before it turns it off again.

I have set it for 3 minutes now and when it came on it was still only 46.3 after 3 minutes - I am still (unfortunately) monitoring it.

I am waiting to see what the installers think after contacting Worcester technical about what the 5-A3 "Minimum boiler output (heating and DHW)" does and the ramifications of increasing it.

Thanks
Colin

 

[John.g]

The majority of boilers only modulate 5 or 6:1 but yours is 10:1 so maybe to replicate these boilers increase the min output to 25/30% (5-A3) and see how it goes, can't do any harm. and can always revert.

 

[colin_]

The majority of boilers only modulate 5 or 6:1 but yours is 10:1 so maybe to replicate these boilers increase the min output to 25/30% (5-A3) and see how it goes, can't do any harm. and can always revert.

I have asked the question of the installers (still waiting an answer) and I was thinking of having it changed from 10% to 20-25% as a test (can put heat on full and see how it performs)

I can eventually manage to get the temerpature to 60 degrees if I let the boiler come on for 3 minutes min time and off for 7 minutes (it cycles every 10 minutes) and this at least lets the radiator get warm (at the expense of gas) after about 4 cycles (so 12 minutes gas)

Hopefully if the change to 20% ish makes the boiler start modulating higher this will help the Evohome system and I can probably back off the 3 minutes to 2 (it should eventually learn what is what) and also get the heat up to 70 degrees quicker when the zones are fully open.

Thanks
Colin

 

[John.g]

I can't see any reason for a increase in gas usage, your house requires a certain amount of energy to keep it at a set temperature, the only reason that Evohome is range rating the boiler is to prevent too much setpoint room temperature overshoot?.

 

[colin_]

I can't see any reason for a increase in gas usage, your house requires a certain amount of energy to keep it at a set temperature, the only reason that Evohome is range rating the boiler is to prevent too much setpoint room temperature overshoot?.

Hi John

I think my concern was that if it was on for 6 x 1 minutes and I set it for 6 x 3 minutes then I am using 3x the amount of gas.

However if the 1 minute does not warm the radiator (above say 32 degrees) then it is probably never going to stop the cycling (until Evohome learns?) whereas the 3 minutes one will (after about 4 or attempts => 40 - 50 minutes get it up to around 60 degrees (at the end of the 3 minutes) so may be better.

I am waiting for them to get back from confirming with Worcester that changing the mosulation to say 20-25% (from the 10 it is now) will make it heat quicker and if so then all should be OK.

Thanks
Colin

 

[ShaunCorbs]

Set it to the maximum run time

 

[EvilDrPorkChop]

Your issue isn't the boiler as i've previously said. It's the on time rate from Evohome not working correctly, probably because of the algorithms it uses, thrown in with the fact it's been installed in a time when heating wasn't being used. Any boiler won't ramp up in 1 minute, Vaillants take about 2 mins to get going also. When you say the zone isn't meeting the set point, what temperature is the zone and what should it be?

I'd suggest deleting the troubled zone and resetting it back up. This will reset the learning for that zone. I'd also suggest looking at the flow rate to the rad, making sure the TRV on the rad is working correctly. Have you had all new TRVs throughout with the new EvoHome system?

 

[colin_]

Your issue isn't the boiler as i've previously said. It's the on time rate from Evohome not working correctly, probably because of the algorithms it uses, thrown in with the fact it's been installed in a time when heating wasn't being used. Any boiler won't ramp up in 1 minute, Vaillants take about 2 mins to get going also. When you say the zone isn't meeting the set point, what temperature is the zone and what should it be?

I'd suggest deleting the troubled zone and resetting it back up. This will reset the learning for that zone. I'd also suggest looking at the flow rate to the rad, making sure the TRV on the rad is working correctly. Have you had all new TRVs throughout with the new EvoHome system?

Hi

I have set the on time for 3 minutes and the water will eventually get up to around 60 degrees after 4-6 cycles of the 3 minutes on/ 7 minutes off which at least lets the radiators get warmer now (it still spends a significant time on lower modulation and lower temp before hitting the 60 mark at the end of 3 minutes - after sevral cycles of it to get there).

The set temperature was 18 degrees, the Evohome said it was 17.5 and never previously got to 18. With the on time at 3 minutes it eventually gets there (after around 30-40 minutes of the cycling on/off).

That zone was deleted as a new HR92 was fitted on it but it still misbehaved until 3 minutes on time set.

There was also a new zone set with multiple HR92s (with one as sensor) but this has started to misbehave. When the hot water zone comes on, one of the raidators in that zone can also be hard on (gets very hot) and the temperature ramps up (read with a min/max temeprature unit) from the set point of 18.5 degrees to 21 but the zone says it is still requesting heat (all the other HR92 units in that zone are cold) and thinks the read temerpature is 18.5 even though clearly it is not.

I had this in the recent past (as new system) when there were 6 radiators in a zone but when the zone was split, a HR92 was replaced as it was thought to be the cause. I have tonight changed the HR92 with another radiator in the zone to see if it follow the HR92 or remains at the radiator.

Now the installer says that my zone with multiple HR92 units cannot be set to multiroom (can only be used single room) as the person he contacted at Honeywell says that my system cannot do this (I have had no explanation as to why).

Thanks
Colin

 

[EvilDrPorkChop]

Hi

I have set the on time for 3 minutes and the water will eventually get up to around 60 degrees after 4-6 cycles of the 3 minutes on/ 7 minutes off which at least lets the radiators get warmer now (it still spends a significant time on lower modulation and lower temp before hitting the 60 mark at the end of 3 minutes - after sevral cycles of it to get there).

The set temperature was 18 degrees, the Evohome said it was 17.5 and never previously got to 18. With the on time at 3 minutes it eventually gets there (after around 30-40 minutes of the cycling on/off).

That zone was deleted as a new HR92 was fitted on it but it still misbehaved until 3 minutes on time set.

There was also a new zone set with multiple HR92s (with one as sensor) but this has started to misbehave. When the hot water zone comes on, one of the raidators in that zone can also be hard on (gets very hot) and the temperature ramps up (read with a min/max temeprature unit) from the set point of 18.5 degrees to 21 but the zone says it is still requesting heat (all the other HR92 units in that zone are cold) and thinks the read temerpature is 18.5 even though clearly it is not.

I had this in the recent past (as new system) when there were 6 radiators in a zone but when the zone was split, a HR92 was replaced as it was thought to be the cause. I have tonight changed the HR92 with another radiator in the zone to see if it follow the HR92 or remains at the radiator.

Now the installer says that my zone with multiple HR92 units cannot be set to multiroom (can only be used single room) as the person he contacted at Honeywell says that my system cannot do this (I have had no explanation as to why).

Thanks
Colin

Your multi room HR92s need to be set to Multi Room (Zone Configuration>Said Zone>Parameters>Single/Multi Room Zone>Multiple).

Advanced Load Scaling> Is this set to None?

Swapping HR92s will only confuse the learning, but you can give it a try.

You also didn't answer my question regarding the TRVs, are they new valve bodies or existing?

Is the Evohome system been installed new with the boiler or existing.

 

[colin_]

Your multi room HR92s need to be set to Multi Room (Zone Configuration>Said Zone>Parameters>Single/Multi Room Zone>Multiple).

Advanced Load Scaling> Is this set to None?

Swapping HR92s will only confuse the learning, but you can give it a try.

You also didn't answer my question regarding the TRVs, are they new valve bodies or existing?

Is the Evohome system been installed new with the boiler or existing.

Hi

Advanced load scaling is set to disabled.

The installer changed all the radiator valves and fitted new HR92 and the Evohome system.

They also fitted the new Worcester boiler.

According to the installer, he says that he has rung Honeywell and my system should only be set to Single room as multi room is not supported on my system (without giving any reasons as to why it is not supported). I have filled in the form on Resideo asking why there is conflicting information on whether it can or cannot be based upon who in Honeywell/Resideo is answering (the online instructions also say to set it to zone valve and not radiator valve for some reason) but I have not had a reply back from them yet.

The systems consists of 12 zones (2 of which have multiple HR92 units), a hot water sensor and wireless relay box for it, and another wireless relay box for bringing the boiler on.

At the moment I can hear the boiler come on for 3 minutes and off for 7 minutes (for the last hour) as it thinks that one of the zones with multiple HR92s want heat even though none of them are warming up.

I am currently wishing I had never changed from the simple 2 zone solution I had as at least it worked, hopefully if I can get the Evohome working I will learn to like it (worst case get them to remove it and go back to the simple system).

Regards
Colin

 

[EvilDrPorkChop]

It's not hard to change it and try it, but so be it. Wait for your reply.

Good luck getting the system sorted.

 

[colin_]

It's not hard to change it and try it, but so be it. Wait for your reply.

Good luck getting the system sorted.

Thanks, I think I'll need it. (hoping the system will not be 3 minutes on/ 7 minutes off for the rest of the night as may be tempted to turn the boiler off.

I have set to multiroom on this zone to see if anything changes.

 

[colin_]

It's not hard to change it and try it, but so be it. Wait for your reply.

Good luck getting the system sorted.

Thank you for your help and assistance.

Regards
Colin

 

[John.g]

Thanks, I think I'll need it. (hoping the system will not be 3 minutes on/ 7 minutes off for the rest of the night as may be tempted to turn the boiler off.

I have set to multiroom on this zone to see if anything changes.

Your house must require some level of heat to keep it warm so even though you are not seeing any rise in room temp this just proves in a way that the evohome is working by just firing the boiler long enough to keep the house exactly at your required temperature by keeping the rads at the required temperatures.
Except that your rads are at the room temperature then they must be emitting some heat so even if they are only at 25C and the rooms temperature is 18C then they will still emit ~ 8% of their rated output say 1.6 to 2 kw of a 20kw rating which isn't going to break the bank.

 

[colin_]

Your house must require some level of heat to keep it warm so even though you are not seeing any rise in room temp this just proves in a way that the evohome is working by just firing the boiler long enough to keep the house exactly at your required temperature by keeping the rads at the required temperatures.
Except that your rads are at the room temperature then they must be emitting some heat so even if they are only at 25C and the rooms temperature is 18C then they will still emit ~ 8% of their rated output say 1.6 to 2 kw of a 20kw rating which isn't going to break the bank.

Hi John

I think the main issue is that the boiler starts up at its min modulation (10%) which means 3KW of heat to warm up the water. It remains at this level for several minutes before ramping to the next level. It keeps ramping up and it can take over 12 minutes to get to 70 degrees.

I heave set the Evohome for a minimum on time of 4 seconds and iduring this time it can barely raise the water temerpature to 45 degrees (from around 30). It thus keeps coming on for 4 minutes in every 10. It eventually gets to around 60 degrees but that takes arind 5-7 cycles so around an hour. It is worse if more radiators want heat.

I suspect that the system will work much better if the start modulation is set higher (20% -> 6KW) and I am waiting on the installer to get back to me and set it as a test.

Thanks
Colin

 

[John.g]

Yes, understood, but Evohome seems to be saying so that as long as the the room temp is within 1.5C of its setpoint that whatever minimum time you have set is in fact a fixed time and not just a minimum?. So if the temperature offset is 0.75C then the controller just looks for the TRVs to be open say 50% or something like that and during this x weeks learning curve if the room temperature isn't rising then it might look for 75% opening or whatever but has no effect on the actual run time?

Is this your understanding of how it works?

 

[colin_]

Yes, understood, but Evohome seems to be saying so that as long as the the room temp is within 1.5C of its setpoint that whatever minimum time you have set is in fact a fixed time and not just a minimum?. So if the temperature offset is 0.75C then the controller just looks for the TRVs to be open say 50% or something like that and during this x weeks learning curve if the room temperature isn't rising then it might look for 75% opening or whatever but has no effect on the actual run time?

Is this your understanding of how it works?

Hi John

I think that when near temperature the Evohome is supposed to know how long to bring the boiler on to get the desired temperature (it is supposed to learn this over several weeks).

In the settings you can set the minimum time that the Evohome will bring the boiler on for, the defualt is one minute every 10.

I have had to set this to 4 to even get the radiators warm (it gets the temperature from the boiler to ~50-55 degrees in an hour of cycling 4 minutes off, 1 minute on).

I am now on its max setting of 5 (so boiler spending 50% of its time on whilst doing this - but presumably ok as modulated down to say 10% for firt couple of minutes).

So far the Evohome has not worked out that it needs to adjust the on time.

I do believe from what others have said is that the Evohome tells the HR92 how far to set its actuator.

Thanks
Colin

 

[fronty]

Another evohome user here, been reading this thread with interest, I do believe when evohome is doing this TPI thing (eg firing for 1 minute in every 10), the flow temps are not supposed to get up to anywhere near what you'd expect, it's literally just warming the water slightly to dump a small amount of heat into that zone, the idea is to prevent an overrun.

My system seems to work quite well as it will maintain the temps in each room once the set point has been reached. However what I did find is that some rads did not get warm at all despite calling for heat. It seems than for low demands of 10-20% when the boiler is firing as per TPI schedule, the valve does not open enough inside the TRV to let any water pass, I found that on a couple of rads I had to set the HR92 stroke parameter (setting 6) to 1. That seemed to fix the problem and even on low demands I can feel some heat in the rad, it's not hot just warm..

I don't think anyone has mentioned this so give it a try.

 

[colin_]

Another evohome user here, been reading this thread with interest, I do believe when evohome is doing this TPI thing (eg firing for 1 minute in every 10), the flow temps are not supposed to get up to anywhere near what you'd expect, it's literally just warming the water slightly to dump a small amount of heat into that zone, the idea is to prevent an overrun.

My system seems to work quite well as it will maintain the temps in each room once the set point has been reached. However what I did find is that some rads did not get warm at all despite calling for heat. It seems than for low demands of 10-20% when the boiler is firing as per TPI schedule, the valve does not open enough inside the TRV to let any water pass, I found that on a couple of rads I had to set the HR92 stroke parameter (setting 6) to 1. That seemed to fix the problem and even on low demands I can feel some heat in the rad, it's not hot just warm..

I don't think anyone has mentioned this so give it a try.

Hi

I am not sure what the system is supposed to be doing when in TPI mode but it seems that if I put the on time of the boiler to 4 minutes then the radiators will get hot (obviously as more time to heat) and that allows the system to get to/past the set temperature quicker and after a few cycles of that it will no longer need to come on every 10 minutes as no longer calling for heat.

My situation is made worse by the fact that the bathroom radiator is, at the moment, fully open and being used instead of an automatic bypass and if I do not have the boiler hotter then any heat that is output (even at 3 minutes, hence move to 4 minutes) is lost into this radiator and does nothing for the radiators that are wanting the top up heat.

I also have a Worcester boiler that seems to slow start. It comes on at a minimum modulation (default 10%, mine now 20%) and will stay there for several minutes before deciding it needs to up its modulation. This again means I have to set the minimum on time high. I hate to think what the gas usage is going to be like (Honeywell mention that the system will use less gas but in my case it looks like it will be much more).

So conflicting system needs and trying to get it sorted is a nightmare (Honeywell connected specialist installed it - they say they have escalated it with Honeywell). It would have been nice if Honeywell state what happens in TPI mode, especially with what the boiler is expected to do.

[Q1] When in TPI, do you happen to know what temperature your boiler is getting up to when it is turned on - when I had mine at 3 minutes it barely got to 40-45 degrees out of the boiler and so much less at the radiators?

[Q2] When in TPI mode you mention that the radiators are only warm, on yours is the most warm near the top of the radiator with the rest simply warm or is it evenly distributed around it?

[Q3] When in TPI mode, I presume that it takes many 10 minute cycles before the HR92 units are demanding 0% (hence why mine seemed to be coming on every 10 minutes for 4-5 hours)?

BTW: I had to put all my HR92 into full stroke mode to ensure that they opened far enough given what little heat was being given out.

Thanks
Colin

 

[John.g]

This means so that its opened more for any given HR92 deltaT?,

I never see any mention of the position of the HR92, ie on the rad flow or return as if installed on the return will give a more representative room temperature, obviously doesn't make any difference with a cold rad and a few bursts of 1 minute boiler run time.

 

[colin_]

Dear John

I think the Evohome may decide (as part of its learning process) to open it up more if the temperature has not moved in the last 10 minutes so that next time it gets more heat through it but that is just conjecture on my part as not looked closely at that yet.

Thanks
Colin

 

[John.g]

Talking generally,

"Normal" PI control integrates the (proportional) error over given time, for example if the error was looking for 10% valve opening then with a 1 minute integral time the valve opening will increase by another 10% in 1 minute (if the error remains constant) eventually and would be 100% open after say 9 minutes, normally the error is reducing as the valve opening increases so the integral add on progressively reduces until there is no error and the valve will stop opening, eventually the measured value may be > the SP value (integral overshoot) so the integral effect starts reducing the valve opening until eventually the SP value is achieved.

EH must clearly interrupt this integral effect when the boiler is not (EH) switched on otherwise all the HR92s would be 100% open irrespective of their room temperatures after a relatively short period and certainly after a overnight boiler shutdown.
If, as you think, the EH does not increase/decrease the valve opening with integral effect until there is a change in temperature after a certain time then that is not true PI control so maybe this is why its called timed PI control and doesn't increase/decrease the valve opening until each burst of run time unless the temperature has actually changed.
Or maybe the EH integral time is just the on run time/cycle.

Still a bit confusing to me IF it doesn't increase the valve opening to 100% say overnight whatever way I look at it.