HR92s driving me nuts

[garmcqui]

Hi all,

After installing Evohome at the weekend, I'm trying to get my head around the temperature measurements they take in each room.

I've done some checking using two different room thermometers. With the heating off earlier today, the HR92 was reading 12.5C but both room thermometers were reading 15C+.

However, after setting the the room temp to 19C, I came back an hour later and the HR92 had shut off the radiator and was displaying 19.5C. However it still felt cold, and both room thermometers confirmed this, reading 17.2C and 17.6C respectively.

So what do I do? It seems they're reading too cold when they are cold, and too hot when they are hot. Thus its calling for boiler heat too early and shutting it off too early.

For now I've disabled all optimisation settings, and the window open setting.

Thanks

[Wally©]

You can change the temperature offset + or - 3 degrees...

Parameter 8 – Temperature offset
Since the radiator controller measures the room temperature in the area of the radiator, it is possible
that this temperature deviates from the temperature measured at a different point in the room.
If, for example, 20 °C is measured in the room and 21.0 °C at the radiator, this effect can be compensated
by an offset of –1.0 °C

[garmcqui]

Yup, have tried changing the offsets. However if, for example, I set it to +1 then when it's cold the HR92 will read 13.5C (when room thermometers read 15C+) but then it will reach its set temp (19C) even sooner, before the room thermometers even reach 17C!

I can't get it right

[Wally©]

If I read the manual right you need to set it to -1 in your example...

+ I would only do a temperature offset adjustment when the actual room temperature feels right to you...

[SteveP]

After my initial installation (done twice now as upgraded the unit) plus when I added new zones, initially the rooms did feel unbalanced and I did the same checks as you have done. However, I had set optimisation and was advised to leave the unit to "settle down" and learn the temp demands of each zone. After two weeks suddenly the whole house felt "right". When I upgraded I had the same situation until the optimisation was learnt and then the house felt right. I have a mix of HR80 and HR92 and regardless of which zones they are in the zones are all working sweetly. I do record the temps from each zone including set points on an hourly basis using the gateway and the temps are all within 0.5c max variation once optimisation complete. My suggestion is to set optimisation start back on and leave the system for a couple of weeks and then see how it is.

[G4RHL]

I concur, let it settle down as it seems to learn all by itself. I installed Evohome shortly before Christmas 2014. I was keen to see how accurate the TRVs were and religiously moved thermometers around the rooms to compare, always using at least two thermometers at a time and leaving them for awhile to adjust. In some zones (I have 11) the readings seem the same or within 0.5C most of the time and in others the TRV was always reading lower than the thermometers. I put this down to the fact the thermometers were at waist height and as heat rises it would be slightly warmer there. However, the differences could be 2C or more than the TRV indicated. I went to menu 8 and dialled in compensation but it did not seem to achieve anything. I put them all back to nil compensation and stopped playing. After about a week I noticed greater accuracy but not a lot more. What I did notice was a greater balanced heat throughout the house.

As I type this I am sitting right next to a radiator where the TRV is set to operate at 21c, the display reads 20c and two thermometers are each reading 19.5C, only 0.5C difference. I have just checked another room where the TRV is set for 21C, it reads 21C but the thermometer reads 18.5c (in this case the thermometer is Honeywell's single zone one and it, whilst at waist height is 3 feet from the radiator). At a different time of the day I know these readings can reverse. In my lounge for example, set at 21C the TRV will read that when it thinks it has got there but with the curtains drawn at night the actual temperature is showing as 23.5C. My wife likes this, I don't it's too hot.

Am not therefore convinced that using the compensation setting achieves much and probably best left alone on the assumption that in calibrating the TRVs Honeywell have allowed for the proximity of the TRV to the heat source.

It is tempting to play with new toys but best advice I think is do what is already said, leave them to get on with their own life and they will adjust and settle down. In my case if I consistently get higher readings than the TRV shows then perhaps the better answer is reduce the temperature setting itself.

[Rameses]

Hi - there are other posts which we detail this but I am glad you are arriving at the right answer eg http://www.automatedhome.co.uk/vbull...vohome-Install

Rule of thumb

- takes 7-10 days to learn
- HR92 temp measurement is measuring updraft
- does not take into account humidity which has a big impact on 'comfort' - so what you feel is greater than just what temp it is.
- leave optimization and window function on
- you can only have one 'sensor' point for a room. In the example above - if you have bound correctly the SZT would be the best primary choice, and evohome will work according to this.
- evohome will either overshoot or undershoot utilising the residual heat in the system depending upon what it learns, dynamically.

The trick is getting a sensing point which gives a good room average, AND is closest to how you feel. The Hr92 are designed to give this. But there are instances (like behind curtains or radiator covers), another sensor point is needed. I have a room where the thermals are lower than the waist height average, because (I found out eventually, a not properly close chimney) .

Dont worry, EVERYONE I know has broken evohome and played around with the settings. I know I have a number of times, as have my friends etc. If it's been installed correctly - any loss of settings and playing can easily be amended via software choices etc.

[G4RHL]

Thanks Rameses.

What I have learned from these pages and in particular some splendid detail and advice from the Evohome Shop is take care with the set up process once all is installed. In particular the advice to not let the Evohome Controller's internal sensor be operative but to leave it to the HR92s. That makes sense (unless you have a bad location for the HR92 when a separate sensor may be better) and probably accounts for some odd readings I have had. This morning I started from scratch, went back to factory settings, hard reset the controller, removed all bindings and started again in the recommended order of sensor (for HW), HW relay, CH relay, then zones and in each case preventing the internal sensor in the Controller being in control.

All is up and running. I now wait to see how it all settles down. Hopefully better than I had before but I was not dissatisfied with that. Did get some odd readings though, like one small room coming on when there was no need and reading a temperature that had no bearing on reality.

My wife just thinks I like playing with gadgets. Perhaps she is right!

[Wally©]

My wife just thinks I like playing with gadgets. Perhaps she is right!

We'll always be boys...Just the toys get more expensive...

[Rameses]

Regarding your comment about one room coming on - again this is a common question - it depends on evohome thinking about determining which direction your room temp is going. Temperature is NEVER static - its either rising or falling - evohome modulates both the room and the boiler to get the longest average. if it turns it on, and the sensor is saying the desired temp, then evohome is predicting the turn and operating to compensate.

My wife still finds it amusing I just 'Had' to have a Pebble watch to work with evohome.

Our years total gas bill reduction helped :-)

Wait till you discover IFTTT . . .