Flexible CH controls

[Captain Nemesis]

Dont know if here is best to ask or in Plumbing and Heating.

Basically I would like to be able to set a different time/temperature schedule for each room in the house independently of all the others.

Not interested in fiddling with the settings from a cafe anywhere in the world but I can see how using a phone or tablet app to do the programming could be better than a programmer in each room or a central controller like Evohome. I think I can trust the people here not to set someone elses bedroom to 10 degrees for a laugh.

Geofencing might be of interest if I dont have to pay a subscription, but even when the days of going out and coming home at an unpredictable time return Id probably be able to cope with turning it up if I got home early and it was a bit nippy. With a reasonably well insulated house how much do you save anyway by dropping the temperature by a few degrees if youre out for a few hours?

Do TRVs work ok to measure room temperature or is a thermostat on the wall better?

My boiler does opentherm and all the rads are in one zone.

 

[ericmark]

I have 5 eQ-3 and 4 energenie TRV heads, and they do work. However a lot depends on design of the house, unless linked to wall thermostat there is nothing to make the boiler run.

So I have carefully set the wall thermostat and programmable TRV heads so boiler will start at same time as the TRV changes temperature, basic idea is turn down 0.5 half hour before change then back up on change.

So I got eQ-3 for £15 each with bluetooth. And for me they have worked well, as good if not better than the wifi Energenie TRV heads.

Yes I have Nest gen 3 wall thermostat with geofencing, and also the Energenie with IFTTT can also be set for geofencing, however I find not used much, and there is a problem with geofencing in my case with over shoot.

The TRV also has a problem the Energenie has OTT anti hysteresis software so set to 22 for hour then back to 20 to speed up reheat, which will not work with geofencing.

 

[ericmark]

The first house I used programmable TRV's with had a modulating boiler, this house is oil so very different. However I had a problem, which was all around having bay windows, they were sun traps, and I had around 4 attempts at getting around the problem when sun low in the sky, i.e. winter, in the morning the living room temperature would raise very quickly before the TRV could act and cause 32°C to be recorded.

I thought easy cure was programmable thermostat free standing as only two rooms used, and move it to room in use, but the thermostat gradually lost the RF link, and I was loathed to buy a second one which would likely have same fault, so tried the first pair (they were sold as pairs) of MiHome Energenie TRV heads. It actually worked very well, OK sun still caused room to over heat, but 25°C not 32°C when set to 21°C. We then moved into the house to look after my mother and added 2 more. Had a problem at first, mainly due to being fitted on return to radiator not feed, but they displayed both current and target temperature so if current over target I closed the lock shield a touch and if under opened it a bit, and once set there were spot on, so 4 rooms now well controlled.

The wall thermostat was in hall, and getting hall temperature right was a problem, very large radiator and when front door opened it could reheat hall fast, but if I set lock shield to do this, then boiler turned off, so rest of house cold, so fitted the programmable thermostat in kitchen in parallel with hall one so if either called for heat, boiler ran, improvement but still not really working well.

So I had been told you should not fit a TRV in same room as hall, but desperate thought worth a try, bingo it now all worked A1, well had to adjust hall radiator lock shield and TRV to match the wall thermostat which took a little time, but basic idea was, which worked, front door opened and TRV would cool and turn on hall radiator, as the hall warmed the TRV starts to close, so hall radiator starts to cool and so hall would not get warm enough to turn off wall thermostat in winter, it would only get warm enough Autumn and Spring, so in real terms all the wall thermostat did was stop central heating boiler from cycling on warm days, in winter at 10 pm hall wall thermostat turned off, back on at 7 am, but if really cold night kitchen thermostat would cut in and start boiler.

On mothers death house sold and new owners did not want the computer controlled TRV heads so removed, and we were surprised now all lock shield valves set, how well the old mechanic TRV heads worked.

So this house central heating was in a right mess, had to go outside and down to flat under house and manually plug in circulation pump, so a major rewire was called for, but using existing wires, after problems with mothers house and wireless, not keen on wireless controls, but just two wires main house to flat, so got Nest Gen 3 as two wires would carry supply and data allowing both DHW and CH with just two wires. It was not fitted because I wanted wifi controls or geofencing. Also the Energenie were claimed to work with Nest.

However the pairing of the Energenie and Nest did not work out, using the phone to alter Nest with the Energenie app and all the TRV heads followed Nest, but with a schedule change or turning dial it failed, phoning Energenie we found support by Nest had been withdrawn, also the wall thermostat telling the TRV what to do seems wrong way around, seems there were no TRV heads designed to work with Nest any more, so unpaired and simply set the TRV to same schedule as Nest, however no where near as good as with mother house as boiler does not modulate so TRV heads opening will not warm room unless boiler running, but still worked reasonably well, and since nothing works with Nest any more I bought an extra 5 programmable TRV heads without wifi, just bluetooth at £15 each, bluetooth was a little of a disappointment as will only work with one device, so 3 on my phone, and two on wife's phone, and it only displays target temperature not current. However have open window detection and are really easy to manually control, I can set eco and comfort temperatures not fixed like energenie, so walk in room press one button and switches to comfort, rarely do I press when leaving it turns down again at next scheduled change. And the window open feature turns off kitchen radiator when unloading my car.

Because Nest has geofencing I use it, but my wall thermostat in this house is too far from radiator so tends to over shoot, in the morning I have the wall thermostat lift temperature by 0.5°C per hour so it does not over shoot and the boiler is running when TRV heads call for heat, may be not ideal but in the main it works well, and I actually find the cheap eQ-3 work better than the Energenie TRV heads.

The OTT anti hysteresis found in mothers house actually seems to work well in this house.

The problem is very little is said about programmable TRV heads, one sees what seems a good system, and you ask people how it works, only to find either not set up, or bits missing, the Hive idea seems good, but not found many reports where the TRV heads have been fitted, those I have they complain the wifi signal is lost so wall thermostat does not turn on boiler when it should.

Drayton TRV heads claim to have algorithms to work out when to switch off so they get around the OTT anti hysteresis software found with Energenie so should heat the room up faster so should work better with geofencing, however when you look at the price, so it should.

We see many using the MoesGo WiFi Smart programmable thermostat, at £35 must be about the cheapest, and you have to question would that and the eQ-3 TRV heads do the same job as these super expensive systems?

I look at even this house with old double glazed units, thin to modern standards and turning down from 20°C to 16°C over night it never seems to cool that much, no room ever seems to cool below 17°C except when not used all day and heating turned off. So in real terms the rooms are only going up/down by 3°C, however by setting the times in sequence for return home, kitchen, then dinning room, then living room and after a gap bedrooms the reheat time is reduced for first room to be used, so there is an advantage.

If I had the money to fit the Myson fan assisted radiators which alter fan speed to control heating then I could speed up heating, but there is a limit on how much heat standard double panel radiators can put in a room, and that is my weakest link, I see there are fans you can fit to standard radiators and that would seem to be next step, but don't leave the house enough to want a fast warm up time.

 

[Captain Nemesis]

I have 5 eQ-3 and 4 energenie TRV heads, and they do work. However a lot depends on design of the house, unless linked to wall thermostat there is nothing to make the boiler run.

Sorry, should have put that in my post - what I want is for any room to be able to call for heat if its program says it should be warmer at this time than it is and opening the TRV(s) hasnt worked. Other rooms may have to close TRVs if they then get too warm at that time. Each room can send boiler commands but no room can force it to go off if another one wants it on.

 

[ericmark]

Linked to a hub or thermostat then, so Drayton, EvoHome, or Tado, Hive is not opentherm, and Nest and EPH does not connect to the hub/thermostat. And Energenie seems to work wrong way around, the thermostat tells the TRV what to do.

 

[Captain Nemesis]

I would have thought that if you have a wall thermostat then you wouldnt have TRVs, just remotely activated ones being told what to do.

 

[ericmark]

The problem with non linked TRV heads is they can't stop the boiler from cycling. In the heart of winter you don't really need a wall thermostat, the modern modulating boiler will measure the return water temperature and by so doing adjust the output to what is required.

However once the boiler output hits the minimum then the boiler starts to cycle off/on, and by again monitoring the return water temperature can adjust the times of the on/off to reduce the cycling, but can't actually turn the boiler off completely as it would not know when to turn it on again.

So we are told we should fit a wall thermostat in a room normally kept cool, with no outside doors, on the ground floor, with no alternative heating so it can turn boiler off when we get warmer weather.

However in my house and most other houses such a room does not exist, so we look for a compromise. There is no reason why we should not have a wall thermostat in every room all wired in parallel so if any one called for heat the boiler would run, we would also need TRV's in every room to limit the room temperature when another room has called for heat, however in real terms likely two wall thermostats would be enough, as long as placed in a room which tends to be cool.

So in most houses the hall is likely the coolest room, the problem is when front door is opened we want rapid rewarming, so back to the compromise.

If in heart of winter the temperatures set on the TRV are too low for the wall thermostat to be activated, but in autumn and spring when there is less heat loss it can activate the wall thermostat that is ideal. Idea is once the wall thermostat switches off, it stays off, so an old bi-metal thermostat with neutral disconnected is likely the best, that is if the hall is kept at the same temperature all the time.

However today we like to think we are not wasting money heating an empty home, so in my case both the wall thermostat and the TRV are programmable, the problem now lies in setting the temperatures so they work together. I have found by experiment the TRV needs to be a degree or two lower than the wall thermostat if it is not going to switch off wall thermostat too early. But this will vary home to home.

Hive had a great idea, as to if it works I don't know, read some poor reports, but the idea is the wall thermostat is set low, but signals from the TRV's send a demand for heat to the wall thermostat when required and the wall thermostat will then run boiler for ½ hour, so while any TRV is sending demand for heat, the wall thermostat stays switched on. How this works when you access Hive with phone I don't know, I would assume to access the TRV heads rather than the wall thermostat, but I don't have Hive so don't know.

With my Nest gen 3 as I leave the house it detects my phone is not at home and if also my wife's phone is not at home, and the occupancy detection has not detected anyone walking around, then it turns the temperature down, so boiler switches off, even though the Energenie TRV's also have geofencing there is no point setting it up, as if boiler not running they can't heat the rooms. When either of us gets closer to home, the Nest turns heating up again. Not perfect as in my case the hall radiator is too far away from the Nest thermostat, so on arriving home I need to turn Nest down a degree, and around an hour latter back up, or I will get a hysteresis.

As said not perfect, it is a compromise, yes I could have selected better, but it would have required new wires, and I am lazy and did not want to thread new cables from the flat where the boiler is, to the main house, and it works reasonably well.

I have got Nest Mini's and in theory I can tell the mini what I want, however they do make errors, I will say turn off music, and it replies turning off 5 switches and plunges me into darkness as it turns off the lights, so simply don't trust it with heating. So I can see with PC what is going on, or phone, but don't trust the Nest Mini so get some thing like this

today actually two light switches removed and a 4 output extension lead added, in theory could use IFTTT in summer to turn on AC unit, in practice I look at room temperature and switch on manually using Plug in switch/m as it shows there, so I can see the power it is using, so know if actually switched on.

I think impossible for reasonable money to get perfect system, so you have to decide what is near enough.