Can the heating be automated using the temperature from TRV.

[ericmark]

The homebridge.io looks interesting, I am not sure if I will go much further or not. EvoHome was to my mind when I first looked at control about the best, but the price ticket put me off a bit. So I bought a pair of Energenie TRV heads, and latter another pair, which I have taken with me to this house, the are installed in living room, hall and dinning room.

The lack of control of the boiler from main house needed correcting, the main problem was sheet floors so access down to wiring hard, and a false ceiling in the flat under the main house again making access to wiring rather hard, it seemed I had a triple and earth cable only, however it changed from red, yellow, blue to brown, black, grey and one core not connected so I only have two usable wires.

Nest needs just 2 wires from heat link to thermostat, so it seemed this would do the job, it also had volt free contacts on the relays. So I bought Nest.

I looked at this very old C Plan

and the way the pump and boiler were wired, so the timer could run just boiler or boiler and pump allowing domestic hot water only, I have a problem with no tank thermostat, however even with a thermostat really that's not enough as for full control you want thermostat low down for bath and high up for washing hands, but with 40 gallons of water it stays warm for a long time, so wondered if time control of DHW was enough? So thought worth a try.
So wiring Nest in a similar manor I have

So copying the old idea for thermostat on tank and using it with the timer instead, so I have the option to set it for ½ hour every other day well in practice Sat, Sun, Tue, Thurs so I have warm water to wash hands, if I want a bath then select Boost feature before I start to run bath, at moment motorised valves not fitted, and there is a temp link 5 to 6 on bottom wiring centre, and it seems to work.

However there are two faults with the system, one is the flat heating will only work when the boiler is being used by the main house, don't really see this as a big problem as flat will be rarely used. The second is because I have TRV's on every radiator and the pumps are on the return, I am unsure what will happen if the TRV's close and the pump is running?

This

is rough tracing of pipe work, assume filling and expansion is on the cistern and bathroom radiator supply, but one pipe not a clue where it comes from, although using motorised valves the micro switches will switch off the pumps, and the Nest and Energenie are linked, so the Nest should not call for heat when the TRV's are not open, the flat is not linked, and it could happen all TRV's closed and pump running.

The plumber said not to fit valve on the DHW so always some where for the boilers heat to go, but although boiler protected, pumps I suppose could cavitate? I know pumps can be damaged when outlet blocked due to motorised valve closed and micro switch failed to switch over, and often a by-pass valve is fitted, but that's on pressure side, with my system it's on return side, not sure if you can fit a by-pass to the return side? Or even if all TRV's close will it damage pump or not?

For radiators not easy to reach, considering cheaper heads, the EQ3 Bluetooth Smart Radiator TRV head is only £15 each, and fitting them in the bedrooms, office and craft room would allow easy switching off and setting up a program so bedrooms only heated at night, I am not a fan of the TRV head marked * 1 2 3 4 5 6 it is rather hit and miss with what temperature is set, and also can't program them not to heat when room not being used. May seem odd, but more worried about a room being too hot than too cold, over heat a bedroom and I can't get to sleep, open window and get early morning call from birds and lambs. Plus odd wagon.

Without Bluetooth the EQ3 is just £10:20 but worth another £4:80 not to have to crawl to where the valve is to set it. I have never used geofencing or even manually change room temperature away from house, and even if I did want to change heating I can still access Nest when away, even if not the bedrooms etc, so can't see the point in more Energenie heads when from in the house the EQ3 with Bluetooth has same control.

I had all big ideas when I first got the Energenie TRV heads, but then found rooms take time to heat and cool, so the idea of only heating as set times seems good, in practice it does not work. Rooms retain the heat so switching off for 8 hours means maybe if lucky 3°C drop, hardly worth the effort.

 

[SimonH2]

... the main problem was sheet floors so access down to wiring hard

I feel your pain - work of the devil those large sheets. And with building regs now (AIUI) more or less mandating them, and that they be glued both to each other and to the joists, new builds are IMO unmaintainable

... it seemed I had a triple and earth cable only, however it changed from red, yellow, blue to brown, black, grey and one core not connected so I only have two usable wires.

Ah yes, there'll be a hidden junction box somewhere - probably where the old boiler used to be before something got moved. Had something similar when I was helping a mate "do up" his new (to him) bungalow. Fortunately, it was easy to re-do the wiring as it was largely a rip out and re-do job in the kitchen (where the old boiler had been, and the programmer and hidden JB were).

... not sure if you can fit a by-pass to the return side? Or even if all TRV's close will it damage pump or not?

You can fit a bypass around the pump itself - and the gravity feed to the DHW tank should protect the boiler from the reduced flow rate. Or less work and probably no extra cost, just replace the pumps with modulating ones - they can go down to zero flow rate and back-off as the TRVs close.

May seem odd, but more worried about a room being too hot than too cold, over heat a bedroom and I can't get to sleep, open window and get early morning call from birds and lambs. Plus odd wagon.

Not odd at all - I know exactly what you mean. Nothing worse than trying to sleep when it's too hot. Luckily where we are, it's fairly quiet (apart from the twittering of the birds) so having the windows open is OK.
I several work hats ago we had a customer down in London - long story, something to do with a friend of my business partner. Anyway, went down there a few times to do stuff. Using their contacts, I generally got rooms above pubs and the like, and one time had this small room above a pub when the weather was "stifling". Not only was the weather warm, but this pub was diagonally opposite Mount Pleasant sorting office, across the road from a Fire Station, and both roads that crossed at the junction were busy roads - so choice between not sleeping because fo the heat, and not sleeping because of the noise

I had all big ideas when I first got the Energenie TRV heads, but then found rooms take time to heat and cool, so the idea of only heating as set times seems good, in practice it does not work. Rooms retain the heat so switching off for 8 hours means maybe if lucky 3°C drop, hardly worth the effort.

Well when we moved in there were no controls other than a timer. Luckily (seeing as I didn't really understand what it was - thought it was like a combination of a timer clock and room stat in one unit) I bought a programmable stat for the wall. Instead of setting on and off times, it's a case of setting different setpoints - a faff to set up, but works well when it is. I understand what you are saying about "is it worth it ?" but IMO yes it is. A lot will depend on things like the weather, insulation, and the thermal storage capability of the walls - so YMMV For us, within the severe limitations of the building and heating setup, it's been a huge benefit just installing this one stat. Looking forward to seeing if the Radbots are any good - can't tell at the moment as the weather is far too warm Needs some zoning as we tend to have "upstairs hot, downstairs cold" when the weather is moderate - hoping the electronic TRVs (especially when boiler linked) will do this for me.

 

[ericmark]

You can fit a bypass around the pump itself - and the gravity feed to the DHW tank should protect the boiler from the reduced flow rate. Or less work and probably no extra cost, just replace the pumps with modulating ones - they can go down to zero flow rate and back-off as the TRVs close.

That is very useful, expect plumber tomorrow so now I have the knowledge to debate options with him.

As to fitting a programmable thermostat, my house hard wired, around £35 worked very well, mothers house for some unknown reason when new central heating was fitted the hard wires were ripped out, and a Honeywell Y6630D thermostat and a timer was fitted, I decided a Horstmann HRFS1 programmable wireless thermostat would be an improvement, however the Honeywell has a fail safe, if the receiver does not see the transmitter for 30 minutes it switches heating off, not so with the Horstmann so went to visit mother and room was at 27°C. So this time more careful with selection, wanted some thing where batteries would not fail and cause over heating, so selected Nest.

Actually not sure with Nest if wifi or hard wired? I think the two wires which power thermostat also carry data, but not sure. In set up there is a option for hard wired or wifi and it says it's hard wired.

At moment reports set to 17°C and at 20°C since it's been installed only used DHW so really don't know if it works or not. It seems odd if I go to Energenie with PC it says nothing about Nest, but will phone Nest is shown with all the TRV's, I have set it to follow, but not sure if I need to remove the program for Energenie, don't know which has priority.

Since writing reply, I have read about modulating pumps, they have a minimum inlet pressure, so not suitable.

 

[compynei]

Have a read through this, interesting approach that I will try and roll out.

https://community.openhab.org/t/my-central-heating-solution-using-thermal-actuators/41320

 

[ericmark]

Have a read through this, interesting approach that I will try and roll out.

https://community.openhab.org/t/my-central-heating-solution-using-thermal-actuators/41320

An interesting read, the controlling of my house with a PLC which I already have was one of my thoughts, however I an 67 and at some point I will be unable to work on the system, so want some thing which others can come to and repair.

The second point is I tried with mothers house different positions of the room thermostat, I bought one of these

and it is designed so it can be free standing, it in the end lost RF sensitivity and was found to have no fail safe, but before it failed idea was move it between the two rooms mother used, and use the TRV to stop other room getting too hot. And I tried it in many places in the room.

It was a surprise to find very close to the radiator worked best, it was placed on a tea trolley that was right in front of the radiator, the thermostat set about a degree higher than wanted as so close to radiator, but it worked very well with very little hysteresis, in other locations the hysteresis was much higher, so when it failed, not wanting to buy another the same, I tried an electronic TRV,

it was selected because also wanted wifi sockets for an extruder alarm to tell me when mother had gone wheel about in her wheel chair, the units have two sensors one air and one water the latter used to compensate the air sensor and they are to be fair very accurate, they did have a tendency to over shoot to start with, an adjustment of the lock shield valve stopped that. We moved into the house shortly after so increased to 4 Enegenie valves which I have brought to this house when I sold mothers.

However in mothers house I used two wall thermostats, second one which became the main one was one of these

a very good thermostat, but not programmable and it has built in anti hysteresis software so as it approaches set temperature starts a mark/space pulse system to stop over shooting. Not really suitable for a modulating boiler, but wind direction would change which room in house was coolest, so double thermostats in parallel allowed for change in wind direction, and it worked, however likely using more gas than it should have done because it was switching a modulating boiler off/on.

What I felt was annoying was each TRV head reported target and current temperature, so in theory one should be able to use IFTTT and a relay, so "If" any TRV shows "this" a target below current "then" let "that" boiler run, otherwise turn boiler off. However could not find how to do this, plus it seems there may in the future be a charge for using IFTTT.

On arriving in this house, I found the thermostat receiver but no sender, and the programmer had just two wires between it and the flat which had the boiler, it could clearly not select DHW or CH with just two wires, and the pump which circulated CH water around main house was simply plugged into a socket in the flat, the flat which used a second pump did have a thermostat so it seemed flat central heating worked OK but main house was pot luck, even the flat the thermostat was in the kitchen close to and above the cooker, all but bathroom in main house radiators had TRV's fitted, and the DHW was thermo syphon with no tank thermostat. So it was clear some thing had to be done.

Just to compound that it was found the support under the cylinder was giving way, some floor boards were sagging as we walked across them and shower showed signs of leaking, in all too much work for me to DIY it all, so found a pair of cousins one a plumber the other a chippy so between them they could put things right, when the shower was removed it was found beams underneath were rotten, so more work than planned, so they made the house safe, fitted new shower, but arranged to return to finish job, as no real rush to get central heating running in the summer.

However the plumber put his back out, which further delayed the work, so to speed it up, I agreed to do the wiring. So for me, problem one was only two wires house to flat, how can I control pumps, valves and boiler in the flat with just two wires, and floor made from sheets of MDF so not easy to fit new cables.

What I realised was Nest Gen 3 only needed two wires between the thermostat and the heat link, so supplying heating from flat, which was a good idea anyway three FCU's supplying one central heating system is not a good idea, I could use the old wires now with 12 volt instead of original 230 volt, also volt free contacts allowed more flexibility on how wired. So new motorised valves were dropped off, and with two wiring centres in the flat, I designed and fitted my control system.

This was final version, there is a fault in that the flat central heating will not work unless house demands heat, but this is not really a problem as the flat will never be used when the house is not being used.

Since the Energenie are designed to work with Nest, the hall, living room and dinning room are all set to follow Nest. We note upstairs as with previous houses tends to be hotter than down stairs, so used cheaper bluetooth heads upstairs and in kitchen, used the cheaper bluetooth in kitchen as they have open window detection so should switch off automatic when kitchen door opened to unload shopping from car.

Today got word plumber catching up on work after operation so soon motorised valves will be plumbed in, however until winter not really a clue how it all will work, so fingers crossed. Once we have done a winter we will consider if improvements are required, I hope we can like our last house (not mothers) forget about central heating, with my last house we also had to do some changes, the DHW was made fully independent from central heating, and TRV's added up stairs, down stairs another radiator as well as the myson added, but once done it simply worked, myson fan assisted radiator ensured air movement so with open plan all ground floor same temperature, as once it worked, we forgot about it except to swap wall thermostat batteries once a year. I hope this house will now be the same. And if it works, don't fix it.

 

[bernardgreen]

And if it works, don't fix it.

Good advice..... but there is always that little extra improvement that can be added,

 

[ericmark]

Good advice..... but there is always that little extra improvement that can be added,

Not so sure, I was about to ask the question about new houses with zone valves.

There was a post Hive wiring I don’t want to hijack with this question, however it has raised the question in my mind.

I know many new houses are zoned dormitory and living area, and pre the modulating boiler the programmer enabled the thermostat that in turn would work the zone valve and the zone valve would work the central heating boiler, so there were two thermostats.

However as far as I am aware you can’t connect two modulating thermostats to the same boiler, and even when using off/on thermostat it is only there to stop cycling not to control room temperature. So programmer would work zone valve direct, and zone valve would work boiler, so how is a single thermostat be it modulating or off/on to stop cycling used with the zone valve system?

If to improve from a two zone system to multi zone system you need to remove zone valves and add electronic TRV heads then it gets rather expensive, the cheapest wifi linked TRV head is £40 so even two up two down £160 and with Hive the heads are £80 each. So with a three bedroom house, likely 7 rooms, so £560 for TRV heads with Hive, Nest a bit cheaper as only £40 per head but neither Hive or Nest are really good systems, Nest only lets the TRV follow but does have OpenTherm, Hive the TRV heads actually tell thermostat to fire boiler, but does not have OpenTherm.

There are cheaper options like fitting BlueTooth TRV heads which can be programmed and only cost £15 however what ever system you select, to move to next stage up, involves dumping existing and buying new, so in this house if I moved to EvoHome which is clearly an improvement then I am dumping all the Energenie and bluetooth TRV heads and replacing with EvoHome heads, at around £55 each and that does not include the thermostat.

So look at swapping a non modulating boiler for a modulating boiler with an existing zoned system, how would you do it? Remove zone valves and fit programmable TRV heads instead? Or ignore the fact its a modulating boiler? The modulating boiler is analogue and all controls also need to be analogue to work with it, so the zone valve would need to gradually open and close not be either open or closed, except if simple timed.

The new build we looked at was split upper and lower floor, so during the day bathroom got no heating, ups. And I know although my house is 4 bedrooms upstairs one is used as a craft room and other office, only two used as bedrooms, so how would you use zone valves?

 

[bernardgreen]

Can the heating be automated using the temperature from TRV

If the TRV can report the temperature back to the control system then the answer may be yes it can.

But is a TRV a reliable way to measure the temperature in a room ? I do nto think it is a good way to measure room temperature. By its very nature it is next to a souce of heat and fitted on pipework carrying water as a temperature significantly higher than room temperature when the rooms is being heated,

For what it is worth I am about to fit thermal actuators to my radiators fed with 24 volts from a controller. When a valve is open a feed back contact will inform the controller which will then command the boiler ON. The boiler spec suggests it should modulate low enough to cope with a minimal heating load without have to cycle ON and OFF.

Room air temperatures are measured by electronic sensors connected by RS 485 to the controller

I have the advantage of easy cable routing to all radiators.

Reason for adopting thermal actuators is that motorised battery operated wifi connected valves can be noisy as found in a new build I visited.

 

[ericmark]

But is a TRV a reliable way to measure the temperature in a room ?

I can honestly answer yes, it works very well, the main thing with room temperature control is the sensor needs to be in the air flow, and it does not want to sense wall temperature it wants to sense air temperature, I have two makes of electronic TRV heads, I can't say how the cheap £15 ones work, however the £40 Energenie ones with two sensors air and water the latter used to compensate the air reading work very well. If it shows 20°C then an independent free standing thermometer placed in the air flow is within 0.5°C of the TRV heads reading.

The fan assisted radiator is also works, old house has a myson and the sensor switches the fan on/off depending on temperature of in coming air, however there is a problem with my old one at least 25 years old, with fan stopped there is nothing to circulate the air, the newer iVector model has multi fan speeds, so that I assumes works better?

The problem as I see it is, we have to buy the TRV head to be able to find what it does, reading the advert for Hive, their TRV heads do tell the wall thermostat to run the central heating, but seems a little vague on for how long? The cheap Bluetooth TRV head has a boost button, it opens to 80% when pressed, idea is to heat a room fast when you had not expected to use it, it remains at 80% for 5 minutes, so to work the boiler must be running, so likely will work well with a modulating boiler, however non modulating the space is normally more than 5 minutes, so the valve could close again before the boiler has run.

My hope was people would talk about their TRV heads, and we would build up a picture of the good, bad and ugly, however only one guy has replied, he has a modulating thermostat and sings its praises, but would be nice to see more reports.

 

[SimonH2]

Have a read through this, interesting approach that I will try and roll out.
https://community.openhab.org/t/my-central-heating-solution-using-thermal-actuators/41320

Yes, that's one approach to it.

The electrothermic actuators do work very well as long as you understand their characteristics. A couple of jobs ago we used them for the office heating/cooling (we were using Honeywell IIRC). I did enquire of the manufacturer about limitations on duty cycle and they said there weren't any. This means that you can achieve something approaching proportional control by applying a variable duty cycle to the actuator - something that is going to work best if the system allows you to sense whatever the valve is controlling, such as temperature in a mixing valve. It also means that you can run the control with no hysteresis - provided there isn't a relay to annoy people by clicking all the time.

As to characteristics, different makes/models will be different - but the basics will be the same. At switch on, there is a delay before anything happens - the length of this delay depends on the starting temperature (from cold, several minutes; recently closed, quite short). Then the valve will open as the wax heats up - IIRC ours were specced for 2 minutes for this. When power is switched off, there is a delay similar to the switch on situation - it takes a while (maybe several minutes) for the wax to cool down to the point where the actuator starts moving, and then it can be a couple of minutes to close. If you only switch the valve at long intervals, you can experience increased hysteresis due to these delays before anything happens - and we had to have the electronic controllers we were using modified to impose a lockout between heating and cooling modes. Without the lockout, we'd have the heating over-shoot, then the unit go into cooling mode; then it would over-shoot on the cooling; and the room temperature would cycle badly. IIRC, from "been on for some time" to shut could be as long as 7 minutes
For our setup, we could have had things done differently (but more expensively) and operated the valves in a pseudo-proportional mode - but we didn't and this controller modification did the trick for us.

 

[ericmark]

Not a clue what is included in a TRV head to stop it going wide open when the boiler is not running, however they don't, at least Energenie ones, the wax electrothermic actuators would need the software to stop them going wide open writing for the control be it a PLC or other unit. It could clearly be done, and they could work far better than the motorised TRV. But should I not be able to do DIY repairs, what are the changes of finding some one to work on the system to repair it, who would not be charging silly figures?

 

[bernardgreen]

the main thing with room temperature control is the sensor needs to be in the air flow,

so the reality is a TRV with a remote sensor some distance from the actual valve. The sensor sends commands to the TRV either wireless or hard wired ( or even a capillary tube ). The link if wireless or hardwired can also send information to the boiler / system controller

 

[ericmark]

so the reality is a TRV with a remote sensor some distance from the actual valve. The sensor sends commands to the TRV either wireless or hard wired ( or even a capillary tube ). The link if wireless or hardwired can also send information to the boiler / system controller

I note you can actually get these. When the TRV is on the top of the radiator then there will be far more heat from the radiator acting on the TRV, although there are two sensors one air and one water the latter to compensate, there is no user adjustment, so even mounting upright or horizontal will affect how they work.

However when the TRV modulates the amount of water flowing the radiator does not get that hot, with Mold house the boiler was off or on, no modulating so the radiator got very hot before being turned off again, but Shotton house boiler modulated and TRV modulated, so the radiator never got that hot.

New house in Llanfair boiler is not modulating, however there are 15 radiators so not sure how hot any will get. So I don't know how it will go.