@editor Hi, yes we having UFH on the ground floor. We haven't as yet had a discussion with the plummers as yet re the TRV's or thermostats, so thanks for the tip. We do need to think about the rads upstairs. It is a 3 bed house but only 1 bedroom is going to be constantly used, and even then we like a cool bedroom at night and warm in the morning (in the winter only). So some controllable system will be needed. 

@nigel42 I know it's not a popular opinion but if you are having a lot of work done then I'd suggest putting structured network cables in (Cat5e as a minimum) I know everyone bangs on about wireless being amazing but nothing really compares to the reliability of wires. 😉 

Assuming that you have an area where you can have a central network switch...

@ken, as a geek, I fully concur. Ethernet cables trump wireless every day of the week. The problem is practicality though. In our case, there was no chance that we could wire the house without ripping it apart or having trunking everywhere, so we had no choice but to get a robust wireless in. 

Posted by: @ken

@nigel42 I know it's not a popular opinion but if you are having a lot of work done then I'd suggest putting structured network cables in (Cat5e as a minimum) I know everyone bangs on about wireless being amazing but nothing really compares to the reliability of wires. 😉 

Assuming that you have an area where you can have a central network switch...

I dont believe it! At about the time of your post I was with my builder and he asked me about this very same subject! So I will now be getting them in! He suggested putting the central network switch in our new Utility room. So all good!

Thanks

@nigel42 Excellent! At work I'd always say always add at least one (or two...) more ports than you think you need... 😀 

You could always add a mini switch instead but they need power and never look great...

Despite what I first said... And if you can get over the smoke alarm look of them... ceiling mounted WiFi access points might be worth considering or at least having the option of wiring them in.

We use Heatmiser Neo thermostats for all of our downstairs underfloor heating and the Honeywell Evo system upstairs for our radiators that works really well.

With this setup every single room in the house can individually call for heat from the ASHP when required and avoids the all on/off issue especially with radiators. 

@nigel42  I would also look at the Solic 200 electric diverter.  VERY well engineered and built in Britain.  10 year warranty.  Fit and forget.  But it doesn't have any fancy monitoring or app.  Just works

I currently have a Nest thermostat that controls my oil boiler for radiators and hot water.  With TRVs on all radiators except the ones next to the thermostat.  This replaced and old Honeywell mercury tilt switch.  This seems to work well for the oil boiler.  As the Nest "learns" the heating up cycle of the home.

As I replace the oil boiler with the ASHP, I am considering what to do.  I note Derek's v tight control system (I am impressed as I studied Systems Engineering theory at Warwick Uni).  But I do wonder if we need such tight control?

I am still learning about ASHP.  But I do wonder about following the "keep it simple" principle.  The Nest can be changed to learn from the ASHP.  We would still reduce the TRV settings to cool say the spare bedroom as no one is using it.  Or increase the TRVs to 5 in the sitting room, when we sit down to watch TV at night.  I have read something about ASHPs needing a significant volume of water to manage and operate efficiently - you do not want the ASHP cycling on and off as this loses efficiency.

The ASHP has a weather compensation curve that sorts out the issue of -5C outside, so it works harder to maintain the temp indoors.  If the ASHP is sized correctly, one adjusts this over time to minimise the energy use, whilst maintaining the home temp.

But I do like the idea of the Homely Energy control system that takes into account the price and CO2 every 1/2hr of electric (say Octopus Agile).  So I could minimise the cost?  Or is this just adding complexity and I could just set the Nest, so the ASHP does not run during the typically expensive 4:30-8:00pm slot?  An heat the hot water with solar PV during the day and top up over night when electric is cheaper.  

It is a dilemma and one I need to sort as soon as possible 

@julianc Hi, Thanks for the endorsement! We are having the Solic fitted as part of our package. 

I can't help but feel this is all a bit primitive.  We have a mishmash of control systems all fighting against each other.  For example, the heat pump has its own controller that sets the flow temperatures, maybe based on weather compensation (that it picks up somehow?). Then you might have TRVs that are trying to keep rooms at the set point, but have no means to call for heat, and are intended for combustion heating where you can draw a lot of heat quickly by turning on the valve, which you can't do with heat pumps.  Finally people then stick a Nest on the front of this to 'learn' your habits - but heat pumps don't really work with the 'I see you're leaving work, I'll turn the heating on' idea.  While controlling things on your phone is a nice gimmick for five minutes, it's much better if they just do the right thing without you needing to set anything. And all this stuff is intended to lock you into their vendors' ideas of how things should work (or sell your data for ads).

Really what I want is to throw this out and start again.  I want something to hook into the heat pump to control when it runs and the flow temperature. I want to control the valves as to whether it does hot water or which heating zone(s). Then I want to have a hardwired valve on each radiator that can set the flow, a temperature sensor and maybe a light or occupancy sensor in each room.  The controller can see the temperature of every room, can call for heat and direct it to the right room.  It can keep an eye on that process and bump up the flow temp appropriately, or notice that the weather is clear, the sun is setting, so it's going to get cold outside soon and it needs to buffer up some temperature.  It can also take into account electricity prices, carbon intensity, local solar generation and anything else you like. It could also send you a message saying 'it's going to be cold night, fancy lighting the woodburner to help me out?'

It's possible to build a system like this, with Home Assistant. It supports hardware that drives a lot of the sensors and controls you might have in such a system, although it's more event-driven ('if window broken then sound burglar alarm') than doing the fine adjustment of temperature control. What I need to research some more is how to control heat pumps, which all seem to love being locked behind their proprietary apps and cloud services, and I don't trust those to still be working in 5/10/20 years.  Some of them hook into industrial building management systems via protocols like ModBus, so they might be more amenable to local control.

The problems with Home Assistant are that it's fiddly to set up (it's getting better), things move fast and there's a risk you have to tinker to keep it working - and I really don't want to tinker to keep my house warm. There's also the 'sell the house' factor, and any system really needs to be one where the purchaser can get support from someone who isn't me if they need it.  However one possibility is to have whatever fancy smart heating system suits me, and when selling the house replace it with a boring thermostat and timer that anyone can understand.

But I'd rather not have to do this if there's a decent product out there...

Hi Prunus,

It sounds as if you are looking for a scaled down version of the type of control systems that I have designed, commissioned and optimised in the past. As far as I am aware there is not yet a domestic system on the market yet.

There are a number of options you could utilise.

One or more Programmable Logic Controllers (PLC's) to read sensors and then start/stop pumps and open and close valves, dependent upon what is required to control the temperature of each room.

To have a dedicated PID Controller for each room that can give much better temperature control than a standard thermostat. They also have relay outputs to start/stop pumps and open and close valves etc.

If you can give me some idea of what it is that you are trying to achieve I may be able to give you further assistance.

@derek-m Yes, going for the classic industrial control route is one option.  There's a certain merit to hardwiring in valves and sensors and running that through to a bank of PID controllers. It might give a nice oil refinery aesthetic 🙂

The trickiness comes in the 'smart' side of things. For one thing, you may want to call for heat but adjust the flow temp when doing so. That's not a simple relay contact, you need to tell the ASHP to bump up/down the temperature, which means you need to be able to talk some kind of control protocol to it.  Maybe this is overkill, but it would help efficiency.

Next up, you might want to use wireless TRVs or wireless temperature sensors instead of hardwiring, which are harder to integrate into a classical controls setup. As it happens I have a fleet of these (£8 Aqara Zigbee temperature sensors and £20 Zigbee TRVs from China) attached to a Home Assistant setup, which generally works fine for logging. I prefer the wireless sensors because you can place them anywhere in a room - I'm less keen on the TRVs as they can be noisy and tend to eat batteries.  (On oil heating I've replaced the Chinese TRV with Radbots, which use a light sensor to determine room occupancy and whether to heat - these work fairly well although they can't call for heat so end up thrashing when the boiler is off)

And then you might want to hook into external data sources like electricity prices, weather forecasts, solar generation/car charger/house battery, etc.  That needs something that's able to talk to the internet so has a reasonable degree of smarts.

I suppose it depends on the scope of the problem and whether you're happy with simple control or whether it's worth it to do more complicated things.  On the other hand, the pull of KISS is strong.