None yet Mars other than the web based info system for my solar and battery systems. I’ll be automating everything I can to ensure that there is minimum input from me to get the best performance out of all of the separate systems, heating, water, exporting to grid etc ill let thermostats control the need to draw heat from heating 

Hi,

Is there anything you guys would advise I should look for ,whilst having my building work been carried out, to have smart tech items installed?

Hi @nigel42 - controls have been a big headache for us, and last week we filmed a new video which we hope to post tomorrow. We discuss smart TRVs and thermostats, and some of the information might be useful. 

Please refresh my memory, but are you also getting solar PV put in, or just the ASHP?

@editor Hi, thanks for the heads up re your video. Yes we are having both Solar panels and a ASHP. 

@nigel42 - since you have solar PV, I'd suggest adding an iBoost (or equivalent) device that will use excess electricity from the PV array to heat your water instead of sending it to the grid.

I would also suggest speaking to the installers and ascertaining how many circuits you'll have for rads and/or UFH and what is going to be calling for heat for each of these zones/circuits. This was the biggest jigsaw puzzle that we needed to solve in our retrofit. 

So our latest video is out and we explain (as best as we could) how we control our air source heat pump with smart thermostats and TRVs. We also share our thoughts and experiences on Eve Thermo TRVs, Heatmiser Neostats, Salus smart thermostats and Tado.

@editor Hi, yes we are having a 'Solic 200' fitted. (it works in the same way as an iboost) I've just finished watching your video and the email has been fired off to my installer re the 'calling for heat' Thanks!!

Hi Everyone,

As an Instrumentation and Control System Engineer, for over 50 years, this is obviously one of my pet subjects.

I have been very pleased to see that equipment and techniques, that at one time were only available and affordable in the larger industrial complexes, are now becoming available for domestic use.

Let me describe the control system that I designed for our smallish bungalow, though similar techniques can be used for larger more complex requirements.

A Resistance Temperature Detector (RTD), mounted in the hallway, accurately measures the indoor air temperature. This signal is fed to a PID Controller, as the Process Variable (PV) for the 'Master' Controller located within the module. The PV value is compared with the Setpoint (SP), set on the Controller. If the PV is below the SP then the output of the 'Master' Controller is increased, or reduced if the PV is higher than the SP.

The output of the 'Master' Controller, acts as the SP for a second controller located within the same module, this second controller being the 'Slave'. A second RTD, mounted on the rear of the radiator in my office provides the PV input for the 'Slave' Controller. The output from the 'Slave' Controller is via a relay, which operates an external relay which switches our Gas Boiler and Central Heating Water Pump On and Off.

You may ask what is to be gained by the complexity.

1. Once optimised it is possible to obtain temperature control of within +/- 0.1C of Setpoint for most of the time.

2. The Gas Boiler and Central Heating Pump only run long enough to top up the radiators to the required temperature. Normally about 4 minutes each time.

3. The required temperature is automatically adjusted as the heating load varies with outside temperature. It actually does this throughout the day, so that at night, if it is say -5C outside, the control system will heat the radiators up to approximately 42.5C, then if the outside temperature increases to 10C in the afternoon, the radiator temperature would have been reduced to the mid to low 30's. It achieves the different temperatures by running the boiler and pump only until the required temperature has been achieved. The boiler and pump will start and stop as frequently as every 10 minutes when it is very cold outside, but when it is much warmer the frequency could be once every several hours. 

Because we live in a bungalow, and leave most of the doors open, so that the cats can migrate from one sleeping spot to the next throughout the day, then we do not need multiple sensors, but it would be easily possible to have similar systems in larger properties.

Mars, one thing that I did note from the video, was that in one of the rooms you have both TRV and Thermostat. Unless they are correctly balanced they could actually be working against each other.

Lets consider a simple system for a property having 5 rooms, with a radiator in each room. Such a system could be controlled by 1 thermostat and 4 TRV's. The thermostat would need to be located in the room with the highest heating load, and would be used to stop and start the central heating pump. The TRV's should close in as their respective rooms come up to temperature, which should occur before the room with the thermostat. In this way the central heating pump would only run when there is a heating demand. By choosing the correct location for the thermostat it should be possible to achieve the desired temperature in each room within the capabilities of the TRV's and thermostat.

I am not certain how accurate TRV's are at controlling the temperature within a room. I would welcome any feedback.

Thermostats can have a deadband of 0.5C or 1C, which is the temperature difference between switching On and switching Off, so that the actual temperature control achievable would at best be +/- 0.5C, but in practice probably worse.

If my memory serves me well, I believe that UFH systems are fed via a manifold, with solenoid operated valves, that open and close to top up their particular section of UFH, similar to the way my system tops up the radiators. I have not yet researched how they are controlled, so would welcome input from someone more knowledgeable.

In the not too distant future I would hope to see domestic control systems, that not only accurately control the temperature within individual rooms, but measure the outside air temperature and help predict the heating demand before it changes.

I hope that you find this of use, but feel free to ask any questions. 

@editor Hi, thought I'll share with you the reply I got from my installer and see what you think?

The heat pump will effectively monitor the buffer, when the buffer gets below a set point the heat pump will automatically turn on. When the cylinder needs heat it will also turn on to supply this.

Now as regards the controls for the heating system, this will be down to what your plumbers want to install. If you have a simple central thermostat, when the thermostat goes below it's set temperature, it will "call for heat" and will start the central heating pump which will pull heat from the buffer.

@nigel42, that is where things get confusing and need strategic thought.

So, your ASHP comes on because a central thermostat has called for heat. You use electricity to heat the buffer (usually 100 litres) and the water gets circulated. If UFH or rads are on, rooms get heat. If you're going to go with one central thermostat, I'd put it in the coldest room/part of the house.

Have you considered whether you will have TRVs on rads and how many thermostats you're going to have? Can you remind me if you've got UFH too?

Mars, one thing that I did note from the video, was that in one of the rooms you have both TRV and Thermostat. Unless they are correctly balanced they could actually be working against each other.

@derek-m, I don't think they are. We have two rooms (in the coldest part of the house) that have smart thermostats and TRVs. The reason for this is that the thermostats call for heat - the TRVs just regulate whether the room is warm and whether the valve should remain open or closed. 

If the room is cold, the thermostat requests heat and the TRV opens the valve. I have ensured that they are both set to the same target temperatures so they always work in sync. So far, it's worked well in terms of calling for heat. The problem is we're having flow temperature issues to that room, which the installers are going to remedy in the weeks ahead. Fingers crossed.