Posted by: @gfkw1947

Hi,

We live in a very old cottage in Norfolk which has been extended and updated. We have been here for 32 years. Last year we decided to replace our old oil-fired boiler with an ASHP. We received a lot of conflicting and clearly wrong information from installers and eventually found a consultant who for a small fee assesses your needs (using info about your house provided by you), and then recommends a manufacturer and installer. This all worked well and we are delighted with the result - up to the point where we struggled and still do, with the operation of the electronic smart TRVs. The installer positioned them where the original TRVs had been on the rads. But they do not work properly. It seems that long before the room warms up the valves close down because they are reacting to the temperature of the hot water constantly circulating in the pipes feeding through the valves and into the radiators. 

I do wonder if the problem is the position of the TRVs which are all at the bottom feed. We were using Tado valves before but did not have the same problem because we also had room thermostats. The room thermostats would override the TRVs to open or close them and also turn the boiler off and on.

Has anyone experienced this problem or have suggestions, please? 

Hi gfkw,

If you have read any of the threads on the forum concerning control of ASHP's, you should be aware that heat pumps do not perform particularly well when controlled by thermostats and TRV's.

If you still wish to use TRV's then I would suggest that you read the manufacturers manual, which may detail how to set an offset, so that the TRV operates at the correct temperature. Alternatively, if the room temperature is say 2C below the desired temperature, then increase the setting of the TRV by 2C.

@derek-m Thanks Derek, I was persuaded by the manufacturer to use their own smart TRV control system - I did question at the time how they could possibly sense the temperature of the room when they are positioned right next to the rad and constantly warm/hot pipes. I was assured they were designed to compensate for this. Unfortunately adjusting the desired temp to compensate doesn't work. Our bedroom is set to 20° at bedtime and getting up times - but rarely even reaches 17°. But the radiator will be stone-cold because the valve is closed and it is, I suspect because the temperature of the hot water pipe feeding the valve is telling the TRV that it's very warm in here!! Normally I have to manually open the valve to allow a burst of hot water to get to the radiator - but it's not very satisfactory as you can imagine. I have read an article recently by someone at Danfoss recommending that all TRVs regardless of whether or not it's an ashp, should be mounted at the top of the rad horizontally with the outflow at the bottom opposite side of the rad. I can find no one else mentioning it anywhere but it does make some sense!  

@gfkw1947 

Are the TRV heads correctly installed on the valve body, or are they actually compatible? Perhaps you should get your 'expert' back to explain why they do not work.

Thanks Derek. I’ve got both the manufacturer and the installer coming here in a couple of weeks to hopefully to sort it. So far it’s been difficult to get them to accept that there is a problem. I’ve had to get a bit heavy over it and I just need to gather as much knowledge as I can before they come. But I’m pretty much convinced that repositioning the TRVs would be the answer!

Posted by: @gfkw1947

Thanks Derek. I’ve got both the manufacturer and the installer coming here in a couple of weeks to hopefully to sort it. So far it’s been difficult to get them to accept that there is a problem. I’ve had to get a bit heavy over it and I just need to gather as much knowledge as I can before they come. But I’m pretty much convinced that repositioning the TRVs would be the answer!

If you want a real solution to your problem, you should get rid of the TRV's and thermostats and set your heat pump to operate using weather compensation control, preferably with auto adaptation.

@gfkw1947, good to hear you've got the installer coming out in the weeks ahead.

We've been using smart TRVs for three years, and what you've explained is a common issue. The temperature around the rads registers that a temperature has been hit in a room, which it may not be. We use smart TRVs from Eve, and when you get to the app, there's a room offset that you can set – this will vary on the size of the room. For our master bedroom, for example, which is a large room, we have an offset of -2.5C. It's similar to setting the rad to say 23.5C (as Derek described) if you want your room to be 21C. It's just neater having a room offset. There will almost certainly be a setting like this for Tado.

@derek-m Thanks Derek, Unfortunately, what you are suggesting tells me I need someone who understands the complete workings of the system to do that - and I don't. I have asked lots f questions but tend to get very superficial answers like "it works like a fridge in reverse". I understand already the mechanics of how the pump extracts heat from the air and transfers it to the water. It's all the other details that throw me?

Posted by: @gfkw1947

@derek-m Thanks Derek, Unfortunately, what you are suggesting tells me I need someone who understands the complete workings of the system to do that - and I don't. I have asked lots f questions but tend to get very superficial answers like "it works like a fridge in reverse". I understand already the mechanics of how the pump extracts heat from the air and transfers it to the water. It's all the other details that throw me?

Hi,

When you have the time I would suggest that you read through some of the trends concerning heat pump efficiency, where I have explained in detail the reasons why weather compensation and auto adaptation provide the best overall efficiency.

@editor Thanks MARS. I have read and watched many of your videos etc. They were very helpful in getting me up to speed. Prior to the installation of my ashp, I had an oil-fired boiler - so much simpler with few controls to worry about. About 2 years ago I added Tado TRVs plus room thermostats. This worked wonderfully because the room thermostat could be placed wherever was most appropriate in the room. I was also able to use 1 room thermostat to control the TRVs (which were overridden by the room thermostat) in three or four rooms. I was hoping to still be able to use this set-up with the ASHP but apparently, it was not compatible with it. Thanks for your input.

@derek-m Thanks, I will certainly do that. Are these trends on here and are they easy to find?

@gfkw1947, I'm not sure how much of a smart home enthusiast you are, but we've just upgraded our TRVs to the latest version from Eve that are Thread enabled. If it's of interest, you can watch our video which is embedded in this post: https://renewableheatinghub.co.uk/forums/thermostats-trvs-pumps-valves/thread-enabled-eve-thermo-smart-trvs#post-6786