Are there any problems using a smart thermostat with an Air Source Heat Pump (ASHP)?

Hiya @chiefmac !

That’s actually a seriously good question and is definitely one I’d not considered before!

I’ve had a look through the T&C for the Zero Carbon Heat Trial which you can check out right here if you’d like to - just in case I could spot any likely answers or clues. I couldn’t find anything obvious in there, but the full answer is probably a bit more complicated than usual.

If you weren’t on the trial, you probably could swap out the thermostat with a smart one without too much trouble, since all it really does is calls for heating when a room gets too cold, and calls for cooling when a room gets too warm. However, being on the ZCH Trial adds a few other factors into the mix like the Kaluza Flex Platform.

I don’t know the right answer to give in this sort of scenario, so I think the best I can do would be to call in some extra help from @Tim_OVO and @Jess_OVO for this one. They’ll probably need to check with a few other teams, but I’ll try to remember whatever answer comes back in case anyone else is interested.

Sorry it’s not quite the answer you were hoping for just yet, but I hope you’re OK with that.

@chiefmac To be honest, I don't think they'd ever know. The installers had the simple Honeywell stat with them to use but were happy to use my Nest stat to control it.

The best controls will be ones that don't allow the pump to cycle too often. I'm considering trying to let the Daikin box control things and utilise a smart radiator thermostat in any room where I want to have a change of temp through the day such as a bedroom. I will compare the energy usage with the pump on for the majority of the time with a scenario with the Nest's on/off control and see if there is much difference.

Hi @chiefmac,

So sorry for the delayed response on this one - we’ve checked in with the Smart Home team who have advised:

Yes -  you can change the thermostat as long as it doesn't 1) impact system performance or 2) prevent the data coming through to the project. The best way to validate this would be to discuss your options with your installer.

Hope this helps you decide on what to do about replacing your current smart thermostat - do let us know the advice your installer gives if you do decide to make a change. 

Thanks @Jess_OVO, that’s really good to know. It’s not something I’ll be doing immediately, but looking to soon. There are various reasons where it would be very useful to intelligently turn on and off heating in different rooms at different times in our house, so I think a Smart thermostat system could save us some money in the long run. I’ll let you know when I get this done. Thanks again.

Hi @chiefmac @nealmurphy and everyone - I’m looking to reinvigorate this topic because I’ve been doing research on it the last few days. Chiefmac did you come to a conclusion about which smart thermostat (“stat”) is best for your home, and the best way to set it up? I’ve been trying to decide which is best for our home because in a few months we’re changing downstairs from rads to UFH. So, downstairs we will have multizone UFH with a manifold and upstairs we will have rads, all connected to our low-temp Daikin ASHP. We want a smart thermostat to schedule and control the temperature in each zone/room from our phones, for the whole house. I’m easygoing on features like controlling DHW, “learning”, geofencing, etc. I’m unsure about the best way to set up the schedules, etc. since our heating has a slow reaction time and we want to minimise heat pump cycles. At the moment I’m focusing on Hive and Heatmiser. I’ve deprioritised Nest, Drayton Wiser, Tado, and Honeywell. For trial purposes we will leave the Kaluza connected. Are there any other brands you would recommend taking a closer look at? And is there any other advice you can share in terms of how to set up the smart thermostat, schedules, zones, etc.? Thanks in advance.

Hi @briannolan 

I probably can't assist too much as I don't have knowledge of Hive. I was looking at a potential switch from Nest to Tado as part of a Living Lab trial, but the benefits (smart TRVs for radiators) didn't seem to be worth the hassle as my system seems to be working OK for me with most radiators open fully and the thermostat controlling on/off times with some weather compensation from the ASHP.

Will be following with interest to see if there's any tips I can pick up.

@briannolan 

Have you looked to see if the Dakin app  controller might be compatible and if it would meet your needs? Never looked at it myself. I assume you are not already using it of course. 

https://www.daikin.co.uk/en_gb/product-group/control-systems/daikin-online-controller.html

@Jeffus - thank you, I appreciate it. I hadn’t heard about the Daikin app until now, but it looks like it’s only software. I could be wrong about this but I think I need additional hardware. Also, my heat pump isn’t listed as one of the compatible devices.

I did wonder how many pumps it covers and what additional dakin equipment in terms of senors might be needed. As it is a beta product it might be worth asking Daikin if they have any suggestions using their bits of kit. 

I only say this as there seems to be some consensus about using the manufacturers weather compensation controls with heat pumps? As soon as you add a 3rd party control you end up with two controllers attempting to work in sync to control the temperature. The Daikin controller will alter the water flow temperature as the outside temperature changes with weather compensation. The third party controller will be doing its own thing based on the temperature you tell it. I am no expert, i would want to know exactly how the two controllers were going to work together and if i was giving up anything in terms of efficiency vs increased control of scheduling etc. I don't know what the optimum solution would be in terms of running costs. Does Hive and Heatmiser work well with the Dakin weather compensation? 

Both Octopus and OVO have been talking about heat pump specific tariffs recently, depending on how your heat pump is currently controlled. It is not yet clear what controls they expect owners to have or if you would end up having to buy another piece of kit. 

Be really interested to hear how you get on. 

Well done for being so green! 

@Jeffus In the words of Greg from Octopus "Let's not try to have all of these special cases, it's bonkers!" His view is to let price be the single optimising factor, so use dynamic pricing and then let your EV, heat pump or whatever work with this rather than the other way around. It makes sense particularly if you've got both EV and heat pump vying for cheap prices at different times.