JamesDRG Posted March 15 Share Posted March 15 Hello folks, I would appreciate some advice on integrating a 5kw ASHP into our new heating system. I've given a brief overview of our setup before specific questions :) We are doing a complete (self) rennovation on 1989 5 bed property. Approx 2,800 square foot. New double glazing, cavity and loft insulation. UfH on ground floor. Floors dug out with 200mm PIR, 100mm concrete on top. Oversized rads on first floor. 500 litre vented thermal store with 2 internal coils, and a third coil for DHW. Logburner with back boiler attached to thermal store. We also have a fairly new gas combi boiler that accepts pre-heated water from the TS indirect coil to provide mains pressure DHW. Can also boost temp for rads from TS if needed (not got this far yet!). I have a Daikin 5kw ASHP that I'd like to integrate into the system. The main uses will be to: A. "preheat" the TS to 35C for DHW. My logic here, is it more cost effective for the ASHP to heat water to 35C than the gas combi, but over this temp, gas is more economical. Similar logic applies to upstairs rads - combi may need to "top up" rad temp a little. B. To run the UFH. On some winter days, TS will be fulky charged to 85C by logburner. My questions 1. I have 2 options to connect the ASHP to the TS - either directly, or via a spare coil at the bottom half (intended for solar). Which option would people revommend? 2. When running the UFH would you have the ASHP connected directly to the UFH (thinking of using homely) or would you tap the UFH heating into the TS? Second option feels simpler - but not sure how weather compensation would work. Help and advice really appreciated. Thanks for reading James Link to comment Share on other sites More sharing options...
SteamyTea Posted March 15 Share Posted March 15 I am going to follow this with interest as I am a believer in storing energy in water, rather than batteries. Couple of things spring to mind. How often will the thermal store go below 35°C. Water below that temperature is not much use, and even of it drops to 8°C every day, then that is only 16 kWh. What are the thermal losses of your house and your DHW needs? Does a thermal store need antifreeze/inhibitors in it? If each circuit is isolated then I guess not. Link to comment Share on other sites More sharing options...
JamesDRG Posted March 15 Author Share Posted March 15 Hi thanks for your reply. DHW we only ever have a single shower or bath at a time - hence the combi. 2x 10 minute showers per day. I am not too sure tbh rehards the heat loss of the house - can you recommend any good estimators? The ASHP would charge the store everyday to 35C (overnight). And run the UFH 24/7 in the colder months. I am toying with the idea of the UFH only pulling water from TS if the temp is above 35C (the logburner must have charged the store). Otherwise, take water direct from the ASHP. When we light the logburner, this ensures the ASHP will never run until the store drops to 35C. Link to comment Share on other sites More sharing options...
JamesDRG Posted March 15 Author Share Posted March 15 Yes, TS had inhibitor in it. No antifreeze. Is the latter needes for an ASHP? Link to comment Share on other sites More sharing options...
JohnMo Posted March 15 Share Posted March 15 (edited) Generally I think you have to much time contemplating and ended up with a complex solution. Way to complex. Read some of my threads I have been there done most of it. Sounds like you have most of it already. With what you have I would do the following. Sell the thermal store and get an UVC. Combi, blank off the DHW side. Use the boiler as an UVC heater on its own or in combination with the ASHP, in hybrid mode. Use the ASHP to drive your heating. Don't bother with the back boiler. Edited March 15 by JohnMo Link to comment Share on other sites More sharing options...
JamesDRG Posted March 15 Author Share Posted March 15 Hey JohnMo, Thanks for the input. I have read many of your threads and comments, and have found them very insightful. The back boiler on the stove is staying, my wife prefers the idea of paying a local person for firewood than fueling bonuses for energy CEOs - which I do in part agree with. Plus it has an oven which is actually really good! So, that means we need the TS really and have it already (picked up a new Italian made stainless one for £1800, almost half price). Heat pump I managed to get a new Daikin unit for £1,200 which I figured was good. I'd be interested to hear if others think this is good value for money. JohnMo with that in mind, is there any potential issues you can see with my setup? Thanks James Link to comment Share on other sites More sharing options...
JohnMo Posted March 15 Share Posted March 15 38 minutes ago, JamesDRG said: JohnMo with that in mind, is there any potential issues you can see with my setup? One issue with combi preheat is the cold slug of water between TS and combi, the combi always fire up every time a tap is opened. So you need a solar diverter valve close to the TS outlet. Take a look here also. https://originaltwist.com/2016/06/23/eco-heating-system-for-heat-pumps/ Link to comment Share on other sites More sharing options...
JamesDRG Posted March 15 Author Share Posted March 15 Good suggestion - something like this? https://atmos-i.co.uk/boiler-spares/15mm-solar-diverter-valve/ Does anyone have any suggestions on the best way to connect the ASHP? (see first post in thread). Thank you James Link to comment Share on other sites More sharing options...
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