JamesDRG

Hi yes that's a good idea. The tape would create a good seal.

Thanks Dave. The finished floor level will be the same, but the level of the DPM in the new part is 10cm below the original one. Ah I see, so you can paint a DPM. Thanks!

Hello folks, We are retrofitting UFH in our late 1980s house and I have a question on the DPM. So far we have dug out the existing concrete floors, compacted hard-core and laid a 5cm sand blinding. The next step is a DPM, followed by 200mm Celotex, visqueen sheet and finally a 100mm cement screed encasing the ufh pipes. We have left about 30cm of the original floor around the perimeter of the room - so in effect we have dug a pit in the middle. The existing DPM under the undug floor is now 10cm above where our new DPM will be. How should we lay the new DPM to ensure there is no moisture transfer? The old dpm is only petruding about 5cm (we had to cut it to dig out). Any help greatly appreciated. Thanks James

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

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

Yes, TS had inhibitor in it. No antifreeze. Is the latter needes for an ASHP?

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.

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

The Willis heater heats the very top of the tank with hot water and is more efficient than an immersion near the top, which is invariably heating a larger volume of water and promotes more blending of water. As I understand it, you cannot have E7 meters installed anymore.

Good call on this - yes a buffer tank in the plan for the ASHP. Hmmmmm feels like I am breaking some KISS principles!

Thanks @JohnMo Hmmm interesting idea. I'll sketch that out in a bit and see what that could look like. Yes, agree with the above. We have a pump already fitted for the showers and this is more than fine. Filling a bath takes a bit longer but again we don't mind this really. What I am not sure with a DHW from a TS is how much of a temp drop you would get from the TS vs DHW out? Ie what is the minimum TS temp you could get away with to still have a hot shower.

Defo agree with this point. But in our design we are not looking for instant hot water - we would run the Willis just ahead of when we need it. So for a shower, should take 10-15 minutes of heating. We can have this linked to Alexa via Shelly relays so it's not too much of a pain to just give a bit of notice before a shower (or time it of you shower more or less at the same time).

Thanks @joth We were going to run the the ASHP low enough so it can serve the radiators upstairs - which we have oversized. We might get away with 40C if we can get enough insulation in the house? I think this is a fair point, the main reason in the short-term would be for the stove, but if we were to add solar in the future then I think this would "solve" the DHW problem (at least in my head!).

I could add a valve as shown in the third picture that will close whilst the Willis is on?

Thanks for the input Peter. In your proposal would you do away with the second cylinder and take the DHW from the DHW coil in the TS?

Hello fellow members, this is my first post so please be gentle We are working on the heating design for a remodel/extension to a property built in 1990. Our primary source of heat will be an ASHP with Solar to (maybe) follow in the future. We also have a log burner with back-boiler. All heat sources will "charge" a 500L thermal store which we have situated on the first floor. Log burner will use a standard gravity fed system to the TS (out of scope of this thread). The CH side of things we are fairly comfortable with (wet UFH on ground floor, floors dug out with 200mm celtox insulation, upstairs rads, all fed from TS). Where I would value your opinion is on the DHW. I have been reading with interest @oranjeboomand @Jeremy Harrisyour successes with the humble Willis Heater (I plan to use a similar setup as an interim/backup for the UFH until the ASHP arrives). For the DHW I was thinking of integrating a Willis Heater with a direct vented HW cylinder, using the attached "Willis" diagram which many of us are familiar with. The advantage of this is it would require little change to the DHW arrangement we have now (we have a header tank in the loft, gas boiler). In the summer months we would use the Willis Heater to provide DHW "on demand". For example, we put on for 10 minutes before a shower, 1 hour before a bath. That is fine for our needs. In winter, I want to make use of the TS for DHW. With that in mind, I have proposed the second schematic where we essentially have a similar thermosyphon arrangement with the Willis Heater, repeated (in parallel I think?) using the indirect DHW coil in the TS. I hope that if we say light the log burner of an evening (boiler output 5kw), once the TS starts to charge this heat will be transferred to the vented cylinder and provide an extra 150L of hot water. I would like to hear people's view on this approach. Some things I have top of mind: 1. I will need to think about we make the Willis a little "smarter" in not actually activating should there be sufficient water in the DHW cylinder. The thermostat in the Willis could be sufficient? 2. For on-demand heating in the summer months, perhaps there is some optimisation we could do to feed water to the Willis heater again via the coil in the TS so we can utilise this captured from the ASHP. Or would the thermosyphon effect be OK here? The TS would reach about 30C so this should be transferred to the HW cylinder. My assumption (which is only that ) is it is more efficient to run the ASHP at a very low output temp (say 30C) and provide the additional "top of" of DHW temp using the on-demand heating using the Willis. I look forward to hearing what people think