Dan F

Number of alternative options, aside from the Partel product. - https://www.ecologicalbuildingsystems.com/product/phonotherm-200 - https://www.phstore.co.uk/foamglas-perinsul-hl - https://www.cfsfixings.com/products/purenit - https://www.greenbuildingstore.co.uk/product/compacfoam-200/ We used perinsul foamglass blocks for some sliders and then used purenit (recommended by @craig) elsewhere. The purenit I think was available in a lot of different thicknesses and came in a 2.4x1.2m sheet which was easy to cut down, so might be worth looking at.

Yes, it had to be. Can't remember exactly why, but it was either because rules changes or because we moved in before the install was certified. The heat meter doesn't count backwards for cooling, but the electricity meter does continue to count up so you can reclaim less. That said there is an anual limit (based on SAP results) on what you can claim anyway, so it may not have a major impact. We also have metering for perforance (via passivliving) but this doesn't consider cooling at all. Our COP for July according to their dashboard is 0.6! That partly because of the way I hard DHW plumbed which gives bad COP, but primairly due to cooling.

4mths ago. Our application weent in in March 2022. Metering with cooling is complex because while the heat meters have registers for cooling/heating, the electricity meter cannot differenciate between heating and cooling. What happens in practice is that the amount you can claim for heat is reduced relative to the amount of cooling you do. This is because the payments are based on heat meter reading - electricity meter reading. Either that or you have to put a much more complex monitoring solution in.

Our design flow rate is actually 285m3 for some reason, not sure where they got this from! We are 315m2, but ceiling is 2.5m downstairs and 2.4m upstairs making the total volume 780m3 (excluding loft). If you average you room heights, your volume seems to be around 775m3, so almost excactly the same! Building regaulations requirement would be 340m3h based on area for our house (or 310m3/h in your case). Passive house guidelines give 230m3 for of us (300m3/h boost and 120m3/h miniumum), So, looks like it makes sense to reconfigure ours to use the passive house numbers, and then (once I get the Loxone integration working) use the low setting more often e.g. when we are out.

What is the relationship/limitation with permitted development?

I have one. Already taken it out of ASHP, opened it and shared pictures above.

Our "medium" (default) setting is 270m3/h, so no wonder we were seeing FF temperature gradually rise more than you even with blinds down. I dealt with this via running the comfopost a fair bit, but in hindsight I probably could have just turned the MVHR down. This also may have reduced need for GF cooling too (Comfopost if FF only). Our low setting is still 210m3/h, so I might even try away (62m3/h) if there isn't much cooking/showering.

I saw temperature difference of up to around 12C, with a max supply temperature of around 26C when it reached 24C exhaust temp at one point when it was 39C externally. This make sense because the efficiency of say 85% gives: supply temp = 24 + (39-24)*0.15 = 26.25C. Is this correct? We also have a enthalpy exchanger, but I dont see why this woudl have an impact.. in fact ERV generally has lower efficiency than HRV.

Are you referring to RHI? With RHI you can install a ASHP with cooling enabled, we did and also declared it as such. https://www.ofgem.gov.uk/environmental-and-social-schemes/domestic-renewable-heat-incentive-domestic-rhi/applicants/eligible-heating-systems. Also, MCS 020 (permitted development guidelines) doesn't say anything about cooling from what I remember either.

Looked into this a bit futher. Vaillant have used these "code plugs" in their gas boilers to switch between gas type; G20 (yellow), G25 (blue), propane (yellow) for some time. These code plugs sell for £5 in the U.K. What they've done here is is they are selling the same thing, under a different product code for a huge markup! Sneaky! Mine is already installed. No idea what installer paid for this "chip", I don't think he itemized it.

Interesting. Did you reduce MVHR fan speed when it was very hot outside? What (I think) I saw was that unless I turned on Comfopost or reduced MVHR to minumum, then the MVHR supply alone (which got up to around 26C) was gradually heating up the first floor.

Vaillant UK clearly (as two different suppliers have quoted £300+). This sells for €40 in europe. That said this may well be the same thing (probably is), but they are using a different part numbers. https://www.heatingspareparts.com/boiler-spares/partno/0020266328/517003. Google that part number and you get a pircture of what I have here: https://www.glo24.de/vaillant-stecker-kodierung-0020266328

I was deliberately hiding the band somewhat so noone beat me to it selling DIY versions on ebay 😉 Nah. I read it as yellow-black-red-brown-brown. i.e. 4.02kΩ ±1%.

It is. Resistor is worth 5p, connector is worth 10p. Might have to put an order in with RS and set up an ebay shop 🙂

I've got it out of ASHP, but unluckily my multimeter battery is dead and don't have any spare PP3 batteries at home. 😞 It looks like this, with same code on the side. If you dig around on the internet it looks like Vaillant may sell this under different part numbers at different prices (cheeky if true). As searching for "20112219" brings up a different part number: 0020266328. This part is is a blue coding plug which looks like it may be available for £5!

https://www.seconrenewables.com/ are quoting £350+VAT too! Looks like does make sense to take mine apart, take some measurements and make/sell some of these 🙂

Somebody, either Midsummer or Vaillant is making a huge profit on these! Try calling https://www.seconrenewables.com/ or Vaillant directly. Yes €30 in europe, not immedialty available though. https://www.heima24.de/heizung/vaillant-kodierwiderstand-zum-aktivieren-der-kuehlfunktion-arotherm-split-plus-0020269259.html

Yes. 0020269259. It's available in europe for €30-40 seems. Somone who needs one should call Vaillant and ask where to get one in the U.K. without being ripped off.

Our installer supplied and fitted ours. I can't beleive it's £300, I think some UK resellers are just taking advantage of lack of supply probably. Where did you get the £300 price from, Vaillant themselves?

Couple of things I releaised (late) with the data in this spec sheet: - The cooling power is based on 28C supply temperature from MVHR (in practice it's never going to get to that due to the "heat (cool) recovery".. ours got up to around 26C at most today but typically it's only around 24C on a hot day. (a degree or two above internal temperature). - The cooling power is relative to the MVHR supply temperature, not the room temperature. So if room temperature is 20C, MVHR supply temperature is 24C and Comfopost output temperature is 12C, the effevtive cooling power is only 2/3 of that stated. Depends how you look at it though, and if you MVHR would be on at same speed without a comfopost. I'm seeing very minimal cooling of first-floor with our Comfopost (that's with automated blinds down). It does mean though, that on days like today we can run MVHR on medium speed and not heat the house up in the progress. The last few days we've been using UFH to keep ground floor at 22-23C and first floor has stayed under 24.5C throughput. Not sure what it would have got to if we hadn't been running the Comfopost, but we'd most likely have need to put MVHR on "away" mode today to stop the first floor getting uncomfortably hot. While the Comfopost outputs air at 12C, by the time it gets to the plenums in the first floor rooms (even though all ducting is insulated) it's at 16C.

Use the free SMA Sunny Design tool or Solaredge Designer to mock up a system and see what fits and what you'll get. https://www.solaredge.com/uk/products/installer-tools/designer#/ https://www.sma.de/en/products/apps-software/sunny-design.html

No extra sensor no. The sensoComfort (VRC720) controller has this incorportated

Which ASHP? Our does cooling up to 46C external.

Do the Ecodan controls not do any dew point calculation? Vaillant will work out minumum (with a configurable offset) based on RH.