JohnMo

If you want to go that route, I would suggest two small MVHR units, one for upstairs one for down. Wouldn't bother with CO2 as there is supposed to be a strong enough link between humidity and CO2 in a household situation. But if cheap and available why not include. But would use external sensors (in each room), not internal to the unit, then you can operate in four modes, off, on at minimum set back speed, normal speed, boost. Set threshold something like, humidity, below 41% off, above 41% on at min speed, 45% at normal speed, over 50% boost. You don't need very complex units to do the above. But not really convinced the effort is work it.

Run - money pit - you would have to reinstate, would by my option. Just because it's burnt down doesn't mean it looses it's listed status.

Basically it's similar to their MEV system, the terminals respond to humidity and CO2 and open and close as a response to changes. The fan speed ramps up and down as required to keep the pressure within system constant. Would assume extracts and supply terminals are linked so the response is, extract opens a suitable supply in the same zone also opens to keep the system balanced. You would expect you just map the system to say terminal A and B are in zone 1 and C and D are in zone 2 etc. then operate a simple time clock or it just does based on where is sees CO2 or humidity. Reality of saving v cost? Everyone watching TV in zone one, you go for a shower in zone 2. Both zones operating.

Think eco and normal are just different cylinder temperatures. Assume both are amendable settings by the user. Possibly these settings are to save too much time being taken heating the cylinder to temp. Would assume eco would be low 40s, normal high 40s early 50s degs. Put on eco all the time and see how your house copes

So obvious remark, why only 100mm insulation on the GF. That combined with UFH is just rubbish. It's pretty poor full stop with or without UFH. I cast my cold water pipes into our slab, I used flexible electric 25mm conduit. With Hep2O or similar inside. Your option questions - the most direct and shortest route

I have just set mine up I give it 1.5 hrs in the morning (cheap rate electric) it uses 45 min to reheat to 45 deg. I also heat at 12 pm til 1 pm again to 45.

Sounds like you could have a big heat demand, if it's all 3 phase and you have a 100L buffer. Depending on the heat demand and the immersion rating they may not be matched well. More info required. Flow rate Immersion size Heat required

When you look at the benefits of anmdding insulation compared to an unventilated cavity, found it wasn't worth the effort or expense. From build desk The calculation method can sometimes produce the same result for a range of airspace thicknesses. For example, the thermal resistance of air layers (i.e. undivided airspaces) with high-emissivity surfaces and a horizontal heat flow (the case for most unfilled cavities in external walls) is 0.18m2K/W for all thicknesses from 20mm to 300mm. A mineral wool would give a 4 to 5 time better performance, a 25mm cavity with 0.032 mineral wool would add (excluding thermal bridging of wooden battens), 0.78 to your R value The unvented cavity around 0.14. Assuming your R value was already 8 Insulated U value ends up 0.114 (plus some for battens thermal bridges) Empty U value ends up 0.123 (note the thermal resistance of wood and the air space is very similar, so little bridging to add. So impact on U value is circa 0.01 or less

Generally to me looks good, most important is, you and other half are happy. For me, not sure about the units above the sink, banging your head would be my concern. Removing would open that space up. It also a little monochrome, for me, could you use a different worktop on the island? Either different colour or material? Is the colour going to black as shown, if so I worry about looking dated very quickly.

Your profile doesn't say where you are? Very different for different countries.

So a few changes. Mixer valve has been removed. Set heating windows at 6am to 7am (cheap rate), and 12pm to 1 pm (make most of any solar). Heat to 47 degs, and the cylinder heating time is around 45 mins. Had to tweek the shower mixer, flow temp settings down (inside the mixer), but all good. Was too hot for the wife Will monitor usage and possibly reduce set point slightly, over a few days

Had DHW heating and cooling running in the summer, once commissioned, no issues. So thought when I installed the UVC there would be no issues when heating instead of cooling. But this hasn't been the case. It looked like the DHW heating cycle finished and the heat pump didn't start on house heating again. First couple of times I just shutdown the heat pump at the isolation switch and all reset and worked fine. However yesterday I actually watched at the heat pump, to see what was happening. The heat pump was trying to start in heating mode, after a very brief off period when it completed DHW heating. But during the restart it was overshooting the set temperature point by quite a margin, and then seemed to be locking itself out. So issues with my install, the heat pump is around 14 to 15m from the cylinder, so although the temperature in pipes drops fairly quickly, at the end of the heating cycle, there was still enough heat being carried that adding a small amount of extra heat was enough to overshoot. So have implemented a few changes 1. Found in the controller the PI regulator integral time, was set to 255 seconds (max setting). This setting apparently is good for large flow rates and large volumes. So ok on a big heat pump, not ideal on not a small one. I reduced this figure to 60. You actually hear the difference it makes as the compressor starts, as it rains in the temperature rise very quickly. 2. I added a forced 10 minute break, in the underfloor heating timer of 10 mins after the DHW heating period. 3. Increased the shut down hysterisis from 0.2 to 0.4. This allows the heat pump to run at a slightly higher temp than set point. 4. Increased the UFH flow rates to the previous ones. Now UFH resumes around 30 mins after DHW, which fine. But the run time of the heat pump has increased significantly. Previously it would do an on off cycle once per hour, now it seems to run for around 3 to 4 hrs straight. This has allowed me to reduce the flow temp slightly.

The manual for the interface controller, uses the terminology backup heater and immersion throughout. This is used for a legionella function, DHW and heating. It can control cylinder immersion and external heater module. There is also a – Limp home mode Immersion heater: Heating/DHW They (Vaillant) sell a 6kW backup heater module and the heat pump interface controller, controls it. An R290 heat pump may not need external electric elements in the heating or DHW, but they certainly provide for it in abundance. Way more control of external heating than my R32 unit.

Your windows seem to installed within the steel instead of in front or behind the steel. So you have a cold bridge that bypasses the window. So you have a cold source outside in the winter and at any time external conditions are colder than indoors, plus the steel will never be warmer than the ground it's attached too. So will always be colder than either inside or outside or both. So you need equal insulation inside and outside of the house and it really needs to overlap the window frame to prevent a short circuit. You need a minimum of 10mm aerogel or 15mm PIR, ideally more covering the steel internally and externally. You need to tape the whole lot to make it airtight to stop condensation forming. Spray foam isn't you friend here, a couple of sheets of PIR and aluminium tape are. If you haven't done the above where it's been plastered, that will need to be stripped back and redone correctly.

But your real arguement is about the need for venting to drain, as you have mentioned several times on other threads. The requirements of G3 are also supplemented with manufacturer instructions, any UVC sold in the UK comes with a set of instructions and the required safety devices. To not install as defined would go against G3 and OEM requirements. For example my cylinder came with the following • Cold water inlet PRV combination valve/expansion relief • Lift up pressure and temperature relief valve - pre installed • Control thermostat • Energy cut-out thermostat • Energy cut-out motorised valve (indirects only) • Tundish Complete with instructions how to install But back to this thread. Having communication between the heating system and cylinder coil, should be a real concern, for the original poster. Which needs to be fixed asap

You may as well cut and paste the whole doc, because everything that comes after the cut and paste is mandatory anyway. There is very little room for interpretation. They may say guidance, but are all covered by the statement In the Secretary of State’s view Requirement G3(x) will be met if:

The rules are the same either way, they may change in 20 years time, but the rules as they are now, don't care what the heat source is.

Why is it academic, it's not a lawful install. Many heat pumps have an immersion directly inside it's casing or are capable of controlling one in a buffer cylinder. A secondary thermostat has to be able to close a positive shut off valve that fails to that position when power is removed. It cannot (maybe in this case shouldn't have been) be given an installation certificate without it.

Besides all the above about 3 and mid port valves, there is a safety issue here also. If the cylinder is unvented, a mid point valve requires a fail closed 2 port valve between it and the cylinder heating coil - to give a positive close to stop the heat source, from supplying heat when power is removed by overheat thermostat. A 3 port diverter does not need this additional 2 port valve, port A on a 3 port diverter is a fail closed port, this port is always directed to the cylinder heating coil, the other port to the heating circuit. A cylinder being cooled by the heating circuit flow, is therefore a safety issue; as the port from a control valve should have been depowered when no call for heat and in the failed closed position. A mid point valve has zero place within a heat pump system or as @JamesPa says in a system with WC.

Look at cascade ventilation as alternatives to the normal way of doing things. You can do everything bluMartin or Fresh R do, with a normal MVH unit. https://sinfonia.passiv.de/?q=node/130 https://designbuybuild.co.uk/cascade-ventilation-an-innovative-way-to-ventilate-efficiently/ https://www.paulheatrecovery.co.uk/cascade-mvhr/freeair-plus-active-transfer-vent/ Also look at coanda effect MVHR outlets terminals.

The brand you originally linked to can take outside air in with an option kit, so acts as ventilation unit also.

7 degs in the Q&A was a start temp indoors, the unit does not start up when its under 7 degrees inside , mentioned about using a normal heater to get the that temp if needed.

Don't tell them what you or they don't want to hear. Are you living on site at the moment?

The thermostat I linked has an adjustable hysterisis, 0.5, 0.2 and 0.1, it can also be configured to manage heating and cooling. I use as permissive to start and stop my heat pump.

These get my vote https://www.amazon.co.uk/COMPUTHERM-Q7RF-Wireless-Programmable-Thermostat/dp/B00SI1D6FY/ref=mp_s_a_1_1_pp?keywords=COMPUTHERM&qid=1699820036&sr=8-1