JohnMo

We seem to drop down to about 39% worst case

Do a search on 2 port, 3 port and 4 port buffers on Google. If I was doing a buffer a big one only which you have. But would only do 2 port nothing else. This way a fully open system mostly flows around the buffer. A 2 port buffer looks like this A video worth watching, talks 4 and 3 port a 2 port is a simplified 3 port

If you can get export via octopus, dumping to water makes zero sense. But you need to ensure you have all the correct paperwork to get octopus to approve system without MCS certificate. Even if you did dump to water in summer you will have a hot cylinder by 9 to 10am with that size array. So you will get loads of electrical energy from PV, then pay for gas to heat your house. Not really making sense. Yep, plus that many panels, will drive multiple strings on each elevation. Not the cheapest system. You need to do some maths, cost of panels and mounting system? edge uplift on roof for your wind load area, is full roof acceptable? Massive oversized makes sense if you can actually sell it. Gas or oil boiler makes zero sense, not what you want to hear, but... Blue graph is a monthly output average to expect in kWh. So some days will get very good output, wet rainy day almost nothing. Peak generation is in summer when you can use almost nothing you produce, so you export it, zero justification to have that many panels if you have no export agreement.

All makes sense, but the limited flow rate will naturally cap output ultimately. So ok for now, but may be an issue later when installer has been paid and moved in to other things and may be difficult to re engage.

If it ran before it should run now. 1. Walk system have you left any valves closed? 2. Did you change any settings prior to or during new parts being added. 3. Don't see on any of you screen shots, what the set point is - if you have a thermostat jumper in place, the compressor is waiting for the return temperature to drop low enough to get a start permissive. Depending on the target set-point and system dT this may not ever be achieved. Have you altered the target - what is set too? Increase it does compressor start?

I would replace as much for copper as you can - multi layer ok for UFH pipes not sure I would allow it elsewhere. Hep2O is bad enough and they have pretty much full bore connectors, the multi layer connectors I have seen all look have reduced bore.

Is this really a real issue, the bypass is on one side of the system and simply provides a bypass around the heat exchanger. The bypass doesn't cross between the flow and return paths. To get smell transfer, 1. Either piping/ducts are mixed up and giving cross over in the system on the house side. Get two sheets of toiler paper, on wet rooms the paper should be sucked up and stay in place, on dry rooms it should be blown away - check every terminal. 2. The outside terminals are allowing exit air, to be reintroduced into the suction stream. Do you have the minimum distance between terminals outside (see manufacturers instructions) or do you have combined inlet outlet terminal? 3. Are the outside and inside MVHR nozzles connected to the right parts of the system - easy to check, left and right hand units easy to mix up, so be careful check manufacturers name plate and instructions. Does the outside terminals suck and blow as you would expect, same for the house side terminals? 3. The heat exchanger in not right, you are on your second one, so unlikely unless a major manufacturing issue, you could ask supplier to fit a normal HE for test purposes? 4. A seal within the MVHR unit is comprised allowing flow and return air to mix. Would require full strip to find out and unless done by supplier your warranty could be void - so do last2. A seal within the MVHR unit is comprised allow flow and return air to mix. Would require full strip to find out and unless done by supplier your warranty could be void - so do last Test as much as possible with unit on and nothing removed - then its not your fault or becomes easy to blame you.

32mm and 1.25" are the same nominal size, so I assume the writer is actually saying install 32mm copper pipe instead of the multilayer? Thought you were in Europe, so no idea why they refer to imperial sizes, which aren't specified in the UK any more (not for the last few decades anyway) let alone in Europe. Generally sounds a bit of numpty. Quick search "Expanded mode" on a Vaillant heat pump system is a setting that combines weather compensation, room temperature influence, and traditional thermostat on/off switching. It will aggressively heat to meet a target temperature and then switch the heating system completely off once the target is reached, turning it back on when the temperature drops below a certain threshold. So run it like a boiler - not great for running costs and he's one of the experts?

In Scotland you pay by council tax band generally not by m3. There are two rates, one for water and the other for waste water. Water charge is £463.20 and waste water £537.45

Looks like your head losses are pipe related maybe all the elbows used etc. I would put a Wilo 7m head pump in, then you get the ability to dial in the correct settings to get the flow you need and have some flexibility.

Really depends on depth and company. We are 34m depth fully steel pipe lined and was under £5k, the pump and filter package is site dependent our 40L/min pump and filter system was about £3k. So £8k all in. Annual service is about £100 to £150. Water and drainage being off grid saves us £1k in charges to the council.

I had to add an additional pump for DHW due to distance cylinder is away from ASHP and some existing pipe sizes. Just add to anywhere in the circuit, on CH side only not in the DHW part and run at a fixed speed. The original pump will then just modulate as needed, the secondary pump just makes up for the lost or missing head of the original pump. If you install near the 3 port valve you can select the secondary pump on only when DHW is off, either via a relay or if valve has it the secondary contacts.

We are also private water, no-one checked anything. There was nothing on our plans that stated how water was being sourced. There is only so much the inspector will look at, where water is being taken from isn't something likely to even be on the radar.

Is it worth the hassle building from straw bales? The walls of the building are pretty cheap no matter how you build them especially if you are doing most the work yourself. Why not a more conventional system?

Just remember most the sites quoting this stuff, are also selling it, bigger price for item equals more profit. Most claims in the UK are marketing BS, same as MVHR based cooling systems - people still fall it. I like reading technical manuals and understand what I am getting, before parting with my money. If I lived in the centre of Europe I would buy an Enthalpy exchanger every time, but I am located near to the coast in Scotland, so weather changes frequently - we do not gets weeks and months below zero. I also tweaked down flow rates to suit house and number of people in it.

You will a kicker at the bottom of the slates anyway to stop capillary action drawing water up, plus you don't want the states touching the EPDM either, as over time you will end up with a hole somewhere. So it's never going to be a perfectly flat transition

In Scotland to get a building warrant you need a structural design certificate that covers the whole build (or all the structural calculations and pay to have them reviewed) and an as designed SAP EPC. If you both those boxes ticked how you actually build isn't really that relevant, is my take on the system. So would suspect getting an architect and structural engineer that understands the build system, is the challenge, not the warrant.

Most if not all MVHR units have in-built frost protection. If you have no preheater, the system just monitors temperature across the heat exchanger and either stops or modulates down the in coming air to keep unit away from freeze zone. As temp recover the unit increases speed to normal and repeats this until normal inlet temperature resumes. I don't see any ill effects of this down to -9 degs, and have two units operating this way.

Just read the article - this bit jumps out "A problem can occur in homes which are very large but under-occupied, and for this reason an enthalpy exchanger could be a better solution" A different solution is to set the MVHR flow to an appropriate flow rate to suit house and occupancy levels.

More like a few hundred plastic straws in matrix. Real advantage of enthalpy units is in prolonged sub zero temperatures where internal air can become increasingly dry. I monitored our air for 2 years with a normal exchanger, the air never gets to the really dry stage and we are in Scotland. So not sure I would bother getting one for the aded cost and benefits in the UK

101% you have bought too much. But you can always build a shed, so 102%, but you can always build a log shed, so 103%.... No such thing as stupid question, sometimes.

To add - You need to assess if the steel is connected to the outside world. If it is this method will allow you to insulate the steel. Notching will have everything flush and leave a cold bridge.

And it is?

It isn't the cheapest - but for it ticked lots of boxes other system just didn't do when I installed. Main thing is invisible change over in a power cut and the PV string inverters just continuing in a power cut, just as they did with mains available.

Do you need them to move or can they be fixed?