JamesPa

Flexorb is the alternative outfit. Octopus wont accept them though, the decision whether or not to accept is down to the supplier.

Of course you could wire the panels into the same circuit as the immersion, then put the CT for the diverter upstream of both. This will, I think, cause the diverter to feed the dhw in preference to the rest of the house, if that was the effect you desired (not sure why this is desirable though).

Just tell clarify the diverter will feed power to the immersion after other power demands in the house have been satisfied. It's basically a mechanism to use up 'spare' electricity generated by PV. The idea do works a treat, I can't comment on specific models as the one I have (which has worked for 10years) is no longer made.

Ps To clarify the prime function of the diverter is to match the load to the available PV. Immersion heaters are typically 3kW and your PV will generate less than this most of the time. The diverter modulates the immersion down to match.

I have PV with a grid tied inverter, a solar diverter feeding the immersion and currently a gas boiler. I set it up so the boiler dhw cycle is at night. Furthermore the immersion is set to a higher temp than the boiler dhw thermostat. Thus if there is sufficient PV, all the dhw heating is by PV. If there isn't then the boiler tops it up. Works perfectly. I have 4kWp so I can turn the gas boiler off entirely from April to September. However the same principle should work in your case.

Not quite if I read the spec correctly. This seems to balance for delta T not room temp. That assumes perfectly sized rads which is not realistic.

The price is pretty typical of most of the quotes I have received and less than some. @Dave Jones is spot on. The industry, it appears, is currently dominated by grant harvesters. There are of course gooduns out there but they appear to be in the minority.

Proportional control TRVs without shut off is perhaps what we need. Basically valves which somehow auto balance (based on room temp not delta T) in slow real time, but never actually shut off. Leave the lockshields fully open (no balancing needed) and let the valves sort themselves out. Evohome and the other connected smart TRVs, with adjusted firmware, could do that. Hopefully somebody from Honeywell watches this forum; the market is huge and replaces several hours of plumber time.

So taking these together I suppose that 'time and temperature zone control' is one time and temperature controller per zone (or house) and then the second bit mandates TRVs in each (or most) rooms. At least TRVs are cheap, but it does mean that the customer has to be educated to use them sensibly and begs the question, how do you ensure that a minimum number are left open to ensure sufficient system volume if they don't use them sensibly? If you conclude you can't then the only option, because of the regulations, appears to be to add a volumizer/2 port buffer the volume of which is just a shade less than the minimum system volume required by the unit (because, at least in in theory, every TRV bar one could be closed and the system still running, or wore still the master temp setting could be set high, the rads completely unbalanced and installers rely on the TRVs to sort it out). Two control systems working independently against each other, never good engineering, yet mandated by regulation! Hmm, there is a system design/customer education problem to solve here. Minimum system volume, as I understand it, solves two problems namely a) it reduces short cycling and b) it preserves a reserve of heat for defrost. Interestingly a) is more likely at elevated OATs and b) occurs at low, but not lowest, OATs. I wonder what the ASHP manufacturers themselves are thinking is the direction of travel with this one.

Probably right in principle, but not realistic in the real world. Buffers are not a long term solution in retrofits, insufficient space (particularly if you have also got to fit in a new water cylinder) and too much opportunity to mess it up. Lets get over this fetish and move on, retrofits will and should wherever possible be without buffers and this will become the norm. Lets find ways to make that work! I agree the regs are mad. As others have said the room by room controls should be used as temperature limiters, but of course the public are not accustomed to seeing it this way. However, why not argue that the lockshield is a 'room by room control'. Put a knob on it and it is exactly that. Then provide one knob for the whole house. We aren't obliged to fund Drayton (however good they may be). Hmm, not sure I agree with that. A very compact heat exchanger and a small pump can do a lot for this problem, and a 3 sq m coil takes up a lot of space which people don't have. Currently only for comfort cooling based on the snip you provided. Is it the same for heating? Couldn't agree more with this one. How on earth did boiler manufacturers get away with advertising the benefits of condensing boilers of 20 years, and at the same time installers get away with setting them to 75/80 flow temp. I am ashamed that I only recently spotted in my own house (as a direct result of my interest in heat pumps) that I could be more comfortable and use less gas by simply turning down the boiler temperature! My excuse is that, until recently, I had little reason to know much about the detail of heating systems! I guess this will be down to the building control officer (if anyone bothers to involve them when they replace a boiler, which I doubt). Replacing a boiler like for like would not be a 'new' heating system. So what's the argument that replacing the source of hot water with a different technology is any more a 'new heating system'. I guess the grant harvesters will prefer the 'its a new heating system' interpretation and your local plumber will probably prefer the 'its just replacing the boiler with a different heating source' interpretation. Once the grants evaporate the two will hopefully converge. Of course not, that would be stupid. Keep Evohome and valves, adjust the target temps to 1 C above what you actually want, balance the system and you are good to go. Then play if you wish with broad brush zoning (If I remember correctly your house is basically divided into two halves, quite likely zoning of this into the two halves makes sense even with an ashp). Id go for that one! This is clearly an interesting debate and shows that there is unlikely to be a one size fits all solution, which means some intelligence needed at the design stage (thus ruling out many of the current players). But at the same time we cant make every solution totally bespoke. My bet remains on something like (added text in italics based on this discussion): Right-size system based on actual measurement, not GIGO spreadsheetery plus 20% for bad luck Design for 55 and offer 45 as a business case led upgrade (which will likely stack up in many cases) not a 'must do or else I wont play' If necessary use one or two fancoils for any difficult radiator replacements (where the replacement is too physically large) In many cases put a PHE in to deal with the DHW issue, rather than a cylinder with a heat pump coil. If retrofitting a combi, use a smallish cylinder which can be tucked away somewhere (high level in a room, in the loft, etc). (the volume occupied by a typical combi is about 80l, not very different from the 90l (rectangular) tank that was fitted in the flat in Nice which I recently stayed in. A water efficient shower uses about 9l/min. Just saying...) in most cases cut out all the ancillary stuff often done (upgrading primaries, upgrading mains feed to DHW, adding poorly plumbed buffers etc) because its no longer necessary as you haven't massively oversized the system Give some very basic education to the customer on how to run the system efficiently..

Yup Vaillant R290 has a scop of 3.1 (3kW)- 3.6 (10kW) at 55, which is good enough. I reckon, at a helicopter level, the way it might eventually go for many retrofits is: Right-size system based on actual measurement, not GIGO spreadsheetery plus 20% for bad luck Design for 55 and offer 45 as a business case led upgrade (which will likely stack up in many cases) not a 'must do or else I wont play' If necessary use one or two fancoils for any difficult radiator replacements (where the replacement is too physically large) Put a PHE in to deal with the DHW issue, rather than a cylinder with a heat pump coil. If retrofitting a combi, use a smallish cylinder which can be tucked away somewhere (high level in a room, in the loft, etc). Cut out all the ancillary stuff often done (upgrading primaries, upgrading mains feed to DHW, adding poorly plumbed buffers etc) because its no longer necessary as you haven't massively oversized the system = sane retrofit system, at a sane price. A day's worth (maybe 2 days worth) of design by a specialist designer who has some software, measurement tools and can actually think, then fitted by your local plumber. Actually it has to go this way otherwise 1.4M retrofitted heat pumps per year is unachievable (or even 600,000, the Government target). MCS say that they are revising their scheme and standards but dont say how. Will they 'get it right' and build in flexibility so the market can innovate and the cowbows get forced out because new entrants actually think about the problem - hopefully but I'm not holding my breath.

The dhw temp might be an installer setting on the grounds of legionella/efficiency/general distrust of homeowners. Have you tried the installer menu?

Unfortunately the construction industry, it appears, is full of chancers and has only a small proportion of experts. Experts are a good and very necessary thing, chancers less so.

Swimming pools often use sodium hypochlorite as a disinfectant, pH balanced with hydrochloric acid. I don't know if sodium hypochlorite is sufficiently alkaline to neutralise your rainwater, but swimming pool chemicals are relatively cheap and relatively easily available if that helps.

That's a bit small Having said that, 2 MCS installers have recently suggested to me a dhw solution based on a relatively small coil-less dhw tank, a recirculating pump and a PHE. With a counter-flow plumbed PHE the 'approach temperature' (difference between flow temp and dhw water temp) is less than with a coil and you might just get away with a 15mm feed supplying 4kW or thereabouts, provided you could tolerate the longer reheat time. With a large enough PHE you might even be able to get more than 4kW out of a 15mm pipe by having a larger delta T, albeit at the expense of COP for your DHW. The capital cost is probably no greater than for a heat pump cylinder because the latter attract a premium price. Another advantage of this approach in some circumstances is that the cylinder and PHE do not need to be co-located.

Fair enough. On second thoughts even 'guessing' implies an active thinking process, which I sadly suspect is optimistic.

I'm genuinely pleased for you that you have a quote you are happy with, whilst still doubtful you really need 12kW. But even if you need only 9kW, the 12kW Vaillant will likely be a reasonable choice from the specs I've read. Re 28mm upgrade, 22mm is good for 6-8kW as you doubtless know. If all the flow passes through one pipe then the installer is likely right If it's split (mine splits 3 ways-upstairs, downstairs, dhw), then they are over-engineering. I hope your LPA is saner than mine. I took essentially the same approach as you are planning. My LPA is currently setting a requirement of 27dB(A). This is 10dB stricter than the pd requirement of 37dB(A), albeit 7 dB better than their starting point of '10dB below a night time background of 30dB'. Their newly elected Green party executive member in charge of planning is tending towards defending this stance because, 'as a keen gardener', she 'wouldn't want to be inconvenienced by her neighbour's ashp'. So I take that as 'Green' unless it causes any personal inconvenience! https://www.ioa.org.uk/catalogue/publication/briefing-note-heat-pumps-–-professional-advice-note is worth reading and maybe quoting. It's a professional briefing note jointly by the institute of acoustics and institute of environmental health. It basically concludes that an adapted MCS methodology, and a target of 35dB(A) (but if necessary applying a penalty for 'tonal characteristics) is justifiable in all cases, with some justifying a more relaxed target. PD is 37 with no penalty for tonal characteristics. So this is a bit more stringent than pd but nothing like as bad as my LPA.

Doesn't this need express planning consent >0.6 cu m. Apologies if you already have that but if not you won't get it in 30days!

... and in other posts people comment on how _professional installers_ manage to get things wrongly connected. Just saying! BTW I would probably agree it's a load of tosh except for the possible risk to whoever inhabits your house next. There is _perhaps_ a public interest argument here.

In fairness to local government, it can only do what the law and funding allows it to do. Both are, in practice, controlled by national government. The cynic would say that, so far as National government is concerned, the principal reason for local government, is to take the blame for difficult decisions which, in reality, are so heavily constrained by national government, that the 'local' discretion is tiny.

There are such things as slow blow fuses, designed to deal with start up spikes, is there any chance you need one of these?

I sort of thought that. But the only current alternative is a full noise impact assessment according to BS whatever (I have the number somewhere), which is well over the top for a replacement boiler. Possibly as a consequence of my own application, my (Green party controlled) LPA is now demanding the latter for any new applications involving ashps. That should kill off any attempts to install ashp other than under PD

How does the above stack up with the below? My real question is, does a fence panel really give the 5-10db attenuation that the MCS calculation method would have you believe, and if so whats the advantage of high mass soundproofing - unless its to stop reflections'?

The solfex https://solflex.eu/en/ range seems to be one of the most comprehensive, don't know yet if the deliver to UK. I'm also now wondering about a DIY job, the prices are crazy and surely must come down. Extremely heavy too!