Beelbeebub

Ah good point! But an odor chemical would make things alot safer, and the quantities are pretty small, basically 2 or 3 plumbers blowtorch cylinders. I feel careful monitoring for leaks in the unit by looking at temp, pressure and compressor load, could alert the user would mitigate the risk. Maybe even portable gas detectors located on the floor similar to CO2 and smoke alarms. Leaks would mostly come from bad joints and could be mitigated by premade "pushfit" connectors only, no DIY onsite brazing, and damage (surface mounted pipework or armoured and vented trunking). Very small leaks (mg per day) are unlikely to cause any danger except in a very sealed space (say a wall cavity). Larger leaks only cause a (relatively) short term danger window before even a heavier than air gas disperses through natural currents.

I know millions of a2a sets are made and fitted each year. Mostly for cooling (globally the biggest use). If the UK were minded to go the a2a route (as I believe France are) then we could absolutely tap into that market. As @markocosicsays, it would massively improve the logistics. If r290 splits were allowed for home DIY then it would make the cost of installation much lower. If a r290 to water invented cylinder could be made readily available it would solve the dhw issue. The only other hurdle would be interoperability between brands. .The *only* issue with r290 is the flammability - admittedly a pretty big issue! I beleve china and India have been using mini and multisplit r290's for over a decade. Be good to see what the safety record is. But in the UK we (currently) prefer air to water which, as has been pointed out, have more stuff in them and globally, the volumes are small Vs a2a type units. To be honest they are a suboptimal solution, except maybe when it comes to underfloor heating (but that could easily be solved with a r290 to water PHX/manifold/pump unit) but it is where we are. One potential option for my upgrade path is getting an F-Gas cert and fitting a2a units. My one reservation with a2a is the long term spare parts/interoperability issue. If one of my head units plays up in 7years time can I get a drop in replacement easily? With water based systems it's easy. Edit: side thought. The big issue with r290 is the flammability, but we already accept a far higher potential source of flammable gas in the home. The issue as I understand it, is that main gas has an odour chemical added so any leak is deemed to be easily detectable far below dangerous levels. It is currently impossible to use that chemical in the refrigerant circuit. If that hurdle could be cracked why would having an r290 unit in the home be any different from the canister of lighter gas or mini camping stove in the house and why would a DIY fill be any different from changing your BBQ cylinder?

It would seem that improving the modulation is fairly crucial for heatpumps. Gas boilers have good modulation. So as long as you get the heat load about right there is plenty of wiggle room. If you oversized the boiler a bit, no problem. With HPs that is more difficult. If it were easier and you could just fit a "12kw and under"cunut that would be fine down to 2kw output it would make installers life a lot easier. I did notice York heatpumps seem to have a broad output range , from 6kw to 14kw in the same chassis size. That does open up the possibility of a very easy swap over of units if the power supply is rated for it.

One outcome of this is a universal standard HP interface would be useful. The proprietary control box costs just under a quarter of the price of the physical unit. The good news is that these "fire sale" Samsung units prob sky indicate how much HPs could be sold for regularly. The current 4k for a 5/6kw unit average seems to be a combination of demand and the fact these units are fairly new, there's lots of R&D and setup cost to be amortized. Vaillant have spent £4m on upgrading and expanding its.uk factory and £55m on its.german r&d plant. Hopefully, as more competition comes on the market and volumes (and supply channels) increase the cost will start to drive down.

Honestly, if "sticks out too much" and "not in keeping" are objections..... That's what you end up with.

What is the bivalent temperature? I've seen it a few times.

I beleve it"s "revolutions per second" of the compressor. Basically the modulation of the HP from full power (120rps) down. Note the most efficient speed is not full speed and varies with external temp and flow temp. Also note the max power delivered can increase with falling external

That's what I plan for the elec only flats, they have electric showers and immersion cylinders already. It's the heating load thata makes.tge bulk of consumption. Very useful info, presumably that means I can claim the 5k subsidy which might tip the balance.in favour of that route. It would pay for a cheap pump and some fan coil radiators, I only plan on

I wish I could. Current problems (apart from the cash and space).are the restrictions around fitting them (planning) and the biggie - unless I can "tune" them really well the bills will go up, even if the carbon goes down.

I know grant gets.stick.for.dumbing down the HP.and not running it in theost efficient way, but there is something to be said for making it as close to the boiler people are.used to as possible.

Calm down, it proves you *can* get the cost of HP down to boiler levels. That low cost is fairly unusual cut price. It needs to be come the usual cost. That is pretty much the same as a system or regular boiler. Which is what we want. The flies in the ointment are the mcs requirements, the probability that just a boiler to HP without any other upgrades won't be cheaper to run and (importantly in this case) the control system isn't compatible with a straight swap (afaik) you can't just connect up to the existing system. You need some sort of interface, and you only have one to choose from, the Samsung. Which is why I mentioned the control box cost (which seems extortionate). Shows what's possible tho.

£1,300 or less is exactly where we should be aiming! If the rules allowed that to be stuck on a little flat and run for the same cost as a gas boiler (however that is arranged) uptake would soar and heating related CO2 would start to fall (and fall further as people optimised the systems with experience)

Yeah I've seen those, I think they are being flogged off cheap because the next gen has been released. Basically clearing the decks. But it does underline that they don't need to cost a fortune. Also Samsung's need a Samsung controller which is £400(?!). But IIRC they are the.moat bare bones units, no pump, no expansion vessel, just a HP with a plate heatexchanger. If it had an "open source" control system so you didn't need to use a manufacturer specific one. It would be pretty close to my concept. (Also, paint the damn things black!)

Basic HPs for split Aircon, millions and millions. You can get a 5kw unit for well under £1k. And 8k won't be much more. But stick the monoblock stuff on..... Much lower volumes and much higher prices. A 5kw vaillant is about 4k. Ok, it's well made but where didn't he £3k it costs over a 5kw Aircon unit go? Diamond Heat exchangers? I think a bare bones 5kw monoblock could be under 2k eventually. And yeah market rate for elec would help. Anything that drops the unit price for heating elec. But the difference system they use does drive renewable generation install. So that does need to be considered. The only down side to measuring heat and subsidising is the extra parts needed to do that, but the potential benefits are pretty good when it comes to driving post install optimization (and user awareness)

But the problem is relying on the install to keep the noise to acceptable levels will *always* result in problems, the upfront planning to get the noise levels down, the installation being done correctly and the process missing edge cases (eg line of sight) mean the process will be more costly and fail more. It would be better to make sure only HPs that are quiet in the first place are sold. Of course this will require manufacturers to put in more effort, and there may be compromises with performance. We also need a more general national conversation about noise. Nobody has the right to absolute silence. There ahs to be a level of noise below which you can't complain. Do I complain about my neighbours trees rustling in the wind? We have constant road noise at a low level and sometimes high when someone with a suspect exhaust blasts past. I think noise is another stick that the foot dragging lobby has bigged up to beat HPs with and slow uptake. To listen to some people they think a HP next door is equivalent living next to Heathrow.

The point is to get the price of the install down to 5 or 6k so the 5k subsidy really does make it affordable for the normal person. I think the Units should end up around 4k or less as the volume increases and the install 1-2k (2 men 2 days). The key is to not have to upgrade and replace lots of stuff, especially the cylinder! an unvented cylinder is easily north of 1k, more like 2 by the time you've added all the extras. then another 2 men for a day to remove the old one and install new one (assuming no redecoration!). You could burn most of the 5k subsidy on the cylinder swap alone! I agree about the opening up the installs. And yes, low flow temp training, but not absolutely mandate them. that route leads to replacing pipes, rads, cylinder etc. They are definitely a nice to have and crucial for maximum efficiency. Now we have HPs that can achieve high flow temps at reasonable efficiency (which we didn't used to have) Vaillant r290 units can hit 2.5 at rated output at 55C which should do most places heating and can hit 2.0 at 65 to use the existing water cylinder. The issue with the smart meter for the HP with different unit pricing (which was my first thought) is I can see lots of fraud. Lots of people wiring the rest of the house up etc. It also doesn't give any steer on the actual cop. That's crucial for the feedback loop to the customer so they can see the gap coming up when the subsidy runs out.

One idea just occured. If each install had a subsidy pot, lets say £5k, upto 3k of which can be used for the install and any remaining to subsidise any shortfall between the price it would have been in gas and the actual. After 5 years any left over would be split between the bill payer and the installer. Give an installer and householder an incentive to do a good job? Not go overboard on the install.

I mean I guess it makes sense, "PD rights are for installs to a certain standard. The industry body will set out that standard" I don't directly disagree with that approach. The problem is that the standard is too restrictive and ends up hindering uptake. Anecdotally they have failed to prevent poor, noisy installs. If MCS was altered to be less restrictive and more "good enough" focused they could tackle the issues separately. The noise issue could be tackled by a requirement for a "hush mark", basically a set of noise limits (and testing) that HPs have to meet to get the mark. Same as windows needing kitemark for various glass safety standards. The performance issue is partly solved by technology. If a "performance mark" were needed, which meant the HPnhad to have a certain performance envelope, specifically 2.5COP at a given flow temp (say 65c) and rated output (and noise!) during certain external conditions. If a HP can achieve that then it can keep someone warm and burning less gas (in the power plant) than a boiler even if it doesn't save them money. So your "good standard" requirement becomes "use an approved HP". The final bit is the gov have to come up with the "price guarantee" scheme to prevent bill shock and align it with schemes and subsidies to bring installs that are below the final (ie. Above the 2.5 figure) efficency required up to that level, 12 month post install tuning using accumulated data, radiator scrappage schemes, more insulation etc.

Kinda.

Ahem, there might be specific spots on the building that a box can be put and not be visible at all. It's a bit tight for the larger monoblock HPs, which is why I'm thinking the external boxes need to be as small as possible to help with retrofit. But again, planning rules which make installing solar panels, heatpumps, carchargers etc are all political decisions that slow up adoption. I often hear noise cited as an issue, but that could be solved by just having a standard noise limit on the units. As long as it has the "hush mark" you don't need permission. Manufacturers making the damn things in almost any colour other than bloody white would help! As far as I can see the default white comes from air con units which are used in hot, sunny countries and any additional absorbed solar radiation hurts their efficiency. For aheat pump, any additional (however slight) gain from a dark casing on bright winters day can only help, and a black or brown or brick red box on the outside of a building is much less intrusive than a bright white box. How many of those plastic "garden lockers" are proposed up against the side of houses in the UK? Are planners up in arms over the visual blight?

All the faff is to do with the grant. I've looked at grants because I have potentially 30 odd properties to do. So I'm thinking £5k a property....nice. But the key bit is the cost to me. The fact that I'm getting £5k off something that would cost £14k still means I pay £9k, and if I could get a system for less than £9k without a grant it'm still better off. I plan intialky to tackle the electric only properties because they are going to win whatever. Then the gas properties, that will be harder as I will have to hit financial break even or the tenants will get cross. The other wrinkle, is I asked our EPC assessor what effect swapping to a HP would have (on an electric flat). His answer was "almost none". The EPC appears to be based on the state of play 10, 15 years ago when the grid was 50% coal and heatpumps were assumed to get cops of less than 2 at best. Until that's solved the EPC is a barrier (in fact it drove us to install gas in several properties as the easiest (almost only way) to get a C in an old property was stick a gas boiler in.

Exactly, and yes, if you can get away with heating only to 55 or 50C then great. That's an optimisation that can occur after you've fitted the heatpump. You can dial back slowly until you hit the point you're running out of hot water. But you can only do that once you've got a HP installed. The current system attempts to get your system to max efficency before install, which results in alot of upfront work, and because they add margins to make sure you aren't cold, they often end up overspeccing the system which adds a bunch of cost, and then if the system estimation has gone a bit wrong they still need up paying a bunch. If we could get installs cheap and easy and allow a "running in period" to get the system right, I think we'd get alot more installs *and* probably higher efficiency at the end. Maybe this analogy might help NASA take no risks with their SLS. Everything is precalculated to the Nth degree. Lots of custom stuff, expensive parts all contribute to the huge cost of rockets. Because they cost so much, they must work first time, so they spend even more time and effort making sure it works perfectly. Space X (and this is in no way am endorsement of Musk) took a different route, they were happy with the first rocket just taking off then blowing up. Because of that, each rocket was cheaper. Because if that they could afford it it to be perfect each launch. By the end they had a better system. The analogy isn't perfect of course, but my point is we need to aim to just get HP's out there operating at better than 2.5 SCOP and we're winning on CO2, after that it's just tuning them over time to get more an more.efficent. To do that we need to change regs and crucially remove the "bill shock risk" to allow the tuning period.

That would also be an option, and as you point out, fairly simple to arrange. But an immersion will only ever be a COP of 1. Even if the COP of the HP running at 65C, with defrost cycles etc is only 1.2, you are still using less electricity than an immersion. I think alot of HP thinking is still based on the old R410a systems that couldn't even hit 55C. The newer r290 units can hit a Cop of 2 at 65C and 5kw from a nominal 5kw unit. That's gotta be better than a 3kw immersion.

sadly most are not well set up. There are numerous old boilers kicking around that have one input (on/off) and a knob for cutout temp. The control system is a basic timer box that turns the boiler on/off and activates the diverter valve and pump. DHW is via simple timer, cutting out when the return temp hits the target. CH is via timer and thermostat, again cutting out when it hits the target. The flow temp has to be 65+ anyway to sterilise the DHW and the rads are all tiny single panels, which was all they needed to be with a flow temp of 65C. And it's microbore piping. He won't switch when his boiler dies because he'd have to change the rads, the plumbing etc. And if he has a gas boiler it's cheaper to run it at high temp and accept the slightly higher gas bills. But, if the swap were for a HP, that could deliver similar performance at the same cost, he'd go for it. The trick is how to do that? Same performance is an engineering problem, just need a similar flow temp and power output. He could probably get by with 10kw at 65C. Same price is a political problem - the 3.5:1 elec to gas price ratio is partially a political choice. It's not that in other countries. Some have gas and electric prices that are 2:1 others closer to 4:1. Some of that is engineering (the efficiencies of gas to electric conversion, generation mix etc) but as the price cap shows, it can be controlled by policy. If the price cap has capped elec at 20p and gas at 10p, the break even ratio for heat pumps would be really easy to hit (as it is in France and Sweden)

Yeah, the things that make a HP more efficient are also the things that make gas boilers more efficient. If we had been pushing for higher efficiency in heating systems (rather than just higher efficiency of the heat source in the lab) we would already be most of the way there for straight HP swapovers. That's partly why I like my price guarantee subsidy scheme. During the proce guarantee period you'd be getting bills saying "you generated X thermal kWh which used Y electric kWh that would have cost you £Z but for the subsidy. That subsidy will reduce over time, would you like some help with reducing your electric consumption?" (QR code to stuff about low temps, new cylinders, insulation etc) If the elec company has access to your thermal kWh, your HP electrical use, your flow temps and configuration and your EPC data, they could provide a really good steer on what you need to do. For example they could work out your cops, see if your flow temps were too high so suggest weather comp or bigger rads or maybe your thermal demand was too high for your house type and they can suggest insulation.