Beelbeebub

"Gas boiler lobby trying to delay UK’s heat pump plans, leak shows Trade association, which promotes hydrogen for home heating, called for clean heat market mechanism to be pushed back to 2026...." https://www.theguardian.com/environment/2023/jul/20/gas-boiler-lobby-uk-heat-pump-plans-leak Shocked! I tell you! 😱 Shocked!😱

I thought CO2 heatpumps were supposed to be good for situations where the majority of the demand is DHW. I believe they have been used for quite a while in Asia where there is no heating demand. AFAIK the only unit readily available in europe is a mitsubishi one https://les.mitsubishielectric.co.uk/products/residential-heating/outdoor/ecodan-quhz-monobloc-air-source-heat-pump

Ah! Thought I'd missed something! I don't know if CO2 will catch on here. It seems great for hot water heating but not so good for heating due to the requirement for a low return temp. I can see maybe it might be good for those all in one extract/heatpump/hotnwater cylinder things.

Those are listed as r32 on the website? Is there an r744 variant? Special order?

Which model is that? Do you mean an r744 pump? I'm quite interested in those, they have very different characteristics from usual pumps but apart from a mitsubishi unit seen any others.

As I mentioned earlier, if the HPncan achieve pasteurisation temps (65C or so) on it's.own then we no longer need any immersion booster. That means it is physically impossible for the heat source to overheat the cylinder and cause a catastrophic event. Which means the safety features aren't needed, just a PRV, venting to the drain in case the expansion vessel fails. Which simplifies the installation back to that of a vented cylinder (DIY) probably easier (thus cheaper)

Sorry about ☝️ couldn't get rid of the boxes Anyway.... Yeah something like that. I did wonder if we stored the DHW at about 35/40C and then used the HP to instantaneously heat up the DHW.flow by another 5-10C? The power required to lift a shower flow from 10C to 45C is too much for a HP, without it being oversized for heating. But the power required to lift a shower flow from 35C to 45C is much closer...

Higher thermal mass housing construction would help. I've got a UFH concrete slab, about 20 tons IIRC. During the winter, when I operate my woodstoce, it dumps heat into the slab at about 7kw which then rides us through the night and next day no problem. When I eventually get round to fitting a HP, I imagine it will do the same, run for a few hours then shut off for a day or so.

The flexibility of the system is the important bit. Where.we.get that from, fancy HP with wide operating range or a buffer to provide that flex instead, is not important. I'd note that any buffer needs to be compact for retrofit. I can see milage in combining the DHW tank with a buffer and even the expansion - this is more or less what some of the indoor modules are. But the big issue (from a retro fit pov) is the size. They are fridge sized. What we really need is a unit about the size of a boiler, somkitchen cupboard. At an absolute pinch washing machine sized.

Yeah, tge cheapness of gas combined with the very high power density mean you can pack way more power in to a boiler package than any house is likely to use. This has allowed installers to get away with sloppy installs, eyeballing the rad sizing, knowing they can get round any cockups by just turning the wick up on the boiler. Rhe same approach comes unstuck with Heqtpumps. Dumping a load of cash into R&D to develop HPs with a broader operating range would be useful. If hearing installers and retro fitters just need to go and grab a white label "3-15kw" unit and know it will work pretty well for most homes, it would be very beneficial. What would enable that? Twin compressor models? Maybe smaller units (like 2-3kw) that can be installed in parallel to boost power? Just keep adding units until you get the right power and gives much more "turndown" than an individual unit can offer?

From reading @markocosic it seems that heatpumps (despite recent advances) are rather inflexible beasts. The combo of compressor characteristics and working fluid charge mean there is a narrow range of efficency power/temp pairings for any given external air temp. If you stray from this zone your efficency starts to drop away. Would this be correct?

I suspect there is a seasonality element. The price of gas fluctuates lower in the summer The price of electricity will often go higher as it is generator constrained and southern Europe is guzzling electricity for cooling. I had a look at what makes up unit prices. Both gas.and electrify have a "per unit green tax" If you look at the absolute amounts Gas - about 0.2p/kWh Elec - about 1p/kwh You can see elec has a much higher level of taxation We could move almost all the cost of green taxes to gas. That would help. But this is where my subsidy pegged to the gas.price.wouid come in. It would effectively make the swap risk free. Even if electricity Soares away from gas your bill.woiod be capped at what it would have been if you remained. You may (if your setup beats the official COP) make a little.from it (winks). Human nature being human nature that fact may motivate people to increase efficiency. People will often work extra hard to get "free" stuff. This will remove one of the barriers to switching "what if is spend all this money and my bills go up?"

Seems.lije a good system, are you happy with it? Strikes me that could be packaged in a pretty small, neat unit. Also strikes me, it could be used as a defrost volumiser. If heat was pulled from the PHE. You have a huge reserve of heat for the defrost cycle. Ideally the system would simply work via back thermosyphon. the cold water sinking tgrougbt the PHE to the bottom of the tank and fresh warm water coming from the top.

I'm not sure! Ultimately it's a question of PHE size. You'll get heat transfer, but it's a question of how much Vs the modulation of the HP.

As you say the real win is in the retro fit. I think you are right that we need to stop clinging to ultimate efficency and just go for good enough.(¹) One idea is a subsidy for the electricity used by your HP so the cost of heating is pegged to the cost of gas. IE it will not cost you any more than a gas boiler to run for the duration of the scheme (say 10 years) This could be done by fitting heat meters to the HPs so they can measure the heat delivered. These meters would be linked to your smart meter so the energy co get the data. The company eatimates out how much electricity you used by taking your actual heat delivered and dividing by an assumed SCOP (say 2.5). It then works out the price difference between the p/kWh you paid for electricity and what you would have paid for the same kWh of gas. That is knocked off your bill. If your system is more efficient than the assumed 2.5, you actually end up "scamming" the scheme. This would be an incentive for people to boost their SCOP by upgrading the system (eg better emmiters) the scheme is paid for by a levy on gas. This means the price of gas increases which also drives adoption by makeing the payback time shorter kand also makes the scheme sort of self regulating as the price difference narrows as the schem grows) alongside this would be a big effort to help manufacturers develop "drop in" HPs (tank aside). An effort to develop compact hot water tanks (phase change?) Optimised for HP use so combi swaps would be easier. A boiler sized DHW unit and diverter valve inside, replacing the boiler with the pipes and cables to the outside unit exiting via the old flue hole to a unit outside would be a step forward. as an aside if the HPs could provide 70C flow, they wouldn't need any electric immersion backups. That means your DHW system could *never* go above 70C. This means the risk of boiling and catastrophic overpressure on your invented cylinder is zero. Thus you could ditch the safety regs (g3) around install and inspect reducing cost and faff for install. So you could have the boiler replacement system (inside unit goes where your boiler is, pipes go to external box, maybe via flue route) at plumbers merchants for 2-3k installable by any plumber to install, you register with the subsidy scheme and away you go. At that point retro fit would take off. (¹) I think the magic COP needs to be about 2.5 at the design lowest outside temp. The reason for me picking that number, is the efficiency of a gas fired power station producing electricity is about 40% (Inc transmission losses). So with a COP of 2.5 the heat delivered to your house from the source gas is the same as if you burned that gas in your house. If you drop below this figure you risk potentially burning more gas than you do do with gas heating. Granted the actual break even COP might be lower at 2.0 or something due to boiler and gas network inefficiency etc. But the 2.5 figure kills the naysayers "but we'll actually burn *more* gas!" argument dead and also ensures we don't accidentally do that!

Very interesting topic Tomget back to the original but about a PHE retrofit to a vented cylinder. Has it been suggested that you ditch the circulator pump and just fit a big arse PHE between the cold inlet at the bottom and the top and rely on thermosiphon to circulate the water? With a big enough PHE this should get around all.of the capacity/modulation/dT issues? My only concern would be if cold water might be drawn via that external circuit during hot water use. That may need some careful design of the plumbing connections top and bottom. My second point is about encouraging HP adoption in new build prior to the.offical ending of gas (which will forever be punted down the road) Just change the building regs so the house has to be designed for a max CH flow temp of 40C. It doesn't matter if you're planning a boiler, before you get building approval you need to show the emitters, losses etc are all capable of working at 40C. At that point HP retrofits become.much easier. It's mad we are.still.building houses today that will require extensive rework to fit HPs in a few years A new build estate near me went up with heatpumps. But because the developers cheaped out and stuck crappy tiny rads in that drove the flow trmpsmup and COPs through the floor, the majority of owners have ripped them out for oil boilers, and then advocate against HPs socially because "they don't work and cost a fortune to run" One of the things the heating industry like about boilers is, because they provide high powers in a compact package at high flows they can be lazy about speccing and installing. If you balls up the calculations and the client complains they are a bit cold because your rads or pipes are too small, you can just nip back, crank the flow temp up a.few degrees and done. Sure it costs.a.bit more to run but the customer won't notice and you've got a happy customer. HPs don't give installers that margin. I've estimate demand, and you've spent alot more on a bigger unit that takes up more space and short cycles ruining efficiency etc. Underestimate and your client is cold and you have no headroom to compensate.

On the plus side, I read that the gov seem to be (finally!) about to drop H2 for heating as a thing! How many years have we wasted carrying on as before, installing gas boilers and tiny radiators, on the promise that one day the magic Hydrogen would just make everything ok?

We've have tenants that struggle with a combi boiler and a single non-programmable thermostat! Complained hot water wasn't working at various times. Eventually worked out they were turning the boiler off at the wall when they didn't want heating. <Facepalm> Then there was the lady who complained her heating was erratic, sometimes not coming on when she wanted it. Quickmcheck showed no problems. Then I asked to see the thermostat. "What's that?" - I described it. She looked puzzled then rummaged around in a kitchen drawer, pulled it out and said "oh you mean this?". She didn't know what it was, so stuck it in her random drawer of stuff.....next to the oven! Heating wouldn't come on for a couple of hours after after she'd cooked! 😂 The ideal would be two buttons "I am too hot" and "I am too cold"!

I have got a quote for that. I'd keep the hot water system as is (electric shower and immersion tank - though I may ditch the immersion tank for a direct water heater) I am tempted My only concerns are 1) the Daikin units show a minimum external temp of -15C. We don't get that temp very often, maybe once every couple of years, but it makes me nervous of the heating system shutting down exactly when you need it most! The York (and other A2W units) tend to go to -25C, which I am more comfortable with. 2) (and this is A2A in general) - I'm nervous of the proprietary nature of the systems. Apart from thr F-Gas issue for working on them, it doesn't seem that easy to swap/move/add individual modules (indoor units or the outdoor unit). With wet systems you can change the boiler and leave the rest of the system as is or swap out a faulty boiler with any other similar one you can grab for peanuts at any builders merchant that day. We have a lot of systems to maintain and niggles with individual parts of the heating system are fairly common. At the moment swapping bad rads or trouble shooting is easy(ish). Sure if a boiler goes we get our regular boiler engineers in, but they can put (nearly) any brand or model in. it's not like we have to use a Worcester Bosch boiler because we have WB rads! I still might go the A2A route, but I thought an investigation of A2W would be worth it. I quite like the Vaillant units, but they are a little bulkier and crucially alot more expensive - hence the queery about the York units. If they aren't mickey mouse, they would make the A2W type system alot more viable. I'll have a look at Midea, but I found that York USA seems to be associated with Johnson Controls who are big wheels in the home automation/control world. It's possible the Midea control units are Johnson ones! Edit: Had a look, I don't think they are Midea - the dimensions of the units are very different

Good point. I did a quick napkin study. Right now EON E7 is 40pkwh/14pkwh day/night Standard tariff is 30pkwh So as long as the SCOP is greater than 2 (which should be doable) the tenant will end up ahead. That ignores the advantage of lower day rates for things like electric shower etc. Servicing the storage heaters doesn't really do anything. In their favour there is bugger all to go wrong. The main issue is the old one of leaking all the heat away in the day and having none at night. The only way we've found to get around this is to replace them with new ones which do, to be fair, have better insulation. But they cost £700+ each and are only marginally better. Plus the fancy electronic "predictive" system that they rely on to get better efficiency, makes them harder for tenants to understand and use so we get lots of "call backs" to sort out. I also worry there is more to go wrong.

It's not a prepaid meter, but i suspect there is some sort of FUBAR with the billing and EON are asking way too much.

Has anyone got any experience with York Heatpumps? BRS seem to a be a UK partner for York, who seem to be a large US aircon manufacturer https://brsheatpumps.co.uk/products/ Their monoblock range seem very compact and also very competitively priced. What's the catch? Is there a catch? I'm looking to start refitting some flats I manage that are currently using storage heaters. The tenants are complaining it's costing them a fortune (£100 a week!). I'm limited in what I can do on the fabric side for various reasons. It seems that using a heat pump would be an obvious win, even if the efficiency isn't spectacular, it would still be cheaper than storage heaters. I am considering an A2A multisplit. My one concern is the systems are tightly integrated. You are tied to a certain manufacturer for parts and servicing for the entire system. You could end up needing to replace the entire system because you can't get a part for a single unit. With a wet system the emitters are more of a commodity, and the various parts can be more "mixed and matched". But the cost of wet systems is really high and the outdoor units tend to be huge. Hence the interest in the York.