Beelbeebub

Absolutely.

Exactly. Maybe we have a standing charge with X free kWh included (like the mobile deals). And maybe there could be discounts on the standing charge for low income etc. With smart meters you could vary the free kWh based on things like temp. So during cold snaps vulnerable households could get an extra free allocation

Can anyone say why Weather Comp gets all the plaudits and Load comp seems to be ignored? pure WC adjusts flow temp by using the external temp only. It doesn't actually know what is going on inside. Things like solar gain or open windows are beyond it. If you have huge windows and it's a sunny day it will happily keep pumping heat into the house as you all cook. Likewise, if your windows are open, it won't do a damn thing about it. The saving grace is if you have a low temp emitter system (cough UFH) there is a built in regulation of the heat input due to the dT between emitter and internal temp being pretty small. My floor slab is about 23C for a room temp of 20C at the moment. As soon as the sun comes out and the temp climbs to 21C my heat input (dT) has dropped by 1/3. Likewise if my room dropped to 19C, my heat output will jump by 1/3. So as long as I can keep my slab at a stable temp I'm pretty good. But I don't think it would work if I had rads running at 40C, there the difference in dT would be much smaller until i drifted uncomfortably high or low in temp. It also (as has been noted) means the installer has to get the curve dialed in well. With Load Comp, the HP/boiler adjusts the flow temp based on internal temp. It doesn't really care about external temp, just staying at the same internal temp. As internal temp drifts down, flow temp raises, and vice versa. it would seem to be inherently self tuning. All you need to tell it is an acceptable time to get up to temp (5C per hour or 0.5C per hour?) and then it gets on with it. You can imagine a thermostat with a temp dial and maybe a boost button that will kick the heating response up to a higher level if you want. Installer sets up some basic parameters, which may normally be factory set but may be varied for edge cases, then leaves the homeowner to it.

but with no standing charge that would essentially be free electricity. IIRC there used to be tariffs with no or low standing charge (maybe it was regulated) but the first 5kwh or something were really expensive, effectively making a standing charge On thing (away from heat pumps) I would do is make the prepay tariff the cheapest per unit with a very minimal standing charge.

Is there a reason the blown air unit in the pool room cannot be used by the HP or replaced with a hydronic fan coil unit that can interface with the HP? The Americans have blown air units as they often have warm air heating.

How are your two boilers set up at the moment? Are they linked in parallel or do they serve different functions? Do you ever end up running both at the same time? If most of your DHW is already sorted with solar, then can you use the existing tank but with the Vailant running in max temp mode which should replicate a gas boiler (albeit at poor efficiency - but who cares if it's just occasional use). Then run the rest of the systems direct off the Vailant TBH that scheme looks really complicated and usually the more complex the system the harder it seems to be to get it running sweetly, especially with complex hydraulic schemes.

Which brand?

That NRG manifold looks alot like the manifold Grant are putting forward for their hybrid box.

Ha! I was thinking more along the lines of putting the measured outside air temp, flow temps and inside temps into the system and it working out the best mapping for flow temp given outside temp, desired inside temp and actual inside temp. So starts off pretty aggressively with high flow temps. Watches how quick the internal temp rises. Backs off abit, until it's controlling the internal temp at the lowest possible flow temps. Given desired internal temp shouldn't change much or at least changes in a predictable manner (eg night setback), the system should be able to control to the desired temp profile at minimum flow temp. So for the first few days the system will run at an inefficient high flow. Then back off progressively to the eventual best guess. The extra cost of a few days of inefficient running are negligible. The system would also be able to self adjust should something change eg new windows, more loft insulation, or an extension. Such a system would be more a hybrid WC and Load compensation system. Not dissimilar to the TPI strategy but using flow temp rather than on/off Should be possible

This hits the nail on the head. The installer needs to be a lot sharper with WC (and by extension a HP) and do more work than simply fit the unit and wind the flow temp right up. HP manufacturers need to make the controls much simpler and more intuitive. Nobody needs to be fiddling with curves. A dial with desired temp should be be all they have to interact with. The box should learn the best temps to achive them in the most efficient way. We've got these fancy "AIs" that can compose music, paint pictures and write articles. Maybe one that could set up a heatpump efficiently isn't too much to ask! 🤖

I was more refering to ability to do so. If you want a warmer house you can usually achieve it with aa gas boiler. But yes we do need to change attitudes a bit and price/market forces is a powerful tool. My only worry about being too brutal with the price stick is the effect on the poorest. The people least able to afford the upgrades (or even implement them in rented homes) are hit the hardest by the high costs. They also tend to be the most vulnerable to the effects of cold. Smart meters potentially offer options. For example the winter fuel allowance could be switched to "X free kWh per day when temp drops below Y" or "cap the cost to X on days when temomdroos below Y". The same option could then be applied to vulnerable people at different levels.

It will interesting to see the conclusion of the video "skill builder" recently put up. The presenter there is pretty skeptical about HPs and vocal with it He recently visited a house with a terrible setup where the owner was saying how expensive it was. Plus the fan was horrendously noisy. The Heat Geek chap came along and was going to see if they could get the system running well If he can rescue the system it will be a very good case study on how it is possible even in a difficult case.

But so many boiler *are* badly set up. As long as people are warm they don't care. The cost is just what it is, "I'm on gas, it can't be cheaper". To the extent the cost does cause an issue people just turn down the thermostat or switch the boiler off and accept it's colder. And if they are cold and can afford more heat the boiler has so much reserve power (especially combis) that you can heat practically anything with one if you wind it up enough. But because HPs use more expensive "fuel" and are.mirenpower constrained any flaws the setup are much more evident either as a cold house or high bills.

100% agree, Commissioning HPs is a much harder and potentially longer job than a boiler. Boilers are dead easy to set up so then client isn't cold. Just wind the flow temp up. Customers rarely notice the extra cost. It's just what it is. HPs are much less forgiving and people are watching the costs like a hawk. We def need some sort of auto tuning system for the WC. Pure WC is great in theory but the feedback is via a human basically saying "I'm too cold, I need to adjust the curve up". Then dive into a menu and fiddle This is different from the just turning a thermostat up that we are used to. We need that same "turn a dial if you are hot/cold" experience fronting themkore complex adjustments under the bonnet

Or..... Allow A2A to be easily fitted (planning reform) with a subsidy to make it cheap say £500 for a 6kw 3 room split system. Zero impact on existing system. Just installed "over the top" (literally as pipe work would run along ceilings and top of walls) of the existing system. A2A works to efficiently heat in shoulder months and mild winter. Old system only called on to add supplemental heat in the few cold weeks and provide hot water.

You forget how complex and intricate gas boilers are. There's a huge amount of effort that's gone into making an essentially unstable dangerous system prone to either exploding, not working or just poisoning you while you sleep into a boring box you can slap on the wall. Heatpumps are an intrinsically easier system. They can be made as simple boxes you slap on the outside of a building that will heat your home for less carbon than a gas boiler. That just requires a scop of 2.5ish or better which isn't excessively hard to achieve. The problem is the current cost set up where HPs need to hit 3.5 or better to make financial savings. That is harder and costs more.

So replace the GSHP/Cylinder combo with either a manufacturer specific unit (eg Vaillant Unitower) or a large coil area cylinder then fit a something like a 7 or 10kw single fan monoblock either by the door or across the patio?

Yes, we would need to ramp up electricity production. Ideally by installing more renewables plus Some battery storage. However, some will inevitably have to come from new CCGT plants. They are quick and cheap to build (in the context of a power plant), but the idea is they would be stopgaps. Overall gas consumption (heating and electric) would still fall as a cop > 2.5 (fairly achievable) means you burn less gas per kWh delivered in the home than a combi boiler. And at the end of the day it's overall gas consumption that matters not exactly were we burn it.

Just to be clear, do you have a gas combi boiler at the moment? Or is the "combi" in the Heatpump name just refering to the fact it does hot water and heating as well? Are you able to get an idea if the 12kw unit you had was correctly sized? Part of the higher cost might be that 12kw units are expensive. If you could confirm by data or accurate heatloss assement the actual size you might be able to get away with a 9kw unit or similar. If you already have a water tank and all the emitters correctly sized then it should be near stright swap. All you need to do is locate the new site, put in a slab, run some pipes and cables to it. Locating the pump away from the back door will add cost for the longer runs of pipe (and in particular the trench and patio work) plus the slab etc. you need to be happy with the trade off between cost and location.

I suspect it won't be "stupid people" who will resist. Unfortunately climate change has become enmeshed in the wider "culture war". There are people out there who will resist heatpumps noatter how much financial sense they make because they don't like Greta Thunberg or "the woke" or the EU or something. At the end of the day I don't actually care. They can pay more to subsidie the sensible.

Quick estimate, ignoring standing charges etc. Assume Gas 7pkwh Elec 28pkwh So break even SCoP is about 4. Fairly hard to achieve. Annual Gas usage 12,000kwh Annual elec Usage 4,000kwh Annual Gas cost £840 Annual elec cost £1,120 Total £1,960 Green tax on gas is 5% ie £168 Green tax on elec is 20% ie £224 If we swap the elec taxes to gas Gas £1,064 Elec £896 Unit cost is now 9pkwh for gas and 22pkwh (rounded in favour of elec). Now the break even SCoP is now 2.4, much easier to achieve. Most properties could achieve that with a very mild upgrade to emitters.

Realistically the only way to make people switch is to make it the cheaper option. The upfront cost can be dealt with via install subsidies, though that does just encourage the install price to remain high. The bigger issue is the cost of running the HP. This is a common point brought up by the anti brigade. The government need to make HPs the cheaper option. Then people will be kicking the door down to install them. One issue is the green taxes on electicty Vs gas. About 15-20% of the elec bill is green taxes, less than 5% for gas. If you shifted the taxes over in a moremormlessncowt neutral way, then the average bill of a dual user would stay the same, only the proportion spent on each fuel would change. But the elec only user would see a fall in costs and the break even SCoP for HPs where they cost less than a gas boiler would fall making HPs more attractive.

Actually seems pretty good. Will be better than break even (carbon wise) than burning gas in a CCGT station allmthe way down to -5C, which is fairly rare in this country. Even at -7C it puts out 2kw, enough for most rooms even with fairly minimal insulation and though the cop is fairly rubbish it's still 2:1, which isnvery useful vs electric.

As a follow up, I asked the supplier for some info on the lower temp performance of the units as the literature only specs at 7C external area. Anyway they got back to me (fair play) with ... Low Ambient Heating Performance Ambient Temp. RH humidity Heating capacity in average (W) Power Input (W) COP 0 70% 2560 821 3.12 -5 70% 2477 924 2.68 -7 70% 1862 947 1.97

That heat requirement is very low, and probably mostly hot water. Presumably there is a bigish unit inside for the GSHP? Probably near the back door (boot room?). Maybe the hot water cylinder next to it? This might be a bit out there, but what about one of those integrated heatpump water cylinders? It's an unvented water cylinder heated by a little air source heatpump sat on top fed by two ducts, usually about 180mm. That could replace your water cylinder or GSHP as long as there was relatively easy access route the two ducts outside. So that would take care of hot water The slightly funky bit would be rigging up some way of powering your UFH from that setup. If the cylinder had a secondary loop you could power your UFH from that via a heat exchanger? A bit out there, but it would remove the need for an external unit Edit: Just reread the OP, I misinterpreted 3,000kwh/year as the output no the consumption. So maybe too much for my suggestion