JamesPa

Transmission losses and power station efficiency etc are all accounted for on the published figures for carbon intensity of fuels, which are updated annually. The carbon footprint from UK domestic electricity per kWh is about 10% less than that of domestic gas, furthermore it's falling as we move to renewables. That means that a heat pump with a cop of 3 causes less than one third the carbon emissions (actually it's a bit better still than that because most has boilers are set up by the heating industry in a way that makes them less than 100% efficient). This stuff is well established and the carbon case for heat pumps irrefutable.

Fair enough if you make it that sophisticated. Is that what your average plumber does or do they just have it running continuously? There is a running 'ashp' thread elsewhere in which it's obvious that the main problem is in fact a circulating loop (IE nothing at all to do with the ashp).

Really don't go down the recirculating loop route. In summer it heats your house continuously when you dont want it to, so you will pay to heat and pay to cool. In winter it heats the house at high cost when you could be heating it for one third of the cost. For hotels, fine, for houses no. Instead design out the need by locating dhw storage near points of use. If necessary use point of use heating for everything other than baths and showers. Unless of course neither money or carbon footprint matters to you and you can get joy by showing off about having instant hot water everywhere.

That's very perceptive! Also spot on and a better description.

So long as installers do a reasonable job of heat loss calcs and emmitter sizing Unfortunately the evidence is that a significant proportion don't, instead many slavishly follow the MCS rules which are highly likely to overestimate, but give ironclad protection to the installer. My house may be an extreme example, two surveys each taking 3 Hrs said 16kW whereas it's actually 7kW. Fortunately the better guys understand that the MCS calculations strictly applied may give seriously wrong results, and exercise due judgement, whilst foregoing the ironclad protection that following the mcs rules offers (to installers not customers!).

It was only 2.5:1 in 2011 and its been steadily growing since (until the Ukraine war made the ratios volatile.) I find it very difficult to believe that this wasn't a largely political decision by the previous government.

I'll drink to that (and I'm in the pub so I can!)

Not if you get a sensible tariff. Also don't forget gas boilers are rarely set up to run efficiently because our heating industry never really bothered to understand condensing boilers. Practical break even is more like 3.5. Some may wish to factor the significant added comfort of an ASHP based system.

I think householders do need to understand WC at least a bit. The probability that an installer has correctly set it up is small (particularly if the installation is in summer) and even if the installer has set it up correctly if the householder doesn't understand a bit about WC they wont understand why their radiators are rarely warm. Its hardly a difficult concept though, water circulating through system, is hotter when it colder outside and colder when its warm outside. They dont need to understand scheduling of the CH though, just leave it on! I do think interfaces need to get better. The likes of Vaillant, who have had to cope with boilers featuring WC for a couple of decades (because its been compulsory in some mainland European countries), have more or less got it; the interfaces for some of the far eastern machines are really poor.

Sorry Im genuinely confused, which stupid regulations are these? Is it the fact you can only have one under PD (two on a detached house?) or is it something else in the regulations that causes a problem?

Indeed, and performance/features People bought Teslas because they are cool, because they work, and because they could show off, not because they are cheap. Of course their CEO's antics has rather messed that up. It could be similar with heat pumps. Done properly they will give you much more comfortable heating for less money (like mine does!), for which people will pay a considerable premium. Furthermore done properly is actually the easiest and cheapest way to do it! Heat pumps might even be 'cool'. The installation industry needs to get its act together. European heat pump manufacturing ditto IMHO. I expect the Chinese could knock out a perfectly good heat pump for £500 and sell it for maybe sub £1000. Its basically three motors, a low end processor, a bit of pipework and some bent steel. I have a Vaillant which sells for >4K, Ideal about the same, and what planet are Stiebel Eltron and Nibe on with their pricing? Im not advocating removing grants at the current time, but the fact is that even if it doesn't happen in the next couple of weeks it will happen in the next few years and the industry needs to work out how it will carry on on its own two feet.

I monitor it from time to time through home assistant (which solves the graphing problem) more than I do on the app. It's definitely interesting, but I'm not sure I can honestly say I have made changes to my settings as a result. That said my system worked well from day 1. If it hadn't I don't doubt the data as presented in HA would be very useful in diagnosis. It does provide handy real time information on OAT though, which has uses beyond heat pumps. I can't comment particularly definitely on accuracy. The electricity consumption appears to be good, heat delivered is definitely in the right ball park, but I can't be certain to better than perhaps 20%. I would expect temperatures to be pretty good but have no evidence to back this up.

Eon next drive, but locked in Dec 2024 for 12 months so soon to be re-contracted. There current offer is not as good, but still better than octopus.

Ahh. The install got put on hold and I ended up eighteen months later with a different installer who went down the heat pump cylinder route (by then I had decided definitely to replace my existing vented cylinder). Sorry

100% agreed. But few will fit auto bleeds on every radiator and @Potatoman was asking if air would find its way to the automatic bleed valves. My reply was no it won't, you may need to use in the manual bleeds on individual radiators in addition to whatever automatic bleeds you have.

Only if the bleed valves are at any high points Even if the bleed valves are at the high points air can still get trapped elsewhere. I have a tall radiator downstairs, well below the auto bleed valves, which needed manual bleeding every two days for a month after my ashp installation was done. That's why radiators have bleed points!

Time is another key factor. Dissolved air comes out of solution quite slowly, mine (for example) took a full month. Sometimes you need to be patient.

Nearly. The loss of efficiency comes from the liklihood that cool return water is mixed with warm flow water thus reducing the flow temp to emitters relative to the ft from the heat pump. Since the flow temp to emitters governs their output, you need to increase the ft from the heat pump to compensate. The cop of a heat pump reduces with increased ft hence loss of overall cop. It an be made to work with little or no loss, but for that the water in the buffer needs to be properly stratified, which has implications for buffer design and size, and the pump rates also need to be controlled. This (it seems) almost never happens presumably because the people who know how to do it properly also know how to design out a buffer in almost all domestic situations. The typical dumpy 50l buffer is unlikely to have any material stratification.

It will stop altogether if it detects flow rate too low. Mine did when the filter bunged up. BTW I suspect the mesh filter, normally fitted near the return inlet, has a fairly high pressure loss even when not bunged up. If yours is like mine a model with a larger area may well assist!

Is the heat pump actually complaining. If not leave as is and allow deltat to rise a bit. Or fit an auxiliary pump slaved to the heat pump one, but no buffer. Either is easier, cheaper and will likely give better performance than an unbalanced buffer,which is probably what you will end up with.

Im also interested in this thread as Im having (yet) another try at making the battery business case work (so far I haven't been able to). I have 4kW peak PV, a heat pump and an EV and currently get paid 16.5p for export and pay 7p (midnight-7am) or 26p (7am-midnight) for import. With the optimisation possible in the absence of a battery, that makes quite a challenge for the battery business case, although its close. Judging by the price on the Midsummer site, Givenergy AIO hardware alone looks expensive compared to quotes I am currently receiving for fully installed systems; Is it worth the extra or are there deep discounts available?

The really sad thing is that the question in the title is worth asking! Is says a lot about MCS

None of which will add any value and, if a buffer is fitted, will increase running costs. @Dillsue the advice others have given is sound. You don't need extra kit you just need to balance the kit you have and readjust the WC if necessary so you can operate comfortably with thermostats and trvs at max. You need to forget everything you were taught by manufacturers of add on controls about operating boiler based systems, it wasn't really true for boilers, and definitely isn't true for heat pumps. It needs a leap of faith but once done you should get a house that's much more comfortable than you ever will with a boiler and lots of fancy but irrelevant controls.

Well that's no good then, how do you expect the heating controls industry to make any money if you exclude all of the irrelevant components that are also most likely to break down? Obviously that comment was slightly tongue in cheek but at the same time it's worth bearing in mind that the controls industry is inevitably motivated by selling controls, not by our comfort or cost effectiveness. IMHO (and experience with my own heating system) we have been somewhat brainwashed into micro control over past years and the transition to heat pumps is exposing the futility of this approach.

Not sure what question you are asking. Normally there is a 3 way diverter valve between DHW and space heating, fitted on the flow. All of the space heating water circuits should connect to this. The return is not valved. No need for temperature control for the circuits, water will flow through them if they are connected! You then balance the various circuits/radiators for same temperature (or desired temp difference) and you can operate on pure WC or WC with a little bit of room influence. The Vaillant controls are all you really need, providing bags of well thought through flexibility for setbacks/set forwards and various ways to use the room temperature as an overlay to a system essentially run on weather compensation.