JamesPa

The point I was trying to make is that you asserted that the government was not serious about renewables and cited your electricity connection cost as evidence. Its clearly not evidence at all, however irksome it may be to you. Your situation is an outlier because you are unusual in needing a new connection and new local infrastructure in order to fit a heat pump, not because the amount you have been quoted for that new infrastructure which may indeed be quite normal). I thought I had made that clear but apologise that, apparently, I had not. I would expect Government policy in relation to renewables (and other things) to include VFM considerations in order to maximise the bang for the taxpayer buck, and excluding outliers such as yours is generally consistent with VFM (again however irksome that may be) I note you have now switched to another argument to support your assertion that Government is not serious. This thread has now departed so far from the original question that I will not take this up, others may choose to do do of course.

I can't speak for @Dillsue, but my reason for commenting is to provide a more rich and balanced set of information for readers in general, not specifically (or indeed at all) to influence you. I don't consider that a waste of energy. Now that you have told us that your circumstances are an outlier, that becomes even more important in the interests of getting to the truth in any other circumstances.

Er, thanks for this. So basically your situation is an outlier, and you appear to be basing at least some of your conclusions on that. Most houses don't have a barn and most houses don't need an infrastructure upgrade to run an ashp. Government policy will, very sensibly, be based on the majority not the outliers. I am of course sympathetic to your situation, but now you have told us more about it, we are in a better position to relate your comments to less outlying circumstances.

No tinkering, except the tinkering you needed to do to get it to work as its best!!!! Amusing, if nothing else, but your average customer just isnt going to do that. Nor is the average installer, as he will be long gone.... How much less efficent would it have been if you hadnt optimised it? That's a very good question, and I am sorry it has taken me 24 hrs to work out the answer! which is... about the same (ie no less efficient) assuming that, had I not adjusted the weather compensation, I would instead have adjusted the set temperature (again a simple dial), until I was not overheating. I think it's fair to assume that the 'average customer' would do this. This outcome is a direct result of the way Vaillant controls work. Adjusting the set temperature (ie the adjustment that most 'average customers' will make) actually adjusts the weather compensation curve 'under the hood'. The average customer probably won't know this, and doesn't need to know this, for things to work out right

I did something not dissimilar with my 15+ year old boiler. I upsized some rads, turned it down to min flow temp (50C) and minimum output (8.5kW) and operated it 24*7, resulting in both a reduction in bills and increase in comfort. I then converted to ashp resulting in a further reduction in bills, and a further increase in comfort. Most wouldn't do this however (and even if they did would probably have to run the gauntlet - as I did - of ignorant plumbers resetting it whenever the boiler was serviced) so I'm not sure it's a route to the mass deployment required. For those who can it's a good route all the same

I know. The sequence of comments which followed this was: yours which said you accept that a boiler does nothing for climate change, mine which said ... and you also miss out on the benefits of low temp heating, Roger440 who said you could have that simply by turning your boiler down, and me who pointed out that, while Rogers statement was strictly true, it would require you to change your radiators, which was one of the reasons you quoted for an ashp costing more/you not wanting to make the change. Nobody sofaik is claiming that. However they are more or less the only viable mass market solution which materially reduces the carbon footprint of heating, which accounts for a significant proportion of our carbon emissions, and do work in a large variety of homes. Given that we either need to embrace them where we can, or give up on eliminating the effect of our heating on the climate. Furthermore the low temperature heating that is part of the cost of conversion to an ashp gives comfort benefits which some may appreciate. Because of what he had been told OP asked what the argument was against ashps and has a broken boiler. Presumably the question related to his own situation, not whether they are a 'one size fits all ' solution. Some on here have basically said, without evidence or reasoning so far as I can see, that they are not suitable in almost any retrofit case. Their arguments appear to make assumptions which are not universally true and indeed may not be true in OPs case. Prior to joining this forum OPs received 'advice' appears to be based largely on uninformed opinions which, with a high probability, originate from sources representing or influenced by vested interests. We all deserve better than this. What is undoubtedly true is that it may help to be an informed purchaser, but that is also true for many of the things we purchase.

I realise you are referring to another poster. Just to say however that I didn't do any of that. I had my solar panels already (they have easily paid for themselves) and I haven't got a battery because, for me, it makes no financial sense at present (it's close, though) and doesn't make environmental sense. My heat pump is still cheaper to run than my gas boiler by 20%, it's much more comfortable, and of course warms the planet less (actually the saving is more than 20% because of the solar panels I didn't include them in the calculation because I wanted to be clear what the heat pump alone does). I'm not saying that everyone will have similar circumstances, but those who make a general statement that a heat pump has no benefits to the homeowner are simply wrong.

Not without changing his radiators which was what @gonewest was arguing was a reason for him not to get an ashp. Yours may of course be more oversized than his.

So generous of you. The next generation will really appreciate it! But actually nobody is suggesting you do this. The thread was started by someone whose boiler has broken down.

...nor are you getting any of the comfort benefits of low temperature heating of course. Obviously these are house, and to an extent person, dependent.

This is an interesting point. If gas were invented now, would it even be legal? Pumping indefinite amounts of an explosive substance into our houses is a bit weird when you think about it!

True, but unfortunate, and a problem which more enlightened countries don't have because they made weather compensation mandatory for boilers many years ago. As a consequence of the fact we didn't and the public remain ignorant, we are paying about 10% more for our (gas or oil) heating than we need to, and are less comfortable. Of course we can persist with doing something stupid, and encourage others to do so, or alternatively we and our backward heating industry can grow up! My saving of 20%is relative to a has boiler that was actually condensing. Most people will start with one that isn't!

Absolutely spot on. I could have paid £50 per year for Havenwise ((first 6 months free, no hardware needed) and the easy adjustment I made manually would have been automated (and more besides). I chose not to (I may yet do so) but it's hardly a lot to pay and anyway would almost certainly more than pay for itself even for me.

The operative term being currently. Cast your mind back a few years and oil was the most expensive. That will doubtless happen again at some point. No certainty at all over this matter!

Very true. I'll be replacing my old oil fired Aga with a new condensing oil boiler. There's no way for us that the sums add up to use an ASHP, for installation costs, or running costs in my old place. If I was forced to go all electric, I would use A2A. Can't speak for oil, but my ashp is 20pc cheaper to run than my condensing gas boiler even though was actually set up to condense (unlike the vast majority and despite the efforts of the maintainer to reset it each time he did a service the boiler). It's also far more comfortable and doesn't contribute anything like as much to climate change. What's not to like? I have radiators not ufh, so not even the optimal conditions for ashp. No tinkering needed from when it was installed by a local installer, other than to adjust the weather compensation to the lowest possible consistent with heating the house (which on a Vaillant is dead simple, it's a single number which you turn up or down). No fancy or home grown controls, just the ones that came with. It's not that difficult to get right and what you need to do is now well known and more or less indisputable (unlike perhaps 2-4 years ago when we were collectively still finding our way).

Perhaps this is a good point to throw in a plus for fancoils. I have one Mitsubishi ilife2 slim in a room where even convectors would have been unfeasibly large, and I love it. Smart, neat and small and of course does cooling as well. I wouldn't choose them universally but I do wish I'd fitted a couple more! There are some really swanky Italian designs (actually the Mitsubishi ones are Italian) at really swanky prices if you want a particular look.

I hadn't thought of that (and possibly those drafting the legislation didn't either) but yes I think you are right.

Indeed a phe plus pump plus cylinder without coil is cheaper than a cylinder with a 3sq m coil. PHE plus pump is also a sensible retrofit for an existing cylinder. It's a shame that most of the installers out there haven't yet embraced this solution (some have).

Not really. Reheat time is usually limited by the amount of heat you can get through the coil not the capacity of the heat source. On second thoughts I should clarify this answer. To the question you asked (and assuming the same tank) the answer is possibly, it depends on flow temperatures and whether the limitation is the boiler power or rate of heat transfer through the coil. What I should have added is that you cannot assume that you need a 20kW ASHP to reheat in the same time as a 20kW boiler (because reheat time is usually limited by the amount of heat you can get through the coil not the capacity of the heat source, even with a boiler (which is why there is a market for 'rapid recovery' cylinders.) See my post above for some cylinder size calculations.

Ok so judging by this dhw is your main concern. If you define your requirements it will be possible to do a design and work out what kind of ashp you need or whether it's even possible. How many l/s for how many minutes for each of the 4 showers? For example a 250l tank heated to 60C will do 4 10min showers at 10l/s or 4 5min showers at 20l/s (assuming incoming water temp 10C, shower water temp 40C). Is that enough. Many people with ashps heat only to 48C for better efficiency, but you can heat to 60C provided you get the right model (basically an R290 heat pump). My 7kW ashp heats my 200l tank to 68 C once per week to disinfect. This is natively on the heat pump, not using the immersion, and prompts the app to issue a warning against scalding!

The definite positives are: 1 Low temperature heating is much more comfortable. Of course you can do that with a boiler, but few do and a fair amount of the upgrade cost quoted for ashps is due to the conversion to low temp heating not the ashp per se (and a fair amount of the rest of the upgrade cost is dhw tank replacement which you are planning to do anyway). 2 It will warm the planet a lot less (if that matters to you). 3 It can cool as well in rooms with fancoils or ufh. In addition 4 It may or may not be cheaper to run 5 It may or may not be cheaper (or more expensive) to install with the grant That's about it so far as I know. Not really. Reheat time is usually limited by the amount of heat you can get through the coil not the capacity of the heat source.

Is that actually true (genuine question)? About 100k heat pumps were installed in the UK last year. We hear about only a few, and its surely a heavily distorted sample comprising 1. those who have had a nightmare + 2. those who have an unusually strong interest in heating/renewables (who, as you say, generally experience success with their heat pump) The rest, who have neither had a problem nor have an unusually strong interest in heating, are just getting on with their lives rather than shouting about the success, or otherwise, of their heat pump. My suspicion is that 'the rest' are the vast majority, because very few people have a strong interest in heating so long as it works. I don't have and have never seen the stats, but concluding that the relatively few (compared to 100K) who complain are representative of the majority of installs seems a tad presumptuous. Its also worth pointing out that you hear horror stories about all facets of building work. Yet somehow we seem to have plenty of houses that people are happy to live in.

No offence taken, neither did I take it as a criticism! If we don't exchange differing interpretations/views (based in all cases on the information we happen to have or our own understanding of the situation) we wont ever learn anything! Thanks you for saying so. Im a firm fan of both KISS and Occam's razor, particularly when it comes to services which are mission critical to a house. Its all very well (and fun) doing fancy/unusual things, but if something goes wrong that needs to be fixed in a hurry and the person who understands it isnt around, then whoever is left needs to get the local tradesman to sort it. If its complex that's less likely to be easy!

Fairy nuff.

Two separate questions! Planning: Assuming you live in England the rules are here: The relevant one is G2 (a). You will need to apply for planning permission unless you live in a detached house (in which case 2 heat pumps are allowed under PD) BUS: The rules (assuming you live in England or Wales) are here. The requirements defining which properties are eligible are in section 5. Provided your property meets these then I cant see a problem. The heat pump system must meet the rules in Section 8. Hope that helps.