JohnMo

I suppose if you're a manufacturer, why would you bring up the subject that there could be other options, that sway you to do anything other, than their cylinder. If you mess up by choosing the wrong cylinder, that's your problem not theirs. Looked in my Maxa manual, it doesn't state anything other than if the coil size is to small it will learn this and shut down early, so you don't keep hitting the max temperature stop and go into a repeat short cycling.

If there building it and stating it hold them to it.

I made one window bigger a few smaller, also changed the door sizes -no one went around with a tape measure, unless it a major change I would worry. Unless there is a privacy of neighbours issue.

I used the same one to set my walls heights on a staggered wall, roof is at 12 deg sitting direct on top of wall. Used the Lazer it has, and got the wall heights bob on. You can recalibrate if you need too. I also have a Stanley fatmax, which is very robust and it's used and abused for the last two years. Had a few expensive ones at the start of the build and managed to break them quite quickly.

It is achievable, but very rare. You are stating you are so good you will achieve half the leakage of a passivhaus. Good luck, and well done, if you can.

There are generally, I think, 3 sections. Your house built to min building regs, your house as designed, your house improved. All looks similar but aren't. First make sure you are reading the correct section. Also there are a whole load of assumptions made if they were not given anything different, so shite in shite out if you are not careful. Design airtight doesn't look realistic for one, you are assuming 0.3 or better, not that realistic. Heating efficiency is a basic look up table, that will assume a number of things. Unless your drawings say different. The take away, it is as designed, a further report is generated at the end of the build - as built, that's the important one. This one is just a tick in the box, say it is or isn't compliment with building regs.

Maybe not, they will ask for a commissioning certificate. What does your planning letter actually say?

To expand on @dpmiller, if on the drawing you have to do it, deviation requires an amendment. Your planning notice should say this explicitly. I had a couple things in different locations and prior to getting a completion certificate, amended drawings had to be provided and approved.

Our planning department just assumed we had a heat pump, asked for heat pump commissioning cert and UVC cert, even though the plans were showing a gas boiler. Ask the planners if you have express planning for the heat pump, if shown on an approved drawing, they have approved it. Then do whatever you want as far install.

Average punter doesn't buy their products, installers do, they most likely will do a one stop shop anyway, one invoice. Poor punter that gets the final bill will be given some claptrap about being matched units, so really efficient. Hence the high price, and your grant is paying for it anyway.

HP, big coil cylinder.

No other gas, would just replace with UVC.

For a program hyped as about heat pump, most the program they spoke about the decades it takes to get nuclear and onshore wind on line. If the whole program was about heat pumps and the detail, that for me would have been good, but for most of the public, they would turn over and watch something more interesting to them. Alway a difficult balance act, too much detail people turn off, to little, it's sh*te.

Think most the suppliers make it up as they go along.

So got the control scheme sorted, so preheat will be added to ASHP return when in CH and DHW modes, but not in cooling mode. This is the control scheme I am using (below), but without the diverter valve P3. It's not required for the drain back system. Temperature probe 4 is used to control the diverter valve and start and stopping of pump P2. Placing the temperature probe 4 on the ASHP supply pipe and setting a control permissive of 25 degrees, will keep the P2 pump switched off unless the output of the heat pump is above 25 degrees. If ambient is above 25 it's likely the ASHP will be on cooling duty, so should get very little if any heating when not required. This solution also allows pump P4 to run if the panel is hot to give some cooling. This solution should work all year round without any controller changes, between summer and winter. Then it's just a matter of fine tuning the set points.

I believe that would discount most people using their cylinder, I read the specs a while ago and the coil looked quite small for a heat pump cylinder

I have now installed an ASHP, the buffer is still there with PHE and circulation pump, to increase exchange area. The buffer is a repurposed vented 160L thermal store, I heat it to just over 40 degs with ASHP, it actually settles out at close to 50, with max flow rate from ASHP of 55, but it doesn't give much useful quantities of hot water, nightly washing up and one shower, the next morning using return circulation the taps are warm which is fine. It is also charged via immersion with excess PV, was sat at 80 degs yesterday. A bad day I use 2kWh of gas, many days no gas. So boiler is still there for DHW only. It's only 2 years old to loathed to chuck it just yet. UFH is by ASHP only and is now a single zone, no buffer, no mixer or any secondary pumps. As simple as it can be. Has worked well in the summer on cooling duty, using self generated electric (PV). Couldn't be greener.

That is incorrect I was doing between 105 and 110% eff overall. That was verified by certified heat meter. Combi boiler, with preheat on DHW, big buffer (doing the water preheat and UFH) and running a combination of WC and floor buffering via UFH. If boiler cannot do the required functions it could be replace foc. Plenty on here would verify the issues are common place, with rubbish installs. I know you are fixated on ASHP being the only technical solution, but there could be many.

Didn't say it wasn't greenwash, but you can control how and where the co2 ends up, unlike the home boiler. i.e. pumped underground. You can also make from water, with electric, Scotland is currently 95% renewable energy, with loads more on the way, that excess electric can be used to make green hydrogen. Almost run like a PV immersion diverter, excess electric, hydrogen making process starts. Different discussion through. My point was the heat pump isn't the only solution (and won't be for many), currently way too expensive and generally requires too many modifications to the house to ever be cost effective, without doing the steps I mentioned in my previous post first. one solution will never be fit for all, as you keep saying.

Or would a bigger % drop in gas consumption come from. Setting up and mandating the following on all boilers 1. Running weather compensation 2. Priority hot water or X plan 3. Sorting zone control, so boilers cannot short cycle. Simple logic controller so min flow rate through system is alway maintained - regardless of what an owner tries to do make it run crap. Would instantly decrease consumption by 20%+ in most installed boilers. And/or a really good tariff for heating the cylinder via the immersion and/storage heating, without the daytime uplift in kWh prices. And on all homes insulate them to a minimum defined level. Areas to be insulated first and last would be by a defined priority based on best bang for the buck. i.e. drafts, roof... Etc. Make grants available to do all to this. Stop grants for heat pumps - only funding the well off at the moment, not everyone. This could be cheaper and less disruptive to the house as a whole. Hydrogen is coming no matter what the ney sayer's may have you believe, it will come un-noticed my most, as a dilution of methane gas, 5%, 10% hydrogen etc.

Or just move to a house that is or can be insulated and maybe already has a heat pump or where one can be easily installed. Leave your current house for the next owner to leave as is, or bulldozer.

My heat pump doesn't run like that one does, it wouldn't tolerate the small dT.

18 man days is just 3 days for a team of six. 5 days x 6 men is 30 man days. £400 per day, so £12k labour, not £7.2k.

All the above is great in theory, but the ASHP doesn't put out a set temp all the time, it slowly ramps up as the graph above illustrated. It has taken 40+ mins to get to 52 degs flow temp. Not sure how your small coil manages the heat transfer at the lower flow temp. The dT would too low the ASHP would ramp up temperature quickly and basically run out of temperature rise to manage dT and leave you with a slightly warmer cylinder, not hot or usable. It would then just continue to short cycle never achieving set point.

My go to place is https://www.outsourcedenergy.co.uk/shop/ All decent stuff, good prices and good postage. Their Pert-al-pert pipe is nice to work with no spring back or old memory to fight against. All their manifolds are Ivar, if you are having a manifold mixer Ivar are good and very adjustable. These are also good, the air bleed is actually in the correct place. I also have one these. https://underfloorheating1.co.uk/catalogue/underfloor-heating-manifolds/premium-manifolds Some brands are just expensive for no good reason.