SimonD

Best thing to do is step back and look at the heating system as a whole which could allow you to run the system open-loop and allow the heat pump controls to modulate output as opposed to installing a load of control gumpf from the ufh people - a sensible installer would have made this point. Also, if you're thinking about engaging someone to design and install, don't hive off the ufh design to diy and then ask the installer to tack on the heat pump. You need a holistic approach here.

Who have you gone to? Please feel welcome to dm me if you don't want to publish the list in public - that way I can check if you've been to the sensible ones in your area. I can also point you in the direction of an organisation that can assist you in the design process who are also local but not tied to any particular installer.

I do think you have to be a bit careful making this assumption based entirely on catalogue figures and also just a couple of manufacturer details. For example, the Grant Aerona 290 is rather different: @ air 7/water 35C 4kW effective power input = 0.82kW cop 4.99 6.5kW effective power input = 1.54kW cop 4.95 9kW effective power input= 1.90kW cop 4.93 12kW effective power input= 2.53kW cop 4.81 15.5kW effective power input= 3.42kW cop 4.62 This, I think is pretty much the inverse of the table you show?

On this basis alone, I would go and find another installer who understands heat loss calculations and design. Unless you've made significant changes to your Heat Punk defaults, I'd also caution reliance on those. Since this year, there are 2 ways to complete a heat loss with ventilation losses. 1 is the simplified method that uses a CIBSE design table which is known to over estimate ventilation losses in the majority of cases. 2 is using a detailed method, including blower test results, that is known to reduce calculated ventilation losses significantly. This method takes more time. Then there is an option to deal with thermal bridging. If you are using approved construction details and/or have a SAP calc (which you must have anyway) which also include a bespoke PSI value calculation, you can used reduced thermal bridging values from SAP, for example - not only is this essential from a building perspective, but it improves the accuracy of heat loss estimates too. Modifying all these will help you find a more appropriate heat loss figure. Ignore anyone who tries to tell you what MCS says as that's usually a sign of ignorance. You need someone who understands its nowadays based on BS EN 12831-1 2017, but also be cautious about anyone who just says their tool complies with this standard - ask them to show you their inputs.

I used the European Technical Assessment certification for our woodfibre which was fine by our BC who had never come across the stuff before. I still have yet another stern conversation to have with the building warranty underwriters mind you.

Pls see @MikeSharp01 comment below which clearly says it better than I ever could. Thankfully he woke up this morning with a clear head, unlike you and me that get into discussions late at night when we should probably be getting some sleep, or at least I know I should've been! 😁

You used to be able to use LABC approved construction details but since recent updates of Part L, for example, they're no longer in use. Ty Mawr used to have a load of them for their systems. But, I think your BC may need some guidance as there is no requirement that systems must have a BBA cert. The system just needs to be designed by a suitably competent person to show it complies with relevant standards.

The waste serving as your D2 can go into the soil stack even if that soil stack has other sanitary appliances attached. You just can't have other sanitary appliances attached to the D2 pipe to the soil stack. Hope that makes sense?

I always install these: https://www.unventedcomponentseurope.com/tesla-3-4-expansion-vessel-service-valve-2.html/ Oh, and @MikeSharp01, my usual practise is to have seperate tundish for heating and dhw cylinder as in future it makes life easy to diagnose a problem and where it's coming from.

At the top of the expansion vessel will be a car tyre type valve which is used to adjust pressure in the vessel.

Your D1 which is pipework up to the tundish must be in copper (metal to be more exact). This should be no more than 600mm in length. You can feed your prv/ t&p and condensate into 32/40/50mm waste no problem, even as a D2 after the tundish as long as the plastic is rated for the temperature. But basically, if you have a waste serving several disharge pipes, this pipe must be at least one size larger that the D2 of the others. Probably better to copy and paste from G3: Where a single common discharge pipe serves more than one system, it should be at least one pipe size larger than the largest individual discharge pipe (D2) to be connected. 3.60 The discharge pipe should not be connected to a soil discharge stack unless it can be demonstrated that the soil discharge stack is capable of safely withstanding temperatures of the water discharged, in which case, it should: a. contain a mechanical seal, not incorporating a water trap, which allows water into the branch pipe without allowing foul air from the drain to be ventilated through the tundish; b. be a separate branch pipe with no sanitary appliances connected to it; c. if plastic pipes are used as branch pipes carrying discharge from a safety device, they should be either polybutalene (PB) or cross- linked polyethylene (PE-X) complying with national standards such as Class S of BS 7291-2:2006 or Class S of BS 7291-3:2006 respectively; and d. be continuously marked with a warning that no sanitary appliances should be connected to the pipe So the question is whether your condensate pipe should even connect to this waste pipe serving the safety valves - probably not if there is risk that pressurised release can return back up into your MVHR. Personally I'd run them separately. The discharge pipe should have a fall of 1:200. If you're running the discharge pipes to the soil stacks it's frowned upon to use a strap boss - use a decent mechanical pipe boss like this: https://www.screwfix.com/p/mcalpine-mechanical-pipe-boss-connector-black-40mm/55722?gclsrc=3p.ds&gad_source=7&gad_campaignid=22478593832 Or this one: https://www.toolstation.com/mcalpine-bossconn-22mm-soil-pipe-boss-connector/p57728 (this one though is a pain to cut the required shape in the soil pipe so I'd recommend the above instead). For connecting 22mm to plastic waste pipes, this works well: https://www.toolstation.com/mcalpine-overflow-universal-compression-plain-tail-reducer/p46778 Out of habit, I tend to put the expansion vessel on the return as I do the filling loop too. So don't forget the filling loop within this list of to-dos. HTH as a start.

If it's trailling across site, make sure it's HO7RN-F as that will stand up to mechanical stress and weathering.

If you get something like this, get a bigger box! The spacer on this one has to be trimmed down as it won't fit when you have your stuffing glands and cabling installed and the mcb & relay shouldn't be installed next to each other due to heat! It's a very tight fit with all cables installed.

Have you checked the anti-freeze valves? Big puddle of water around them?

When needs must..😉 This one is on 22mm but works just as well on 28mm with full bore lever valve on the primary pipework.

I've used two methods. One was with a really old work bench where the surfaces could be angled to 45degrees and the tube would just rest in the pocket. The other was just to screw some 4 x 2 together at right angles and gently hold the pipe against those. Eventually you'll get the feel of very light strokes with the hacksaw and you can hold both the gutter and down pipes by hand on any bench and it works fine. For the holes in the gutter, you need to get yourself some tin snipps and a decent dead blow hammer for the edges. Installation instructions attached. Have fun. It's lovely material to work with. Rainline-Assembly-Guide.pdf

Ah, well. A picture says a thousand words! As @Nickfromwales suggests, you have no need for a fill and flush valve as you can use the filling ports on the ufh. I'd just suggest you add a valve on your mains for future filling and flushing maintenance of the primary circuit - you'll need to do this once you get the ashp in and running anyway. I know you say you're going with 2 filters as there isn't the space where the return goes through the wall. The only other suggestion I might give is to consider running the return from the cylinder back to the vertical return near the ufh manifold and then tee the return back to the HP from there, which would give you a longer horizontal run you fit just one filter. Not brilliant, but could work.

That was exactly what I was thinking 🙂 And/or photos with sketches ?

Yes it is. I'm not sure I'd recommend it though 😉 I do wake up some mornings and wonder what on earth I was thinking, especially making the move to MCS accreditation. However I also decided to build my house myself, so not sure how good my decision making is for making my life easy. But from my experience there are two sides to the coin. Knowing what and knowing how. A lot of those in the plumbing and heating industry seem to have missed much of both those sides. A reflection of this is how many times people who have heard a bit about about heat geek training have remarked about how clever it is because they tell you to install complete runs joint free using flexible pipe and minimal joints. Something that has been the mantra on BH forever I think. And then there's the other one about pipe diameters. I just did an unvented installation where the bathroom plumbers insisted to the customer the supply pipes had to be 22mm. I said to the customer that this will mean lots of wasted hot water and long wait times when washing hands at the basin. I suggested running 10mm plastic to the basin while everything was exposed and 15mm to the bath as it gets used mostly for showering, but the plumbers wouldn't have it. Again something you see suggested here on BH all the time. So really BH has to be probably the best source of best practice you can find on all this. I often wish there was a similar resource I could use to help me with questions about paid jobs that is so forward thinking. I've found some useful resources, but nothing even close to here.

All of these tapes come in different thicknesses each of which has a specified compression measurement for water tightness, air tightness, wind tight etc. - e.g. thickness of 25mm, watertight to 12mm, air tight to 20mm. This means that even after expansion into the gap it should be fairly compressed to be water tight. I don't suppose you have any way of knowing what the installers used?

As per @JohnMo, not outside. I do however always install them on a new installation, just next to the cylinder on thd return before the mag filter/strainer close to the filling loop. That way I can connect my thorough flush kit within a moment as you ideally need to flush the system twice, once with old heating system in place (if you have one) and then after installation and the system has run warm for a while. You can get them here https://naturalgreenheat.co.uk/product/bastion-28mm-fill-and-flush-valve/ at under 20 quid. I used to always install a couple of ball valves on tails in an accessible position on flow and returns until I recently found that some idiot plumber had used them to pipe in a new radiator in a bathroom and used the one on the mains to supply cold to the same bathroom!

I think we're mostly on a par with Germany in terms of highest costs. It's no surprise given both rely so much on gas. But there are so many inconsistencies that make little sense from the perspective of an environmental policy. We still subsidise fossils fuels to the tune of £17.5 billion per year. The greatest increase in electricity costs are relating to wholesale costs and social/environmental costs on the average bill since 2021. It seems strange given the profits made by producers and that Gas has not been significantly levied from a social and environmental perspective, but is privy to significant subsidies beyond the subsidies available for renewables. Yes, the government has announced some reductions for electricity in the budget, but we'll have to see how that pans out in reality.

Somewhere recently I saw some data showing that heat pump uptake follows a curve of parity between fossil fuel prices and electricity - the closer the parity the higher the uptake. something which largely disproves the capital cost argument. Interestingly the figures show that heat pumps provide the biggest bang for the buck when it comes carbon savings, even over insulation measures. I still cannot fathom why our electricity prices are the way they are and how this can in any way be justified other than in terms of profits for energy companies and their shareholders.

Yep, maybe it's just my age, but it seems to be getting worse by the parliament.

As is appearing quite typical of this government, they've realised the problem after the fact and are now trying to reassure pensioners that if their sole income is from pension, they won't pay any tax even if it is above the threshold. It's not too dissimilar to the 3p/mile tax on EVs which is another, we're going to do this but haven't got a clue how. Then some clever bean will think we'll just roll out a kind of start meter to be installed, and just like smart meters or fibre broadband it'll be privatised and roll out will maybe happen by 2080....or some other century in the future and use shite technology that doesn't work properly because the infratructure it needs hasn't been installed either. And they wonder why there's a productivity problem in the UK.