SimonD

Yeah, that's pretty much how I'm using it, but with the difference that I've lowered my storage temp so that cylinder temp at the sensor level is at 60C with a 4 degree hysterisis, and this gives me an indicated temperature of 70-75C 1 third the way down from the top of the cylinder. When I tried to have the water stored like a proper TS, the boiler would just run for far too long on reheat. I'll be able to tell you how this compares to a heatpump install with UVC sized to MCS specs with a storage temp of 50C very shortly as I'm just installing our heatpump at the moment. So we'll go from 19kW input into the TS to a max 6.5kW input to the heatpump cylinder. I've already warned my wife that it might be a bit different going forwards and we'll have to experiment with the DHW strategy...

I have to say I think this is just one of those very weird threads we get here on Buildhub where sense seems to be thrown out of the window. If it were a heating question, everyone would be posting to say you have to start off with a heat loss calc. Or the very least some design drawings to provide a starting point, but the basic questions about DHW design are completely missing on this one. We don't know anything about pressure/flow rates to the house - regardless of size of main, what are typical static and dynamic pressures where the op is planning to build. Second is whether the requirements for infinite hot water is even really what the op wants or actually needs (I've been here too and the questions were resolved through careful whole system design taking into account flow volume restrictions we have got until I can dig a trench and re-lay our mains supply to the road at least). I realised I didn't need infinite hot water. The assumptions we often make about both hot water and heating lead to over-sizing, which I think is what is going on here. e.g. So first we need to ask more fundamental questions about use and behaviour (and also how transient that behaviour might be and not make long term costly decisions about a temporary, short term problem). And then look at the variety of ways to deal with those, which probably don't need to involve chucking in the biggest pieces of kit that we can find. Again and again I find the mention of flow regulators and system pipework sizing missing in hot water management discussion. For example, plenty of calculations about delivery of hot water at certain temperatures at certain flow rates, e.g. 30lpm, bit this misses that a lot, if not all drench showers, for example, provide about 16lpm. But it's very easy to buy models that have interchangeable flow regulators that massively enhance perceived availability of hot water but actually massively reduce hot water use. I too have teenagers who disappear into the shower with their bluetooth speakers, put on a rave and appear what seems to be like a few days later. Not once have I ever run out of hot water or had a complaint by someone we haven't got sufficient hot water. All we've got is 19kW going into a 210l thermal store.

We're at the tail end of a project not a million miles different from yours. All our advisers said keep existing building as it would be easier to get planning, so we did. When we demolished the bits that wold be replaced the whole thing turned out to be much worse than we thought, but were too far in then to change direction - even the BCO said on a visit he thought we should stop work and re-apply for new permission, but then Covid hit and we had to carry on as we were. If I had the option on an old bungalow again, I'd most definitely demolish & re-build. Too many headaches with constantly chasing around defects of a crap old building to make real sense regardless of the VAT tbh!

Robbins Timber in Bristol are excellent for just about any timber. Not the cheapest. Don't go by their website price list which is buried on the site, call them and explain quantities to get a good price. They used to do free delivery for me, but with your distance this may not be feasible for them. If you're casting your net this wide, then also speak to Sydenham Plywood (used to be Avon Plywood) based in Keynsham near Bristol.

I'd highly recommend speaking to a local timber merchant specialising in plywood. I found our local merchant (we actually have 2 locally) to be invaluable prior to purchasing several pallets of birch ply a while ago - that's because they view ply not as ply but an important building material that needs to be specified correctly. I also found that when buying in bulk, they were very competitive in price and also have access to ordering in your sizes such as 3.050 as @Gus Potter in both 1220 and 1525 widths.

What ply are you after? What are you doing with it? What kind of grade surface finish do you want? There are just so many different plywoods out there, the question is not that simple. And also quality varies dramatically between them, even with the same so called specification. As an example, I had some 'cheap' class 3 (exterior) grade Chinese hardwood ply that when left exposed to the elements completely de-laminated in no time at all. To compare, I left some interior grade Birch plywood completely exposed outside for 2 winters and 3 summers. The Birch play is still servicable and usable despite greying - but no delamination at all. I've also used some moderately expensive exterior grade structural ply usually used for formwork or site barrier fencing which has lasted nearly 6 years as an outside step.

You won't get unlimited hot water as such but you can have a decent DHW strategy that will satisfy you as a family. Similar to what @JohnMo suggests, make sure you have a priority hot water installation. As I know Viessmann's and I assume your new build is pretty well insulated and not too massive, I reckon you could get away with an 11kW 100-W system boiler. Modulates from 11kW down to just over 1kW on central heating but will give you 19kW output on a 4 pipe priority hot water setup. The system with then start heating your hot water to your cylinder while showers/baths are being used so will give you much longer run times from your cylinder. This way you don't have to massively oversize your cylinder either. Personally and professionally, I'd suggest staying well clear of any combi setup for a large family house with multiple bathrooms and high hot water demand.

Only the mandatory 5 year renewal, but that doesn't govern the update and delivery of the training, which is where I've fed back to some organisations that there's a real need to rewrite and restructure the training itself. Things are happening. It's just that the nay sayers are doing all the shouting much louder than anyone else. I get it too. I was round a customer's house to quote for a replacement DHW cylinder and to convert it to unvented. The customer asked me whether it wasn't just better to put in a combi. So we went into a long conversation about how that would be a bad idea as it's a 4 bed house with several ensuites. I also mentioned future proofing for a heat pump which was followed by a shout from the kitchen by the customer's wife that she hates heat pumps. Needless to say I left and decided not to quote for this particular job! This week I've been asked by half a dozen customers about whether heat pumps actually work and how big the radiators have to be. So yes, there's an uphill battle still to be done. Things are happening, but with the size of the industry it's taking time. 1st we've got more and better training out there like Heat Geek and Kimbo, etc. 2nd we've got regional development going on. For example, I have been funded to the tune of about £1600 in by West of England Combined Authority as part of its move towards decarbonising. And yes, it is also experiencing intertia in the industry. I have given feedback into the programme suggesting they need to modify the training and mentoring available and how it's both run and delivered and I'm currently waiting on a response about funding my time to provide more detailed input to this as I've got a lot of experience in training & development and mentoring from my previous professional background. So we'll see what happens here. They appear to be listening 3rd MCS did make so changes to registration and training requirements to separate design from installation, which in practise I think is a good thing but has had some unintended consequences - which I haven't got the time to go into right now as I've got to go and prep for the installation of about 13 rads this week. 4th NESTA has organised a scheme for new heat pump installers called Start at Home where installers get a free heat pump using the BUS grant to install a heat pump in there homw and use it for either MCS registration assessment and as a sales tool for new customers. This comes with umbrella scheme and manufacturer support. 5th The price relationship between getting a heat pump installed versus a new system boiler with unvented cylinder is getting very close to make it financially viable to go in the direction of a heat pump (obviously with the BUS grant) and with suppliers providing heat pump tariffs etc. I think people with cotton on. 6th There are still lots of positive stories out there. I was just listening to a talk bu the CEO of Octopus Energy which I thought was very optimistic - I don't think it's all doom and gloom, but there are challenges to overcome/iron out.

For my triple glazed windows I used the Soudal SWS thermal and airtight system. It doesn't use a silicon but a hybrid polymer sealant. From soudal's website https://www.soudal.co.uk/pro/applications/airtight-sealing: Soudaseal 215LM Add to quick access Product description Hybrid polymer facade sealant Premium quality, low modulus Hybrid Polymer sealant. Extended open time versus silicones to allow longer tooling of product. Primerless adhesion on nearly all common construction materials such as plastics, masonry, metals and wood - even when surfaces are damp. Can be used on sensitive metals such as lead. Non-staining when applied on natural stone substrates. High performance mechanical properties. UV resistant. Free of isocyanates, solvents, halogens and acids. Paintable with all water-based paints. Airtight when used as part of Soudal Window System - SWS®. The foam is: Soudafoam Gun Win. & Door SWS Add to quick access Product description Elastic PU gunfoam Airtight premium quality polyurethane expanding foam filler for use around windows & doors. Superior thermal and acoustic insulation properties. Totally airtight after curing. The product is highly flexible once cured, based on FLEXIFOAM® technology, which gives improved durability. Single component Gun Grade foam. Rapid curing. Primerless adhesion on most construction materials. And then finished to the interior with: Acryrub SWS Add to quick access Product description Acrylic sealant High quality elastic silanised sealant and gap filler based on acrylic polymers. Conform DIN EN ISO 11600 F12,5E. Used for airtight sealing of interior joints and window connections with movement of up to 12,5%. Part of the Soudal Window System. I used the acryrub on a lot of interior timber frame joints, e.g. between wide sole plate and glulam ring beam and then between ring beam and the stud wall. On other windows I used a different brand of expanding tapes like Compriband. I also used a lot of Soudal Soudatight LQ for junctions and window reveals where necessary: Air- and vapour tight membrane Soudatight LQ is a high-quality fibre reinforced polymer membrane which forms an air and vapour tight elastic membrane after drying. The product can be quickly and easily applied with a brush in the desired layer thickness on almost any mineral substrate. Fills cracks up to 5 mm due to fibre-reinforcement. Once dried a second coat (or more) can be applied if required, after which it can be painted or plastered over. The black variation changes colour after drying, from blue to black. The white version does not have this colour indication. I've also used quite a bit of tapes for windows from Passivehaus Systems: https://passivehousesystems.co.uk/product-category/window-tape/ And also their tapes for airtightness at osb junctions for house airtightness barrier. https://passivehousesystems.co.uk/shop/?filter_tax_product_cat=80&filter_location=internal&query_type_location=or Internally when I need somethng for bathrooms/kitchens etc. I use CT1 as @Nickfromwales has so many times recommended.

You're right in your reading of things. The system, although originally set up with the right intentions, has morphed into a mess. The only value added as I can see it nowadays is the benefit of the BUS grant and that the ones on MCS in the first place have had to jump through a few more hoops re training and assessment - just imagine what it could be like if it were a free for all. I suppose there is something in that and it's the one reason I support the existence of MCS. The problems as I see them are: 1. poor training and development - a good training centre for design and installation would typically do it in 5-6 days, but it is delivered and tested in a way to ensure 100% pass rate so you can make your own conclusions about how that works out for the quality of graduates. There are now apprentice schemes for renewables, so we'll see where that goes. Also the content of the training is pretty rubbish and very boring, IMHO, and needs to be updated. It seems as though the training was written in the days of single speed compressors and therefore by default it tells you how to size a buffer as a necessary part of the system and it hasn't moved on since. You don't actually get to play with heat pumps at all, so no fun there. 2. It's all too fragmented. So for MCS registration you need to be a member of a competent person scheme, which then registers you with MCS. Then you have to join a consumer code organisation - MCS and RECC, for example have a very cosy commercial relationship by some accounts. When you join the consumer code like recc, you then have to join an insurer to provide deposit insurance and warranty backed guarantee of the installation (with HEIS it's all bundled in). Just joining the insurer can cost about £600-700 ex vat, plus there's a payment for insurance for each job. Then you've also got to become verified with OFGEM for the BUS grant. You may also have to pay to register with Trustmark depending on the work you do. In addition there's then public liability and professional indemnity (if you do the design work). So with the designer/installer, you've got 5 parties involved in the whole thing (not including PL and PI), all of whom can quite easily bounce the poor recipient of a rubbish installation around the houses, with nobody taking ultimate responsibility. If you add in an umbrella scheme, you've got yet another party involved. And with all parties, there's a conflict of interest because it's the installer who pays the fees and is the customer of all these organisations. Dare I say it, but I wonder whether MCS needs to be rolled back to be state owned and run with all the ancillary bits pulled under the same umbrella so that the conflicts of interest can be removed - even if the system were changed in a way that the customer, in order to get the BUS grant, pays a defined fee as part of the installation, which is paid directly to MCS for consumer protection, rather than the installer being the member. And then the MCS vetting and assessing the installers regularly to be on the register. I don't know, I haven't reall thought about it in too much detail. So there needs to be more clarity for the customer. Because MCS has essentially farmed out the assessments to the competent persons schemes, that's probably where the buck should stop and they should be mandated to resolve the situation, or otherwise legislate to force MCS to be accountable. There should also be a redress fund for the rectification of crap installations and that is something that each installer should have to pay into on each installation and where the fund essentially sits in escrow with an independent body, far from profit making organisations. I know the estimated numbers in terms of crap heat pump installations in my region and how much they think it would cost to rectify them - it's frightening.

I think it's much wider than that. If you properly read the paperwork for all this, it isn't actually as prescriptive as the majority might have you believe. The current process is defined by EN1283 1 2017 which defines the process for heat loss calculations as well as default values if there are no national appendix figures. This standard has also changed the way in which ventilation losses are calculated. For us, we need to go to the CIBSE Domestic Heating Design Guide which follows this standard and this quite clearly states that while the figures given in the reference tables for things like outdoor design temperature. U-values and ventilation rates can be used when nothing else is available, it permits the use of more accurate figures and that the designer should look for the most accurate data available. The advantage, and problem, with the new standard is that there are now more variables available to use such as differences in ventilation losses due to location and exposure and even cold bridging values, which can have a dramatic effect on the results - e.g. if you know a retrofit or newbuild has used Approved Construction Details you can use appendix K reference values from SAP for cold bridging. But unfortunaly, because the heating industry has been so thoroughly de-skilled over the last 40 years, few seem capable of reading and digesting this stuff properly and using their own initiative. I assume that most designers and umbrellas are probably too lazy to use anything other than the simplified methods. None of the current training even touches this, not even Heat Geek. Nor do many of the software companies make any effort to explain the details and how to modify the settings in the programme for individual projects - and so it defaults to crap. With MCS, if you deviate from default figures, you just need to provide a reasonable justification for the deviation, that's it. As an example, I just went through the process of a design using an umbrella scheme for a design. I'd already completed my own heat loss following a comprehensive survey. The umbrella scheme came back with a result that was almost twice mine. Eventually, we went through 4 iterations until their result was only 300w above mine. It got to the point that I had to tell them that they were inputing the incorrect figures into their design software and that is why we were having the problem. I even had to do some basic calculations on the ventilation design for the property to show that the design was 0.38ACH and not 1.5 just using basic building regs calculations for extract ventilation to show how they were over-estimating these figures. Ideally to deconstruct all of this, you need a copy of EN1283 1 2017 and then navigate your way through a murky world of poorly organised documents to untangle the mess it's all in.

Yup, that's City Plumbing if you don't have an account and a friendly person at the counter. Try these instead. Still a lot of money mind you. And then https://www.bes.co.uk/flexible-hose-1-bsp-f-swivel-x-28mm-x-500mm-pair-25287/ https://www.bes.co.uk/inta-pre-insul-heat-pump-hoses-1-bsp-f-swivel-elbow-x-28mm-comp-x-750mm-pair-26190/ As above, there's just no excuse not to. Unless the system is filled with glycol, I'd also want to see anti-freeze valves on there.

Yes... I have two heating manifolds, one for upstairs, one for downstairs. My longest run however it a lot longer than yours at approx 17m on 15mm pipe and vary from about 3m to 17m across the house. I use the Danfoss self balancing trvs with lockshields fully open. The self-balancing trvs make balancing a dream as you simply download the app, input your flow and return temps together with the size and type of radiator (or required output) and the app will give you the setting on the valve and its equivalent flow rate - it then provides the required flow to each rad. House balanced in 20 minutes rather than 6 hours and then some on following days. Then if you need to increase or decrease the flow to any rads for finetuning its a very simply turn of the self-balancing dial (which is numbered) rather than nuisance lockshields. Obviously it's a bit of work changing out the trvs but balancing even with lockshields is always going to help - it used to have the normal trvs & lockshield setup.

I did, and I still got it wrong 🙄😊 23-24 is exactly what my wife now knows she wants while I'm walking around in shorts and t-shirt.

I've got to go old school with a leftfield approach - I have several air nail guns used with a compressor. Yes, the air line can be annoying sometimes but it's all so reliable. The guns are fairly light weight and they'll run and run and run, even down to -6, then it got too cold for me.... I've also found the support fantastic - next day delivery on all parts and simple to fix.

I kind of knew I'd get some kickback from what I said and I'm not surprised from whom 😉 I'm an approved Viessmann installer so I'm fairly familiar with how they work and most of my installations with Viessmanns are with unvented cylinders and PDHW bla bla bla.... and I don't treat them like a heat pump. CH and DHW need to be considered differently in both design and commissioning and it's not uncommon to see lower DTs when in DHW mode in PDHW but then flow temperatures are much higher .and @JohnMo you have repeatedly talked about the problems you had getting your ATAG to run as you wished it to which wasn't as it was out of the box and it didn't run like a heat pump...e.g.

Yes, the boiler pump is almost certainly able to deal with the index circuit press drop. The reason you need the hydraulic separation is that your flow rates will be different when you have a different Delta T - the difference between flow temperature and return temperatue. So even if you ran your rads and underfloor heating at a Delta T of 7 (7 degrees temperature difference between flow and return) for example, your boiler still wants to ideally see 20. At a Delta 7T you will have almost 3x the flow rate through the system than at Delta 20T and this will cause problems at the boiler side because of the way gas boilers run - typically if the Delta T across the boiler becomes too small it will tend to short cycle. This change in flow rate between what the boiler wants to see and the emitter system will need the addition of a pump post hydraulic separation. A case in point about boiler Delta T is with my current gas boiler. On Opentherm this is set to run at a maximum flow temperature of 53C. On very cold days, I have a typical return temperature of 37C (even though I have a perfect Delta T of 20 across both of my system manifolds - make of that what you will) - I can't get the settings to work any lower on this boiler. When the return temperature at the boiler reaches 41-42C the boiler begins to short cycle with a max flow temperature of 53C. But it will continue to run fine if I increase the max flow temperature to 55 or 60C. So my boiler just will not run well when the Delta T gets to minimum 11-12C. At minimum 16 it will run for long periods of time. IMHO it isn't worth trying to make a gas boiler run like a heat pump, they are different technologies and thus need to be treated that way. No, it wouldn't because it doesn't have the inputs and outputs for temperature sensors and electronic circuit mixing which you need for the ESBE, unless you use an ESBE product that has its own weather comp/room load compensation controls.

I read loads of books....then I just booked myself onto a self-build project management course for 2 days. I attended the one run at the Centre for Alternative Technology and it was very well worth it. There were even a few professionals involved in building on the course, including architects, which made for interesting discussion. Plus we got a site visit to an existing project to talk it all through with the self-builder. So it was all down to earth and applicable.

I have distribution manifolds as central to the house as possible and from these manifolds I run individual pipes to each outlet. This means I can run small 10mm pipe to basins/wcs ect. and 15mm to showers etc. For maintenance it works great as each outlet can be isolated but the rest of the room can be used - e.g. servicing the basin taps while still being able to have a shower and now of those terrible isolation valves that always leaks after a few years. You really don't need 15mm to go to sinks/wc flush etc. and with decent pressure you don't need 22mm to go to a bath either. We have a couple of long runs and as I've used 10mm pipe, the hot water is there very quickly. If you run 22mm to a bathroom and then split from there, every time you need hot water you have to draw a lot of volume to purge to pipe of cold before you get hot.

You haven't really followed what was done in that video. On your system you need: - Vaillant wiring centre to wire in the mixer and additional sensors - really you want the SensoComfort together with the VR71 wiring centre and this has up to three outputs for ESBE mixers and has the inputs for several system temperature sensors that you're going to need as well as the DHW cylinder sensor and pump control output for UFH. - you need a pump on the UFH side of your circuit between the mixer and ufh manifold. This is because as you have a gas boiler you need different flow rates between radiator circuit and UFH circuit because you want a delta T of 20 for rads and delta T of lets say 7 for arguments sake on the UFH but once the flow is outside of the UFH circuit you want a delta T of 20 between boiler flow and return. - you need temperature sensors on your pipework so that the controls can differentiate between the temps of the radiator circuit and the UFH circuit (and provide input to the ESBE mixer). In the video, the first thing he points out is the close couple tee arrangement below the boiler which is to provide hydraulic separation between the two circuits - you really must have this in your system for it to work correctly

No, I said that the research at present suggests that there shouldn't be a great different between heat demand in different areas for this to work effectively. You asked me what the Heat Geek mantra is and I clarified this, then you try to tell me it's not? 🤔

Room influence from a heat pump controls perspective is where a room thermostat is integrated into the manufacturer's control system to provide input data from the thermostat to influence some or all of the below (depending on how you commision it): - the call for demand (i.e. if room temperature is above set room temperature, there is no call for heat) - the system flow temperature based on an combination of weather compensation, actual room temperature and target room temperature - so the heat pump will modulate where necessary. So if my weather compensation curve is set to operate at a flow temperature of 35C at 0C outdoors but room temperature is nearly satifsfied, the room controller modulates the flow temperature of the heat pump accordingly. On some heat pumps you can set the room co-efficient to change the weighting of the room influence to weather compensation. But you can also use modulating mixers for UFH, for example, that can either be wired into the heat pump manufacturers controls to regulate flow temperature going into a specified zone. You can also buy room/weather compensated mixers (like from ESBE) or even room/weather compensated UFH manifolds if necessary that have their own sensor and controls if absolutely necessary. And of course, not forgetting radiator systems, you can employ simple ways of restricting flow using TRVs. Or if you decide on a more permanent turn down of flow to some areas of the home, you can use self-regulating TRVs where you set for flow rate for a specific output and delta T across the radiator. You could also technically use a mixer to the whole radiator circuit, if needed. The main difference in room influence versus the main stream understanding of the zoning term is that with room influence you are not closing down flow to areas of the heating system, simply balancing flow rates and flow temperature, so you don't experience the problems associated with low system volume when zones are closed down. You tend to do this minimally using 1 or 2 room thermostats with proprietary control, but some manufacturers have begun to supply support for up to 6 in their controls. There's nothing particularly complicated about this in terms of overall system install, it just needs a thoughtful design process that understands the building and what the occupants want/needs. As manufacturers now build these into their control systems, it's also something that is fairly straighforward to adapt, should you need to. As a note: @JohnMo's system is technically a system with room influence as it runs very low flow temperatures where there is only a couple of degrees difference between flow and room temperature, which permits a self-regulating effect on the heating system. This is a behaviour of the system that works independently of the controls and heat pump.

Research suggests differently and I'm more likely to trust a balance of trusted research. And you're not doing that John, so you shouldn't pretend that you are. Not quite, it's more subtle than that. The mantra is to use open-loop managed with pure weather compensation on retrofits and less well insulated homes (including some newbuilds) but in highly insulated and airtight homes use weather compensation together with room influence. The balance between weather compensation and room influence is dependant of specific design elements and context of the house. Come one John, I've already said that open-loop is the preference many times. What I've been saying, yet again, yawn, is that the specific circumstances of the building must be considered and that building in room influence is preferrable when dealing with well built, highly insulated homes, with good air tightness, especially if they experience large inputs of energy outside the heating system. This isn't complicated either. Occupants might also like more control in their bedrooms.... Err, so below you're suggesting what? Not room influence by any chance?

There just seems to be some bizarre obfuscating circle going on here John, 1. You are running a very low temperature UFH system that also utilises a specifically designed slab arrangement. 2. You have spent countless hours/days/months/years tinkering with your system to get it working right for you. 3. You are using 1 anecdotal example, which is your own, to base a general conclusion that is being suggested as suitable for all and everyone. 4. You have some very particular views on indoor temperatures such as your view on bedroom temperatures for example. Your system, because it utilises the self-balancing effect, actually manages to self-regulate independently of the controls in your system - that is what these systems are known for. But, it requires a significant amount of pre-planning and integrated design, and if being applied in a retrofit situation, a hugely costly upgrade process. Your graphs therefore don't reflect the nature of the heapump and it's controls but this thermodynamic behaviour which is independent of it, but nevertheless impacts the behaviour of the system as a whole. This is a great solution if you have the low heat loads required and all areas of the house have similar heat demand (e.g. there's no area where there is a significantly higher demand), as a basis to allow it to work. These are highly significant caveats to what you are proposing and I believe people reading posts on this forum need to be aware of this and that there are so many other factors involved, such as floor coverings etc. I'm not saying anywhere that your approach is wrong, I'm suggesting that other approaches may be more suitable for other people considering designing their own system, and whether you accept this or not, is neither here nor there as it's something that good designers and installers of systems are utilising more and more from their vast experience of putting these system in.

Just to add - yes, but if the weather compensation is calling for heat and the heatpump sees an increase in return temperature, it will increase the flow temperature to maintain target Dt, which is one reason why a buffer, for example is less efficient when there's too much distortion. Just seeing an increase in return temperature is not enough - the heat pump needs additional feedback. This is another reason why room influence is useful in circumstances where there is additional heat input into rooms. Hence your description of the heat pump modulating down when it sees a higher return temperature, is not necessarily, nor universally, correct. It depends on controls.