TerryE

There's definitely a sweet spot where using an RPi makes a lot of sense, say to want a decent full Linux stack in the IoT space. I would categorise my CH + DW system here. It's dedicated to a single application, so there isn't much other crap installed or running. The handshake with HA is all through MQTT, and HA provides my User Interface. I do have a minimal UI driven from NodeRED, but this is basic health dashboard and buttons to turn on HW heating to 30 mins, the CH slab heating for 60, and to restart the system: this is there to provide a very basic level of control for the CH + HW if HA is down. Where RPis starts to struggle, IMO, is when you want to do real server stuff, e.g. running a bunch of containers offering a mix of servers. External USB3 is just too fragile an interface for mission-critical storage. OK, there are a bunch of IO extenders for the RPi4 CM that allow M.2 keyed SSDs to be directly attached as well as eMMC, but buying something like this in a decent lead-time and without a horrendous scarcity markup is like hen's teeth. I can understand why the RPi foundation is taking a pause on the RPi5 release. Nonetheless, given that we are fast approaching the 4th anniversary of the 4B launch, it is appalling that we still don't have a standard model with decent eMMC or M.2 SSD support.

You need to talk to your LPA and the Planning Portal. Depending on where the door is this and any conservation restrictions in your area (especially as it is on the principle elevation) you might be able to get confirmation / a certificate of lawful development. The worst case scenario is that a neighbour complains after you've done the work and you get a visit from planning enforcement then an order to reinstate the door -- unlikely, but possible. If you are removing lintels and completely removing the opening, then this work is also subject to building control and approval.

Yup, you can't dig up the public highway. The local authority will maintain a reasonably small list of contractors who are also approved by the LWA to do these works and in compliance with all pertinent regulations. That's the route that we had to go as well. The price was £1K or more than we'd hoped, but TBH they did a really good job -- far better than the cowboys that the DNO and Anglian water subcontacted to.

One or more RPi SBCs seem to be the go-to systems for those wanting to do home automation on a budget. I currently have 3 running my entire home environment: A RPi3 + battery backup hat + ½ Tb SSD doing my CH + HW logging and control on a bare bones overlayFS-based NodeRED stack. An Argon One.M2 RPi4 + ½Tb SSD running my HomeAssistant system. All of my non-mission-critical smart switches sensors, buttons, etc. connect into this using Zigbee, TUYA or ESPhome over Wifi. A Flirc RPi4 + 1Tb USB3 SSD running overlayFS + docker which hosts a bunch of other containers for Pihole, my Wordpress stack, VPN, FTP service for my external cameras, etc. These basically do all of my home automation for a capital outlay of a few £100s, and they generally do it well, except for a few really annoying exceptions. These are: Power-out recovery. This only happens a few times a year, but when it does it can be a real PITA. The overall system does not recover and restart seamlessly, as there is a race between my BT Infiniband modem, my 4×Asus mesh router / access points, these RPis and the various containers / services running on them. Almost invariably I need to manually restart something to get everything talking to each other, which is a slight hassle if I am in the house, but we once had a power-fail when we were in Alonnisos, and the docker stack running my VPN couldn't connect to the router, so I couldn't VPN in to do this recovery remotely. All too fragile. SD / SSD failure causing RPi outage. This has happened about once a year on average over the 5 years that we've been in the house, and this is 5 times too many, IMO. In the course of all this, I have learnt lots of techniques to avoid / mitigate the damage, but I have still had to rebuild / restore my HA system 3 times now, plus a couple of times when the failures were "soft", but I still had to recover the system by logging into the HA console with keyboard + display and hacking. So all of this has got me to the point where I have been asking myself: is this really the best approach? Is a loose cluster of RPis really up to the job? Some of you might watch Andreas Spiess on Youtube, and he has been going on a parallel journey. He has decided to migrate all of his servers onto a NUC-style host running ProxMox. I decided to go on a slight variant route and use an old 8 Gb RAM + 1Tb SSD CoreI5 laptop (that I no longer use since I have swapped to using a far lighter and more powerful Chromebook as my interactive device for this). Think of this lid-always-closed laptop as a small 8 Gb CoreI5 server with inbuilt battery backup. I will keep the RPi3 running the CH + DW, but use this ProxMox host for all other services. As one of the YouTubers on a Speiss topic on this commented: you can pick up a 2-3 year old 8Gb Core I5/I7 laptop with a cracked or fade-damaged screen on eBay or direct from one of the PC refurbishment companies for around £100 or less, as they are useless for use as laptop but are perfectly fine as a small `server with in-built battery backup. Anyway, I just wanted to flag this up as some of you might be interested in this approach as well. Depending on the interest, I can provide more write-ups and engage in discussion. Up to you guys. PS. I do think that RPis have a sweet spot where they are really effective: the RPi3 running my CH + HW system is a good example, and this has run faultlessly for over 5 years now. What really lets down the other two systems isn't the OS, processing power or RAM, but rather SD card and USB3 storage failures.

You can daisy chain up to around 20 DS18B20s quite happily, though you may want to use overlayFS and Log2RAM if you are using an SD card as your system device. A battery backup hat (PiHut has few) might also be useful as well as a strip board hat if you want to bring all of your OW devices back to a central connection board

Depends on the type and how well insulated your tank is. We use SunAmps which have vacuum panel insulation and these stay hot for days.

You get hot spots from adjacency to UFH runs, solar gain, etc. What you really need is a slab average. If you have wet UFH you might consider what I do. I run my circulation pump for 8 mins every hour. I initially did this to help to redistribute heat around the rooms, but I also realised that the return flow temp is a good remote sensor of average slab temp, and so I use the average of my zone returns.

We had a simple rule: no tradesmen were allowed to touch the VCL. We basically pre surveyed and agreed all through penetrations and fixings then we added tall of the through holes using appropriate diameter ABS pipe, the outside of which we sealed and taped, and this left the necessary through-hole for the tradesman to run cabling / pipework. Ditto we fixed dwangs / mounting plates where anything needed fixing or hanging. For example the PB was screwed to vertical service battens but we also had 60° reveals into out windows, we added horizontal fixing strips in the reveals to allow the crew to screw the plasterboard to this. If the electrician or whatever needed another hole then we would do this within a day or so. Prior to the Air tightness test, we went around and foamed + siliconed up the through holes to ensure airtighness. We passed the test first time, with no tweaks.

I have a single central HW and two central CW (high flow and low flow) manifolds. The HW / HF CW are loop fed (see Nick's posted example of how to do this) to prevent running a bath or high-flow shower "stealing" flow from another high flow fitting further down the manifold. This can occur if you have a single end-feed. It can be worse if you start daisy chaining manifolds.

Wow, that's a bit off topic. Time for another thread maybe? We had a 1m 15mm + 22mm SDS drills which we used for this purpose. If we could drill through 2-300 year-old hardened Limestone then going through modern low density concrete block work would a doodle. I once drill some 22mm holes for 15mm on the diagonal and ended up burying the 22mm drill to the chuck. I could tell I was close one the other side so ended up using a 4ft piece of rebar to pop out the facing stone on the far side. 🤣 The big advantage of having your rising main and manifolds placed centrally is that its central. 😁 If it's too late, then que sera, sera. Remember this for your next build. Your layout in your earlier post might be a compromise, but I would avoid daisy-chaining manifolds as this can really screw up dynamically balancing flows. I would personally take the utility and main manifolds in 22mm copper directly of the CW and HW risers (with isolation valves). The FB manifold is a toss up but again it makes sense taking it direct off the risers maybe in 15mm. @Nickfromwales what do you think?

@MortarThePoint, I am a bit confused here about your routing strategy. It looks like you are routing your pipework horizontally within the walls around the living space. What are you using for your ceiling joists? We essentially did all of our horizontal routing with the floor voids as part of 1st fix -- that is before any plasterboarding was done -- which mean than the runs could take a pretty direct route to above or below the fitting, and then drop down or rise up to the fitting within the 44mm service cavity. This is all pretty straight forward if you are using ecoJoists or OSB I-Beam joists, though in the latter case you do need to plan out your cross joist routes and add reinforcing plates around the access holes. (You can also do this with solid joists but you do need to ensure that the structural integrity isn't compromised.) We ran our services in reverse order of stiffness: foul water first, then MVHR, then potable water, and lastly electrics. Perhaps this was because our previous house was a 300 year-old stone-built with Victorian additions, and this was a true PITA for routing electricals and plumbing. Therefore on our new passive-class build we made a point of addressing these routing requirements as part of the initial design and well before any work on site. In retrospect we were lucky in that some planning hassles delayed the whole start of build by about a year, so Jan and I had a lot of time to research issues in depth and to plan in solutions. You seem to be facing difficulties that we avoided before we even laid our slab. Where are you in the build lifecycle? I get the impression that you seem to be struggling with issues that could have been avoided. An example of this is that your main bathroom is 16m away from the manifold and the kitchen and GF loo 8m away. We positioned our services cupboard centrally (the main riser was in a duct in the slab) so the most runs were 4m or so. The longest run was to my son's ensuite in the loft floor and that was about 8m.

Mine didn't 🤣

@AliG you beat me to it, so I'll preçis my reply. The current daily wholesale spot rate [see here] is 13.6p/kWh down from it's peak at 59p in September and back at hasn't been since Sept '21. A lot of suppliers took a bad hit and some failed because of capped vs supply pricing. We are with OVE who had a policy of back-to-backing their fixed price consumer pricing with fixed price supply contracts. This meant they could complete with the likes of bulb, but at least they weathered the crisis without totally draining their coffers which is why their current TIRs are more competitive than the likes of Octopus. I am just looking forward to the majors offering a ToD tariff to smart metered customers.

I fitted my last cylinder over 30 years ago then the Bregs were very different, so I will let Nick reply on this one. 😊

I saw you post on this on another topic, and you concern about having to core lots of access holes. I am not sure what your problem was here. If this had been me, and I needed to run a lot of pipe runs through a block wall, then by far the simplest approach would have been to drill a set of vertical holes and bolster out half a block, then smooth out any rough edges with cement. Feed the runs through and use some short lengths (150mm or whatever fits) crossways in the hole to act as spacers in the hold to keep pipe separation. Pack with mineral wool when all done to create the fire break. Job done. Saving a couple of runs to the manifold at the cost of all then extra jointwork local to each room makes absolutely no sense to me, as it involves extra effort and cost. Sorry but this is flawed reasoning IMO. The Hep2O type pipes have a practical life of maybe 50 years. Earlier failures nearly alway occur in the fittings. That's way the BRegs say that these should always be accessible. By having each appliance / tap on its own unjointed pipe run with the only fittings at end appliance and at manifold, you don't have any hidden fitting within the building fabric. As to running buried pipework, the same rule applies as for electric cabling: only run directly horizontal or better vertical direct to the nearest floor / ceiling void; in the case of Pex pipework, mark run with aluminium tape so that it will be picked up by a cable/pipe detector. Also given that most drill-through accidents occur when someone is adding wall fittings after the house is built, the critical number here is not the 3:1 that you mention, but how many buried tails you have and this basically the same for both approaches. In my case even if shit does happen, and I do drill a tail, then one twist at the manifold immediately isolates that one run, so I have one tap or whatever out of commission until the repair is done, rather than the whole room. PS. I was just chatting about this with Jan, and her comment was "I can see where he is coming from; if we'd had a conventional build without decent floor voids and service cavities, then I have been tempted to do likewise so long as the room manifold were all easily accessible". So maybe I am being a bit too evangelical about 1-1 plumbing. 🙃

@MortarThePoint, one of the side effects of dipping into threads when poked is that you often forget what you said to who, so I had to refresh myself on this thread. I got an excellent resource from on old boy that has now been dead for over 5 years that have all of the static and dynamic flow tables and formulae to make sure that everything was balanced and had adequate flows. In short we have a 3 bar mains feed which is at ~2bar for max realistic flow through the water filter, manifolds, etc. At this head unless you've got pathologically long runs 10mm is easily enough for toilets and basins. 15m for high flow showers and baths. Nothing needs more for a 1-1 run. I made my Clapham junction analogy in an earlier post. We rans all of the pipe runs back into the GFL toilet ceiling space with enough tail left on each run to comfortably reach the manifold (my service cupboard was built and split off the toilet space, but the framing and bifold doors were only added after everything had been fitted). I also put the cold manifolds on a separate wall in their own access panel (above the Gerberit wall-hung toilet mount, and now hidden behind a nice poster of a Cretan harbour scene 😊). This meant that all of the CW tails ran in one direction and the HS tails at 90° to this below above them. Once completed, even Jan agreed that floor void scene did look nicely laid out. We've got evoJoists so its quite easy to plan runs both parallel to and cross joist. And there it lots of space to make the 90° horizontal to vertical turn into the manifolds. No the pipe runs aren't accessible, but so what? All pipe fittings are.

I don't understand your rationale here. We have one run per appliance fitting, so for example our bathroom has 3 cold feeds (toilet, bath, basin) and 2 hot.; our ensuites ditto but shower instead of bath. At @Nickfromwales suggestion we used Hep2O for all radial plumbing. The pipe is relatively cheap and there are no hidden joints so the only real chance of a leak is if a pipe is directly holed, but it this case every fixing is separately isolatable at the manifold. We layed out our house so that most plumbed rooms backed onto a central core so that most runs were short and it was a lot more convenient for us to run each pipe run direct to the fitting. I did all of the copper-work and soldering for the service cupboard, and Jan and I split the rest between us, with me usually acting as the labourer. The pipe runs were pretty direct in within the ecoJiost space and only a short vertical run up the service cavity to each fitting. We've got a kitchen, utility, bathroom and 3 ensuites but doing the pipe runs was a relatively small part of the total job. Still doing this all ourselves meant that we saved a lot of labour costs and did everything to the quality we wanted. If you have only one feed to your bathroom, say, then you need to have an accessible mini-manifold hidden somewhere in the bathroom and then take local runs to the appliances. This can be a PITA to run if the fitting isn't directly adjacent to the mini manifold. The pipe costs about £1.50/m in coils, so using a per room manifold approach might has saved us maybe £10 per room. Just not worth the hassle and extra fittings and plumbing. See other examples on the forum for this type of installation. Nick has posted some lovely examples. Having got used to ours, I would never go back to not having one. We use soft water for everything other than cold drinking water. It makes better tea and coffee, since the Ca and Mg salts in the hard water sediment out a lot of the nice flavour molecules (that's what forms the scum on a cup of tea if you use unsoftened water. The change isn't really noticable either way for other cooking. We keep a jug of cold water and a few sparkling water (Sodastream) in the fridge which I top up with a large jug drawn from the one tap that is plumbed to the hard side of the softener. The main advantage of the soft water is no tide marks on the whiteware and glass screens and no scaling on cookware and kettles; also no scaling on your HW cylinder and TMVs that are in a lot of appliances and feed to the manifold, so everything is maintenance free for far longer. Researching other self-builders experiences here on the forum and on similar resources might help. It certainly saved my bacon quite a few times on our build, and my time doing this proved to be time well spent. Anyway best of luck on your journey. 😊

I assumed from the OP that it was the tank element of this unit (or similar model variant)

This one was more like think classic UFH pipe loops, but with main runs between the rafters in effect sitting on the plasterboard. Any actively blown system such as the inner FCU part of a standard room bi-block won't have this problem since the blown air sets up a moderately chaotic circulation that mixes the air well. No, I am talking about low temperature systems that heat an extended surface to say room temp + 5°C. Whilst a lot of the heat shedding will be radiative, you also get near-ceiling circulation which can heat the airspace immediately adjacent to horizontal surface.

I didn't realise that the Mods considered Ian (@ToughButterCup) a spammer. 🤣 He might have quoted a spammer, but I was quoting his response. But whatever will be 😉

You end up with a stable thermal gradient: head at 27°C and feet at 18°C. A friend had a flat with ICH (in ceiling heating) rather than UFH. The developer though that putting the heating loop in the ceiling as this was a lot simpler than in a floor screed. There is a good reason to heat from the bottom: This flat was almost unlivable in in the winter.

If you look at my blog you will see that my "plant room" is a (IIRC) 1.4m × 0.7m cupboard off our ground-floor toilet in our utility, the cupboard is separated by bi-fold doors that are normally closed but can also easily be removed entirely if full access is needed. This all works well because I use 2×SunAmp PV units for my DHW. This might give you some ideas. Also @Nickfromwalesmany posts and advice here. But some general comments: Maintenance access is essential. I think you will find access to your DHW problematic. Don't forget your thermal calcs. Parasitic DHW losses will turn this into a hot room. You haven't got many potable HW/CW manifold ports. You want one per end attachment. Sharing just isn't worth. It is worth provisioning a couple of spares during design. Move them nearer to the ceiling. You will get more usable wall space. Water Softener? Well worth fitting. Network / control racking? What is your rationale for a combined ASHP/DHW system? We have separate resistive heated SunAmps. Based on our actual HW use we would never get a payback for the extra complexity / hassle of one of these units. Also remember that like most mechanical / compressor based systems, you might expect a 10-year working like if you are lucky. Also if your main heating is water-base UFH then the flow temp should be ~35°C or less. At this temp, an external monoblock ASHP should deliver an effective CoP of 4. Oh, the pleasures and heartache of detailed design 🙂

[Mods: removed quoted material from spammer] At the moment we are heating our house roughly 70:30 slab UFH:oil filled rad. The additional rads are enough to ensure that we can keep the house warm heating only in the low rate 0-7AM window. We use 3 rads which jointly radiate just under 2kW. BTW, don't use IR WP to heat ceilings or external walls.

As @Temp advises there are significant potential issues with converting a roof designed for a cold/ventilated environment into one adjacent to a warm space. You need to be aware of the associated risks, as adding insulation directly under a tiled/slated roof can introduce a leakage trap / condensation trap that can lead to rotting your roof timbers. This risk isn't insurmountable, but needs to be addressed in your plans. You will need to ensure good eave and ridge ventilation with a minimum 25mm and 50mm preferred air gap between the PIR and that sarking felt so that you can get a good (cold) airflow under the felt. Is this all worth it if you are not planning to use this space for some warm function? It will be a lot easier to do as Temp suggests.

A good reference here is The Engineering Toolbox which gives the 0.68 kWh figure for evaporation at room temperatures. However, I suspect that modern near passive class houses have minimal evaporative cooling. Our kitchen probably has the highest AH and its RH hovers around 55% whereas my outside RH is typically around 90% in the winter months, which equates to an RH of 35% at room temperatures, so MVHR input will tend to drop the house RH. On extract in these circumstances, the internal air will condense out about 40% of the absolute humidity in the heat exchanger (which is why MVHRs need an external drain) and thus this condensation latent heat will be covered into the input stream. MVHRs are also typically ~85% efficient at recovery so heat losses in the other 15% are moot. Given that extracts are typically placed in wet zones, I suspect that most moisture is pretty much immediately extracted and I therefore suspect the effective net figure is therefore closer to 0.4 kWh/Kg. We each shed maybe 3-400g moisture through respiration and evaporation, though the heat equivalent is a lot less that 2 kWh or so we radiate. Cooking and misc drying probably add the remainder. Even so from a heat efficiency perspective the best way to dump water is via the plug hole rather the MVHR, hence my other posts about "blading after showering" 🤣 as some regulars might recall.