TerryE

@jack @JSHarris Have either of you got a data sheet on your water softener? I am looking for the pressure drop to flow curves. I did see a couple of figures quoted on one site, and assuming the typical power curve this gives 0.0276×f2.41 kPa for f in ltr/min which is 0.2 bar at 15 ltr/min, 1 bar at 30 and 2 bar at 40, but the 2.41 seems suspiciously steep to me; the power term is normally in the 1.8 - 1.85 range.

@JSHarris @jack this issue of when to use flexible hoses vs copper is an interesting one. The SunAmps are supplied with 2×½" (or 15mm) flexible hoses which seems daft to as the internal diameter of flexible fittings is slightly less that the equivalent copper pipe. The SunAmps give flow:PD curves up to 14l/min which a flow speed of ~1.7 m/s which is getting rather high, IMO. Surely it would be better to come out of the SA in 15 copper and jump to 22mm flexible if we really want flexible connectors. The best price so far that I've found for the Harveys Crown Water Softener is £885 inc VAT from Fountain Softeners complete with 22mm high flow install kit. BTW. Have you seem my latest blog posts giving an intro to SunAmps?

I just wanted to include a brief post explaining from a self-builder perspective why we have decided not to use an Unvented Cylinder (UVC), Thermal Store (TS) or combi-boiler for our domestic hot water (DHW) in our new build. Instead we are using 2 × SunAmp PV heat batteries heated by E7 tariff. So why? We decided that we don't need gas to be installed avoiding the Gas connection charges, per day supply charge and the maintenance costs on gas appliances. Big saving here. We don't have the room for a TS and we've heard too many horror stories about the problems of heat losses in a passive-house class new-build like ours, so no TS. We didn't want to get into all of the regulatory crap around installing and annual maintenance contracts for an UVC. So strike this one as well. So what is the alternative? The SunAmp is a thermal battery with an in-built heat exchanger (a bit like a combi boiler) which can store ~5kWh of heat for delivery in water typically at 50-65°C. Here is a simplified schematic of the store. (Note that I've left off all of the essential safety features such as the expansion vessel pressure relief and overflows to simplify this down to the functional essentials.) The guts of the device are a couple of Phase Change Material (PCM) cells which act as the thermal store. It in essence it works in one of two modes: Discharge Heating, where the CW supply flows through the two PCM cells and is heated to between 55-65°C and then blended with a CW mix in a TMV down to a preset output temperature. Recharge. When fed with an external electricity supply (typically PV or E7 off-peak tariff power), water is circulated internally through the cells and a 2.8kW heater to bring them up to an internally preset maximum temperature. So the SunAmps can only be charged by electricity, and there is no alternative form of heat supply. The form-factor is very small – two SunAmps side-by-side take up (d × w × h) 530 × 600 × 740 mm. The rectangular packaging also facilitates the use of internal vacuum pack insulation panels so the total standing heat loss is ~ 1kWh / day which is a lot less than a typical TS. The exact choice of PCM is specific to SunAmp, but the linked Wikipedia article lists the common ones with a phase change at around this 55-65°C range. However in terms of the physics of how this all works, it is easier to describe another common PCM that we are all familiar with and which has its phase change at 0°C: water. There are three material properties that you need to consider when looking at how a PCM works: the specific heats of the solid and liquid phases, that is how much heat you need to supply to heat 1 kg of water by 1°C and the latent heat of fusion that is how much you need to convert 1 kg of water at 0°C to ice at 0°C. I could give you the figures but a good way to think about is that you need the same amount of heat: To heat ice at -158°C to ice at 0°C To melt ice at 0°C to water at 0°C To heat water at 0°C to water at 80°C. OK these ratios and the fusion temperature differ for different PCMs (as well other properties which reflect the long term stability of the using it in cells, etc.), but that is all the proprietary stuff (discussed in the detailed below from Andrew Bissell). Even so, the bottom line is simple: the systemic heat losses are far less than alternative solutions, and Weight-for weight you can store roughly four times as much heat in a SunAmp PV store as a conventional DHW cylinder. As to why we have chosen the 2 × SunAmp PV approach, there were 2 main drivers for us: 5kWh isn't enough to meet our typical daily use, and 10kWh is so we will be able to charge our stores overnight at E7 rate and only need daytime top-up in exceptional circumstances. The pressure drop across the store in Bar is roughly 0.0142×f1.81 where f is the flow rate in ltr/min, and if you crank the numbers one store doesn't give us enough flow rate. Even so if we look at our planned use (I'll go into the figures in a later blog post), our household of 3 people has had an average use of 280 ltr/day averaged over the last 6 years. Most of this is hot water -- say 80% or at an average lift of 25°C, this amounts to 5,500kgK = 6.4kWh/day or 7.4 kWh/day allowing for heat loses. This will cost us £194 p.a. at my current electricity tariff for my household's DHW. Will I really realise the payback from additionally investing in gas or ASHP based DHW systems? I think not. PS. Slightly amended wording to reflect the earlier comment of Andrew Bissell quoted below.

Nah, I won't keep simple for you, but for normal mortals, that's a different matter.

@jack Jeff it was really useful for me :-) Thanks

@Nick, for sure. It's just that I've had to get my head around the design stuff and dumping it out Jeremy-style will be helpful for others.

OK, we aren't having the exchange that I wanted, so I think that the way that I will approach this is to write up my pipe sizing design as a blog post, and I can always revise this in the light of comments. Hopefully you guys and others like @Alphonsox who also have a SunAmp setup and the others that are tracking my plumbing thread will give me feedback to help improve it.

@SteamyTea Nick, I assumed that you know how to use Google and have a base level of experience here on configuring the device that you want to use. However, I will expand on these for other readers and rather than go into great detail, I've just linked to the relevant Wikipedia article. HDMI and VGA. These are two hardware display interfaces. You plug old-style monitors (and some TVs) into VGA; and modern TVS into HDMI. The RPi has an HDMI interface on board so you need a little converter like this if you want to use VGA. Raspberry Pi ESP. Sorry I assumed that you'd read / not ignored / not forgotten my earlier post on this page where I explained all this. NOOBS, the RaspberryPi.org recommended and supported (and easiest) way to setup a Pi. If you haven't heard of this then no wonder you are struggling to setup you Pi. RTFM Server vs Workstation. In simple terms you have a display / mouse / keyboard and graphics interface on a workstation. You typically access a server using one of more encrypted SSH links, either for backup, console sessions (think of DOS box), and file browsing. This doesn't mean that you don't use a graphics interface to develop / maintain the server; you just use your PC/Laptops and open as many windows / SSH connections onto server as you need. The main advantage of doing it this way is that you don't need to install the OS desktop components or desktop applications on your server. Less footprint both in term of HDD and memory; less security vulnerabilities. SSH LAMP. The standard user interface for servers these days is either a web application or your mobile phone using RESTful API. To do this you need to configure your Pi as a webserver. The LAMP stack is the de facto free open-source stack. Installing it on the Pi is a check-box on the configuration menu. Nearly all automation application assume that you have this installed. Google, YouTube (and your brain) are your best friends here.

? apt-get purge is just short hand for a apt-get remove followed by apt-get clean. I'll just be doing this again in a few days, so if you want, I will update my notes, but IIRC, I just edit my NOOBS config.txt to set the HDMI screen to text mode only -- or you can buy a HDMI to VGA convertor for about £5 on eBay (but watch out, some come from China) and use an old monitor instead. You can also do this through rasp-confg. As well localisation, enable SSH. As far as using the RPi, I don't enable GPIOs or anything since I do this with my ESPs. I just configure it as a bog standard LAMP server plus SSH, then just do an autoclean / autopurge. Just search for raspberry pi raspbian lamp server in YouTube if you want an online video on how to do this. There are euvalent vidoes for using RPis for embedded use.

BTW, guys, if you have a maths or physics A level, then I really suggest that you read those two articles that I linked to or I can email you a copy that I reformatted to make it readable in printable layout. I don't want to put this up as a link as this is technically a breech of copyright. @JSHarris, this is all great stuff for me and I need to think / stew about some of the implications, and I am still getting to grips with some of the non-intuitive implications of my design, like I wasn't going to bother with a water softener, until I realised that (after a postcode search from Anglian) that we are at ~275ppm which is way above the recommended maximum for the SunAmps (150 ppm). I really can't see the benefit of putting a softener on the DCW, unless I do Jeremy's trick of wiring in a direct feed to the sink, but I will need one on the DHW side. There are also some pretty non-intuitive things like the impact of adding the PHE in front of the SunAmps. Adding an extra PHE is bound to increase the pressure drop (PD) isn't it? Well no it doesn't, and you can see why here. The PD through the PHE is tiny compared to that through the SunAmps. If the DCW supply is 8°C, to O/P of the SunAmps is 65°C and the PHE output is 18°C and the final mix is 48°C then a high flow, say 25 l/min through two SunAmps is 12½ l/min per SunAmp: The mix without the PHE is 30:70 cold : SA output so the PD of the SunAmp is 0.72 bar The mix without the PHE is 36:64 cold : SA output so the PD of the SunAmp is 0.61 bar The serial impact of the PHE is ~ 0.02 bar so the second has a higher maximum throughput as well as a more efficient use of the SunAmps. But all this exchange is helping me. My original post was more about how we collate all of this for the others who are just following down this same track and need to get up to speed.

I suspect that we're going to do this as two passes, the first is some heavy and at times geekish discussions. Hopefully the outcome is something that one of us can summarise There's no point in trying to go through the theory and practicalities of the flow calcs, because a guy called John Heartfield has done a good job of this on his articles: Part 1 -- The Theory, and Part 2 -- Real Systems. However, it would be good to have a structured discussion on the pros and cons / ins and outs of pipework sizing and radial vs loop or branching designs. I've been doing the calculations on my system and there is little clear benefit in going to 28mm, as 22mm will carry the heaviest flow rates and as manifold, supply and all central pipework are within a 2.4 × 0.65 × 1.4 m cuboid service area, all of my copper runs are really short. In our system the 2 × SunAmp PVs are the main limiting constraint as these will bottle out at @14 ltrs / sec at 3 bar so 2 in parallel mixing 2:1 with a cool stream will be unlikely to deliver more than 35 ltr/min in practice, but that's enough to have a shower and fill the bath at the same time. Two things that Hearfield doesn't discuss are: Dead carrying capacity. This only applies to DHW connected appliances, but it an efficiency issue. Small is good. Noise. Flow against a pressure gradient is doing work. This is shed as temperature rise or as noise, and goes up on a square law. And if you get the design wrong then pipe (and appliance) noise can be a real pain. An example of the latter is the header tank cold fill in my current house. This runs up a stud wall between our ensuite and the family bathroom in our current house. Our washing machine is an indirect feed cold-fill job and we usually run a washing cycle overnight kicking off at ~4am to take advantage of E7 plus be ready for the morning and every night from 4:00, the ballcock fill on the indirect tank sets up a pssshhhhttt on the fill riser. So laminar flow in pipes is also good = don't use devices which create a lot of noise or tight elbows etc. which cause a lot of energetic turbulent flow at high pipe velocities. So we have got our service area inthe new house on the ground floor, well away from bedrooms, and the pipe runs are short, etc. The room has acoustic insulation on all internal sides. Any other comments / views / advice that we should consider / reflect in an overview? PS. John Harvey does go into a lot of detail on noise issues, manly in Part 1 so I did him an injustice.

@Steptoe, I am not sure of the scientific basis of your assertion, or perhaps it's just an old street tale? As Onoff says, many of the foams include this as one of their purposes. I've got very few penetrations through the TF fabric; mainly exterior lights, etc. All extremely low current in 1.5mm cable or bigger.

@PeterW, it's an ARM chip so this shouldn't really be necessary if you are using it as a server, since the overall CPU utilisation will be well under 100% and the on-chip Graphics Processors (GPUs) will be idle. If you are concerned, then you can buy a passive component like this. I really don't think that you will need an active heat-sink unless you are making heavy use of the OpenGL libraries. (These are a standard API libraries used to access the functions provided in the hardware GPUs in a portable fashion; most 2D and 3D applications and OS functions will use these standard interfaces rather than get into proprietary Broadcom hardware internals).

I use ESP8266 devices for my sensors. And I program them in a language called Lua using the NodeMCU firmware. However, in the interests of full disclosure, I am a little biased since I am one of the core developers of the NodeMCU firmware. I use these to communicate to a central full RPi3 for logging and home automation. The ESP modules do the data collection and relay control, etc., but the RPi does all of the complex stuff. If you don't want to ESP programming at all and essentially use it as a fairly dumb Wifi connected chip, then an alternative that my son-in-law uses and recommends is ESPeasy. This project by default recommends Nodo Domotica as the Home Automation (HA) system, but I would suggest that you stick to either Pimatic or OpenHAB. I run my RPi3s with the SD cards pretty much RO and attach a small USB-powered HDD as the main storage device. You can buy these for £50 up or you can buy SSD ones such as this for £60. I run a standard Rasbian Server installed through NOOBS. It is basically a bog standard Debian build so there is little point in doing anything else. The only frill that you might consider is a Li/LiPo battery hat if you want a battery backup (UPS). As far was the ESP kit is concerned, have a look at the WeMos range. These use a standard form factor and edge pin-out so that you can stack them. You can get a whole range of hats for relay and sensors, and if you want to have multiple DS18B20s, then use the prototyping hat to put the headers for the DS18B20s, resistor and cap on. You can make up a complete battery-backed 6 temperature sensor with WiFi for about £20 if you are willing for delivery from China and buying the stuff from AliExpress. BTW the Wemos ESP boards which cost about £3 already have Arduino-style USB serial + power onboard + FlashRAM which is used for both firmware load and as a pseudo HDD -- as well as Wifi connectivity of course. PS. I've just ordered a USB 120Gb SSD from AliExpress: £39.74 free shipping. PPS. I've decided to SikaFlex my RPi3 box that I use for my house server to the wall of the cupboard under the stairs. That way there is no bloody chance of Jan covering it crap so that it over-heats this time!

The only Radius that I've come across is this: Wikipedia RADIUS and if so then I am not sure how anyone here would know how to answer this. Wrong forum

Another thing that stuck me here was that I would be seriously lagging my DHW copper pipework to keep the heat contained, and I will also lightly lag the DCW pipework to avoid condensation. So by the time the BInp sees it not of the pipework will be directly visible and I will have photos of course. BTW, what is the best tape to use for the joints in the lagging? The stuff that I used on our current house all fell off over the first 10 years or so.

In this case the output will never get above about 25°C so there isn't a lot of point. On a different tack, the two SunAmp PVs have internal PRelVs and the UFH will also have one so am I correct saying that the easiest way to deal with all three is just to have a row of 3 tundishes all draining off into a HepVO and back into the stack?

One issue is that these Willis heaters are spec'ed for a vented system. I'll be running my UFH at roughly 1-bar with pressure relief valve and ½ ltr expansion but technically this isn't unvented. Needs more thought.

How do you buggers know this stuff? You do know that you are going to get a man-hug when we meet.

OK, guys. It's manifold time, and this Q is addressed to those who are wizards and / or have been through this with an MBC frame, such as @Nickfromwales, @JSHarris, @jack, @Calvinmiddle, though PeterW always seems to be very informed on this stuff.. I'll be putting in a basic 3-port system such as this 3 Port Complete Manifold Assembly from the The Floor Heating Warehouse (and this looks very like the one that Jeremy used, BTW). I'll need a pump, but I will probably get a Gunfoss Temperature Controller and Pump Assembly. OK, in my case using an inline heater or as with Jeff using his ASHP unbuffered, the mixer regulator is probably redundant. Even so, part of me says that if something does go totally ape-shit with the heating system then I'd rather keep the problems / damage above the slab where the repair costs are relatively minor, so having the built-in TMV to limit the slab temp to 35 °C is probably a sensible safety back-stop. Finding the water heater that I want hasn't been going well. What I want is essentially a 3 kW immersion element in a tube. I'll be pumping water through it pretty fast, say 20 ltr/min, so it's only going to raise the flow by a few degrees and the water will never be hotter than 30 °C. About the best that I've found so far is something like the Stiebel-Eltron Mini Instantaneous Water Heaters, but these are really designed to lift very low flow rates by ~30°C. If anyone has any suggestions here, I'd be very grateful. Thanks.

In fact Wiltec also sell these through Amazon. Incidentally the Wiltec datasheet gives the pressure drop at 15ltr/min as ~1.5kPa or 0.015 bar which is two shades of bugger all. My only dilemma is whether to defer fitting this until after the BInsp visit since it isn't WRAS approved. So I can get this for 47.29 € + 13€ shipping from Wiltec direct and the exchange rate is 1.17 or £49.24 + £11.00 UK delivery via Amazon. Go figure that one. As far as the water treatment goes, Janny and I had a long discussion about that one and we decided that our local water supply isn't really hard enough to bother. (We descale the kettle about 4 times a year but we could get away with less).

One last post and I think that I've done this to death. I will summarise my conclusions and observations in plainer non-boffin language as a blog post, because the general observations and behaviour of the slab are worth understanding if you are designing a low temperature UFH system. The previous post shows that as you heat the slab through the UFH pipework at this 3kW rate that I've used as a baseline, that the temperature in the pipe gets up to maybe 5°C hotter than room temp immediately around the pipe and this temperature rapidly drops back as you move away from the pipe. As soon as the heating is turned off then the UFH pipe fairly rapidly acts to start spreading the heat uniformly around the slab. So I decided to add a bit of analysis to histogram the heat in the slab over time. There is a slight complication in that the simulation uses an evenly spaced mesh at radial intervals from the centre core, but as I am collecting heat distributions then I need to do this at even volume steps, so that each sample represent the same volume of slab. I did this the simplest way, which was to resample the heat curves (using a simple linear interpolation) so that each sample histogrammed represented the same volume of concrete. A bit of a bodge, but good enough to see what's going on, and here is the result: The first three histograms show the effect as the slab is heated. The main bulk of the slab slowly rises in temperature and there is this very thin long tail (of hotter concrete very near the pipe), so for example by 3 hrs into heating the slab only 3% of the slab is over 24°C. The next four show what happens when the heat is turned off and the UFH pipe is now just circulating water. As can be seen in the previous plots with hot core is quickly cooled as the heat is redistributed along the length of the pipe. This in effect squashes the this tong hot tail back into the main peak . Over the next three hours or so (that is by 6hrs into the simulation) the temperature in the slab is already so uniform that the 80% of the slab is within ±0.1°C of the average temperature. And the reason that the average temperature is slowly falling is that the slab is slowly radiating heat back into the room-space. @JSHarris, @SteamyTea, @jack, does this make sense to you?

One subtle tweak: maybe you put a plug/socket break at the boundary and slip the meter in at that point. Put it in a heavy duty polythene sleeve and ducktape it up to keep it weather-tight. That way both you and the neighbour can read it. The neighbour can be confident that all of your electricity is being metered and you can be confident that only your electricity is being metered. You can pay him 2× or even 3× the standard electricity tariff. It will still work out a lot cheaper than buying a genny.

Back to the flow regulation issue, I've been checking our taps and they all use a standard diameter aerator / flow limiter and increased flow restriction versions are cheaply available, so for any that fail the flow tests, I can swap them out for the test. They all seem to have a preferred 1-5 bar rating and our 3 bar pressure is bang in the middle of this, so the whole "need to do flow restriction" is pretty much a non-issue if done at the appliance end. Phew. Another panic over. However, with all of these restrictors around the place, having a decent clean filtered water seems a really good idea, so I want to find a decent limescale inhibitor and a filter that I can clean without having to do any major disassembly. However, having looked into this there are no WRAS approved chemical filters for potable water, since these work by swapping out the calcium and magnesium ions in the water for sodium ions, and this effects both the taste and wholesomeness of the water. The magnetic descalers seem to be based purely on pseudo-science and there is no real evidence that they do anything at all. As to filters, the magic search term to use is strainer (thanks Jeremy) which yielded the business on the JTM site: Brass Strainer 22 mm. Another step forward. Where is your Welshman when you need him!

Jan prefers to do all of the driving and since I used to have to do a lot for my job before I retired, I am quite happy for her to let her -- a win,win. The main time that she wants me to drive is when we go to friends for a meal and she doesn't want me to drink too much, so she plays the "it's your turn to be the designated driver" card. So if we ever got a digger (and I am thinking of hiring one like Ed had went we do the back garden), then I suspect that she'd want to do the the driving!!