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Showing content with the highest reputation since 27/12/21 in Blog Entries

  1. 10 points
    We moved into our new build mid-December 2017 in time to host an extended family Christmas. We are now over 4 years into living in our new home. We have lots of accumulated experience and made a few small tweaks. However, we are delighted about how the house has turned out, and we love living here. There were no material cock-ups, or regrets on design decisions, so we have probably fared a lot better than most new purchasers or self-builders. Maybe a general experiences post should be on the to do list, but what I want to focus on here, and a couple of follow-ups, is a general topic that others on the forum have asked about over the years: that is how our central heating system works in practice, and how I control it. The system as currently implemented is still largely the same as when I first commissioned it, that is a now 5 year-old RPi-based custom control system directly controlling the CH and DHW subsystems. This is a pretty minimal headless system running Node-RED, MySQL and MQTT client for control. The three material changes that I've made since moving in are: I have followed my son and son-in-law in using Home Assistant (HA) for general Home Automation. My server (an RPi4 in an Argon One case) uses an attached Zigbee gateway, and I have a lot of Zigbee devices around the house: switches, relays, light sensors, etc. and I do the typical home automation stuff with these. There are loads of YouTube videos and web articles covering how to implement HA, so please refer to these if you want to learn more. My HA installation includes an MQTT service for use as a connection hub for these IoT devices. I also have another RPi4 acting as an Internet-connected portal / Wireguard gateway/ file-server for caching video snippets from my PoE security cameras. Note that none of my IoT devices directly access the internet, and the only in-bound access into my LAN is via Wireguard tunnelled VPN, and my HTTPS-only blog. All other ports are blocked at the router. Before moving in, we assumed a target internal temperature of 20°C. In practice, we have found this too cold for our (fairly inactive OAP) preference and so we have settled on a minimum control threshold of 22.3°C. As you will see below, because we largely heat during the E7 off-peak window the actual room temperatures have a ~1°C cycle over the day, so the average temperature is about 22.8°C. This hike of 2.8°C increases the number of net heating days since my design heating calcs and the increased delta against external temperatures in turn increases our forecast heating requirement by roughly 18% over our initial 2017 heating estimate. Because our UFH is only in the ground-floor slab, we found that our upper floors were typically 1-2°C cooler than the ground floor in the winter months. We also need more than the 7 off-peak hours of heating in the coldest months, so I have added an electric oil-filled radiator on our 1st-floor landing; HA controls this through a Zigbee smart plug that also reports back on actual energy drawn during the on-time. HA uses MQTT to pass the actual daily energy draw back to the CH control system. This radiator provides enough upper-floor top-up heat, and does so using cheap rate electricity. Note that all servers are directly connected to my Ethernet switch, and the CH/DHW system has all of its critical sensors and output controls directly attached. It can continue to control the CH and DHW subsystems even if the HA system or Internet is offline. There is also no direct user interface to the system, with all logging data is exported to MQTT, and key CH/CHW set-points and configuration are imported likewise. This integration with MQTT, enables user interfacing to be done through the HA Lovelace interface. If there is sufficient interest I can do follow-up posts on some more of the "Boffins Corner" type details on these implementations, or if this turns out to be more of a discussion then it might be better to move this stuff to its own BC topic. However, for the rest of this post I want to focus on the algorithmic and control aspects of the heating system. In terms of inputs and outputs to the control system, these are: There are ~20 DS18B20 1-Wire attached digital thermometers used to instrument pretty much all aspects of the CH / DHW systems. Few are actively used in the control algorithms but were rather added for initial commission, design verification and health checking. Some are also used to monitor and to trip alarms; for example, there is a temperature sensor on the out and return feed for each UFH pipe loop. These were used to do the initial zone balancing. However, the average of the return feeds is used as a good estimate of the aggregate slab temperature. One of the temperature sensors is also embedded in the central hall stud wall to act as a measure of average internal house temperature. There are two flow sensors on the cold feed to my 2 SunAmp DHW storage units to monitor DHW use and to help automate during-day DHW boost. There are 4 240V/20A SSRs used to switch the power to my (2-off) SunAmps, my (1-off) Willis heater, and my (1-off) circulation pump. These and the rest of my 240V household system were wired up and Part P certified by my electrician. These SSRs are switched by a 5V 50mA digital input, and so can be driven from an RPi or similar. (I used a I²C attached MCP23008A multi-port driver to do this, as this can drive 5V 50mA digital inputs, but its input I²C side is compatible with RPi GPIO specs.) There are many ways to "skin this cat", but whichever you choose for your control implementation your system will need to control some 240V/12A devices and take some input temperature sensors. My preference was to directly attach all such critical sensors and outputs. My heating algorithm calculates a daily heating budget in kWh (each midnight) as a simple linear function of the delta between average local forecast temperature for the next 24 hrs and the average hall temperature for the previous 24 hrs. This budget is then adjusted by the following to give an overall daily target which is converted in minutes of Willis on time. heat input from the heater mentioned above. a simple linear function of the delta average hall temperature and the target set-point (currently 22.3°C). This is a feedback term to compensate for systematic over or under heating. I initially calculated the 4 coefficients of the two functions using my design heating calcs and an estimate of the thermal capacity of the interior house fabric within the warm space. After collecting the first year's actual day, I then did a regression fit based on logged actual data to replace the design estimates by empirical values. This was about a 10% adjustment, but to be quite honest the initial values gave quite stable control because of the feedback compensation. The control system runs in one of three modes: No heating is required. Up to 420 mins of heating is required. The start time is set so that heating ends at 7 AM, and the slab is continuously heated during this window. More than 420 mins of heating is required. 420 mins of heating is carried out in the off-peak window. On each hour from 8 AM to 10 PM, if the hall temperature is below the set-point (22.3°C), then an N-minute heating boost is applied, where N is calculated by dividing the surplus heating into the 1-hour heating slots remaining. Here are two history outputs from HA showing some of the logged results. The LH graph is the slab temperature over the last 7 days. The general saw-tooth is identical from my 3-D heat flow modelling discussed in my earlier topic, Modelling the "Chunk" Heating of a Passive Slab. The 7 hr off-peak heating raises overall slab temperature by ~4-5 °C; well within UFH design tolerances, and no need for any HW buffer tank: the slab is the buffer. The RH graph is the hall temperature. Note the days where on-hour boosts were needed. (Also note that the CH system only updates the MQTT temperature data half-hourly, hence the stepped curves.) So the approach is fairly simple, and the system works robustly. 😊 And here is a screenshot of my HA summary interface, which gives Jan the ability to control everything she needs from her mobile phone or tablet.
  2. 2 points
    We left you with a poured slab and we were chomping at the bit to get the ground floor Nudura walls up before the end of the year. Well, I am glad to report we got there - almost 🙂 After getting the slab done, I figured I'd get ahead a bit and it would be a good idea to talk to someone about the waterproofing we would have to put on the outside the walls before we started backfilling. To cut a long story short using waterproof concrete in walls such as these is a complete non-starter, so Type-B waterproofing cannot be used. Visqueen's R400 Radon barrier is not an effective waterproofing method and so we now face having to use a Type A and a Type C waterproofing method - basically this will mean for us a waterproof screed being added to the floor with channel ducting where the walls meet the floor and the "egg-crate" plastic material across the screed and up the inside of the walls. That should eat into our contingency 💰 💰 💰 But also it meant a dash to get some waterproof slurry to paint round where the Nudura blocks would be laid the following morning and mixing and painting it on under floodlights (it's the dark grey stuff in the picture to the right). Oh what fun!! But, the following day we were up early to welcome out walls, the bracing and two fine chaps (Louie and Harry) from The Fell Partnership who would be helping us Day 1 to get the first row in place. We then scurried around unloading things off trailers and flat beds, and installing the waterbar between those pieces of upright rebar. By 10am we were ready to go. By about 2pm we had most of the first row in and part of the second row (see below). If it hadn't been for some non-standard corners in the design, we would probably have been at Row 3, but that's what you get for following a design religiously ✝️ (FYI - the T-corner is all to do with the design - don't ask yet) On the second day we were left to our own devices, I had to make a dash to collect some extra Nudura parts and some waterproofing equipment (due to the direction our waterproofing system now had to take) so we made a later start but still we were very pleased to get up to 4 rows installed. Day 3 we were ready to begin installing all the bracing system, and after hitting her head SWMBO was made to wear the Christmas present from her children. and on Day 4 it inevitably rained in Cornwall 🙂 , but before our help arrived again we had managed to just squeeze a block on to Row 6 (the final row before the first pour of concrete) After the help on Day 4, we continued to finish things off on Day 5 by constructing part of an internal load bearing wall, and a wall with the only window opening at this level which will be for the family bathroom. FYI - the rest of that side of the house will consist mainly of windows into bedrooms plus some extra small sections of walling (to be determined) Where we were not able to complete things before the pour happened (time didn't allow) was where the internal wall meets the external wall and there are two doorways to construct (this is why I said we almost made it). I will have to do these in the New Year, mixing and pouring the concrete by hand (just under 1 cubic m) so that'll burn off the Christmas pudding 🥣 A week later (during which we had some more high winds) I came back down to finalise a few bits (like lack of scaffold planks and bracing in some places) to be greeted by a snaky 🐍 wall. so that was all straightened up, the rest of the bracing fitted, and the Nudura joist hangers inserted. (Between straightening and the pour we had Storm Barra, but my remedial work held up nicely) I won't bore you with pictures of hunky men doing manly stuff with concrete pumps etc. but suffice to say it all went very well, with no leaks or blow outs so "he who shall not be named from Channel 4" would have been very disappointed if he was allowed onsite. And so, last weekend (after a midweek pour in the remnants of Storm Barra) I was able to deconstruct the bracing and we are now the proud owners of some freestanding, high-wind-proof walls. Really happy at the attention to detail that Louie and Harry paid to ensuring the walls were straight and true before the pour began - right up my street. So now we have a tidyish site again (for a short while) ready for steels installation in the New Year. We have to finish off the internal wall, then waterproof and backfill outside, and install joists and flooring before we can continue with building the upper floor walls. We're hoping that by middle of next year we can start on those upper floor walls. So until 2022, and the inevitable next lockdown, I wish you all a very Merry Christmas 🎄 and a Happy New Year 🥳
  3. 1 point
    Well the combo is coming together and my wife insists that I make the controls as clear as possible "in case your not here". I wondering what she means. Still a lot to do though..
  4. 1 point
    Finally having time to update you(and me) about the progress. It s happening fast now. Finally. https://tintabernacle.blogspot.com/2021/12/the-frame-is-going-up-fast.html
  5. 1 point
    Greetings! Apologies for the crass title but I am still a kid at heart. 😇 After a brief delay due to Covid-19 the carpenters were able to attend site and erect our timber frame. Thanks to the accuracy I insisted on and ensured for the coursing blocks the sole plates were a doddle and were done in no time at all although we did have a bit of rain and I had to get the puddle pump out! We used Flight Timber for our timber frame and they have their own lorries with cranes built in and so each stage of the build was delivered by the lorry and then craned in to place. Here’s the ground floor panels arriving. It took them just 2 days to finish all the ground floor external and internal wall panels. The speed of it all is very impressive. Then the posi-joists arrived These took a few days to do but thanks to the 8mm designed deflection and 300mm centres they are rock solid even across the 6.2m spans. It’ll be a bit of a nightmare trying to run MVHR, electrics and plumbing but we won’t have any bounce on the floors! Plus when the sun shines through it creates some lovely lighting effects Next we had a weeks delay as Flight didn’t have any chipboard flooring in stock as they were let down by their suppliers. This was a frustrating delay but with the current material shortages not one that I should really grumble about too much. It was eventually delivered and the chippies got on with laying it and the first floor panel starter plates. And then it was on to the first floor wall panels. These took 2 days to do as well and so within a couple of weeks of starting we had both floors done ready for the attic trusses They were also a couple of days delayed due to Covid-19 but arrive they did They didn’t take long at all to go up and I love the symmetry of them Then it was another week or so getting the roof finished and building the vaulted ceiling in our entrance hall etc and then they were done! It was 18 days on-site from start to finish. Amazing to see. I took some time-lapse footage and you can see the video below: And so we have a superstructure! The roofer is not far behind so my next blog will be about the roof slates and Solar PV array. Thanks for reading and until next time…
  6. 1 point
    It's been over a year since we finished our home and I thought it would be good time to reflect. We have not had any major snagging issues with the house. The only product which required some additional work was the LVT flooring, we found thermal expansion was causing some warping. This has since been resolved with the addition of two expansion joints. In my last blog post I discussed how we were heating the house with just a wood stove during colder times of the year. In the first year I had to build up our wood stocks quite quickly, but going into the second year I decided to focus on collecting sticks. I'm still burning home grown split logs but I find that collecting a bundle of sticks to be a great way to maximise the amount of firewood. By the end of the summer I had collected quite a large pile. Nearly all of these sticks are either dead wood, wind blown trees or from trees needing to be cut down for other reasons. In these times of uncertain electricity and gas prices, it's very satisfying to be able to collect and store fuel to heat my family. For our hot water, our exhaust air source heat pump has been very efficient and with no need for electricity to heat our house our usage has been 10-11kWh a day. During the course of the self build I collected a huge amount of stones from the ground. I used the smaller ones to extend the parking area. The larger ones I sorted and then had a go at dry stone walling to line the ditch. In the spring I stumbled across videos on YouTube by Charles Dowding discussing his no dig approach to gardening and I decided that it would be great to grow more vegetables. My take away from his videos was that having access to large amounts of compost was critical to making this a success. I started to hot compost from lawn clippings, hay and a variety of woody materials. I recycled the last of the pallets from the self build to make this four bay system By the end of the summer I had a huge pile of homegrown compost. This is now ready to grow some vegetables in the Spring, any suggestions?
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