TerryE

SD cards have a very primitive controller and don't support TRIM. Whatever the weakness of SSDs they are materially more reliably than SD cards if you are using them as a RW device. Whilst the RPi3 can now boot off a USB attached FS, I find it just easier to leave the /boot partition on the SD. It's almost never written to, so this is fine. If you do want to use an SD for R/W then the trick is to use a reasonably large one so that the FS utilisation is small. Also from what I gather one of the main reasons for failure of an SD isn't wear exhaustion, but rather a power fail whilst the RPi is in the middle of a write to the card. You can avoid this entirely with a small battery backup hat which can keep the RPi up for 10 mins say and does an orderly shutdown after 5min without power, so that any unwritten buffers are properly flushed to SD and written through before the FS is properly dismounted.

This is yet another RPi thread. Some of you might be interested. I was originally intending to use 2 RPis for my HA, but on reflection I have decided that one of the two is hardly doing anything and it actually makes life simpler to collapse all of the functions down onto one RPi. I had considered moving to a more powerful SBC (such as the one discussed in this companion thread) but in the end I decided to stay with an RPi for now. This will host a MQTT broker, a MYSQL (InnoDB) database, a limited lighttp webservice and a Node RED instance, all on a minimal headless server -- that is no desktop and only SSH access for login and file transfer. I want to keep battery backup (mainly for orderly shutdown on power outage) and some reliable mass storage device and this really means SSD if I am going to be battery backup friendly So I really want to cover two topics here: using DietPi to provision my server, and some issues around SSD performance. DietPi. This makes building the Pi a doddle. You download and image onto an SD card a smallish (<100Mb unpacked) provisioning file system and if you want a headless install there is a single config file, /boot/dietpi.txt, that you need to edit to select your Wifi credentials, some passwords and software that you want to install. Plug it into the RPi, turn it on and come back 15 mins later and you can SSH into the build server. There is a simple terminal-based menu system for doing further configuration S/W installation, etc and also maintenance functions such as move the root partition onto a USB-based device, e.g. memory stick, HDD or SSD. and so configuring the SSD is a couple of click operation. Once you've done this, you still have /boot on the SD card, but the OS and user directories run off the SSD (in my case). All very good. SSD performance. Because of the underlying page-base nand storage technology, this does have some significant performance and lifetime issues if not actively addressed by the OS and the filesystems on the SSD. The RPi uses a Linux family OS, and both the OS kernel and the main FS used on the RRi (Ext4) are SSD aware, and the OS includes a TRIM function to enable the SSD controller to align its garbage collection to the use of the file system. Without this, the performance of the SSD can significantly degrade over time as unused clusters my contain garbage and the whole page need erasing and rewriting to do a write. (This is a good article explaining how TRIM works) The gotcha that I've found is that the TRIM command is a native ATA one, and Linux does support this for directly attached SATA disks. However, it is not in the standard USB FS interface, so the USB-to-SATA chip needs to support ATA pass-through, and the Linux kernel driver for these USB chips don't yet support this. So the nice features which prevent SSD performance degradation effectively don't work with RPi's USB attached SSDs. Bugger.

IMO, we can get a bit too paranoid about this. If you pack something loose around the pipe insulation such as wool insulation or even rockwool, then the difference in local U value will be fairly small. OK, you might lose the few W along the pipe, but it's also leaking waste heat so it will probably be a wash. The odd few W here and there isn't going to matter, so long as there isn't a material thermal break which is causing a cold spot near the condensing temperature. In this case if you insulate the pipework and any gaps around the pipework, then I doubt that you would be able to detect any difference in surface temperature with an IR thermometer.

We are in the process of carrying stuff into the new house (which is next door to our old one) because we are vacating the old one next week. I thought that the temperature in the new house was dropping a bit and I put it down to the fact that we were constantly opening doors to walk furniture and other contents in. So in the end I checked and the slab had definitely dropped a couple of degrees in temperature. What was going on? It was then that I realised that I have made a boo-boo and the heating hadn't been on for over 2 days!! Well insulated houses stay warm for a long time without being heated.

I have never had any such probs with compression fittings for normal house plumbing. The pastes work well, but I have found that they tend to set hard, so can be problematic if you every need to break the joint. And Peter, your installation counts as a piece of artwork!

Sounds to me like you've got a plan ?

If you've seen my posts on my plumbing then you will see that this is pretty much my heating system. 7 hrs of Willis heater on E7 keeps my house to temperature.

AFAIK, something like this falls under the scope of your planing permission. Read the NoD. It will normally include a clause like: The development shall not be carried out otherwise than in complete accordance with the approved plans Drawing Nos: ... received on the DD Mon YYYY, unless a non-material amendment is approved by the Local Planning Authority under the Town and Country Planning (Development Management Procedure) Order 2010. Reason : To clarify the permission and for the avoidance of doubt Unless the Velux literally can't be seen by your neighbours, I suspect that the LA will treat this as a Minor-Material Amendment rather than a NMA.

Doing copper plumbing is a skill which takes some practice to acquire. So my suggestions are: Don't bother, and If you really want to then do it at the bench and Use compression fittings to joint your work to the stubs coming out of the wall. The videos say that you don't need PFTE tape, but when I do this I find maybe 20% weep, so my suggestion is at least 4 turns of PTFE covering the olive and you just won't get weeps. Less hassle. Or Use the Peglar Tectite range if you want some smart looking joins. They are a bit pricey, but they are the dog's bollocks, and wont leak. Just make sure that your copper pipe is clean. You can use Hep2O fittings to connect Hep2O to copper. If you use Hep2O then ready the Wavin guide at least a couple of times and never forget to put the inserts in. A decent pipe cutter is essential. Use a ratcheting cutter for the Hep2O -- it's just easier. If you need manifold work, just use the Hep2O plastic range. The lifetime isn't as good as the brass ones, but you should have sold the house long before there is an issue. Also remember to check that you copper pipework isn't being used for earth continuity anywhere in your house, because if it is then you need to add 10mm straps copper to copper to preserve continuity or get your electrician to do it properly. Also remember all of the bollocks about controlled activities v.v. BC when it comes to selling your house.

@Nickfromwales, Nick, I think that your approach / design template will fit many architectural layouts where there are clusters of HW services physically remote from the boiler / DHW tank. it will provide responsive HW without significant delay, and without any material running cost. So long as it is implemented as you describe. My concern is that few plumbers are at your level of sophistication. Proper insulation is essential. The asymmetric 22 / 10 loop plus trickle flow HRC pump will help. Activity based priming will help, but you could consider on of the new Doppler radar sensors in lieu of PIR. That being said, our setup where there is about 1m of pipe between the SunAmp and a heavily lagged HW manifold is a lot simpler. The first person in the morning has an extra 30 sec of so delay as the manifold warms and that's it.

Just thinking off the top of my head if we are talking about 1W/m ish and are happy to have, say, a 3°C drop along run. Again picking numbers out the air say 10m, then this would be radiating roughly 30W and 10m of pipe has 10*pi*9.8^2l or just over 3kg of water in it, so the flow rate needed to achieve this would be tiny.

The data sheet quotes 0.034 W/(m ∙ K) for the 25mm insulation so for a hot return circulate at ambient + 30 °C and a 15m pipe run this would work out at roughly ⅓ kWh per day.

Nick, normally I would do, but we are aiming to move into the new house in 5 days time +/- and we have 3 "kids", 2 spouses and 1 grandson staying for Christmas! So every room has to be commissioned and things are a tad hectic here. ? Since we are only working in the new house and only run the hot occasionally, I have noticed that heating up the hot manifold does add a good 30sec lag to the flow coming hot at the tap, but the manifold box is pretty lagged so it then only loses a few degrees an hour. But I put 2 hours of heat, E7, into one SunAmp every couple of days and that keeps the hot available.

Clive, you daft bugger. We use one in our house every night 1-7am, but we are on E7. Mind you, the washing machine is now in the new house and we (or to be honest Jan, so far) just hang our clothes on a multiline indoor dryer which is in the service room in the warm loft and the MVHR extract takes care of the moisture. But my daughter just uses a couple of airing racks either side of a dehumidifier and she gets her clothes dried fast with no humidity problems.

Dave, is there no way that you could convert this to dead space, e.g. shuttering around the skirt of the caravan and maybe banking soil up to floor level or whatever. Can you get some old fashioned bales? You could create a skirt from them.

Get yourself a small dehumidifier and a cheap timer switch.

How about http://excelcalculations.blogspot.co.uk/2012/12/heat-loss-from-insulated-pipe.html.

My immediate thought is to use 10mm runs for all of the low flow runs -- the hand basins and toilets, and only use 15 for the baths and showers, and keep the manifolds central. Route the 15s first, then the 10s and it doesn't really matter that much if you have to take a slightly roundabout route for the 10s because they have a third of the cross section of the 15s, so even if the run is twice long, there is still less dead water in the pipe runs. The alternative is as @Nickfromwales says and to use an HRC, but in this case you will get heat losses because of the standing water at 43 °C or whatever in the main 22mm even if insulated as it will be radiating 24hrs a day. One to do the sums on, I think. I defer totally to Nick on matters plumbing, but it's the potential heat losses that I would check.

@Ferdinand, I wasn't being sarcastic. My point was that dehumidifiers (as in this case) take X kWh to condense out humidity into water and in doing so release 3X kWh of heat into the environment -- plus the X kHr which also ends up as waste heat, so 1X in and 4X out.

40l = 40 × 2200 kJ = 24 kWh latent heat released for 8.4 kWh electricity so a CoP of ~ 4:1 -- pretty good, eh?

Thermal gain? Our new house is now toastie just heating it overnight with the Willis heater And we haven't moved in yet!

Nick, there is a caveat here. If the total residual evaporateable water is too great and @AliG prematurely starts to seal the house, to heat it and to lay coverings like carpets then he's going to beset by mould and damp problems. I've just picked up A's last cross post and the 40% RH is a baseline; if the house is sealed it will only climb from that. A, if you do want to start sealing and heating the house then IMO industrial dehumidifiers are an essential precaution. What does our resident scientist say, @JSHarris?

@Ian, that will be true for external walls, but not for internal ones and any floor slabs, and as you say the latent heat loss will still be an issue.

When was the concrete poured? We only have 10cm across most of our slab and it still took 10 months to dry out properly (Nov -> Aug). Before that if you laid a square of polythene on the dry slab for a week or so, then you'd see the colour change as the residual moisture came to the surface. So, I was thinking also about this. 600 tonnes of concrete = maybe 100 tonnes of water to be evaporated off. Let's guess 100 tonnes of water, this will take 2,200 × 1000 × 100 / 3600 = 61,000 kWh latent heat (loss) of evaporation. Even if it was half that, this is still a lot of heat energy. If the structure is damp, then cranking up the temperature will mean that more dampness will evaporate off and the internal RH will just stick near 100%. So I'd concentrate on getting it properly dry before trying to warm it up too much. As @PeterW says, a couple of industrial dehumidifiers running around the clock will condense out this water and return the latent heat back into the structure.

Ouch!! If you look at my last blog post you will see my calcs: And I reckon we have 33 tonnes of concrete / wood/ plasterboard within our envelope. 600 tonnes seems a huge amount. At the moment we aren't living in the new build so we don't have indirect waste heat in the house's heating mix, but my rough estimate is that 7hrs @ 3kW (my E7 quota) is keeping the temperature level but I am slowly cranking the base tenp up with another 2 hrs. We are now at a toasty heat level. after about 10 days of heating. All for < £2 / day.