Jeremy Harris

Who has quoted that a foul drain has to be 3.5m from a water supply pipe? Sounds wrong to me, as if that was the case there are a lot of lanes around here where there wouldn't be any sewers and water pipes. I can't see anything in building regs to support this at all, as @PeterW says, I reckon someone has their units mixed up, and has assumed that 350mm is 350cm...............

Easy enough to do, just use a venturi eductor, driven by a fan that's sucking in outside air and using that as the motive drive to draw in cooking fumes. With a bit of cunning a bleed could be arranged to to inject some of the venturi drive air across the cooker before the extraction point, to help keep the system balanced. Venturi eductors are not that efficient, and one draw back is that you need to raise the velocity of the motive air stream a fair bit to get them to pull, but I think the idea still has promise. Given that Dyson have been using venturi eductors for a while in their fans and hair dryers, I'm surprised they haven't come up with one. The basis of a venturi eductor are the same as the water-powered suction pumps you may have seen in a lab, except in this case the motive liquid would be air, rather than water.

The building regs require access to AAVs for servicing, in fact it was one of the the things the BCO confirmed with me before giving the go ahead to fit one. I fitted ours in the eaves space, as our house in room-n-roof, so there are sizeable crawl spaces down either side. You can fit them so there's a removable service panel, but they do need an air supply to operate, so need to be somewhere where they can draw in air. There are several ways of providing a service panel that might work. In one house I fitted a shower valve that needed rear access for maintenance to a tile that I fitted in place with sealant, rather than tile cement. I did once have to get at it and it wasn't too difficult to cut around the edge and remove the tile to gain access.

The snag is there is no SATA interface available on the RPi, only USB 2.0.

AFAIK, this isn't possible. You can certainly boot from a different SD card, plugged into one of the USB ports, but I don't think you can run a RAID controller over USB, and bear in mind that the SD card slot and the USB slots are all USB 2.0 on the RPi, so not that fast. The problem with SD cards is primarily as @TerryE has already said, their internal controller doesn't give the full of degree of freedom needed to manage locations in the storage. Using a board with a dedicated storage interface, either SATA or eSATA, means that the operating system can have better control of the filing system, and it is also massively faster. The USB 2.0 interface to the SD card is a fairly hefty bottleneck, in fact the USB 2.0 interface in general is a bottleneck. I've been using a RPi 3 as a file server, with a 1 Tb HDD plugged in to one of the USB ports, for a while. The RPi boots directly from that HDD, which is a LOT quicker than booting from the SD card, but file transfer speeds are still slow, because of the USB 2.0 speed restriction. It's a shame that the RP Foundation have no plans to introduce any new versions, as an RPi 3, with a SATA port and USB 3.0, but with all the other stuff as-is, would be a big step change and make a lot of people happy, I'm sure.

I've already had one SD card failure with a RPi, so now completely boot from a HDD, with nothing on the SD card. The real problem is the RPi not having anything but USB interfaces, even the SD card is on the USB bus, I believe. I've been tempted by some of the newer SBCs that have a SATA or eSATA port, as at least you can then have much better control of any HDD/SSD that's plugged in. The problem is that the RPi has such a massive user base, so if switching to one of the other SBCs then there's no where near as much support available. I'm still tempted to try, though, and might get something like a Banana Pi to play with.

There's also the effect that all practical sensors use some power, even if it's a tiny amount, and some are generally compensated for self-heating from that power to some degree, if they are "smart" sensors, like the DS18B20 or similar. "Dumb" sensors, like thermistors, have to have a current flowing through them to measure their resistance, and that current very slightly heats the sensor. Airflow over it will then enhance the rate of convective cooling and change the shape of the resistance versus temperature curve.

Probably best to go back to basics and assess the boundary parameters of the thing you are trying to measure. In this case, you're looking to measure changes in the temperature of atmospheric air masses at a particular height. Because of natural air movement, the scale of the terrain etc, these changes will only happen over large areas, certainly many tens of metres across, most probably hundreds of metres across. Additionally, you need to separate out still air temperature (the thing you are trying to measure) from the cooling effect of air motion on the sensor, plus the cooling effect of evaporation if the sensor gets wet. That means the sensor needs to be in a shielded location where it won't be affected by either the air flow around it or moisture. Decide how accurately, and how quickly, you need to measure the air temperature, then look at what is realistically achievable with any form of sensor. We used to measure outside air temperature using a sensor tucked inside the static tube of a pitot, inside the head but not directly affected by the air flowing around the head, because it was buffered via an air pocket. That generally worked well, but I can say with certainty that atmospheric air temperature changes are both small and gradual, over a wide area. We used a mix of different sensors, from fast reacting thermistors and diode junctions (both a complete pig to characterise and linearise if you want accuracy) to thermocouples and hot wire sensors. The latter can react very quickly but are more sensitive to accelerated convective heat loss, so are better for measuring air flow rate than they are for measuring temperature when placed in a shielded container. If you want to experiment, without having accuracy then you could try just using a thermistor probe, placing it in a well-shielded location, and measuring the variation of resistance. It won't be linear (if you want to get the temperature from one you have to compensate for both offset and the inherent non-linearity) but you can get very low heat capacity, fast response time, miniature glass bead thermistors (I probably have a few somewhere). My guess is that you will rediscover what others have found, that air temperature doesn't change quickly and that the variation in temperature across small air masses (those with dimensions in tens or hundreds of metres) is very small indeed. My experience of doing this with aeroplanes has been that by far the biggest factor is altitude, specifically the environmental adiabatic lapse rate, which varies with humidity, but is around 2 deg C per 1000ft in still air (more info here: https://en.wikipedia.org/wiki/Lapse_rate ). Finally, you can get the DS18B20 to read to 9 bit resolution in around 94ms, if that sort of resolution is good enough for what you are looking to do.

A plain DS18B20 takes around 750ms to measure and output a 12 bit temperature, already calibrated in deg C. Easy to read and display the data, too. https://datasheets.maximintegrated.com/en/ds/DS18B20.pdf

Go up there for a holiday. Stay in one of the hotels in Portpatrick (the Fernhill is pretty good, avoid the Portpatrick Hotel up on the clifftop). Drive around the local area and see what you think, the area is great and it's the most friendly place we've ever stayed. The main issue around there is unemployment, when we left it was still running at around 20%, and we were the biggest local employer, so things got worse when we closed down. The only employment locally is the creamery and the ferry port, everyone else is just scraping a living from smallholdings and some bigger farms, plus some fishing.

I used to drive past that twice a day, driving to and from work at West Freugh, from Portpatrick. It was still a dairy farm back then. Lochans is a nice little village, inland and far enough away from Stranraer. There was a fair bit of housing development going on there just before we left, so my guess is that Lochans may well be bigger now than it was. There's no pub there, though, or wasn't when we left. Portpatrick has the advantage of half a dozen bars, including at least one really good music bar, with live traditional music at least one night a week.

Looking carefully at the manifold, it seems that the right-most loop is always on, as it has no actuator, but is fitted with a cap to hold the valve open, so it is acting as the bypass.

It should be set to G83, but TBH, it probably doesn't make a jot of difference with a 16 panel system, as I doubt the peak output exceeds the 16 A per phase limit of G83 anyway, even with the inverter set to G59. There's no practical difference between G83 and G59 in terms of how the inverter operates, or the safety provisions, and the chances are that the inverter may well be limiting the output to less than 16 A anyway, based on its rating. I'd not worry about it, if it were me.

It's further from civilisation than it looks, though, as if you want to do any serious shopping (DIY stuff etc) then you're faced with a 60 mile each way drive, either up to Ayr and back or across to Dumfries and back. We found it was easier to get the Seacat across to Belfast - 20 mins and you're right in the centre of Belfast practically. No good for heavy stuff, as you can't take the car, but as a shopping centre Belfast is pretty good. The main snag is that none of the roads are great. It's nearly two hours to get to the border at Gretna, for example, or about an hour and half to get to Glasgow airport. Stranraer is also a bit of an iffy place, very rough at night. Out on the Rhins peninsula at Portpatrick it's like a different planet though, and a very nice place to live indeed. House prices are low up there - when we moved from there to West Sussex we ended up paying nearly double for a smaller house, and went from a 30% mortgage to a 95% mortgage, not nice. Luckily I had relocation assistance that covered the first five years of the mortgage cost difference, and by then inflation had increased the value of the house we bought, so the LTV on the mortgage came down a great deal.

TBH, I've stopped using it for anything except permanent threaded (iron) joints now, as Jet Blue is far easier to use on compression joints, as it can be undone more easily. The liquid PTFE stuff works very well (but is a PITA to get out of the bottle) and if you want to take the joint apart you need to warm it up a bit, which makes the sealant go soft. Now I use a mix of PTFE tape on any threaded plastic fitting (there are a few of those in the water treatment system, on filters mainly), liquid PTFE on any threaded metal fitting that I don't think I'll need to take apart again, and Jet Blue on all other metal fittings.

Nick, You could look at doing a version of what I did with our electrician, but with the client doing the heavy stuff and you imparting your knowledge. I'm pretty sure that one of the biggest problems many self-builders have when it comes to doing work themselves is a lack of confidence, as they are tackling something unknown. Just having someone around who has masses of knowledge and experience and who can help them tackle work they otherwise might not feel able to may well be something a fair few would appreciate, and pay for. In your case you may not have a properly working left arm for a while, but the rest of you still works OK, and the most important stuff is in your head, anyway. There has to be a way of using that to tide you over while your arm gets sorted out.

No problem, if you include the window and door areas and U values I can work through the heat loss spreadsheet pretty quickly, and give some more useful data for you.

This thread has prompted an idea. Some of us are competent to teach others to do some basic stuff, I'm sure. There's nothing like an hour or two chatting and working through some typical jobs, like making soldered or compression pipe joints, making plastic pipe connections, and other jobs, like fitting MVHR stuff, and all the myriad jobs in a build. How about setting up a "I'll volunteer to help you learn about that" group? I'd happily take the odd day out to drive up with some tools and stuff to spend a few hours helping someone else pick up some of the skills I've acquired, for example. Anyone else think this is worth exploring further as an idea?

Sorry, I can't read the image on this screen. To get the U values for the walls, floor, roof etc, you need to work out the impact of all the materials, plus any sealed air gaps. The method for doing that is obtain the lambda value for the material, work out the thermal resistance for each layer, add up all those thermal resistance figures, and then take the inverse to find out the total U value. I have some simple U value calculators to do this for common building materials (timber, OSB, plasterboard, sealed air spaces, insulation materials, concrete, stone etc) but rather than guess, if you can give the build up of the walls, ground floor and either the ceiling or roof (depending where the insulation is) I can then post back here the calculation for all to see and use.

Most painted surfaces of any colour will usually be around 0.9, probably the reason that these things are calibrated at that value, so it should read OK.

Yes, most of them are fine. I have a similar one, bought from ebay a few years ago, and it works pretty accurately, at least as accurate in terms of measuring heat from surfaces as the thermal imaging camera I have. Like all these types of device, it will be calibrated for a surface with an emissivity of around 0.9, so if you point it at a surface with a substantially different emissivity it will give an incorrect reading. There is a handy list of surface emissivities here that may help give an idea as to what surfaces may give errors: https://en.wikipedia.org/wiki/Emissivity#Emissivities_of_common_surfaces

Parish Council objections do definitely count in the scoring mechanism for triggering an application to go before the planning committee, rather than be decided by the planning officer, using delegated authority. Avoiding an application going to the planning committee is, at least around here, something very well worth investing in, as it's a political nightmare when compared to dealing with a planning officer. Here, any more than 5 objections (and that includes the Parish Council) results in an application automatically going to the planning committee, so whilst it's true to say that Parish Council objections are often ignored in some respects, they can add to the total number of objections and trigger the situation where the decision is taken out of the hands of the planning officer.

My experience has been that the granules are both more effective, and, if you want to save more money, they can be regenerated, in the same way that older NBC respirator filters are regenerated. To regenerate used carbon granules you need to lay them out on a tray and heat them to a temperature that will drive off all the volatiles that they have absorbed. In general, heating to around 250 deg C in a well-ventilated area for around 2 hours will more or less regenerate the size of granules used in these filters. An alternative, that works just as well (perhaps better in some ways) is to place the tray of granules in a very sunny location, so they get direct sunlight. Around half a day of being heated to around 30 to 40 deg C and exposed to sunlight should do the job OK. Might not work too well where you are, though......... If you want to turn the granules into highly activated charcoal (which is better at absorbing volatiles) then you could look at making up a superheated steam regenerator. Not for the faint hearted, as you need a pressurised boiler capable of blowing hot, dry, steam over the carbon at around 300 deg C or so.

Mount the towel rail to a plate (perhaps polished stainless) that looks as if it's flush to the wall. Behind the plate secure it with some slightly resilient mounts plus a load sensor in the centre. Use the change in weight of the towel rail to sense whether or not a towel is present. You could also detect the change in weight as a towel dries, to turn the rail off, or turn down the temperature. Personally I think you have to ask whether any sensor system is going to work more effectively, or be sufficiently more efficient that it will recover its capital cost, than a simple time switch. I have a cheap and simple programmable timer on the landing, that controls the power to both the bathroom towel rail supplies. Each towel rail also has it's own switch, so we can turn them off if that bathroom isn't in use. The timer comes on for an hour in the morning and and hour in the evening, which is long enough to get the towel rail up to temperature and the internal thermostat to operate. This seems to work OK, and combined with the way the MVHR dries towels pretty quickly, anyway, seems to be as much automation as is really needed.

Very likely. With temperatures as low as you've been having the air is going to be pretty dry by now, and one snag with the caravan being so cold, and probablyu not very airtight either, is that the humidity level inside it probably isn't getting very high, either.