Jeremy Harris

Right now, it seems that some building control bodies will only accept a lodged electronic EIC from a member of one of the competent person schemes. Technically this seems wrong, as there should be the option for any competent person (not just someone registered with one of the cartels) to do the design and installation, with someone that holds the required third party inspection and test chit coming along afterwards to inspect, test and sign off the work. In practice it seems hard to find anyone that holds the required third party inspection and test chit. I tried, and failed, as it seems that none of the Part P cartels encourage their members to do third party inspection and test, and none of the local building control bodies here had anyone on their books that could do it. If this option was practical, then the person doing the work would still have to sign off the design and installation parts of the IEC, and the person doing the third party inspection and test would have to have a degree of trust that the person that had done the design and installation was competent. As far as liability goes, then in my view doing a third party inspection and test is no different to doing an EIRC on an existing installation, and that doesn't require membership of any of the Part P cartels. I do a few EICRs, for example, and being retired I'm prohibited from being a member of one of the cartels (none will accept retired people as members).

On the subject of MFTs, you can often pick up a second hand one for a couple of hundred pounds or less. Mine's pretty old now, but IIRC it cost me about £150. It's a PITA to use, as the test button is on the right (must have been designed by a left handed person), but it stays in cal and I knocked up a proving unit to check it before I use it, just to be reasonably sure it's still in spec (no point paying for a proper calibration for my use, anyway). It seems that some electricians MUST have the latest MFT, so often seem to sell off perfectly good units on eBay, Gumtree etc. I bought mine via a friend of a friend years ago, who bought it back when part P first came out, then started working for one of the big contractors locally and got issued with a much nicer machine.

Still no COP given, but, as we know that this is a non-inverter unit, the input power will always be between 3.5 kW and 4.8 kW. That gives a COP for the A-3/W35 condition of between 1.67 and 2.28, and a COP for the A-7/W35 condition of between 1.56 and 2.14. Frankly, these are not great figures, especially as the unit cannot modulate down if required to deliver less than full output. For example, the figures for my 7 kW Glowworm (really a Carrier with a different badge) are: A7/W35 power input = 1.82 kW power output = 7.2 kW COP = 3.96 A7/W45 power input = 2.32 kW power output = 7.4 kW COP = 3.18 This is an old unit, too, so not as efficient as some of the newer units available. I bought it in 2014, and it was old stock then, having been made in 2012, so it's 7 year old technology, yet seems a fair bit more efficient than the Cool Energy unit.

How is the electrician who signs this off going to be able to sign to say that he has seen all of the cable runs, that all are in compliance with the requirements, including supports, clipped securely at not more than the maximum allowable cable clip spacing, cable physical protection provided where required, cables in both the right zones and at least 50mm below surfaces, no serviceable connections in inaccessible locations etc? Is the electrician going to lie when he "signs" the IEC and states that he/she can confirm that all wiring is run as per the requirements?

I think this is probably related to supply voltage variation. It's a non-inverter drive unit, so will run at a higher input power with the supply at the maximum allowable (probably 253 VAC, as that's the UK grid max) than it will when run with their lowest supply voltage (stated as being 220 VAC, but could be as low as 216.2 VAC for the UK 230 VAC nominal supply). The compressor probably isn't a resistive load, so my guess is that there might be a significant input power variation with supply voltage.

Compliance with the law when it comes to electrical work is fairly complex, as unlike gas work there is no requirement to adhere to any standard in order to ensure a safe installation. BS7671:2018 isn't law, and doesn't have the backing of statute, and whilst adhering to the guidance within it may be deemed to absolve any individual from liability in the event of an accident, it would not constitute a complete defence, and it's quite possible that someone who has followed the letter of BS7671:2018, and then been prosecuted for negligence as a consequence of an incident arising from the work they have done, could still be found guilty. I must have dealt with several dozen cases where proving negligence has been involved, and none of them have ever been clear cut. Thankfully 99% of them never get to court, but if they did then I can pretty much guarantee that just adhering to guidance would not be enough, on its own, to get someone off the hook. BS7671:2018 is full of incomplete advice, as well as the occasional bit of conflicting advice. For example, BS7671:2018 mentions that the total demand should be taken into account when inspecting/testing an installation, but is silent when it comes to the detail as to how to do this. Clearly this is a critical safety issue, as it's well known that running the cut out fuse at close to, or in excess of, its rated current for long periods of time will cause it to overheat. There are also examples where such overheating has cracked and damaged the fuse holder and housing, such that live parts are exposed. The OSG (again, just guidance, not law) has some advice about calculating diversity, as ONE way of estimating the likely maximum load, but it's common knowledge that this isn't either foolproof, or even that applicable today. For example, lighting circuits are most probably far less lightly loaded than the (very old) diversity calcs in the OSG might suggest, due to the widespread use of low energy lighting. Equally, we now have some high power loads that aren't yet specifically included in the latest OSG guidance on diversity (or at least aren't yet in my 2018 copy of the OSG). A common approach taken to try and estimate maximum demand is to fit a clamp meter to the tails and leave it switched on in peak hold mode for a day or two. This works well enough, but nowhere in BS7671:2018 does it state that this is an acceptable method for ensuring that the maximum load is within the supply rating. In fact, pretty much all that BS7671:2018 has to say on this is:

You need to make sure you're comparing apples with apples when looking at power output and COP. For example, at A7/W35 (which is an unrealistically optimistic figure for anything other than heating) then the IVT is rated at 9 kW and the Cool Energy unit is rated at 9.4 kW, so nothing much in it. The IVT has a rated COP at A7/W35 of 2.6, but rather significantly, the Cool Energy specs don't seem to quote the COP for these conditions at all. Why not, I wonder? Looking further, the Cool Energy unit gives a rated power input of 3.5 kW, and a maximum power of 4.8 kW, so that means the COP for 9.4 kW output is probably somewhere between 1.96 and 2.69 (the higher the COP the better the efficiency). All told, it looks as if the Cool Energy unit is probably less efficient than the IVT, especially as we know that inverter drive heat pumps tend to give very much better efficiency under light load conditions (ours pretty much always operates with a COP of over 3.5, despite the spec giving a lower figure).

I think the snag with water in the refrigerant is that it can cause permanent damage, so degassing the unit, giving it a good long time at hard vacuum to dry it out, and then re-gassing the unit might not fix the problem, if the water has actually damaged the insulation around the motor windings in the compressor. It might be worth doing, but I'd guess you're looking at around £300 to de-gass, vacuum and re-gass the unit, with no guarantee that it will fix the problem.

@DeeJunFan, That advice you've had is spot on. Moisture in the refrigerant would be my best guess as to the cause of the failure in the first place. Hard to prove that it's a manufacturing/commissioning fault now, though, even though I suspect it may well have been.

This sounds very much like a compressor that's suffering from an insulation breakdown when it warms up. Not a particularly unusual failure mode, I've seen a fair few electric motors over the years that have tested out OK when cold but then develop a leak to earth when they warm up. Replacing the compressor is a simple job mechanically, but does mean degassing the unit, most probably brazing up the pipes to it, putting it under vacuum to get any moisture out (and it may well be moisture in the refrigerant that's the cause of the problem) and then re-gassing it. The snag is that the likely cost of a compressor replacement, including the labour, will be a fair chunk of the price for a replacement ASHP. If it's not covered by warranty, then I think my inclination would be to look around for a replacement unit, as the odds are that will be a lot quicker to fit than replacing the compressor on your existing unit.

Yes, no problem at all. I got guidance from HMRC before buying the unit and they assured me that I could reclaim the full Danish VAT (25%) as long as I provided proof of the exchange rate on the date of purchase. I believe that @PeterStarck did much the same, as he bought his unit from the same Danish supplier.

Agreed. This is essentially what my simple heat loss spreadsheet does, with some limitations, as I wrote it for a house that has no thermal bridging (all thermal bridges were pretty much entirely designed out).

It varies a great deal. In warm weather, with a light foot, you might manage around 230 Wh/mile, in cold, wet weather, then 350 Wh/mile might be more typical. Since November last year I've been averaging 284 Wh/mile, over a mix of long and short trips. Short trips are the worst, in winter, as initially heating the car up takes a fair bit of energy. So, if you were paying 5p/kWh and charging at the normal domestic maximum of around 7 kW, with an average consumption of around 275 Wh/mile, then 4 hours of charge would get a bit over 100 miles of range, for a cost of around £1.40, or 1.4p/mile. I charge in winter at E7 rates, so 8.148p/kWh, so can add around 178 miles of range on an overnight E7 charge, at a cost of around £4.00, or about 2.25p/mile.

I was after a very similar battery system, but it seems that the arrangement I thought I had for buying one has fallen through. Pity, as I've had the set up, cabling, shed to locate everything etc sitting waiting ready for the stuff to arrive, and the cash sitting herewaiting to pay for it, since early last year...

All I can say is that in our last house I fitted Multipanel to the whole bathroom, including around the shower. That was around 2006/7. Ten years later I was so impressed with the way it had performed, that I did both bathrooms in the new house with the stuff. The only thing to avoid with it is to seal the base as described, with a ~3mm thick bead of sealant under the lower edge, and to never use the plastic seal moulding that Multipanel recommend. That stuff is a design disaster, and should be avoided. There was a cheap and nasty laminate board around for a while, that used an MDF core. I can't recall what it was called, but it was far from being a good design. At least the birch ply in the Multipanel stuff is a heck of a lot more robust, and with a layer of decent laminate either side it's a pretty damned good product.

Going to be useful for anyone still running a Win 7 PC after the end of support in the next few months. I have two tiny fanless boxes here, sharing the same monitor etc, a Mint machine and a much-doctored Win7 Ultimate machine. both running on on very low power Kaby Lake processors (an "unsupported" i7-8550U in the case of the Win 7 box and a slightly slower i7-7500U for the Mint box). I'd love to get rid of the Win 7 box, but there are a handful of bits of software I regularly use/am very comfortable using, that won't (yet) run on Linux. The daft thing is that the much slower Mint box runs a LOT faster than the theoretically much faster Win 7 box, despite the fact that the Win 7 box now has 16 Gb of Ram, and both are running on SSDs. Still have my old a trusty Win 7 machine that I've had for years, too, although I don't turn it on much now, as it practically dims the lights with the power it draws. The fanless mini PC boxes are great, they idle at around 5 to 6 W, and run at 15 W maximum, whereas the old Win 7 box uses a couple of hundred watts or more, almost as much as everything else in the house added together.

I believe that it's best to fit the Willis heaters so that the immersion is at the bottom, rather than the top, so as to avoid getting an air pocket adjacent to the element that cannot be bled out. Alternatively, they can probably be mounted on their sides, with the side pipe poking upwards. I'm no expert, mind, it just seems more logical, and potentially a bit safer (in terms of avoiding overheating the small bit of element in the air pocket) if they are arranged like this. It may be that the MIs say different, and MIs always trump any other advice.

If using Multipanel or similar for part of the walls, then you have no choice as to order, the floor HAS to be laid before the wall board. There's no way to seal Multipanel if the timber edge ends up below the finished floor, and sooner or later it will fail. Tiling is sometimes better done the other way around, but either way works.

I purchased a 4ft x 4ft internal galvanised steel scaffold tower for our build, complete with extension legs, wheels, locking pads and a hinged door platform. It was definitely very useful through the build, but it was a bit heavy, and not that easy to set up single handedly. It was relatively cheap, though, and when I'd finished with it our plasterer bought it from me, so overall the cost was a great deal less than if I had hired a unit. Aluminium scaffold towers are a lot lighter and easier to set up, but also more expensive. A 4ft x 2ft one is barely adequate, in my view, although it is more compact. Being narrower there is a lot less working space, but it will get into smaller areas. The other issue with the 4ft x 2ft ones is that, without the bracing legs fitted they tend to feel a little less secure. In your situation I would look at getting an aluminium tower, as you will find it a lot easier to erect and dismantle. They are just a fair bit more expensive, though!

Mirrors my experience of always getting soft blockages in a fairly flat run of pipe. It may be that very slight variations in the fall along the pipe create enough flow variation to cause some "stuff" to just start to stick and build up on the pipe at that point.

In my experience, the usual cause for soft blockages like this is a build up of stuff (often partially dissolved toilet paper) on the walls of fairly flat runs of pipe, inside the house. I think what happens is that a few bits get stuck, then dry out partially and stay stuck, then more bits stick to them, until such time as the restriction is enough to trap a "wodge" of stuff coming down the pipe. At that point the liquid slowly filters through, leaving solids behind. Things gradually get worse, as more and more solids build up, and toilet paper, which usually breaks down into fine fibres fairly quickly, ends up not being in enough liquid to do so where the blockage is. The advantage of using strong sodium hydroxide (caustic soda) is that it aggressively breaks down organic matter, including paper. This fragments the blockage and allows it to be flushed away. The first house we bought had the foul drain run relocated, when the house went onto main drainage, and this resulted in a run across the back of the house that had very little fall. It used to regularly block, and at first I used to borrow rods, poke hoses down it, and generally get covered in muck clearing the blockage. Someone gave me the tip about using sodium hydroxide and I've never had to rod a drain clear since. A strong enough dose of sodium hydroxide solution, ideally as hot as a bucket can withstand, will generally work its way through any blockage within an hour, often less. This will also clear rainwater pipes etc that are blocked with dead leaves, as it will dissolve them just as well. On the shelf behind me I have six1 kg packs of sodium hydroxide, left over from the last time I had to do this job. I think there may well be another couple of 1kg packs tucked away in one of the cupboards.

Pretty much, but they usually work by balancing the current needed to maintain two hot wires (which are usually very, very tiny bead thermistors now) at the same temperature. One of these will be a held at close to ambient temperature in a sheltered location, the other will be at the top of the probe that's poked into the moving airstream. The flow of air past the tiny exposed sensor cools it, and measuring how much current needs to pass through it to bring it back to the reference temperature is directly proportional to flow rate. The handy thing about using very, very tiny bead thermistors is that you can measure their resistance to ensure that the temperatures remain equal. They are also extremely sensitive, and able to measure very low air flow velocities. In the flask variometers I used to repair, the tiny bead thermistors were placed on opposite sides of a tiny hole in a plate made from double sided PCB material (maybe a 1mm diameter hole, or thereabouts). This plate had a glass pipe bonded either side of it and was connected by flexible pipes from the glass tubes to the static port(s) on the fuselage and a lightweight air flask. With no air moving into, or out of the flask, both would remain in equilibrium. If the glider started to gain altitude, then air would flow from the flask out of the static port, as air pressure dropped outside. This would cause one thermistor bead to cool faster than the other and indicate that the glider was climbing. The same would happen the other way around when descending. They were tricky things to repair, even when I was a lot younger, with sharper eyesight, as the thermistor beads were maybe 0.1mm in diameter, with even finer wires coming out either side, and both beads had to be exactly centred on the small hole, with the wires soldered in place to the board, so that stronger wires could be fed off to the instrument electronics.

One reason I bought a Testo hot wire meter (the one that I donated to the tool share scheme here) is because it measures the true flow velocity past the hot wire elements, and can be fitted inside any duct to measure that flow velocity, with just a simple bit of arithmetic to convert flow velocity to volume, or mass, flow rate for the size of duct. I first came across these super-sensitive hot wire air velocity measurement sensors years ago, back in the 1970's, when I first learned to fly. Some of the gliders we had in the club used a bottle, connected to the static port via a pipe with a differential hot wire flow sensor, and this sensor was sensitive enough to work OK as a variometer (a sensitive form of vertical speed indicator, near essential when seeking out lift). Somewhere I thing I may still have a glider variometer hot wire sensor, as I had a few spares left over from when I used to repair and calibrate instruments. The tiny thermistors used as the "hot wires" were prone to damage from shock and vibration, and I seemed to often end up having to repair and recalibrate the things.

Not sure, as there can be some flakiness associated with booting from USB and installing GRUB on some older laptops, in particular. It should be possible, but might be worth trying to pin down what in the configuration has been causing the problems. As an aside, when I was doing the shopping yesterday I noticed that one of the self-service check out machines was out of order. It had crashed, yet was displaying a standard Windows XP desktop on the screen, complete with an error box. Probably running embedded windows, but does make you realise just how many older versions of Windows are still in daily use. I gave in and bought my wife an iMac for Christmas, which now frees up a tiny, 15 W maximum, fanless i7-7500, that had been running Win 7. It had a nice aray of ports, a 250Gb m.2 SSD, plus a 1Tb HDD and 8Gb of RAM, so I', probably going to clear it out and load Ubuntu, or maybe Mint, on to it, running on my second desktop monitor. Although my laptop runs Mint, I've kept my main desktop on Win 7, really because I still use a couple of Win 7 software applications that I can't get to run on Linux. As the car runs on Linux, my new NAS I've built is running Debian, and the new interface I've playing with for the car is running on within Docker of Armbian, but about to be ported into either micropython or Lua on a very low power device, it would be handy to be able to work on a native Linux box, especially when taking directly to hardware. It also makes talking to my wife's iMac easier, as that's essentially a Unix-like machine, too, from what little I've played with when setting up. Much as people like to be critical of Apple, I have to say setting up one of their desktops is a million times simpler and easier than doing the same with Windows. We had the advantage that my wife already has an iPhone and an iPad, so the new iMac just recognised both of these as soon as it was powered on, and then just set everything up automatically, even our non-Apple network printer (which previously needed a special app to work from the iPad).

In the past I've found that sodium hydroxide usually clears anything pretty well. Make up a really strong, hot, solution and pour it carefully into the pan, ensuring there's enough to flow down to the blockage (a bucketful will do). Leave it for an hour or so to do its thing, then flush several times to clear everything out.