Jeremy Harris

@Matjaz, I'd be very interested to see your LV Directive and EMC Directive approvals, too, as I used to be a UK Head of Type Approval and an EU Notified Body, accredited to allow the use of the CE mark, some years ago. Selling a product in the EU that does not carry the appropriate approvals is a serious matter.

As pointed out before, be very wary of only looking at COP, it can be extremely misleading in terms of real-world performance, especially in the sort of cool and damp weather common in the UK heating season. Far better to use SPF, which takes account of the true energy used versus sensible heat out through the operating season, taking account of all defrost measures. These defrost measures can range from actively switching the heat pump into reverse to more subtle measures such as turning the heat pump on and off, or modulating it up and down, to allow the evaporator to naturally warm and reduce the icing risk. The COP also varies a great deal with cycling and the control methodology, as the EST showed in the adjunct to their series of heat pump trials, with COP dropping to as low as 1.5 when an ASHP was caused to short cycle due to a light demand. All measures intended to reduce icing, or that induce short cycling, impact on the SPF, but not necessarily on the published COP, as COP is usually measured without taking proper account of any defrost system or short cycling. There's the added problem that ASHPs may tend to have defrost controls that may be optimised to give a good COP under the two standard air/water test conditions, rather like the infamous Volkswagen emissions cheat. Edited to add: Just found this quote, from here: http://www.hodkinsonconsultancy.com/ashps-and-the-code-in-the-british-climate/ that sums up some of the problems with just using COP in the UK climate (my highlight of key points about COP and icing): The article is worth a read, as it highlights many of the points that I've found out by experiment with our heat pump and the UK climate.

Doesn't even need anything that complex. I could knock up a bit of code to provide proportional control with a PIC costing a pound or so in less than an hour. Doesn't even need full blown PID control, just PI would be fine as the response time of the ASHP is going to be pretty long. I've probably already got code that would do it from the "sensitive thermostat" project I was playing around with when looking to use slab temperature control of our UFH. Would be dead easy to modify that to use a pipe sensor and drive the three binary lines for the heat pump proportional control. Making a controller would be pretty cheap, even allowing for the case, power supply etc. Of course it would be illegal to sell it in the EU, as it wouldn't be approved against the LV Directive or EMC Directive, so could not be authorised by an EU Notified Body to carry the CE mark. OK as a DIY project, but unlawful to sell - even advertising it for sale within the EU could get the seller into trouble.

From what I've seen, it does regulate the temperature using the thermostat, but just runs it as if it was a non-modulating heat pump, like many of the earlier models. There are tens of thousands of heat pumps in service that only allow on/off operation, including all of the non-inverter controlled ones. There's no risk in doing this, it's just not the most efficient way to operate them, that's all. Efficiency can be improved a fair bit by modulating the heat pump output to match the demand at any time, which is what most inverter controlled heat pumps do. In this case the supplier of these heat pumps is only supplying the basic heat pump, not the rather expensive proportional controller. The information @PeterW has obtained shows that there is a three connection binary power control system, that allows the heat pump to be modulated from off to 100% in stages: 0%, 30%, 42%, 53%, 65%, 77%, 88%, 100%. Looks pretty easy to make a controller up to do this, TBH, and not expensive either.

4mm² butyl should be fine, it's rated at 35A in free air and it's reasonable to assume some diversity on that 7.4 kW max that the hob could draw. IMHO. The one potential gotcha that slightly concerns me with our installation is that our supply voltage is always over 240 VAC, and with the PV generating on a nice sunny day we're often sat with the inverter limiting output because it's hit the 253 VAC limit. It seems our inverter soft limits and just reduces output when it hits 253 VAC, rather than shut down, which is a nice feature, but it does mean that the house is often operating with a supply that's around 250 VAC in nice weather. It probably doesn't effect a load like an induction hob, which almost certainly controls the true power to the coils, anyway, but it does impact on simple loads, like the resistive heater in the Sunamp, which runs at around over 8% above it's nominal power rating, and consequently draws over 8% more current than it's nominal current rating. I'm still trying to get the DNO to drop the tap on the local transformer, as even in mid-winter we never see less than about 240 VAC on the supply. I'm sure they could knock the supply voltage down by at least one 2.5% tap step and still stay well within tolerance. I'm pretty sure they could drop two steps and still stay within tolerance, as we're almost at the end of the cable (there's only one house beyond us) and two steps would only drop the mid-winter, max load, voltage down to about 228 VAC, still well inside the 216.2 VAC to 253 VAC allowable tolerance band, yet would allow us to export more in summer and reduce the max voltage we see by a few volts.

Not sure about "Any decent main builder would be able to pace around your site and work up a plan in his head within 30 minutes". My experience has been that very few builders I've met (in fact none so far) have been either aware of SuDS or know of ways to design SW drainage in order to comply with it. Foul drains they do know about, but any build today not only has to have some means of dealing with roof run-off (where old fashioned soakaways may or may not work, depending on the soil conditions) but any hard paved or surfaced area (drive, patio etc) needs to have a SuDS compliant drainage scheme. Combined sewers are becoming a thing of the past, I think, as water companies cut back on investment. It's far easier for them to just say that there is no capacity available and so force the use of a SuDS compliant SW drainage scheme. Around here, there are no combined sewers anyway, so everyone has to have a SuDS compliant SW scheme for any new build or alterations to add impermeable surfaces to an existing dwelling. I speak from experience when I say that working out our attenuation requirements and designing both the attenuation tank and controlled rate drainage from that certainly took a lot longer than 30 minutes. The very experienced and competent chap I had to lay the drive and install the underlying SW drainage works hadn't come across the need to do this sort of work before either, and I've seen two new drives built in the village that are non-compliant, so could have enforcement action taken against them.

Interestingly, the frame company that built our house seem to work on multiples of 400mm as far as they possibly can, as that then fits their standard way of making the prefabricated panels. My initial drawing dimensions were all subtly changed so they fitted multiples of 400mm, which in my case only made a very tiny difference, as I'd already designed the house so that rooms like the kitchen, utility room, WC and bathrooms would all end up able to accept multiples of 300mm, 400mm, 500mm and 600mm units (we have built-in furniture in all those rooms. Doing things like this saves labour cost at second fix, as there are no infill pieces needed - standard cabinet sizes just fit the available spaces near-perfectly. Another advantage was the saving in plasterboard and the labour needed to fit it. Whole sheets of metric board fitted with little need for cutting - the ceilings were all made to be 2400 high and the walls and ceilings being multiples of 400mm wide, plus them being dead square (in part because all the panels were factory made in jigs) made it easy to board out with minimal wastage. On the topic of fasteners, our frame isn't bolted to the slab, it's fixed with expanding hollow "nails", which are a lot quicker to install. Most of the frame fastening is already done in the factory with nail plates and a hydraulic press, and having seen them being assembled I can say it;s a very quick process - just a few second to make a frame sub-section that if hand nailed would take several minutes. The key problem is getting those that design houses to understand, and work to, the sort of production techniques that allow a high degree of standardisation in factory-manufactured sub-assemblies. We have a long way to go to get those who design houses to start thinking about designing cost out at the initial design stage, IMHO. I get the distinct feeling that there has been a big divide between architects, who design spaces and features primarily on the basis of aesthetics, and who then metaphorically chuck their design over a wall to engineers who have to struggle to find ways to actually realise the design and solve the structural and other problems.

I hate trying to find other people's screw ups and then trying to fix them. That outside light cockup really had me going, especially as we'd been living with a switch that had a clipped live cable just tucked in the back box for over 18 years, I can understand hating domestics, there are always going to be bodged DIY stuff in any house that's a decade or more old, I suspect. Worst I've ever seen was when I was still lecturing. Over 90% of the students were South West Electricity Board apprentices, so I was known to SWEB. They had a case of meter fiddling, uncovered by the police during a drugs raid on a cottage. I was asked to assess the meter bypass method the druggies had used, as the SWEB guy hadn't seen it before. The usual method was to break the seal and lift the test link there used to be on old meters, which just stopped them recording energy. These guys had gone one step beyond and come up with a way of reversing current through the meter, using a modified Radiospares 50VA transformer. They rewound the secondary with two or three turns of heavy gauge wire, connected to one side of the primary and with both the heavy cables coming out and soldered to two insulated brass spikes. The other side of the primary was connected to a lead with a croc clip to connect to earth. It worked by poking the brass spikes up under the meter line connections, and when they were the right way around there was enough reverse current through the meter to make it go backwards, even when current was being drawn to feed the house. It was damned clever, but bloody dangerous, all the same.

My experience was that planning was concerned that I ticked a box saying that I'd install a SuDS compliant surface (and roof) water drainage system, but BC really weren't that interested, and didn't even accept my request that they come over and look at the 20 Aquacell crates I'd buried under the drive as an attenuation tank.

And there's no problem at all in claiming back VAT that's been applied by any retailer in any EU state (at least until March next year - no idea how HMRC are going to deal with purchases made before we leave the EU, but claims submitted after we've left...).

I used to go caving a lot. One of the golden rules when going into any tight squeeze was to ALWAYS go feet first. Doesn't matter if you're male or female, your chest works a bit like the barb on a fish hook. The bottom of your ribcage tends to rise as you try and come out feet first, and that makes your chest jam in the gap. The more you try to push yourself feet first through the hole, the more you exert yourself and the more your chest will tend to rise. If you make the decision to go feet first on the way in, you can be pretty certain you won't ever get stuck, as it's always easier to get out head first, as your chest will tend to just flatten down. If you look at the geometry of your ribs and their attachments, you can see that your rib cage tends to pivot outwards around the upper part.

Just watch the temperature rise! Postcrete gets bloody hot as it cures, especially in large quantities. I found this out when casting up concrete bollards in a plastic bucket. I'd been mixing concrete to make them, but had a bag of postcrete left over from the fencing. so made one bollard from that. Not only did it get hot enough to distort the bucket, so I had to cut it off, but it also ended up with cracks right through it. Not sure how postcrete and a fibreglass tank would get on together - it might be that the water in the tank plus the natural ability of the soil to absorb heat would keep it cool enough, but there was steam coming off the bucketful I mixed up, so I'm not sure I'd trust it not to cause heat damage to the fibreglass.

I'm inclined to think that there may be an issue with the angle that the MVHR is fitted at, and that perhaps the drain tray isn't allowing condensate to flow easily to the drain hole. It should be pretty easy to check if the MHVR has been mounted dead level, some are quite critical of being mounted level as the angle on the drain tray often isn't very great. For the longer term, once it's been levelled properly, then I'd go along with the suggestions by @JanetE and @Nickfromwales and fit a waterless trap, but before doing that I'd want to be absolutely certain that you don't have condensate pooling in the drain tray inside the unit.

Here's a true "cold revenge" story for you. In 1984, the girl I'd been living with for a few years decided to have a fling with someone else. I caught them at it (literally - I went around to see one of her friends, as I couldn't find her, and found her and her bit on the side in bed together around there, much to her friend's embarrassment at them being caught at her place). I rushed home, packed up all her stuff threw it on the drive and when she came home told her to bugger off. I neither saw nor heard from her again, until around a year or so later, when I was driving back to Helston from Penzance on my own, in the early hours of the morning, in torrential rain, with virtually no other traffic around. I spotted a car stopped at the side of the road, apparently broken down, so stopped, got out, and ran over, intending to try and offer to help (this was before mobile phones were around). As I got level with the car, the driver's window wound down and I asked if I could help. No sooner had I said this than I spotted it was my ex driving the car, on her own, so I said something like "Oh, it's you. Well you can go f*** yourself then", ran back to my car and drove off. I grinned all the way home about the way that revenge had handed itself to me, just like that...

Our guys backfilled around ours with a dry mix, poured down a plastic waste chute fitted in a channel cut into the side of the hole to get it to the bottom. They kept the tank half full of water suspended from strops on the digger whilst they did this. The hole was around 1/4 to 1/3rd full of water at the time. It was a bit like using postcrete, pouring a dry mix into a hole with water in it. They poured concrete up to around 150mm or so above the triangular anchor lugs that stick out near the bottom of the cone, let the concrete go off a bit, then filled the rest of the hole up with pea shingle, which added to the ballast holding the tank down as it was resting on the ring of concrete at the bottom. As soon as the pea shingle was in, they untied the tank from the digger and pumped more water into the tank to hold it down.

Best tip I heard was to immerse the bit of glass/mirror in a shallow tray of water. Apaprently the water damps down the vibrations that lead to stress cracks and makes drilling glass really easy. I drilled a hole in the centre of a thin (2mm) bit of glass a few years ago by immersing it in a bowl of water (sat on a weighted down block of wood) with a Dremel and a diamond bit. Worked a treat and I was then able to screw the glass to a mandrel with a fibre washer (stopped it spinning with some superglue - easy to get off with acetone and then scrape the residue off with a Stanley knife blade), chuck it in the lathe and use the Dremel to grind it into a disc (long story, but I was repairing an old instrument that had a broken glass face and had a hole in it for the needle zero mechanism to fit through).

I've been thinking about this for some years now, and I know roughly what the fees are. My intention is to be able to offer a service to committed DIY'ers that's free, but for which people can choose to make a donation towards my costs if they wish. People are always going to do electrical installation work they shouldn't, and I don't think that will ever change (I'm sure you guys who work as electricians see it all the time). By offering free inspections and testing at least I can (hopefully) make a small dent in the number of really iffy installations there are around. As a side effect, I can make some of my own "unofficial" wiring in the water treatment plant shed and in my workshop legal, which alone will probably come close to covering the initial costs I'll incur.

I reckon you can be rightly proud of your achievement so far. I think we've all seen some real abominations done by some people who consider themselves to be competent DIY'ers, and for someone with little or no DIY experience I reckon you've done a damned good job - a better job than many so-called professionals would have done, IMHO. Please let us retain all the earlier posts, they are a really good lesson in how someone can go from knowing very little to tackling what is a pretty big DIY job very well, and will be of benefit to others who read the whole story, I'm sure.

Thanks for that, NAPIT is the one body I've not delved into yet, that sounds spot on. When I had a 15th Ed ticket I retained that as a part-time lecturer with a similar scheme run by C&G.

It's a one day course for £169, plus the cost of the 18th Ed, plus the fees to an accreditation body (Elecsa/Niceic or whoever), plus assessments by the accreditation body.

Just to back up what @Onoff has very rightly said, I'm just about to send my £300 multitester in for calibration, at a cost of around £35. That bit of kit alone is near-essential, just to check that any bit of electrical work is as safe as it can be, and it's not economic for most DIY'ers to own such a bit of kit or keep it in calibration (I only have one because I was going to wire our new build, but couldn't, because there's no one locally, not even within Building Control, who's prepared to inspect, test and sign off 3rd party work). It's the main reason I'm looking at getting a ticket to do just this, as I reckon it's a lot safer to offer a free inspection, test and sign off service for local DIY'ers than it is to let them go ahead with a little bit of knowledge and end up with a potentially dangerous installation. I can give an example of how potentially dangerous electrical installation faults can catch out even those who try to be pretty diligent about electrical safety, from some work I did yesterday afternoon. We're selling our old house, and it still has the original wiring from 1986, with a fuse box. I've made one or two minor alterations, like adding a light in the loft off the existing lighting ring final, and the previous owners had fitted an electric shower (which we took out), but the purchaser is looking at getting an Electrical Installation Condition Report (EICR) done, which will get an "unsatisfactory" mark purely because it has no RCD protection - just wired fuses. I've advised the purchaser that she'd be much better off just getting the fuse box changed for a 17th Ed Amendment 3 one, and not bothering to get the EICR right now, as she'll get an Electrical Installation Certificate with the consumer unit installation and that will include most of the key tests done during an EICR anyway (with the exception of a visual inspection of the visible wiring plus checks on the outlets). For my piece of mind I decided to do my own EICR, not that it would be valid for the purchaser. I found all the wiring to look OK, all the outlets checked out OK when tested and the first issue I found was that the person that removed the electric shower (at the time we fitted the combi boiler - it was their electrician who I asked to disconnect and make safe the electric shower wiring) had failed to remove the cable from the fuse box - they had just pulled to fuse, which is a bit iffy as the cable has been cut off and is buried in the bathroom wall now. It was easy enough to isolate the power, remove the unused electric shower cable from the fuse box though and get rid of that problem. I then disconnected each ring final in turn, and measure the loop resistance for the earth, neutral and line for each. All went well until I got to a lighting ring, which was open circuit on all both the line and neutral when tested, but the earth looked OK. It looked to me as of the outside light was newer than the rest of the lights in the house, so I went and checked that, and found that one side of the lighting ring had just been cut off in the hall switch. This switch had clearly originally been a single gang switch, that only turned on the hall lights, and had been replaced with a double gang switch, with an extra feed to the outside light. I've no idea why on earth someone chose to break the ring at that point, but it may well have been because space was a bit tight, as they'd used big sections of choc block to connect the neutrals. An hour of cursing followed as I tried to get enough free cable to neatly and safely connect everything in the back box, using wagos to save a bit of space. The key thing here is that for at least 18 years that fault had existed, with the potential that one side or the other of that broken lighting ring final could have been overloaded. Clearly no one had done a proper check on the installation (and that's as much my fault as anyone else's, I just assumed it was OK). This isn't an uncommon type of fault, either, I've found loose screws behind outlets a few times, occasionally so loose that wires have pulled out when it's been pulled away from the box. One failing with our usual system of having ring finals is that a line, neutral or earth connection can come loose and it won't show on a simple socket test, as the other side of the ring will still be connected.

I have a scanned PDF copy of the 17th Ed if anyone wants it. It's too big to attach here, I think. Happy to send it as an email attachment, but bear in mind that it's intended to be read by people who already have an understanding of electrical installations. The On Site Guide (OSGs) are easier to read, but restricted to those who hold accreditation. As an aside, I'm seriously looking at getting a Part P ticket, primarily to offer a test and inspection service and supervise straightforward DIY electrical work. Given that I've already got the test gear and knowledge, the only expense would be the costs I'd incur from one of the accreditation bodies, plus getting my multitester recalibrated (it's about a year out of cal at the moment). I'm currently looking around for the most cost-effective route to getting a ticket, and have already been told that I only need to do the one day refresher training on the 18th Ed - they will accept my 15th Ed C&G and teaching quals, something that surprised me.

As above, normal for triple glazing. It puzzled me at first, as I'd never ever seen condensation on the outside of windows before (at least on the house) but we're now used to it. It happens regularly in autumn, winter and early spring, and is a minor nuisance in terms of obscuring the view, but it does show that the heat loss through the glazing is a lot lower than it was with just the double glazing at our old house.

If you want another example, the projected RHI I had from a heat pump installer was £84 a year for 7 years, on an installation that was going to cost around £2,500 more than a DIY job. If they were projecting that I'd get a total of £588 from the RHI, I wonder what the actual RHI would have been? Either way, neither figure was going to come close to covering the additional cost of having MCS approval for the installation. Back on topic, that installed cost for the Ecodan looks pretty good to me. They seem to be well-made heat pumps with a good reputation for both reliability and performance.

You can check the retail price of the boiler easily enough, and then work out roughly what it should cost to install based on normal labour rates, plus a bit for any additional pipe and fittings. For example, back in 2008 when we had our old system boiler replaced with a new Vaillant combi, the new boiler cost about £800 at that time. We were converting from a system boiler to a combi, so the labour included removing two water tanks from the loft and the old hot water cylinder, adding new pipe runs, bricking up a fairly large hole in the wall where the old rectangular boiler flue had been, as well as drilling a new hole through the wall for the new flue. The price included a power flush (mandatory in order to get the boiler warranty). Total cost came to a bit over £2k in 2008. Labour involved two blokes for about a day and a half doing the boiler swap and plumbing, plus an electrician for an hour or so to wire things up. Some of that labour time was just hanging around, as the power flush took a couple of hours and there wasn't much they could be getting on with whilst that was going on. If you assumed rates of £200/day, and were generous and said there were four man days, then that comes out at £800 for labour. On top of that there were probably a £100 or so of pipe and fittings, plus VAT, so their price to us back in 2008 was definitely on the high side, but they were a big firm who I thought at the time presented a lower risk of doing a bad job. They were also Vaillant agents, so could give the 5 year warranty. As it turned out I'd have been better using a smaller local firm, as they screwed up and we were faffing around with warranty calls from there for over a year before things got sorted properly.. I've just checked, and a similar boiler today costs around £900, and labour rates around here for decent plumbers/heating engineers are around £220/day now, so the same job today should cost around £1900 +VAT, so around £2,280. I reckon the top whack price for something like this should be around £2,500 for an expensive part of the UK, less for areas where labour costs are lower.