Jeremy Harris

I was peripherally involved in some of the consultations for the LV Directive and harmonisation, and what was interesting was how focussed the UK was on earthing, and how almost disinterested some other member states were about it. From talking to some who were involved in the decision to adopt PME, which sort of morphed into TN-C-S (although they are not always the same) I gather the major concern at the time (it was before I'd even qualified, let alone was teaching) was that earth rods were often found to be damaged, the cables or clamps broken and that a lot of the time the real earth protection was being provided via earth bonded iron pipes, rather than the earth rod. There seems to have been a lot of resistance to the idea of PME, which I think stemmed from the shift of responsibility from providing the PE from the householder to the supply corporation (as it was at the time). My view is that they would have been better off tackling the cause of earth rod/mat failures, as they have in the current regs for a TT connection, and specified protection for both the cable clamp to the rod and the PE cable coming into the house. The other relatively recent change that questions the PME/TN-C-S model is that the incomer rarely comes into the house now, anyway. External meter boxes have been the norm for decades and some of us here have gone one step further and fitted the box away from the house altogether. That then creates the "caravan problem" for the house, in effect, although with far less conductive material around in a house the risk is great deal lower. I quite like the idea of having a local intermediate earth, for the same reason as I wasn't too keen on exporting the earth out to my workshop, so wired that as a local TT installation, with a very well protected earth rod. It's reassuring to know that you have a fair degree of local protection should the local distribution network develop a CNE fault. Having said that, so many appliances are double insulated now, and as RCD or RCBO protection is mandatory, the risk for users has reduced a great deal.

Simple illustration. Fitted immediately under our meter box is our old site supply, a 16 A Commando. When it was used as a site supply the DNO insisted that it have a TT earth. Now that the house power is on it has a TN-C-S earthing arrangement. There was far more outside work done after the TN-C-S earth was connected and the house switch was thrown for the first time than there ever was before the house went up. At a guess, 90%+ of the use of mains connected outside electrical appliances were used on site after it was switched over to TN-C-S. The 16 A Commando is still there, and I still use it. Is it now far less safe to use than it was when it was connected with a local TT earth? I can add a clue. Like all these small site supply boxes it has a 16A 30 mA, DP RCBO. An RCBO doesn't have anything to do with the earth arrangement, but trips within 30ms when it senses an imbalance of greater than 30 mA between the current in the line and neutral. I contend that, no matter what the earth arrangement, the practical safety of that 16 A site supply was pretty much the same, and that the fact that the vast majority of the time it has been used has been after it was connected as TN-C-S supports the view that insisting on TT for the short time before the house was wired and the house isolator switch thrown for the first time did not, and does not, make practical sense.

As before, I full accept this, but fail to see how a remote PE/neutral fault is worse for a site connection than for a domestic installation. All site equipment will be running on transformers, anyway, lowering the local risk. If there is a network fault that pulls the neutral up at the incomer then that will affect domestic installations every bit as badly. My 16 A Commando is now connected to the combined PE and neutral, yet I am still using that as a supply in the garden, and it ran my car charger for a while before I installed the proper charge point. Is it more dangerous now than it was when it was feeding site transformers?

Looks like a very expensive stud/pipe/cable locator to me. I've had mine for around 20 years and it still works fine. Cost around a tenner, IIRC. A posh one now might set you back double that. I think the screen is just a mad gimmick that will give people a false sense of security, as there are things that no detector will find, like plastic plumbing. I thought ahead when fitting ours, and stuck strips of alloy tape down everywhere there is a run of plastic pipe, just so they show up when using a detector.

Fully understood, but when the impedance of a TT earth is allowed to be a higher than the impedance of a TN-C-S earth it does tend to throw that official argument for using TT for a site supply into question, doesn't it?

The daft thing is that it really makes very little difference which arrangement is used, as long as the PE has a low enough impedance to accept potential fault currents without raising the potential at the connected equipment earth to an unacceptably high level. Some of the arguments for moving away from TT were that local earth rods and their connections were more liable to damage (have a look at some older installations where there will often be no protective box over the cable clamp and decades of old paint over the thing), plus some soil types can give a poor, or very variable, impedance. Without measuring the local soil resistivity (which can be a bit of a palaver, I did it as an experiment before deciding to TT my workshop) there's no way of knowing how consistently good, or bad, a TT earth really is. My personal view is that a good TT system, with a properly protected cable clamp at the top of the rod, and a properly protected earth cable run to the board, may well give a better level of protection than a PE that has been imported along a long length of cable. Add in that intermediate earths on poles may well get damaged (or nicked) and having a decent earth connection locally makes a fair bit of sense. Quite why the DNOs insist that a temporary supply, even one connected directly to an adjacent permanent incomer that has a combined neutral and PE, should not use that PE but have a local rod and be connected TT I don't know, but I do know that they were adamant about it - there is still a felt pen written warning inside our meter box about it, together with their measured Ze on the combined neutral and PE they fitted..................

DNOs won't provide a TN-C-S (PME) supply as a temporary site supply, they will only allow a TT supply. I've no idea why, in our case it was barking mad, as before we flicked the isolator switch to connect power to the house and test everything, we moved the PE connection to the combined PE and neutral on the head, and pulled out the earth rod. The 16A Commando socket that we used as the temporary site supply is still there as an outside power point, but the earth for it is now via the TN-C-S connection, rather then the TT arrangement that was in place until the house was wired. In your case, there will be several intermediate earth to neutral connections along the supply line to your house. By chance it sounds as if you have one at your nearest pole. The network uses several intermediate earths to ensure that the neutral is close to earth potential and that the impedance to earth is kept low (usually lower than some TT earth systems, because often the intermediate earth may be buried earth mats, rather than slim rods).

I can only comment on the MBC twin stud, filled with cellulose. The performance is very good, in that the insulation value is pretty good and the decrement delay is pretty long, but the most noticeable effect is the soundproofing. The house is very quiet inside, and acoustically pretty "dead", in that the reverberation time, even in our large, 6m high, entrance hall. The result is that you can't hear what's going on outside at all, plus any sounds created inside the house seem to be absorbed. We hadn't really expected this, but it's something that several visitors have mentioned, with comments ranging from "it feels snug", to being surprised at the noise (we're in a very rural area) when a door or window is opened. I'm really glad we opted for the cellulose fill, as it seems to have so many advantages over the other options.

This was exactly our experience, too, building control apologised, said they had no one certified to do test and inspection on work undertaken by someone else and suggested that we use a Part P qualified electrician. It annoyed me a bit, as I was intending to do our electrical installation myself, but after a day spent ringing and emailing around I couldn't find a single electrician within 50 miles that had the required ticket to inspect, test and sign off work done by others. I suppose I could have done the Part P chit, as I used to teach apprentice electricians electrical engineering science many years ago, but the thought didn't occur to me. As it happens, I think I gave a newly qualified electrician a bit of a helping hand, but giving him his first whole house wiring job (he used it as a part of his assessment by Elecsa), so I feel I gave a bit back by paying him. He also let me work as his "labourer" which reduced the cost a fair bit!

I went and had a dig around in my crate of "may come in handy" plumbing stuff this afternoon, hoping that the silver/grey kit would be there, but it looks as if I chucked the whole thing in the skip, I'm afraid. Unusual for me, I'm well known for hoarding crap...............

My experience with 3D drawings is that the interoperability between different CAD packages can be pretty dire. Much as the ancient .dxf format has it's limitations, at least I was always able to import and export emailed or downloaded files into my (also ancient) copy of AutoCad. The only issue I can recall, and it was a pretty minor one, is that the Ordnance Survey files for the base map were out by a factor of 1000. I never did find out quite what the problem was, but my guess is that whatever software they use to create the .dxf file has a scaling error, and sets the units to mm rather than metres in the .dxf header.

It'd be interesting to get the views of our resident architects on these. Would @Dudda or @caliwag care to comment? I know that, as prospective clients, we wanted to impose as few design restrictions as possible on our architect - what I valued was the design knowledge and understanding that an architect could bring to our new home, and we didn't want to impose too many restrictions. With hindsight, I think we chose our selection of architectural practices to approach badly. I should have spent more time researching the background, previous work and, in particular, each practices particular field of expertise, before approaching them. Sadly, I found this very frustrating, as many of the local architects had websites that were so arty and impossible to get useful information from that they were, to all intents and purposes, useless for informing potential clients.

I've sprayed both Wickes Trade matt emulsion and Leyland Vinyl matt emulsion and both seemed exactly the same as far as I could tell. I did have problems until I realised just how very thoroughly the paint has to be mixed. Ten minutes of very vigorous stirring with a power drill and decent paddle stirrer seemed essential, as I did have problems initially when the paint just wasn't well enough stirred. I would guess that stirring, to get rid of even the very slightest trace of thicker areas of pain in the can is probably the most critical thing. The adjustment of spray pressure, nozzle size etc, seemed relatively tolerant to errors compared with mixing.

That's interesting, as I've just dug out our 12 point brief that we hawked around several architectural practices locally: The sad thing was that every single local architect we approached completely and totally ignored the first point, and seemed to have very little understanding of low energy design at all. It was the only reason that I took the rather desperate step to walk away from having an architect and investing a great deal of time and effort in how to design a house, so I could do it myself. I should add that since then I've become acquainted with a very good local architect who we would definitely have used had we known of her practice in the beginning.

Gets my vote. I don't think there's any problem at all with waiting for hot water in a bathroom or shower room, as the chances are that a shower or bath is going to be drawing hot water for long periods and only a few times a day, and most probably in a usage pattern where one user will follow on fairly quickly from another. The two rooms where you need hot water almost instantly at the tap are the most-used WC in the house (the downstairs one for us) and the kitchen. Invariably these are low usage outlets, in terms of overall volume, but high frequency usage. Hand washing, for example, is something that happens several times a day, at intervals long enough for the water in the pipes to cool down. The same goes for washing or rinsing stuff in the kitchen .

I'd actively encourage everyone to do the design SAP themselves, if they can. The main reason is that spending a bit of time learning how SAP works gives you a bit better understanding of the things that impact the EPC. The EPC score is far from being the Holy Grail, though, as you can have an appallingly energy inefficient house with an apparently very good EPC score. SAP is really optimised for conventional new build houses that "just" meet building regs and that don't have a lot of renewable energy generation. The latter is a significant flaw, as any house that has been trimmed back, in terms of overall energy efficiency, can be made to meet the building regs requirement by just sticking a few solar panels on the roof - not exactly what was intended when the legislation was framed, the idea was to encourage builders to build more energy efficient homes. Finally, I would take any heating requirement figure that you get from SAP with a pinch of salt, if you're building to significantly better than building regs standard. Our as-built SAP worksheet shows a heating requirement that is just over double our actual heating requirement, for example. If I'd been daft enough to use the SAP heating requirement to size our heating system it would have more than double the capacity, and would consequently have cost a fair bit more.

You can download and use FSAP for free: https://www.stromamembers.co.uk/downloads/fsap2012/publish.htm

On Construction Domestic Energy Assessor. Someone who never looks at your house, takes the information the builder/you gives them and then lodges the EPC officially. The government have tied the system up so that only accredited assessors (who never actually see what they are accrediting.........) are permitted to lodge the as-built assessment. For example, I did all the assessment, calculations, physically checked and double checked the as-built specification, including making sure with my own eyes the specification, workmanship and paperwork for every single part of our build was correct, but was not permitted to submit the final EPC. I had to pay someone who had nothing but the evidence I gave them to do this.

The famous "three F rule". If it flies, floats or f**ks, it's going to cost you.................

I can't see how there can be, as the door panel just screws to the built-in dishwasher and uses the dishwasher catches. You need a decent handle at the top to open it easily.

We're not, either. We did think they looked good until we stayed in a holiday let that had handless units, the ones you push and they spring open enough to grab the edge. One of the most impractical to use design ideas I've seen, IMHO. Try opening a high gloss finish drawer with slightly wet fingers. I ended up having to use both hands to get enough grip a lot of the time. After two weeks we'd definitely decided that proper handles made things a great deal easier to use, especially thinking ahead to how we might struggle if either of us developed arthritis in our hands.

Yes, I learned about drilling an oversize hole and lining it with a bit of plastic waste pipe a bit too late! I fitted a wood burning stove, with back boiler, to the second cottage we owned, in the late 80's. I borrowed a Kango from work and spent an entire day drilling two holes around 30mm in diameter through about 2ft of granite, in order to take the 28mm pipes. Two years later both pipes had corroded through..................

Wood is flammable too, and yet it's been common practice for decades to fit back boxes to timber noggins. PIR is no worse in this specific application than timber, IMHO.

I did solder then heat shrink sleeve the cable I drilled through, but only because I didn't have enough room to fit crimps easily. I'd not recommend it unless you're a dab hand with a soldering iron in tight spaces, as it was far from easy to do. It probably took three times longer than using crimps, too. I was just reluctant to make a bigger hole in the wall, so was trying to do it with the wires pulled out as far as I could get them and sort of bent around in a loop to meet each other. TBH, I think I'd have been better off just making a bigger hole in the wall...................

Our old floating piston type stopcock seizes up - the piston gets stuck in the bore. The cause is limescale build up. It may well be that the Surestop suffers something similar if used where the water is hard.