Jeremy Harris

This is what we do, limit the supply temperature to the manifold with a thermostatic valve to ~28 deg C. Relatively cheap and easy solution, and some UFH manifolds come with a thermostatic valve already fitted (ours did).

Same place I bought mine!

The 10% figure comes indirectly from building regs, in that the area-weighted average floor U value should be less than 0.25 W/m².K, which if translated into ground heat loss works out at about 2 W/m² maximum heat loss at design conditions. Using 10% as a maximum allowable may result in a heat loss of greater than this, but should be under the design target of less than 5 W/m² loss. Building control bodies don't seem to pick up on the fine detail of floor heat loss with UFH, because SAP doesn't account for it either. Strictly speaking they should look at the underlying principle behind the area-weighted average floor U value criterion, and take account of the increase in heat loss that always results from fitting UFH. At the moment, the assumption is that the design conditions are focussed on heat loss arising from room temperature alone, which it clearly doesn't for a house with UFH. Worth bearing in mind that the heat loss from radiators or other similar forms of heating will often be lower than from UFH.

I biscuit jointed a couple of 20mm thick oak boards together to make the lower part of the box, so it projects out around 120mm from the wall.

Definitely looks like two supplies coming in, assuming that incomer on the extreme right goes into the top of the cut out at the top right. Lots going on there, too, and it does looks as if the installation may have had a separate supply run in to feed storage heaters.

The main "gotcha" I've encountered is when a manufacturer decides to use a finer thread than standard. I got caught out replacing a pressure reducing valve by this; one had a standard thread and accepted any normal 22mm compression nut, one had a fine thread that didn't, so it meant pulling the olives off. Perhaps worth trying to have a look before you start, so if the threads do look different you'll be prepared (I wasn't, and I wasted a lot of time doing what should have been a simple job).

I wanted a similar shelf under the TV in our kitchen/dining room, and as that's a stud wall, and as I'd already fitted a bit of plywood between the studs in the wall (behind the plasterboard) the TV was centred between two studs. I made up an oak box, with the lower edge projecting into the room, but with around half of the depth of the box set inside the stud wall. This box/shelf just houses the Freesat box and somewhere for the remote controls to live. Not a solution that would work for an outside wall, but works well on a stud wall.

I've knocked up a spreadsheet to calculate ground floor U value, heat loss to the ground, % efficiency and required floor surface temperature for a given UFH heat output: Floor heat loss and UFH calculator.txt As before, the file needs to be saved and then the extension changed from .txt to .xls, as the forum software doesn't allow any spreadsheet file types to be uploaded. All and any feedback welcome, together with any bugs that are found!

We fitted a glossy finish in the old house, and it looks OK, but is a bit of work to keep looking clean all the time, although far less work than cleaning grotty grout between tiles. I fitted matt, slightly textured, finish panels in a sand coloured shade in the new house and they look lot nicer, and are less hassle to keep looking OK.

I think I'd be keen to hear one working, too, before committing to fit them. Having said that, some friends have trench heaters fitted around the edge of most rooms in their house, and they are fan assisted, yet very quiet. I've no idea if trench heaters will work OK with the lower flow temperature from an ASHP, but it might be worth looking into.

IIRC, the 3 phase models were late to shift to inverter control. This makes sense, as an inverter controlled unit has a three (sometimes more) phase motor. They rectify the incoming AC to DC, then drive the multi-phase motor with the inverter drive, which is really a variable frequency AC drive. For a 3 phase inverter controlled unit, the 3 phase would be rectified to DC, then used to drive the motor variable frequency inverter. From the symptoms described, with a shorted motor phase, it sounds like direct AC drive to me. One "feature" of variable frequency drives is that they rarely, if ever, damage the motor; the electronics in the drive unit tends shut down a hell of a lot faster than a motor under fault conditions, and will usually just instantly fail. I've built a lot of variable frequency motor drives, for things like my electric motorcycle, electric bikes and an electric boat and have yet to damage a motor (and all my motors are three phase machines in essence). I've blown a fair few motor controllers, though, until the current generation, where there is so much protection built in that the controller just shuts down within a µs or two if a problem develops (or if I do lunatic things on the motorcycle - hard not to when you have 100% torque at zero rpm...).

Some do latch for a time, I have a couple feeding my PC etc and they stay on for a time after a surge. Not sure how long, as I've only ever seen them come on a couple of times, but it's long enough for you to notice that the light's on, so of the order of tens of minutes. Given that there would probably have been a lot of spikes, as the motor intermittently shorted and then cleared, over a period of about three hours, then it seems possible that it just kept on being regularly triggered.

If the >30V N to PE was recorded by a surge protector some distance from the supply, then it could well have been a false reading, especially if the surge it measured was just a short spike. Cable inductance comes into play when there's a catastrophic failure, as seems to be the case with the ASHP motor, as it's unlikely that an over-voltage event on the supply caused an insulation failure in that motor, much more likely to be the other way around, I think. 3 phase motor insulation is rated at over the maximum phase-to-phase voltage, with a fairly high factor of safety (a normal domestic insulation resistance test would be conducted at 500V), so the motor failure may well have been the cause, rather than an effect, of the problem. Fast, high current, spikes can be generated under insulation breakdown in a high current motor, perhaps as a consequence of over-heating for some reason, that won't trip a breaker, as they typically take around 20ms to operate (the max allowable is usually 30ms). These short duration spikes may well have resulted in high voltage, short duration, voltage surges, that over-stressed some of the equipment in the house and caused it to then fail. This neatly fits the three hour event timeline, with the motor intermittently shorting internally and then clearing, and with every short clearance event the motor inductance would generate a high voltage spike. The interference suppressor almost certainly failed as a consequence of the high dV/dT, which again fits with the pattern of events. An RCD on the 3 phase supply would have almost certainly picked up this failure in the early stages, I think, as it sounds as if there were some high current imbalances in the 3 phase supply, before the catastrophic failure at midnight.

I'd suggest using the Aquamandix unit with the air injection option. I went for ozone injection because we have a very high iron concentration in our water, well over the acceptable limit for drinking water, and also because we have some hydrogen sulphide, and the combination of the two still resulted in the water having a funny taste and smell, even after the aquamandix filter. Injecting ozone into the raw water, and adding a contact tank, completely fixed our water taste and smell problem, and had the advantage of being a pretty good disinfection system. However, finding a supplier of an ozone injection system here in the UK proved challenging and expensive, so I opted to make one. This involved machining up the injection venturi (which itself involved a bit of trial and error) and building a home made ozone generator and air drier. I'd not recommend that anyone goes down the ozone injection route unless they really need to, or they have an interest in making a system themselves. The ozone system does work very well for our water, but we have 480µg/litre of iron, versus your 100µg/litre, with the acceptable maximum for drinking water being 200µg/litre. Given that you don't have an iron problem and you don't have a hydrogen sulphide problem, then I think ozone injection would be over-kill for your needs and an added complication. Best keep it simple, with an off-the-shelf solution that you can easily get spares for, I think.

That was one idea I had when I posted the same thought earlier. The sticking point with it as the possible cause is the low Ze that's just been measured. It's hard, but perhaps not impossible, to see how a damaged PEN in the cable could still give a Ze as low as 0.2 ohms. I guess a cable fault could have somehow fixed itself, or maybe there's a fault condition that changes under load. Most testers don't measure Ze at a high current; IIRC mine does loop impedance testing at either a steady 4.5 A (in non-RCD mode) or pulses the test current faster than the RCD response time when measuring in RCD mode (so as not to cause a trip). I've seen dodgy joints that have acted in some odd ways before now, including one in a low current circuit that acted as a crude diode, so it's certainly possible for cable faults to change their behaviour depending on the load current. Taking this hypothesis one step further, then if there was a phase imbalance at the consumer end, such that a high neutral current was flowing, then maybe a possible PEN fault could only appear when there is a fairly high current. Damned hard to find out whether this may or may not be the cause without digging the cable up, though. Also, I'm pretty sure SSE now specify wavecon for all buried LV supplies, and that has a copper PEN with aluminium phase conductors. Copper shouldn't corrode if water gets through the outer sheath, and I have a feeling that's why wavecon uses copper for the PEN.

We have the same ducting and air cooling and there's no condensation at all on the internal fresh air feed ducts. I did look for it the first few times we turned the cooling on, just in case there was a problem with condensation on the outside of the ducts, but in practice the outside surface doesn't seem to get cool, probably because the design of twin wall ducting inherently provides a degree of insulation. In cooling mode our system usually runs with the fresh air feed air to the rooms at around 12 deg C, and the outside of the ducts, where they are exposed, don't seem to get more than a degree or two below room temperature, so well above dew point for a typical day when cooling would be needed. Might be different if we lived in the tropics, but here it seems that we rarely, if ever, get the combination of high temperatures with high humidity that might pose an external condensation risk on that ducting.

We used Multipanel (https://www.multipanel.co.uk/products/walls ) in our old house to finish all the walls in the bathroom, and we've were so impressed with it after around 5 years of use that we chose to do the bathroom and shower room in the new house with it as well. I fitted a plain sandy coloured panel in the shower room, and we're every bit as pleased with it as we were with the stuff in the old house. One thing I particularly like with Multipanel is that it has a 9mm hardwood ply core, rather than the MDF that some other types of panel use. As a system it's very good, with the exception of the truly awful bottom seal system they offer, for going around baths and showers. That is one of the most stupid designs I've seen, and was the only thing we had problems with in the old house. In the new house I opted to not use their sealing system for the bottom edges at all, but left a small gap where the panel met the shower tray (having tanked under the try and up the walls). I then went around and filled this gap with sealant, then when that had cured I went around again with another bead of sealant and whilst that was still wet used it to bond a PVC trim in place, cleaning up the squeezed out sealant.

I'd not worry about a short dead leg, as the incoming supply will have some residual disinfection capability (as long as it remains sealed) and there are often longer dead legs within a system anyway, like runs to outside taps that may stay unused for months. I'd be inclined to find a way to disconnect things like your disused temporary supply, though, if you can. To put the stagnation issue into perspective, though, it's worth also thinking about all the dead legs in the incoming supply, from things like communication pipes fed from the main (usually without a NRV or stop cock) to houses where occupants might be away, or where the house is empty, or even all the communication pipes that will be laid and may sit for months without being used on a new development. One of the reasons the water supply companies still use chlorine treatment is because of the residual disinfection effect it provides to deal with areas where water may sit in pipes for a long time. Some countries are switching to using ozone disinfection (which is what we have on our private supply) because it doesn't leave chlorine, and perhaps more importantly, the breakdown products of chlorine, in the water. This goes down well with consumers, as the water tastes and smells better, but has the disadvantage that there is no residual disinfection from ozone; it breaks down far too quickly to have any effect beyond an hour or two of being injected into the supply. Provided that the system doesn't develop problems such that contamination can get into the water, then the lack of residual disinfection isn't a problem, but our water infrastructure still has lots of pretty old pipes and tends to suffer from a lot of leaks as a result, with the potential that contamination could enter the system.

Especially if, like us, you have an MVHR with a built in air-to-air heat pump. I've seen ours blowing out exhaust air at below freezing on the few times I tried it out in heating mode. I insulated both the external ducts, the fresh air in and the exhaust air out, but most of the internal ducts are running in areas surrounded by insulation, and even the short sections of duct that aren't don't have any condensation problems, even when the supply air side is handling cool air with the air-to-air heat pump running in cooling mode. I'd be surprised if there was any problem with condensation, as that cooled air is pretty dry, having had a lot of the incoming vapour condensed out in the heat exchanger.

A common arrangement for an underground pot joint would be to add an additional intermediate earth at the time that the joint is made. This is usually a length of copper strap that's connected to the outer PEN conductor inside the pot joint and then trailed along the trench to provide an additional intermediate earth. I doubt that the earth conductivity would be good enough, if the PEN wasn't connected properly through the joint, to explain the low loop impedances measured, though. I'd not rule it out, but without digging up the incoming cable to physically inspect it and maybe flex it to see if there is a problem, either at the joint or somewhere else where it may have been damaged, it may well be really hard to be certain that this isn't the cause. I wonder if anyone else fed from the same local transformer has experienced any supply problem symptoms? Might be worth asking around some of the neighbours, as they may not have experienced anything as serious, but may have noticed something like the lights flickering, and that may possibly give some clues for the DNO to follow up.

Normally, yes, given the cable is relatively new it would almost certainly be wavecon three core concentric, with the outer copper being the combined PE and N.

Sounds like a hell of a puzzle. If the ASHP was the cause, then I doubt it can have been a start up current surge or shut down voltage spike, as, from the description of the damage, it sounds like there was an over-voltage event that lasted for some time, perhaps a few tens of minutes or more, from the description of 3 hours of flickering etc. If the neutral is OK (and the loop impedance tests imply that it's fine now) then even if there was a phase imbalance problem, perhaps originating from the ASHP, then the phase to neutral voltages would all have stayed within limits; all that would have happened is that the neutral current would have increased, which isn't going to cause a problem if the incoming PEN is OK. The joint in the garden sounds suspicious, especially given the cause. Makes me wonder if there may be other damage to the cable somewhere, but it seems a bit improbable for this to have somehow fixed itself. I'd agree with your chap's view, that there should be some evidence of a fault in the incoming cable, most likely a high Ze, and yet the measured impedances seem spot on to me. Fitting an RCD in the 3 phase supply will be a very good move, but it must be worrying to not know the cause. Let's hope that they find something later that suggests a probable cause, if they don't, then I'd be suspicious of the incoming cable that was damaged and repaired. I'm assuming the cable is the DNO's incoming supply, is that right?

A couple of times I've chosen to notify an insurer of something, when I was pretty sure there wouldn't be a claim, and both times I did so in writing and made it clear (with a bold heading) that I was not making or initiating a claim, but was merely informing them so that they were aware of the incidents. I took the view that it was better to be upfront with the insurer as quickly as possible, so as not to jeopardise a possible claim if things didn't go as expected, just in case they used any delay in informing them as a reason not to honour any possible claim that might arise. On both occasions I made sure I closed things off with the insurer afterwards by writing to them saying that the matter had been resolved privately, with no claim, and requesting that they confirm that my claim history hadn't been adversely affected.

No, you can't filter sodium ions out of water with the sort of activated carbon and phosphate dosing cartridge that's normally supplied with boiling water taps. You can remove the sodium ions by more expensive (and lower flow rate) systems, but it's not worth the hassle, IMHO. To put the sodium content of softened water into context, it's worth looking at how significant it is in terms of the amount of water you drink. An ion exchange softener exchanges calcium for sodium in a ratio of 2.17:1, so if you had water that was really hard, say 400mg/litre calcium equivalent, then there would be 184mg/litre of sodium in the softened water. So, every litre of softened water you consumed would give you an intake of 184mg of sodium. A litre of milk contains about 400 to 600mg of sodium. The recommended maximum daily intake of sodium is currently 3400mg for an adult, although I monitor my sodium intake reasonably closely and rarely exceed around 2000mg per day - I think you have to have a pretty unhealthy diet to get over the recommended 3400mg daily intake, although it's surprising just how much hidden sodium there is in some foods.

Just a note of caution. Some older storage heaters contain asbestos, and your description of crumbling insulation is a bit worrying. Do you know how old it is? I believe they stopped using asbestos in them back in the 70s, but also know that these things can carry on working for decades, so it's possible that there may still be some around with asbestos in.