ProDave

It will be interesting to see what the fault is before the finger of blame is pointed. If it is the DNO's neutral corroded and floating neutral, you can hardly blame the installer.

There was much discussion at the time of rather than fix the problem, they "solved" it by putting it in a tin box. Won't stop CU fires just might stop them spreading. There is much wrong with modern CU's that nobody seems bothered about fixing, like nothing to stop a busbar finger going the wrong side of the cage clamp, and what happened to having 2 screws on the incoming L and N connections?

Even though it is 3 phase, I will bet it has a neutral connection and used that and 1 phase for the control circuitry (so it can use the same controls as the single phase version) so if it is a floating neutral that would be as likely to go pop as your sky box.

The important thing as are they all reading the same at one instant, or is one going up when another is going down? Nothing surprises me any more. Some electricians are simply rubbish at fault finding. They seem to be taught how to wire and installation and do a standard set of tests and nothing more. Let us know what they find, and a picture of the CU and supply head would be interesting.

I suspect it is not TNC-S. Since N and E are the same cable and usually even the same terminal at the supply head, it's virtually impossible to get a difference between N and E. What usually happens with a N break in a TNC-S is the whole installation rises to near 230V but you bizarrely don't notice it or get a shock from anything as everything has risen so there is no potential difference. Last one of these I found, the DNO then spent days digging up the guys drive and a lot of the street until they found the fault. I am really disappointed the electrician who has already been has not found the fault. I suggest the next one measures Phase to neutral voltage on all phases, phase to earth voltage on all phases, and neutral to earth voltage. He also needs to measure Ze on each phase, and also do a phase to neutral loop impedance test on each phase. This is one aspect of the wiring regs I disagree with. They are fixated with measuring Ze which is the loop impedance from phase to earth. If this is a TNS or TT supply, that could still measure perfectly fine with an open circuit neutral. I think it is very important, particularly when looking for a fault, to measure phase to neutral loop impedance.

My inclination is high impedance neutral, so the neutral is floating about all over the place, making one phase too high in voltage and another phase too low, depending on what loads are applied to each phase. Neutral faults are very common due to the abundant use of concentric cable. But you would have thought (hoped) the electrician would do a loop impedance test from each phase to N to confirm this. Also you would hope SSE's monitor is measuring each phase to neutral and logging it. If it is measuring phase to phase, then it would miss that fault. Get a basic multimeter and measure each phase voltage with respect to neutral. Also measure neutral voltage with respect to earth and report back. I had this once after a storm, SSE installed a mobile generator to a care home to get power back quickly and blew up half the stuff in the house because they habe neutral and a phase swapped over. When I called them out to show the problem, unbelievably the guy started the generator and waved a volt stick over each phase and said "what's the problem" I had to show him with my meter. They had a big bill for repairs, including several televisions, a computer and a new fire alarm system.

The space issue is taken care of in Scottish building regs. A minimum circulation space of 1400mm by 1800mm so in a galley kitchen you must leave at least 1400mm space which is ample for a conventional oven door.

Best of luck with that. I take it you personally will not be carrying the washer up the stairs?

Bedrooms are the place for a laundry basket, one per bedroom, that is where you get undressed. Having then to carry your clothes to another place to put them down the chute would then just be a PITA.

No that was 150mm of mineral wool type insulation. New house has 300mm

Yes the 600mm refers to the overall width. More important is finding one the right height to fit the gap in the unit. They come in several different heights, as do kitchen units, and sometimes spacer bars are used to make up the gap. It's a lot simpler buying the oven and unit from one supplier, in fact Howdens had a much better selection of Ovens than anyone else in the local area to us.

I have said this before, but there is nothing "new" in what this thermostat is doing. All it is doing is mimicking how a mechanical thermostat with an accelerator heater behaves. People shun them now as "old" and "inaccurate" but I am finding our new mechanical thermostat is working very well indeed. To overcome the inherent hysteresis with a mechanical thermostat, they have a small very low power accelerator heater that warms the local environment very slightly when the heating is on with the effect of cancelling out the hysteresis. A by product of this, whether by accident or design, is the modulate. As you approach the set temperature the thermostat turns off, then a short while later back on. As it gets closer to the set point the on duration reduces and the off duration increases. I think what I am saying is unless you actually want a programable capability (different temperatures at different times of day) then it is hard to beat the simple humble mechanical thermostat. At least everyone knows how to work one of those!!!!

You don't see people working outside in shorts and a tee shirt at this time of the year up here.

^^ For that reason, you should not put Propane cylinders next to a drain, and why gas bottle storage is such an issue on boats (where any gas leak will end up in the bilge)

So the message to anyone reading and about to do their plumbing is DO NOT put the ABV right in between two 90 degree bends. All seems to be working fine and silently now, both HW and heating working as they should. So I will leave it as it is.

What is of more concern to me is we used a total of 47KWh on heating and HW in the week, but the total used in the week was 130KWh so 83KWh on "stuff" so I am looking to find how we can reduce that.

I would love to know the back story. Is this a new house or was it fitted to an older house? Who paid for it and why was it ripped out in preference for a gas boiler just 4 months later?

You could be right. That is the flow and return both coming up out of the floor and 3/4 of the way up the cylinder to where the coil connections are. The ABV is connected between these just above the floor. Above that and to the right is the 2 port motorised valve for hot water The flow rate is relatively high at 15l/min so water is indeed more likely to go straight on, rather than make a 90 degree turn to pass through the (now nobbled) ABV. My guess is the noise was an unfortunate resonance thing, with the workings of the ABV oscillating at the resonant frequency of the coil and making it vibrate. No ill effects so I will see how it goes.

So I have finally got around to trying to investigate this. The one thing I wanted to eliminate before I contact the cylinder manufacturer, is the automatic bypass valve. This is situated in the airing cupboard between the flow and return pipes, immediately before the 2 port motorised valve for the cyilinder, this puts it as far from the heat pump as possible. Adjusting the ABV does not stop the cylinder noise, but it goes through a transition as you close the ABV down you momentarily get silence before the noise starts up again a few seconds later. It is impossible to find a setting where it remains silent. To replace the ABV is not easy, will need a bit of pipework stripped down (didn't think that through enough) so I pondered what I could do to eliminate it. Well what I have done, is remove the top of the ABV, remove it's spring and plunger and put it back together. So now it won't be operating as an ABV but as a permanent bypass and probably way too much bypass. The result. Totally silent hot water heating. Hot water still seems to heat up okay in spite of almost certainly too much bypass. I assume convection ensures enough flows through the heat input coil rather than all bypassing? No detrimental affect noticed on space heating. Even with too much bypass, the manifold pumps seem to ensure enough circulates through the UFH and it maintains it's temperature. What now? Leave it like that? Replace with a new (different make) ABV? replace with a gate valve to give manually adjusted fixed bypass?

If it's monoblock, then what is the "inside unit" looks like a split system to me. Why was it only used 4 months?

You seem to be missing a bit of the model number. It should end in ,A04 (3Kw) .A07 (5.6KW) .A10 (7.7Kw) or ,B10 (7.5Kw) https://translate.google.com/translate?hl=en&sl=de&u=https://www.energieheld.de/heizung/hersteller/viessmann/vitocal-222-s242-s&prev=search

It's a split system so will probably need re gassing.

12.5mm here. I never see anything else used except where 15mm fireline is specified (garages for instance) and then it's 2 layers of the stuff. Regarding strength though, I have noticed a difference recently. When I did the upstairs, it was "normal" plasterboard, as I had always known it. Easy to score and snap to cut to size. But all the stuff I have been getting for the downstairs (just ordered as normal PB) when you score and snap it, it is much tougher, and looking at the raw snapped edge, you can see hundreds of fine strands of fibre. I have never seen mention of this "reinforced" PB anywhere?

Well it has been exactly a week since the meter was installed so time to take a reading and analyse what has been used. Firstly Hot Water. My meter tells me I have used 23KWh in the week heating hot water. If I take a guestimate that it might be running at a COP of about 2.5 that equates to 57.5KWh of heat, or 8.2KWh of heat per day. Some of that will be loss from the HW cylinder (that will at this time of year add to space heating) Now space heating. My meter says we have used 24KWh heating the house. Again taking a guestimate at a COP of 3.5 that gives 84KWh of heat, or 12KWh of heat per day, or just taken as an average over the whole period equates to a constant heat input to the house of 500W At this point some of you (in the south still basking in summer temperatures) will be questioning why we need heating yet. Well it's been a long time since we had anything like "warm" up here, and for 2 or 3 weeks it has been averaging about 10 degrees, and the house had gradually cooled down to 18 degrees, so apart from anyhing I wanted to make sure the heating worked and was actually capable of heating the house. That heating usage seemed to be mostly in the first dew days as it was gently warming the house up again from 18 to 20 degrees. Now it is up to temperature, the heating does not come on often, so next weeks figures should be interesting and probably more relevant.

Wiring a plug is a "life skill" not taught any more.