sharpener

This is why returning from the HX direct to the hw outlet will temporarily result in lukewarm water at the taps. Of course it doesn't matter provided you do it in the small hours. And by turning over the entire contents you can guarantee it will all be hot. I don't think there is a perfect answer which avoids this, achieves best CoP, maintains stratification and doesn't involve additional valves and pipework. It's all a compromise.

Yes but you will only have to heat up the replacement water for what you have drawn off, not the entire contents. So from the energy requirement pov it will be much the same, there will theoretically be a tiny saving bc the outside of the bottom of the tank will be at a lower temperature so the parasitic losses (something like 1 kWh/day) will be fractionally less. I doubt you will avoid disturbing the stratification in the tank when the pump is running, wherever its outlet is connected. My thermal store was configured with that in mind but it is one of the things that did not work; even with a baffle near the bottom to create a volumiser section the whole 300 litre contents get heated whether I want it or not, unfortunately there are not the valves to isolate it so I can modify the pipework without draining down.

I don't think that will work. The NRV will do nothing there: when the pump is off it will still allow water straight from the cw inlet to the hw outlet bypassing the tank completely. [In my tank where the pump serves a different purpose (stirring the tank while hw is being heated by the coil) the flow is the other way up, and works fine. ] If you do not care that there is lukewarm water at the outlet at the start of the run then that will work for the OP too, though it will be less efficient as the HX isn't fed with the coldest possible water. But I think that benefit may be illusory as the tank will get mixed very quickly unless the flow through the HX is heavily restricted.

I don't know what your HW scheduling is like but if you are heating it at off-peak times like 0400 and 1300 when you are not likely to be showering then I can't see it matters if you put the heated water from the HX back into the existing outlet at the top which will save a lot of b*ggering about. You will need the two-port valve though.

He is probably right. 7.23 is on the right side of neutral. A bit of hardness is fine. Duplex stainless should be good for many years.

Looks plausible for a DIY job. Have a weighted hook handy to hang on the wire puller so it doesn't drop inside. I would have liked to see some kind of centreing device - maybe a step on the external washer - though if you cut the insulation to a close fit that would do it. Is your cyl a foam sprayed one or does it have a metal enclosure? ATB with it, rather you than me!

https://www.heat-exchangers.uk/online-calculator/

Two week and two weeks later a bill from 19 June to 18 Aug arrived by email today, and also downloadable on web page. But not on iPhone app and that still has an incorrect balance of +£119 despite them having paid it out a week ago. So much for award-winning customer service.

You may be right. You might though want to restrict the flow through the HX so it slowly pushes the thermocline down rather than mixing the entire tank when the pump starts, that way the inlet to the HX will get cold water for as long as poss. You could achieve this with either a flow setter (expensive for what they are) or a simple gate valve. This would also reduce possible flow through the path you don't want when the pump is off, but any flow at all will dilute the hot water supply with a proportion of cold. Like you I would not want to try adding an extra connection to an existing tank! I have tried various heroic repairs and mods in the past, not all of which have worked.

This web site seems to provide some useful services e.g. comparing Octopus tariffs and checking for missing smart meter readings. Anyone else using this? Is it genuine or just a way of harvesting/selling on your data? Mods can you please remove the misposting in Photovoltaics, TIA

I don't think you can do that bc of the parasitic path from cold inlet to hot outlet when the pump is not running. If you do it the other way then the NRV will stop that. Or use a 2-port valve not an NRV. However my application is slightly different, to stir the tank while I am heating it bc of the small coil, so I am not sure what is usual. Worth looking to see what Mixergy do.

Yes, if you run the secondary pump off the HW valve supply then it will not de-stratify when you are not heating the water. It will in addition need an NRV so you do not get back flow from cold inlet straight to the hot taps when the pump is not running. For best heat transfer make sure you plumb the HX in the counter-flow configuration.

This web site seems to provide some useful services e.g. comparing Octopus tariffs and checking for missing smart meter readings. Anyone else using this? Is it genuine or just a way of harvesting/selling on your data?

12kW Vaillant is v conservatively rated so good for a lot more: Don't know about the Mitsi but @JohnMo can probably tell us.

12kW Vaillant is v conservatively rated so good for a lot more, don't know about the Mitsi but @JohnMo can probably tell us.

HG cheat sheet suggests 30 - 50 W/m^2 so 11.2 to 14 kW, Vaillant 12kW sounds a good match. The 10kW is basically the same unit so has the same minimum output. 2023 of course.

In 2003 it was said to be Chofu (see upthread). Maybe the delay in getting to market was bc of a change of horses.

Had a poke about the web yesterday but couldn't find anything very specific. What is the most appropriate forum on this board to discuss this issue? I am surprised I can't find any recent discussion if the problems are widespread.

Our installer has contacted us to say that (13 months after installation) the MCS want to visit as a random site chosen for QA follow up. It would be useful to know from anyone who has had a visit how long they take, what they want to see in terms of equipment and documentation, whether you get a written report or any other kind of feedback, anything else of note. TIA

Yes and no. On the one hand the Pylon BMS tapers the charging current a good deal as 100% is approached. OTOH I seem to recall most of the physical expansion in the size of the cells (which AIUI is the root cause of degradation) occurs in the top 10% so avoiding that would be good. But would cost me quite a lot in extra peak rate consumption. Victron s/w allows 5 separate Scheduled Charge periods and you have reminded me that I used 3 different targets for the afternoon charge to max out use of solar: 40% by 1400 70% by 1500 100% by 1600. the idea being to allow room for solar without forgoing the chance to fill from the grid if necessary. So runs a bit counter to my declared philosophy upthread. ATM I am more concerned that Octopus are 2 months behind with billing and have rates for Cosy on the app that are different from those on my latest bill (to June 19). Anyone else got similar problems?

If you install a heat pump you will have to find a home for a hot water cylinder anyway bc it is very unlikely you will need an HP big enough to provide "instant" water heating. They can go in the loft if necessary. Then you can get rid of the electric shower for the cost of plumbing in an ordinary mixer shower - which will be small compared with the rest of the project. If you have already got forklift batteries (what chemistry?) and they are or can be wired for 48V then you can use them with a Victron inverter and probably many others. The 8kVA Multiplus is probably the one to get, it has 15kVA surge capacity ? for 2mins? and 100A (23kW) passthrough capability. Charged overnight at cheap rate this would enable you to timeshift/arbitrage your aqua blasting usage as well as providing grid reinforcement.

Yes. The other fly in the ointment is the electric shower. No-one would sensibly keep that once they had had an HP installed. As upthread 80A is sufficient for an EV, a cooker and an HP all at the same time. But evening cooking load falls mainly in a peak rate period, which is where the battery comes in handy and of course that avoids demand on the grid.

Yes, but high energy density! Which is why it is used for storing the energy for launching torpedos from submarines, my sometime employers had contracts for the refurbishment of the pressure vessels which were expoxy lined steel.

Seems to me that storing the energy as compressed air is a plausible solution (and has been trialled at utility scale), what are the economics of fitting a ginormous receiver? Even with a bigger house, a 12 kW (thermal) HP and a zappi 7kW EVCP we have found an 80A connection quite workable. The demand planner here is very useful for carrying out thought experiments.

I'd be tempted to put in my own borehole to be independent of the farmer (and whatever he puts on his land by way of cow muck, fertilizers and pesticides). There was a recent case near us where a village was supplied by a communal borehole but the farmer still got PP for a great new slurry pond near it. Have seen quite a few borehole threads on here and don't have any great personal interest, but high single £ks are what springs to mind (sorry). You would also need to budget for break tank, pump etc and treatment depending on analysis, but present owner may be relying on farmer for adequate treatment anyway. A local co will probably be able to advise on that too.