sharpener

It would be helpful to tell us the overall floor area and the general nature of the construction. Then you can get a very approximate estimate using the heat geek crib sheet. But IMO much better to start again using a modern R290 unit than throw money at upgrading such an old setup.

This may work if the HP is an old one with the compressor driven by a plain old 3-phase motor. But all modern HPs have inverter drives which will present a power factor close to 1.0 so no scope for improvement. I am still puzzled by the size of yr HP, this must be a record for anyone posting to this forum. What make/age is it?

Vaillant 12kW would do nicely IMO. Specd down to - 20 so at -3C the data sheet figures give quite a bit in reserve for DHW and defrosting. Quite good turn down ratio so cycling not too much of a problem. Very quiet. The 10kW is the same hardware de-rated so no point in choosing that, min o/p is the same. Mitsi also a sound choice if that is what you have been quoted.

Sounds terrible. Would suspect incorrect refrigerant charge or a faulty expansion valve but am not a refrigeration engineer. Is it under warranty? What do installers say?

If you are running a HP you would probably want to fully cycle the battery in each of the 3 charging periods, on Cosy they are 0400 - 0700, 1300 - 1600, 2200-2359. Though IME the last one is the least useful for charging the battery or TS, but it does at least keep the real time cost down when the battery has run out of an evening. In order to make full use of the idea, as well as the 20kWh/10kW battery pack you are going to need a 10kW inverter, they are neither small nor cheap.

Yes I think you are right, I was confusing this scenario with my thermal store where recirculating the water through the rads ceases to be useful when the temp has dropped by about a half. Usage of C/n to denote charge rate as a fraction of rated capactity of batteries is unfortunately long established so I fear that ship has sailed. 20kWh of batteries would in rough terms occupy about the same space as an UVC. Also to be able to charge in the shortest (2hr) Cosy window you would have to charge at 10kW as well, this has quite big implications for mains intake capacity (no, not in Farads @SteamyTea!). I was lucky in that my DNO was OK with a 7kW EVCP, 12kW (thermal) HP, 7kW PV and an unrestricted 5kVA inverter all on an 80A fuse (which I can't increase bc of the 16mm^2 meter tails that go through a thick stone wall). WPD used to have a policy of offering free uprating to 100A but I read recently that under NGED they are no longer doing this, IIRC you will have to pay for a 3-phase upgrade now.

This is the bit where it goes slightly wrong. Yes the energy stored in the cyl is ~10kWh from stone cold. But the water is not useful below 30 or 35 deg so in practice the useful stored energy is a bit over half that. Whereas the energy in the battery is available at any temp you want which is in its favour. The problem is with the power, most battery systems are power rated for ~ 2 hour charge/discharge so you would get ~ 5kW out (i.e. 100A at 50V), this is not enough for an instantaneous shower. Yes, I installed a 5kVA inverter/10kWh battery 2 years ago. But now I have put in a 12kW HP as well, the battery is too small to bridge the 3 hr evening peak period even with tricks like having the HP in noise reduction mode then. (Would be worse still if we didn't cook on an AGA. In summer we use an electric cooker, I had to increase the battery from its original 7.1 kWh to 10.65 as it would not survive cooking supper.) However the economics seem quite good as the battery makes 3 round trips every 24 hours. Difficult though to justify doubling the battery capacity just to meet peak demand in the depths of winter. Outside the heating season and with 7kW of PV, 10kWh is more than enough to power the house from sundown to sunup. Even yesterday as it was nice and sunny we managed to export 25kWh. BTW I would not like to be wholly dependent on the electricity supply. It is nice to know the AGA will keep alight come what may, we also have some oil lamps and the bedroom is over the kitchen so never gets truly cold.

Tks for yr reply @Nickfromwales. Pipe o/d is 20 mm. Wholesale replacement not a project I would want to embark on in Feb, just trying to turn down the flow to/from the HP a bit so the return does not pull the temp down for the rads. Do you have any pet methods of cleaning the sight glasses, or any thoughts on whether the mixer is thermostatic or not? By chance I found a circular offcut of MDF so at least I have a replacement knob now!

Certainly you can self-certify electrical work, by co-incidence this morning I received the final cert for installing my own battery system, new CU in garage and EVCP. But they require a Building Notice and then inspect, and also want you to complete the usual elec installation paperwork. Re DIY plumbing IME they just visit and inspect unless it is something highly specific like G3 work. In the case of flexis I personally would not want any part of them to be inaccessible. The whole point of them being able to flex is rather negated if they are encastered in the building fabric.

Anyone able to tell me what brand this manifold is and more importantly if/where I can get replacement flow gauges? I think it may date from 1995 when the barn conversion was done, certainly before 2007 when we moved in. The gauges have a 10mm a/f hexagon at the top. For reference the flow adjustment takes a 5mm Allen key. I have tried all manner of cleaning agents, detergent, vinegar, citric acid descaler, nylon scouring pads, you name it. Nothing will shift the black deposits inside. Also one of them seems badly out of calibration wrt the others, perhpas the spring is damaged. Also this mixing valve. Unusually the hot inlet is opposite the adjustment knob, the cold comes in at the bottom (as installed) and the mixed output goes out the top as you can see from the arrows on the body. Which makes replacing it difficult. It had a lot of limescale encrustation so I have cleaned it up with descaler and the internals are now free to move with the knob settting. Howevere there does not seem to be anything inside that depends on temperature, so is it just a fixed ratio mixer? perhaps someone (? @Nickfromwales) will be able to draw on their decades in the trade and tell me. TIA! elp

Sodium bicarbonate is probably your least bad option.

Another problem with this approach is that if you have to turn down the flow very low then the temperature will not be even remotely constant along the loop. It will decay exponentially along its length so may end up being very uneven across the room even if the total dissipation is correct.

Sodium bicarbonate. I think that is what is sold as "pH booster" for swimming pools. We use it to raise the pH of harvested rainwater. A water treatment specialist once told me his rule of thumb is that 100g will increase the pH of 1 cu m of water by 1.0 but it hasn't seemed very accurate in practice. For treating house water supplies there are also Juraperle (Calcium-based) and Corosex (Magnesium) https://www.wrekinwaterfiltration.co.uk/wrekinwaterfiltration/category_final.asp?department=Private Water Treatment&category=PH Correction Media#scroll Any salts you add will increase the conductivity, and the Ca and Mg carbonates will increase the propensity for limescale to form neither of which you will want. This is a good free water chemistry tool here www.aqion.de. My Vaillant HP installers just used Adey tests and pronounced my tapwater to be fine (pH ~7.5).

Have put in many Drayton TRV4s in several houses. They seem to give reasonable analogue control rather than a bang-bang servo and in the steady state end up on a trickle setting. Also Honeywell Evohome wireless TRVs. These have too many faults to list, but when working can also deliver quite fine control. After the bedroom warms up in the morning you can hear the motors closing the valves in stages, high gear ratio so must only be a fraction of a turn on the valve itself each time. Yes I wondered if they are basically the same as salus autobalance actuators - is the threaded coupling for rad valves and manifold actuators the same? It would be interesting to know how they tackle the problem of UFH and rads requiring different flow temps, which is still continuing to vex me. First thought is are they still trading, the web site is very basic, seems to have no clickable links whatever, and refers to taking advance orders for a product launch in Autumn 2024.

As suggested upthread, measure the diameter and height and calculate the apparent volume of yr cylinder, though I am surprised there is not a capacity label/rating plate somewhere on it. If you mean overheating of the pump motor, I don't think it would make much difference and it says it has a thermal cutout anyway. If you are getting 1.1 or 1.4 bar pressure at the level the pump is installed at i.e. in the loft then some of my earlier remarks do not apply. Though it doesn't explain why it takes such a long time to refill/re-pressurise. I think the main problem is simply the setup is too small for your usage pattern as @Nickfromwales states. A simple answer may be to fit aeration-type shower heads - by drawing air into the water flow these are supposed to give the sensation of a bigger shower while using less water. They are alleged to work though I haven't tried them myself.