sharpener

I am planning something similar as I too have an Evohome setup, my house is long and thin and like you there are rooms we do not use much. However my plan is to wire the existing BRD91 to the Vaillant VR71 to act as an overriding call for heat. Doing this would allow you to shut the system down properly when you are away and re-start it remotely before you return. I think balancing the flow through the two pumps might work as you describe but it is notoriously difficult and relies on quite a number of factors to get right. Using an automatic bypass valve with a volumiser on the return flow might be a lot simpler. I am not sure you will get away without a sensocomfort control, much of the functionaility seems to be in that not the HP itself. There is a simulator here and a configuration tool here, which may help. There is also an Arotherm Plus fb group but I have found it not very tolerant of this kind of query, the general Heating Design group is better and there is much discussion there of buffers. Heatpunk website has also got useful info on what can go wrong when you use them, generally they are to be avoided on thermodynamic grounds because the mixing causes an increase in entropy which results in irreversible losses. There is also a Caleffi site discussing different buffer topologies. HTH

Yes. I wondered if mine was using the aircon to keep the battery cool on Monday's journey. Difficult to say because the range readings are not always consistent. But the range is overall much better than it was in winter when I am pretty sure it uses it to keep it warm. Another long hot drive tomorrow, I might be more adventurous in the use of the aircon. Fortunately the LiFePO4 chemistry in my house battery is much more forgiving and doesn't need all the mollycoddling. But its energy density is nowhere near as high.

so on that assumption a 6 hr journey would use 9kWh which is >10% of the battery. Problem solved! The Air Balloon pub was being demolished when I passed by in ?April this year.

Yes, the rotating shaft seals are the Achilles heel of car aircon. Was once quoted £800 to replace the seals and re-gas with new(er) legal refrigerant on an old Volvo. You may find yr "long distance BEV with a/c" becomes a short distance BEV once you actually turn the aircon on. It shortens the apparent range of mine by some 10 - 20% so we did not use it a lot on Monday despite the OAT of up to 28C. In fact though we arrived home with 66 miles to spare so might have had more benefit from it in retrospect.

On further thought this may not work. At wavelengths much shorter than the slat width it might be OK (say 4 ins == 3kHz) but around the 3kHz mark it will act as a diffraction grating and might give you quite marked side lobes (think Yagi antenna) - you could model it and see what you get! For reflections at significantly lower frequencies I think the detail will be unimportant and the orientation of the overall screen surface will be dominant. So it very much depends on the nature of the noise. I remember reading somewhere that Vaillants have an annoying whine resulting directly or indirectly from the inverter drive, I will be asking my prospective installer for a reference site with the same model to check this aspect as well as for general comparison purposes, did you do the same?

As well as Newark you could try Gledhill, their slimline range is only 475mm dia cf the normal 550. If Vaillant would accept a slight reduction to 90 litres it would only be 976 mm high as well.

Since you are going to be buying a lot of quite expensive cedar for this your local friendly timber yard will probably rip 4 x 2 into two bits of triangular cross section for a nominal charge. Or you could use arris rail section in treated softwood and stain it to match. Or use fence boards, which are already slightly tapered, and put packing pieces under one edge of them - it's not as though it has to be structural beyond staying upright in the wind. IME this kind of construction works well. The trouble with it out of doors is that almost anything that is a good absorbent for sound is also a good absorbent for water. Though there are some specialist materials which are not badly affected, there was a thread about this in the spring.

+1, it is what I said days ago. I have in the past had a water tank in my bedroom cupboard and it was unnoticeable. If the buffer is technically necessary and that is the only place it can go then it is a simple yes/no decision for you. If they fit it then if it does make a noise then you have a solid reason to get them back and fix it but if they don't fit it in the first place you will never know and not make any progress.

If there is scope to cant the screen outwards (i.e. rotate anticlockwise in plan) then any reflections would miss the window on the right. In other respects I think you have a good chance of it working. The hit and miss screen will give rise to multiple internal reflections between wood surfaces which should absorb a lot. I don't think scrap iron would be very effective, you have the mass but OTOH the surfaces are reflective and it has virtually no internal damping. Now if only I could remember the handle of the acoustics consultant who was posting on here in the spring...

If you have got a working (boiler) system to begin with you can learn a lot by comparing how long it takes the individual rads and their return pipes to heat up. Ideally they should all take about the same amount of time, then the flow rate is proportional to the volume of each rad which if they are of similar construction will be directly related to the heat output rating.

Even the Vaillant installers themselves don't seem to know about this. Scroll down to the 19 Aug posting by Rob Samuel Kinghan on this site. Total tale of doom and woe, not helped by them also installing a volumiser as per a Daikin schematic! Fortunately they agreed to move it but I doubt there was much profit in the job after that.

Not quite an integrated heat meter but a useful intro here. I used to work for the firm that developed the first u/s gas meters. You have to make assumptions about the flow profile across the pipe, I don't exactly know how they do it.

If you mean the static head between the one and the other that isn't the right figure, you need to take it from the excess head graph for the circulating pump in your HP.

Pressure drop is indeed an important consideration, see this link.

Unfortunately there are good reasons why in a small house you might need a buffer to achieve Vaillant's minimum system volume requirements. Without knowing more about yr existing HP model (type and size) and the proposed replacement it is not easy to know why they are proposing a buffer where none was fitted before. As @JamesPa and I have found, Vaillant are rather inflexible about these things. The installers will only fit systems that conform to their approved system schematics (drawings) and will not depart from them for fear of (i) warranty callouts (ii) loss of warranty cover (iii) loss of their approved installer status. I do not think you need to worry too much about noise from the buffer tank, it has no active components or moving parts. In any case the installer should be able to programme the system so it does not run at all at night. If indeed you plan to run it at all, I am puzzled by your statement that you will not use it for heating, is it for hot water only then?

No it is an expansion vessel.

You would not want the complication of changeover valves in the refrigerant lines or the possibility of refrigerant being transferred from one circuit to the other. So I think you would need two separate coils in fancoil unit C, then pump B (which I assume is the more efficient one) could supply them both when demand is low. Don't know how you would control it. Commercial refrigeration specialist might know, having many units in tandem operation is fairly common, usually they are the same rating and are operated in a cyclic sequence to equalise usage (like the mulitpley redundant pumps in a water treatment plant for example).

Now that Octopus have decided not to require MCS accreditation if you want to sell them your surplus PV do we think the same will happen to the requirement for MCS and heat pumps? Of course they are not involved directly in BUS except as an installer but I suspect they may have quite a lot of clout.

+1, we have 210l, it is fine for four showers in the morning when we have visitiors. I think the key is good stratification, will not be so good with a horizontal cyl.

OTOH I am also with WPD and they required my 5kVA battery inverter to be limited to 3.68kW. Which is why my second lot of PV panels is wired direct into the battery through an MPPT so they don't restrict them as well.

Ah, didn't realise there was already a 1ph cable passing the new location, which changes the logic somewhat. I have a similar setup in that the supply comes in the drive and goes underground all along the back of the house to a point at the other end which is only a few feet from the road again. Have just had WPD check out their fuse, it is only 80A bc of the 80A meter and 16mm^2 meter tails so with EV charger am a bit restricted in the size of HP, no auxiliary heating allowed. Make sure they give you 100A when they do it!

Several limitations IME and the worst is that the rad picker didn't put the correct rads on for me. Also I couldn't find a way to do a new solution based on a drawing I had done earlier (can't remember exactly what). Tried a whole load of variations but then one of the installers sent me his room-by-room heat loss table which agreed quite well so like @JohnMo I eventually gave up.

This was definitely a feature on the old Fortic tank (very similar in principle to the RM one from screwfix upthread). There was a cold fill pipe which went from the bottom of the cold tank to the bottom of the hot tank like @Beelbeebub has just drawn, and also a vent pipe from the top of the hot tank to the top of the cold tank above the water line. I imagine the RM tank will have a similar arrangement but you can't see it because of the integral lagging - which the Fortic in my flat did not have, only a loose jacket. It seems cheap of them not to fit a ball cock and overflow arrangement. I suppose it allows you to choose the orientation but they should at least supply compatible parts IMO. I have seen the table on the MCS guide somewhere before, I think all the material on p1 under the heading "Cylinder Sizing Example: a manufacturer produces a range of 90 to 300 litre indirect domestic cylinders" is taken, presumably with permission, from one of the tank mfrs literature, maybe Gledhill or Tempest. The rather long-winded calcs were new to me. I am not sure why they think "Mixing rather than stratification is typically realised with an indirect cylinder". Maybe this is the case for HP cylinders which have long coils to get enough surface area. It doesn't happen with my old OSO 210l cylinder. The coil is right at the bottom and we can get 4 good showers out of it before it runs cold. Another reason not to replace it.

This discussion needs to include the benefits of heating water using off-peak electricity and storing it for daytime use. As this is typically half price or less the losses are dwarfed by the savings leaving a big net gain whether or not a HP is part of the process. Power showers and "rain showers" are fashionable but use dreadful quantities of HW. Will perhaps try one of the aerated shower heads. (Saving water is also a consideration though the rainwater tank is unseasonally full just now.) But so far I haven't read anything that suggests I will be better off with anything more complicated than keeping the existing conventional small-coil UVC, heated to 55C with a HT HP*. At the same (off-peak) times I plan to heat a separate 200l TS for the radiator circuit, that alone will halve the cost of some 360kWh(e)/yr and should act as a big parallel load so the HP will be happy. Except that my prospective installers do not understand and/or like the idea. *This is the temp the PV diverter immersion is currently set to. Anything higher gives a green deposit in the shower tray which is to be avoided for obvious reasons.

What deal are WPD offering? IIRC they are now fitting 3ph as standard for new housing, if you are considering more PV or an HP or an EV charger in future it might be better to take their offer now. EV chargers are a max of 7kW on 1ph which is quite slow if you are trying to recharge at night rates but 3ph 22kW will fully charge most cars in 4 hours. You can leave the existing PV on one phase and @Dillsue is right, it should not affect your FITs, and put more on other phases, WP should be very happy with that. 3-phase inverter not worthwhile unless a massive amount more PV. Germans e.g. Sunny Boy very keen on them but domestic 3ph almost universal there. OTOH if you have to change the (moved) single phase supply to 3ph later you can be sure WP will want to charge you £££ at that point.