sharpener

I have a similarly complex charging regime but have been considering just charging battery to 100% every cheap period. The thinking is that every unit bought off the grid at 12.65p liberates a unit of PV which can be exported for 15p. Is there a flaw in this?

@JamesPa has a spreadsheet which I used to good effect when I was doing my system design. But it was a bit optimistic, never managed to quite work out why.

You can improve the heat transfer on the outer surface of the coil by using a bronze pump to circulate the water in the tank while it is being heated. I did some experiments which showed a 2x improvement but in practice I don't get as much as that. You also need an NRV or you will have a parasitic path through the pump when it is off. Vaillant tech accepted this as part of the scheme to re-use the existing tank with a 12kW HP. Incidentally their smallest is 3.5kW - but that is just the 5kW with restrictive software. I don't see how you get a better CoP with a PHE, there has to be a temperature drop across it (typical design figure is 5C) so the HP runs hotter for a given DHW temp therefore the CoP will be worse.

IMO 200 l would be plenty for this situation, assuming the wet room does not imply any great medical/disability requirements.

Once the TS is up to temp it doesn't take much. My 210 l TS has a rated heat loss of 1.9kWh per 24h. Somewhat less in practice (maybe the rated loss is at 60C but in summer I have it at 45). So with a CoP of 3 that is about 10p a day at cheap rate. This wasn't the original plan but at that cost it is not worth trying to change it. Given the above I don't think you could justify the capital cost of doing that.

Gledhill have reportedly had quality probs with leaking fittings and loose/rattly internals. OSO have a good reputation (and make Vaillant cyls under contract). Mine dates from 1995 and has needed only a replacement pressure reduction cartridge since then. The HP installers re-used it, as changing it out was going to involve substantial building work. Ideal are rebadged cyls made by another major mfr (I forget who) but are actually cheaper to buy from Ideal. IIRC the recommended size is 45 l x (# of bedrooms + 1). This is designed to give you 1 shower p/p. Should be plenty as with an HP you can reheat cheaply several times a day (depending on tariff e.g. 3 x with Octopus Cosy).

There are several seemingly decent schemes like this. One in Hants ?Andover IIRC. Also Cool Energy will design under MCS and supply for yr ppl to fit.

We started with 7.1 kWh of battery and quickly added another module which I had allowed for so now have 10.65 kWh In an ideal world I would add a fourth module but that would mean moving the consumer unit so cba. Cosy suits us well bc the 1300 - 1600 cheap slot allows the HP to precharge the thermal store at the same time as the inverter charges the battery, all ready for the evening meal and keeping the CH going through the evening peak rate. With yr enormous slab @JohnMo you will probably do entirely without the HP during the peaks. I decided not to go for the Octopus Go etc EV tariff bc you need to play continual games to optimise the behaviour for the HP. Cosy is fit and forget. All I have to do is change the settings when I am away so the house can run from the battery during the allowable charging times, when the house is occupied this is not desirable as it cycles the batteries too deeply (simple explanation but not entirely correct).

Yes there was an intermittent feed that sprayed cold water into the air circuit. Brought the circulating air down to the temp of the cold water inlet but also ensured it was 100% saturated. Next to useless, worst machine I ever owned.

Ironically we discovered an acquifer only 1.2m down and right under our new rainwater tank location. So they had to bring in a dewatering pump - but the flat outlet hose kinks easily and I was up in the night sorting it out so the tank didn't float out of position before they backfilled the hole.

Even after the capital cost of having the borehole drilled and the treatment plant installed you need to factor in the recurring cost of replacement filters, UV lamps, chemicals and periodic water quality checks none of which you need with mains water.

For a friend they didn't remove the blanking plug in the connection to the sink waste so the machine threw an error code and didn't work. Can't see the point of paying £25 for someone to connect 2 pipes and plug the thing in. If there is anything out of the ordinary they won't do it anyway. IIRC hot and cold fill washing machines only draw from the hot on the high temperature programmes so you will not save anything on everyday washes.

Fit a solenoid valve then you can control it by a conventional time switch or over the internet by a Shelly plug.

Don't know about Panasonic specifically, but in general it would seem you pay a lot for the convenience of having these components packaged in a glossy white unit to sit alongside your kitchen cupboards like a boiler.

R290 is propane but the quantity is relatively small (960g) so even if it is inside the house (not clear from a quick read) the danger will be much less than an unlimited supply of natural gas. The compressor will be in the outdoor unit either way so not a problem.

Will make it worse. The cutaway view here shows the main active component is a standard plate HX, and from the description is it clear this is used to provide separation between the HP loop and a pre-existing heating system. Assuming there is the typical dT of 5 C between primary and secondary of the HX it means the HP will have to run 5C hotter for the same heat delivered to the home. It will not reduce the need for larger emitters in many instances, in fact it will make this more of a requirement to get reasonable CoPs. Their video is misleading about this. I don't see why they are targeting social housing in particular, or emphasise the saving on glycol. Anti-freeze valves are a readily available alternative. The remote controllable backup heater is novel but I can't see what form it takes. It does not seem to have a standard immersion heater boss, and if more than 3kW will need a new power supply to the airing cupboard. As it is designed to fit under the HW cylinder it would not appear to avoid the need for a new cyl. I would not have one.

Because the 12kW outdoor unit is more than 0.6 cu m we needed full PP. Our site backs on to a river in an AONB so visual impact is important. As well as the specified plans I included (i) a photograph of the house from the river demonstrating that the HP would be out of sight and also (ii) a photomontage showing that it could not easily be seen from the street either bc the level of the kitchen yard is about 5 ft below the surface of the road. The only objection was a technical one about my home-produced plans which was fixed by paying ~£20 for online ones. I would think so. Good luck!

Nothing about height, this is the full extent of the MIs on the subject: I suppose the accessibility guidance would be the same as a light switch but I do not have my IEE On-site Guide to hand. More important is to site it in a sensible room. Hallway is not always a good choice, it may be draughty or unrepresentative of the rooms you are actually trying to heat. There is an offset adjustment which may help circumvent this. If like me you are not using it to sense room temp and just rely on the WC then it may be more convenient to put it with all the other controls in the plant room. Often I have seen pix where it has been installed in the airing cupboard where it is neither use nor ornament.

The key point here is that the turn-down ratio of a heat pump is usually about 3:1. So the 6kW unit would happily run continuously at 2kW output. Hence on the face of it the 9kW would not be too bad, at 3kW. But if as @JamesPa says it is a 16kW unit derated by software then the min output is going to be over 5kW which is 2 1/2 times what you should have had. So it is going to spend most of its life cycling severly which is poor for efficiency and also poor for the compressor lifetime. I think you might usefully consider a Small Claims Court case for "not fit for purpose", the threat of this might miraculously cause a 6kW unit to be found!

Vaillant require only 200mm from the wall (250 if used for cooling). But their own ppl will not work off ladders so if you needed a repair under warranty you would have to arrange scaffolding or a tower. An approved installer might be different though. (I had a single-storey rear extension built and the main contractor had to provide scaff for the s/c brickies even though the brickwork is only 7ft high!). Sounds a situation best avoided.

Agreement between the gauge and the HP control panel depends on siting of the sensor wrt the internal pump in the outdoor unit. On the Vaillants the pressure sensor is on the suction side so what looks like adequate static pressure when off turns into not enough when pump is running. Not helped by my installers leaving the EV pressurised to the factory setting of 3 bar, which is too high for an HP and means it was not doing anything.

Not exactly. The black needle shows actual system water pressure, 1.25 bar might be a bit low depending on the instructions for your particular HP. The red needle is an aide memoire, you set it by hand to where the black needle is so you can see if the pressure falls subsequently. If this was set correctly then you have lost 0.25 bar since this was done. You may have a slow leak somewhere. You may need to top it up by opening the two black valves slightly until it is the black needle is correct.

Have had to do a similar job as a result of bodging by plumbers. Plywood is probably not a good material for this as half the grain runs in the wrong direction, you want all the grain running parallel to the joist so it will be maximally strong in bending. I put a sister joist of half the width on each side of it using long Timberlok screws. Bolting through would have been better but I could not get a drill in to make the clearance holes. The theory of bolted joints is that the bolts or screws pull the joint tightly together, then the shear loads are transferred by the friction between the faces (and not by the bolts). Consequently rough faces will improve the friction. I don't think adhesives are much help in this scenario though I did use Evostik Resin W - which has long been my favourite woodworking adhesive, I think it has a new name now.

As title, I looked on the Yale support web site, you would think there would be some info but nada. So I enquired via the comment facility but have not had a reply, and judging from previous useless experience don't reallly expect one. Hence I am assuming my HSA 3000(?) series alarm's central control box will require upgrading to something new with an internet connection. Can anyone tell me if their current offerings are backwards compatible with all the sensors in the house which use 433.92 MHz AM signalling, or am I going to have to change them all as well?

Have tried to follow the convoluted interaction of the SI, the explanatory memorandum and the original legislation but gave up. Can you say what you think it all means?