ReedRichards

You would think that if it is a known problem there would be a good stock of spares to enable a quick repair.

You get up to 14 kW out of what is nominally a 10 kW heat pump?

It really annoys me that heat pumps are singled out whilst noisy oil or gas boilers are unconstrained, except possibly by a complaint to Environmental Health. What is really needed is a unified standard.

Isn't the problem that you have the weather Compensation curve/line set wrongly? There's not even one right answer to this, if you run your heat pump 24/7 you can get away with lower water temperatures than if you don't and the heat pump is off some of the time. But it should be possible to adjust the settings if they're not working for you and get settings that do work.

If you have an Energy Performance Certificate that should estimate the heating and DHW power requirements. In my case, the estimated DHW requirement was 22% of the space heating requirement but the SCOP for DHW was a bit worse. So very roughly 20% of power used for DHW, 80% for heating.

Yes, sure. I have a Weather Compensation curve that is supposed to cover the full range of temperatures but I actually have to manually intervene to move the curve when the temperatures get low enough that the heat pump requires frequent defrosting. I could even set up an outdoor thermometer that sets off an alarm whenever the temperature outside gets too low. Either something is properly automated or it isn't; I don't want to be part of the automisation.

From time to time your flow temperature is lower than your return temperature. The only time that happens in my case is when the direction of flow is reversed in order to defrost the heat pump. I cannot think of another reason that could cause this to happen. My heat pump reports that it is defrosting when it is.

Today it's a little below zero outside, and foggy. My heat pump is having to take frequent breaks from heating the house to defrost itself. But I have never seen a heat pump a with means of taking this into account when operating in Weather Compensation mode; do these exist? If the heat pump was metering its own heat input into the house then some sort of Defrost Compensation should be possible. This would also allow more accurate compensation for time off heating the DHW cylinder, which could vary from day to day.

I have this wacky idea that as we are all going to end up driving electric cars, then cars of the future will need to be much better insulated than those of today.

No, they were just an optional extra unless you had a hybrid system, in which case they became mandatory. But you got paid a bit extra from the RHI scheme if you had a heat meter fitted.

If you know the leaving and return water temperatures and the water flow rate then you can calculate the heat that has been output. I suppose this is slightly wrong because you really need to know how long it takes for water leaving to return and take that delay into account but I suppose that doesn't make much odds.

Thank you, @Transition. That's a really disappointing outcome but useful to know as I would have been tempted to try the same thing.

I have seen a picture of a modern Therma V controller display which shows the outside temperature as well as the other usual parameters. That would be really helpful, when optimising the Weather Compensation settings, for example. But as far as I am aware this is not available as a software update for older models like mine stuck on software version 3.05.6a. Unless anyone else knows differently?

When I was looking for a retrofit heat pump I consulted three installation companies. Two employed teams of fitters and promised me a large reduction in my heating bill over my then oil-fired boiler. The other installer was a small company saying my heating bill might be slightly reduced. Since I had done the sums for myself I went with the honest installer and was very pleased that I did because their workmanship and after-sales support were excellent. Unfortunately with the change of fuel prices since then, oil would currently be cheaper.

I have two Grant aluminium radiators that look very nice to me; I would consider then "Designer". But their heat output is good. https://www.grantuk.com/products/aluminium-radiators/afinia-radiators/

Heat pumps typically run at lower water temperatures than a gas boiler so each radiator will give out less heat. But your existing radiators might be over-specified, they often are, in which case you could be okay with a heat pump. Or you might be able to keep your existing radiators but add some more to achieve the necessary heat output. We added a small low extra radiator in a bathroom to avoid having to replace the towel rail.

Completely off topic, but presumably you could complain about smoke on environmental health grounds?

Auto mode gives you Weather Compensation. If there is an issue it may be that the parameters that set the Weather Compensation line are not correct. You can change these in the installer settings.

Plus people need to learn that in milder weather a tepid radiator can provide as much heat as you need.

I don't disagree @JohnMo but every installation will have its own WC curve and so its own right answer. I would be shivering in a cold house if I used your suggested values. And for heat pumps to become mass-market items there needs to be a way of setting up Weather Compensation quickly and fairly accurately, not using the play-safe values a typical installer will program at present. Perhaps a bit of software that will tell the installer what values to use?

It can be a bit more scientific than that. If your heat pump was sized for a maximum flow temperature at some particular outside temperature then that gives you the finish parameters. For example, my heat pump (a retrofit with new radiators) was sized for 50 C output at -3.8 C so my finish outside temperature is -4 C and my finish flow temperature is 50 C. I then made a spreadsheet about how radiator output varies with flow temperature and used a fit to this to get a start temperature and flow.

Unlike a normal fan heater, which you can position to blow air directly at you (or at wherever you want), these go directly into a socket so they are less convenient. All electric heaters are 100% efficient in converting electricity to heat, the only difference if in getting the heat to go where you want it and I imagine that would be awkward with these things. AVOID.

I think so, Vaillant Arotherm + certainly, don't know about the OP's Daikin. I think most HP controllers probably cannot do different WC curves for different zones. I have an LG Therma V; it can do different zones but not with different WC curves. Nor can it do a programmed set-back, although you can do this manually very easily. And you only benefit from different WC curves for different zones when one of the zones is off, not demanding heat.

Also the report is testing heat pumps with "single fixed speed compressors". I take it that means heat pumps with non-inverter drives that were incapable of modulation.

My reading of the manual you quote is that this built-in function is not intended to work standalone. So maybe it just throws a switch but requires the pump to be powered independently. Then you wire it so the live goes to the recirculation pump via the heat pump so the recirculation pump is energised by a switched live as required.