ReedRichards

It wasn't changed, the RHI scheme was closed to new applicants on 31st March 2022.

@Pocster, if you were referencing the RHI scheme then pretty much ALL the comments you posted on this thread are wrong for the current scheme.

That sounds very much like the old RHI scheme, NOT the current one.

Proper Load Compensation requires that your heat pump knows the target room temperature and the actual room temperature. When the actual temperature approached the target temperature it can modulate the heat pump down to a sufficiently low output to maintain the room temperature at the target value (or to minimum output if that is not possible). If the actual temperature falls far short of the target temperature it can boost the leaving water temperature so something higher than the value determined by Weather Compensation to warm the house more quickly (but possibly at the expense of efficiency). My Atag gas boiler bought in 1998 would do this; it's hardly a new thing.

Called "Load Compensation" in the context of gas boilers. Not with radiators. You need a room thermostat set a couple of degrees higher than your desired room temperature to act as a backstop if you don't have Load Compensation.

There really shouldn't be a grant for a heat pump in a hybrid system because it's not doing enough to cut down on greenhouse gas emissions. If you're convinced it is worthwhile to tack one on to an existing boiler and heating system (and I'm not) then let it pay for itself.

Great. So you end up with a system that uses 9 kW of gas for every 1 kW of electricity (my figures are guesswork). That's not really much of an improvement is it?

But if you get a hybrid system are you going to bother to change your radiators? It will seem like too much trouble and expense for many people so that 3 degs might be 10 degs.

If you had a gas boiler that was OpenTherm compatible you could buy any third party controller that also supported OpenTherm and that should give you the option of Load Compensation. There is no standard equivalent to OpenTherm for heat pumps and (I think) only one obscure heat pump that has OpenTherm compatibility. So if you want Load Compensation you have to use the heat pump manufacturer's own controller. Your next problem is that I'm not aware that any heat pump that can do Load Compensation calls it by that name. For example my LG Therma V heat pump calls it "Air + Water" control, as opposed to Water control. Load Compensation should help your heat pump to modulate down to the best output to maintain a steady room temperature. It should also help your heat pump to warm up your house quickly when required, although that could cost you more than a slower warm up.

I'm sorry but you can't do that either. You can install measuring equipment that will determine your COP and thus your SCOP. At the time my Therma V was installed it was a requirement for the heat pump to have a dedicated electricity meter so I can tell exactly how much electricity my heat pump uses - but I don't think that is done anymore. And my EPC has a very inaccurate estimate of the heat and hot water requirements for my house so I can make an equally inaccurate estimate of my SCOP.

It's usually a straight line; nothing sophisticated.

You haven't misunderstood. The Therma V has all the data to give you a COP reading but it doesn't. But anyway it's really the annualised figure, the Seasonal COP, that matters.

I beg your pardon, @JohnMo? I think he means "not necessarily". Heat pumps have a target flow temperature. But it may take them a while to reach that target. They will indeed shut down if the target is exceeded (by some pre-set margin) at their minimum electrical input. You would try to establish the the minimum flow temperature needed for your desired interior temperature at each particular outside temperature. Once you have done that, you use weather compensation to render it automatic so you can stop playing around.

My OH has a small studio tacked on to the back of our garage, which is external to the house. I've been thinking I should get an A2A heat pump to heat that room; it's only 10 square meters in floor area, although being a garage the walls are not insulated. Any recommendations for a make/model?

I have a few radiators that make some noise. I think the fundamental problem is that you are trying to achieve a 5 C temperature drop across each radiator and this requires a much higher water flow rate than the 20 C drop that is typically used with boilers. This high flow rate can lead to noise. You might be able to throttle the radiator valve to reduce the flow rate and so reduce or eliminate the noise but this will reduce the radiator output so you may or may not be able to do this and keep the room warm enough.

Yes. I only have a 6.5 kWh battery but I charge it up overnight, charge my EV and get my heat pump going, including the DHW which I now heat to 55 C to make sure it lasts the day. All this before 07:00.

Maybe Eon NextDrive 00:00 - 07:00 would work better for you? It will depend on whether you have solar PV and need the good export rate Octopus gives to its import customers.

There is a setting which gives you various control options for the circulation pump. Not all of these (e.g. the option to aim for a particular delta T) are likely to give you a fixed flow rate. Which option have you chosen?

When my heat pump was first installed it seemed to drain randomly from the base but then my installer fitted a small drain pipe to the base that runs to a soakaway and that has worked perfectly.

Maybe you can post a picture or two because your description isn't making sense to me?

I don't think there is a "correct" answer; it's up to you to choose. One might suppose the optimal setting is "Optimal". Or you'll just have to experiment.

Maybe, but then you can't use the Load Compensation capability ("Air + Water").

No. Unless, I suppose, it is an undocumented feature.

Switching 240 V seems like something out of the dark ages but it was the norm for boilers. Just looking elsewhere, it seems a single channel Hive uses voltage free switching but a dual channel Hive (heating and hot water) switches 240 V.

I have a Drayton Wiser system with two wireless room thermostats and a control box which is wired in to the heat pump. I got this before I got my heat pump and it controlled my old oil boiler. I'm sure that oil boiler used a switched live and I have no reason to believe that the heat pump was rewired differently.