Hi @powysperson, first, if you have solar + battery and an SMES2 smart electricity meter + ASHP then get yourself signed up to a variable rate import tariff product. Most of the larger utility providers offer them, such as Cosy Octopus. Set your battery to charge up whenever there is a low rate period, Octopus has 8hrs a day: 4am-7am, 1pm-4pm and 10pm-12am. Shift as much electricity consumption as possible to low rate periods. Become a 'load shifter'. The battery will probably not have capacity to last fully between charge-ups with a 13kW ASHP, and may be limited to 3kW maximum output, but that doesn't matter, you'll save hundreds of pounds each year in the winter heating season. It's a no-brainer. If you don't have a smart meter, enquire about getting one, there may be a wait for installation, if you're very unlucky, your area might not have a good enough signal coverage for the smart meter to reliably work.

Radbots are a new product for me, but they are cheapish electronic TEVs by the look of it. The problem with TEVs (thermostatic or manual) is they restrict flow, and many heat pumps, including Grant Aerona 3, have fixed flow rate. Forget controlling room temperature with TEVs and room thermostats - that's old school and bad. Crack TEVs open to at least 1 number higher than you want the room, so that they purely stop a room overheating. Set the main room thermostat temperature way higher than you ever want the room, 30degC is fine - it should be constantly calling for heating, else it is cycling the ASHP on and off - which is very bad. Control room temperature with weather compensation, which is automatic adjustment of heating circuit supply temperature relative to outdoor air temperature - that's good, very good. The ASHP should just be left to run for long periods with weather compensation enabled to fully warm the fabric of the house and to do it's thing. If you switch the heating off a lot, the house gets cold, and the ASHP has to run more or less flat out to play catch up. It'll consume electricity like crazy doing that.

That high pitched whine? It may well be a bypass valve near the HW cylinder, which will open if the TRVs all close down and restrict the flow too much. Anything that restricts the flow creates noise, turbulence and is inefficient. Sound energy is just wasted electrical energy at the end of the day.

Video on how to check basic user info on Grant standard controller:

https://www.facebook.com/share/v/1EMrgaHBK6/?

And one for checking Grant Aerona weather compensation settings. (You may need to join the FB group):

https://www.facebook.com/share/v/1AQBhbLZQu/?

Thank you @allyfish! Sorry for my late reply, I've been working out of the house for the last few days.

It does feel like the ASHP is cycling on and off throughout the day. The radiators feel warm and cold on and off all day, I'm guessing this is bad??!

I've taken off most of the hateful radbots and just left them with nothing on, hurrah!! It does feel a bit warmer and I haven't heard the noise (although I haven't bee here much!) I've had to leave some on so the bedrooms don't get too warm at night. The valve itself doesn't fit a normal valve top sadly so I'll have to source some kind of adaptors.

I just have one normal room thermostat it's set to 18 but you mean I should crank it up to 30 and control the actual temp through Weather Compensation? How do I do that please?

Sadly I'm not on Facebook so can't access those videos.

Thank you so much!

I do have a smart meter and am on Intelligent Octopus Go which is kind of similar?

I set the battery to charge 23.30-5.30 (on the Fox ESS 2.20 app) but have no idea how you can tell when it's discharging.

@powysperson You should certainly turn that thermostat up above the desired comfort level - perhaps 2 degrees above your preferred temperature. The heat pump controls ought to be set to Weather Compensation mode as this is almost always the most efficient arrangement for a consistent temperature range inside with varying Outside Air Temperatures. You should have a manual explaining how to set the controller for WC and it should provide details or at least a guide on setting the WC ‘curve’.

An open system runs more efficiently than almost any other and that means having all radiator thermostats fully open and using the Lock Shield valves to balance (ie. regulate) the radiator outputs to provide the comfort levels in each room. If this is all new to you, please see my article on balancing radiators:

RENEWABLEHEATINGHUB.CO.UK "https://renewableheatinghub.co.uk/how-to-balance-radiators-the-role-of-the-lockshield-valve"

Heat Pump Radiator Tuning | Renewable Heating Hub

Optimize heat pump efficiency with expert radiator and lockshield valve settings for cosy, even heat.

Apologies if I am telling you how to suck eggs though!😉 Regards, Toodles.

You will also find many presentations on YouTube (which is a lot less busy or cluttered than FaceBook might be!) for most makes of heat pump, these might well assist you to set up your weather compensation parameters. Regards, Toodles.

No, this is awesome help, thank you so much! I've read a fair amount on balancing radiators but this is the only thing that makes sense.