Sorry don’t think pictures attached 

Under this is my bedroom wall, I think the noise is from here somewhere. Do these vessels make noise? 

@clairelp finally I can see that you have a volumiser, not buffer setup. So there should be not extra pumps on the system. The pump built into the Daikin is quite strong, I can't see a bypass (but it's hard to tell with the quality of pictures)

This is what they look like, it maybe in the airing cupboard, do you TRVs on every radiator. 

Does the noise stop when doing hot water.??? 

@clairelp only if they don't have enough water in them, system what's the pressure gauge reading.

@clairelp there should be an air release valve behind

@clairelp I'd expect the primary pipes - which is the ones that connect your heat pump to to the volumiser, to that black and red Esbe valve, and to any manifolds or branching off in your cupboard, to be at least 28mm diameter. From the pictures it looks like they >may< be 22mm? It's hard to tell though.  

Apologies - I've forgotten the output of your heat pump..... There's a limit to how many kWhs you can get down each diameter pipe to not go over 0.9 - 1m/s velocity. For 22mm the limit is around 6kW. For 28mm it's more like 10kWh. * Could you please check what the diameter of the pipes going to your volumiser are please? The volumiser is the small gray tank thing in the attic. 

Did you then say that each pipe heading off around the house is 10mm? You can get around 1kW down each one of these to not go over 0.9 - 1m/s velocity. 

The reason you would want to keep to that velocity limit is it tends to get noisy above it. Also much above 1.5 and it starts to erode the internal of a copper pipe.    

As Ken and others thought previously the pipe clips attach the pipe directly to the wood in your attic. An alternative would be to use a clip that goes to the outside of the insulation material. There is a brand called "Primary Pro" that is a favourite with heat pump installers. As you have a cold attic I'd advise consider this a cold space and upgrading the insulation up there - you'll save money in the long run.  

Ken's suggestion to check the air vent is a good one too. 

*These numbers assume you have glycol in your system, and that the dT of your heat pump is 5. dT means the delta T - it stands for the temperature difference between the hot pipe from the heat pump and the cold one. Delta means "difference" in Latin. As dT increases you can get more and more heat down a pipe within that velocity limit. 

Thank you for looking at pictures for me. I cannot see one, but will get husband to look. 

the two heated plumbed towel rails are the only radiators without a trv 

no still noisy with water heating in fact probably worse. It’s at its noisiest probably when doing water and that frost cycle.  

@clairelp here is the bypass valve

This is the filling loop and gauge.

@clairelp 

What's been happening ? 

@kenbone 

Hi, we not had chance to get in the loft to look at the valve yet, difficult to go up in loft making noise when children asleep in the evening.

I did look at pressure gauge in cupboard and it about 1.6.

Friday installers are coming so I will keep you posted. We also have installers msc compliance department checking the install following week. Hoping they will have an answer 🤞🙏

the ashp does have anti freeze valves, with it not been below freezing hoping be okay to keep turning off for a couple of nights.  

also looking into sound proofing and insulation for the loft.  

Hi,

Installers, have turned down the velocity to I think he said 21-22 and was previously 24. Think he said in the bypass valve. And I sorry can’t remember exactly but I think he said like it around 21 and maybe 24 was making too much noise. 

At moment, I don’t think I could hear it and running quieter, it’s only just done so I will test it later when doing hot water and have to wait for a cold night. 
🤞
They also did some settings on the frost cycle. They said it shouldn’t be coming on when not cold enough and shouldn’t be constantly going. Said there is two defrost settings one I think he said for the pipes and one for actual pump. They said if changes didn’t help they will contact Daikain, as some setting they can’t change.