@editor

ah such a shame when that happens. I don't want to hijack the post but basically the pump outside is vibrating through the pipes when the pump is on. Identical to Cally. It didn't always do it but has in the last week and the kids has dropped 4lmin. No air in the system and balanced well after me going round temperature checking each rad. The fan is quiet and when I put my hand on the flow and return at the pump u can feel it. The house is warm and so is the tank. It's just noisy and vibrating thru the house, not super loud but I can tell. I've raised it with installer and I have a service in a few weeks so I'm hoping all is OK.

I will report back.

Thanks so much for reaching out 

@heymikey, you’re not hijacking the post. I’ll email Cally (maybe notifications are off). There’s clearly interest in this subject as it’s had over 7,000 views. Let me see what I can do to help you (and others).

Hello @heymikey,

I'm not Cally and I haven't read the whole of this thread, but I did have noise problems with my Grant before I rewired it. So just chipping in a couple of pennies just in case I can turn up any clues.

Can you describe the setup you have? When was it installed? Is it an R32 or the newer R290 heat pump? How do the pipes run - do you have a buffer tank or low loss header? Do you have the Grant control boxes (eg one with a 1 inch display and tiny rubber buttons that's a timer for the immersion) or the Grant smart controller? Does it use an external boiler controller (like Nest/Hive/etc) or do you program it via the heat pump's own display on the wall?

When you say 'it didn't always do it' can you describe the timeline of what happened - eg when the system was installed, how long it ran before hearing the noise, if the noise was intermittent when it started (and any clues as to when it *didn't* happen), has it got longer/louder as time went on?

My first line of thinking is that you could have air in the circuit between the heat pump and the buffer (if you have one), which is effectively a separate loop compared with the loop with the radiators (even though they are hydraulically connected, air goes up and if you have two 'ups' then air could collect in either one. But we'd need to know a bit more about your system first. Do you have automatic air release valves (they stick up above the pipes, supposed to be fitted at the highest points)?

Mostly some vague stabs in the dark - more info would be useful to understand your system.

@prunus 
Thank you very much. I'll do my best to give all the details. 

So I have the 13kw Grant Aerona3 R32. No buffer or volumiser at all. I know the manual says to have one but I have 19 Radiators and fairly long pipe runs so I "think" that's possibly why I don't have one. So I don't have any air in that as I don't have one. I've been very into learning the heat pump and I've driven out any air as I was getting locks when it was first installed. I went round and did each radiator at time and you could literally hear the air being pushed out. Since I did that I've had no air locks all issues. It was a poorly balanced system. The pipes that leave the Pump are 28mm Copper and they run up the side of my house into the loft. This is where it changes to PVC and goes to the Flow Cyl 250l hot water tank FCHPD3250. Then to the radiators it is all run on 22mm PVC throughout until it goes to the radiator on 15mm copper from the loft. 
Installed September 2024, I have the basic Grant Aerona3 with the white display (rebranded chofu). Definitely not the smart controller and I have it set up on Weather compensation. This is all controlled by the Drayton Wiser Wireless Heating & Hot Water 2-Channel Thermostat. 

Weather Compensation details: 
Design outdoor temperature: −3 °C
Flow temp at −3 °C: 41 °C
Flow temp at +20 °C: 27 °C
Max outdoor temp: 20 °C
This was much higher when installed and kept reducing it until it didn't feel as warm as it should.

It's hard to say but since install I guess it has been dropping slow. The flow rate was around 22l'min when installed on a medium pump speed. Then it has slowly dropped over that year to where it hit 18l/min a few weeks ago and that's when I noticed the noise as I was in the loft, I was checking the Automatic Air Vents, I have 4 in the loft and one in the airing cupboard on the hot water tank. This morning the flow has dropped to about 14lmin so something has affected it. 

I checked the Inta valve strainer yesterday and the filter is missing. I have raised it with the installer and they said they are coming out in a couple of weeks and will install the strainer and will power flush the system and check the other filter. 

I think I covered everything 🙂 

@heymikey OK, so that rules out a number of things. I would lean towards thinking you do actually have a flow restriction of some kind. If it's not air then 'something' is reducing the flow. Do you have any additional pump or are you using the outdoor unit pump only?

If you look in the New Zealand Chofu manual page 15 there's section 3.4 'Pressures and quantity available at heat pump outlet'. There's a DIP switch on the outdoor unit you can set to adjust the pump speed. On the AEYC-1242U (12kW in NZ, 13kW in UK) there 3 levels of flow based on the required head, with below 15L/min being the danger zone.  So sounds like something is wrong with your flow. You could look at what these are set at and see if a higher setting improves the flow rate.

But I suspect somebody needs to check if there's a blockage somewhere. When you say 'PVC pipe' do you actually mean PVC (garden hose type) or PEX or Polybutylene? Both PEX and PB are rated for heating while PVC collapses when hot. If it's in HDPE (blue water supply pipe) then that's only rated to about 38C.

@prunusk

I guess I was being generic with PV The pipe is the below. 

JG Speedfit WC22BPEX PEX Pipe. 

So an update but not much success. System was power flushed which seemed to get rid of the vibrating, but my flow rate still is awful. It slowly degraded down to almost nothing. Loads of air in the system and even Grant came out to check the unit as they suspected it was the heat exchanger but the manifold test came back at 46lmin.

So something is restricting but no answer as to why yet. Couple of guys are coming in the next few weeks to do a trace, flush and some other bits. 

@heymikey thanks for the update and sorry to hear that the issue persists. Hopefully they can identify the problem area. What a nightmare.