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Is this normal? Click of the DHW returning to space heating

 
Air Source Heat Pumps (ASHPs)
Last Post by ASHP-BOBBA 3 weeks ago
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 Grantmethestrength
(@grantmethestrength)
Estimable Member Member
Joined: 3 months ago
Posts: 40
Topic starter 12/04/2025 10:16 am  

 

This has been bugging me for a while and I just wanted to check if this is normal. At the start of the video you hear the click of the DHW returning to space heating and then you hear the clunk. It just really doesn’t sound right to me. We know that there is a fault with the diverter valve as the first four radiators in the circuit are still getting heat when the DHW is on. Is this the start of a bigger issue?

This topic was modified 3 weeks ago by Mars

Kind Regards
Si
——————————————————————————
Grant Aerona3 13kW
13 x 435w Solar Panels
Solax 3.5kW Hybrid Inverter


   
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 ASHP-BOBBA
(@ashp-bobba)
Reputable Member Member
Joined: 5 months ago
Posts: 116
16/04/2025 3:53 pm  

No this is not normal at all, most systems are not clunking like this. I thought (I don't know every brand Inc Grant) when the ASHP switches over the flow is reduced or stopped to allow the diversion. This sounds to me like hydraulic back pressure or something snapping over once the valve gets to almost closed on the DHW circuit and that the pump is still running full speed or it is moving something loose as the flow hits the line? hard to tell just from a sound video.

This could also indicate the the system is using the DHW loop as a bypass and something is blocking part of the heating loop so in effect slamming the ball of the 3 port against the closing section on DHW.

Little test you can try:

Turn off the ASHP DHW and only start the system in heating, then try the opposite and only start the system in DHW and see if any of the sounds are there on either, if they are not it is likely something wrong with the change over function of the 3 port, back pressure, pump command or that element of control.

  


   
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 Grantmethestrength
(@grantmethestrength)
Estimable Member Member
Joined: 3 months ago
Posts: 40
Topic starter 16/04/2025 4:11 pm  

@ashp-bobba thanks for confirming this, I do notice that the water pump doesn’t modulate at all and pretty much runs constantly. We are still waiting for Smart Energy Homes to come and rectify this and the leaks, they have said someone should be with us next week hopefully!

Kind Regards
Si
——————————————————————————
Grant Aerona3 13kW
13 x 435w Solar Panels
Solax 3.5kW Hybrid Inverter


   
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 ASHP-BOBBA
(@ashp-bobba)
Reputable Member Member
Joined: 5 months ago
Posts: 116
16/04/2025 4:20 pm  

@grantmethestrength Oh sorry to hear that, there should not really be leaks and clunking valves from a new installation, I assume its new as you have leaks? 

 

Good luck and please let me know what they find, it will be good to get an understanding of what it was, I have only ever seen something simular once before and that was hydraulic hammering on the 3 port as a result of a closed line much further down the circuit (kind of like TRV hammering on a large pumped system) 


   
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