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Octopus Cosy 12 Heat Pump Regret: Incredibly Loud, Poor Heating & Constant Hum - Help!

 
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Air Source Heat Pumps (ASHPs)
Last Post by L2jad 1 day ago
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 razz
(@razz)
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Topic starter 04/02/2026 7:15 pm  

@l2jad Glad to hear it. Hope it'll be sorted for us all. 

BTW, did they install a 4 port buffer or a 2 port volumizer for your system?

From an earlier conversation on here, I was told that the if the volumizer/buffer is 4-port system is about 15% less efficient. I've asked Octopus for an explanation of why a 4-port system, and not a 2-port system was installed, heard nothing back so far.



   
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Mars
 Mars
(@editor)
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04/02/2026 10:04 pm  

@razz I’d certainly love to hear their rationale for a 4 port… definitely update if they get back to you.


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 L2jad
(@l2jad)
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05/02/2026 1:44 am  

@razz its a 4 port system they installed



   
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 Harriworld
(@harriworld)
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05/02/2026 5:41 pm  

How has everyone been finding the latest firmware update? My Cosy 12 is a bit quieter but still above 61dB 



   
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 L2jad
(@l2jad)
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05/02/2026 5:56 pm  

@harriworld yes mine although better is still not right, had to turn it off at 2am was just going mad. Way too loud!!

i am setting up the deci meter tonight to check every minute and record. Meeting the head design lady next week. Was very stressful here again last night even 3 year old woke from the racket she normally just sleeps through anything, it affects everyone. Really don’t understand sometimes it’s perfectly quiet under 50db then boom off it goes, fan spins up and you can hear it through double glazing!!

Do you notice what causes yours or is it random? Still they are looking at it as know they have a problem, its a good company so no doubt will sort.

 

tonight i’m turning off the hot water cycle to see if that is having an affect? Will just boost in the morning.

but hey ho getting old so don’t need sleep!!



   
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 LivingGreen
(@livinggreen)
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05/02/2026 6:07 pm  

@harriworld it's better but hard to tell so far how much better. I'm really not going to believe a fix until we get some cold weather to test it, need some sub 5deg temps.



   
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 Harriworld
(@harriworld)
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05/02/2026 6:17 pm  

@livinggreen Colder temps definitely set it off. Mine had been less loud but still registered and 70db this morning. And the house is taking all day to get to temperature. I would still like it to be quieter (nearer the 61db would be an improvement). Although at point of sale I was told it would be 40db!!



   
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 Harriworld
(@harriworld)
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05/02/2026 6:18 pm  

@l2jad What time is your hot water cycle set for?



   
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 razz
(@razz)
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Topic starter 05/02/2026 6:32 pm  

@editor Another heat pump engineer/installer from Octopus came by. He said, the reason for the use of a 4 port buffer is to get "hydraulic seperation", couldn't explain what exactly that meant because he himself apparently doesn't do this very often.

Then he explained that when they first rolled out the cosy 6 and 9, they used a buffer and eventually switched to using volumisers. Since the 12 is so new, they're playing it safe by using a buffer, and that eventually they'll likely be using volumisers too.

Which isn't much consolsation for me, as my heating bill is a fair bit higher, while having a colder home. 

He also told me that they're getting a lot of calls about the cosy 12.

EDIT: I just saw your brilliant video on buffers, really do think Octopus might have made the mistake you mentioned. 

They put in absolutely HUGE K3 radiators in my house that are a genuine nuisance by how much space they take up, which is one of the ways to compensate for the water mixing caused by a buffer.


This post was modified 1 day ago 2 times by razz

   
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 L2jad
(@l2jad)
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05/02/2026 7:16 pm  

@harriworld it was roughly 3am  for  an hour as that’s my cheap iog time, my water heats to 50 degree quickly as its generally still quite high in the cylinder. originally the intension was to then raise the house temperature after the hot water cycle by a degree using cheap energy haven’t bothered just want peace and quiet!!!, the house loses heat very very slowly so normal house day time is temperature is 18 or 18.5. 
i moved hot water to between 6 and 7am after the earlier time woke the wife, daughter and grand daughter.

 

my house warms up very quickly being its generally only a degree out, rads get warm 50 degree flow. Bedrooms are turned down as gets too hot. The

IMG 5519

pods are within .5 a degree at most

 

 


This post was modified 1 day ago by L2jad

   
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