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Octopus Cosy Heat Pump Owners & Discussion Thread

AndrewJ · 2025-10-23T11:37:06Z

I'd like to discuss how you find it, how you run it and so on.

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Air Source Heat Pumps (ASHPs)

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swwils

(@swwils)

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Joined: 7 months ago

Posts: 92

26/01/2026 2:52 pm

@razz very bad ones yes, but I am waiting from contact from the Octopus tech team to share, its not something customers should have to do.

I sent a message to TJ about it, the leg kit has also now been rubberised and ive seen a FB post where that solved it for someone else.

Ill drop them a call to nudge.

The best insight I can give is use your phone accelerometer (phybox app) not microphone a dB(A) to capture it, you can do this at the heatpump or any wall in your house - a dB(A) measurement will most likely have a low-cut filter applied and wont show up non-airborne noise. Remember it could be the compressor, the fan, or both!

This post was modified 3 months ago by swwils

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AgentGeorge

(@agentgeorge)

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26/01/2026 7:15 pm

@kevh cant notice any difference, I have a better COP at lower temperatures, can speculate they did something to the efficiency curve?

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KevH

(@kevh)

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26/01/2026 7:41 pm

@agentgeorge Interesting. I understand that both Cosy 6 & 9 owners are having visits (in and out of scheduled service visits) to have the pcb replaced but that the engineers are pleading ignorance as to why.

It must be important whatever it is.

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swwils

(@swwils)

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26/01/2026 7:56 pm

@kevh it's can be any reason really, they might just want every unit on the same hardware version to make things simple.

There was a software update sometime in August that made my hot water COP alot better. Literally a jump like 1.5 extra.

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AgentGeorge

(@agentgeorge)

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26/01/2026 8:10 pm

@kevh the engineer told me

he had a box full of old pcbs that get sent back to NI for processing; likely he means new firmware coded onto the pcb

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swwils

(@swwils)

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26/01/2026 8:53 pm

@agentgeorge mine was a over the air update. Just did it by itself.

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KevH

(@kevh)

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27/01/2026 2:38 pm

Posted by: @swwils

↑

@kevh it's can be any reason really, they might just want every unit on the same hardware version to make things simple.

There was a software update sometime in August that made my hot water COP alot better. Literally a jump like 1.5 extra.

How would I know of an OTA update? I cannot recall seeing any difference in performance, though I wouldn't complain if whatever is being done benefitted efficiency.

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KevH

(@kevh)

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27/01/2026 2:42 pm

Posted by: @agentgeorge

↑

@kevh the engineer told me

he had a box full of old pcbs that get sent back to NI for processing; likely he means new firmware coded onto the pcb

My home battery receives occasional firmware and software updates OTA; it seems odd to to me require a pub to be exchanged.

Having said that, whilst I love tech gadgets I have little actual understanding of the limitations of particular pcb components, so in many ways I am literally tech ignorant.

I've got my service in March so I'll engage with the engineer and see what he says.

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swwils

(@swwils)

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28/01/2026 1:57 pm

@kevh good question. No way of knowing afaik. I only found out because I was keeping a close eye trying to work out my issue and the ramp up behaviour significantly changed.

Look at my MID graph for hot water COP after end of August, it's very obvious on the DHW. Keep in mind i run a very hot 55C 300L water charge

This post was modified 3 months ago 2 times by swwils

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AgentGeorge

(@agentgeorge)

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28/01/2026 2:09 pm

@swwils OTA can only occur if the code is held in electrically alterable rear only memory, EAROM. Often a processor has code baked into it, which is why its called firmware, as opposed to software, that can be altered or corrupted.

This post was modified 3 months ago by AgentGeorge

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swwils

(@swwils)

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28/01/2026 2:12 pm

@agentgeorge dude the hub has an ESP inside we've been doing OTA firmware for a decade now.

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AndrewJ

(@andrewj)

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Posts: 205

Topic starter 31/01/2026 3:43 pm

I had two radiators upsized in the porch and downstairs wc as these two rooms just never got up to temp, even with the rest of the house overheating. I was running the heating thermostatically with the Primary Pod in the WC set at 19: this typically kept the rest of the house at around 22.5 give or take. The landing is a lost cause and is always over 23c and its radiator hasn't been on for over 2 months now. With the upgraded radiators I haven't moved the Primary Pod, just upped its set temp to 21c. This hasn't affected the rest of the house at all except for the porch which will now reach 20c. It seems to indicate that the concept of "setbacks" is a non-starter in this house which doesn't surprise me as everything heats/cools based on the heat loss of the WC.

Wife is happy as she likes these temps and mostly, so do I. The bedroom is nearly always 22.5c or so at bedtime which is too hot for me (she likes it!) even with the TRV set to 3, nominally 18c. I tested the valve and the pin isn't stuck, and it's a relatively new valve and head (say around 1 year old) so I'm making a guess that the temp by the radiator, on an external wall, at around 6" off the floor is relatively cool given the location of the temp sensor 3m away at chest height. The LSV was open about 0.5 of a turn so I'm working on that to see if I can bring the overall room temp down to around 21c as a compromise between the two of us. With it closed to 0.25 of a turn and the TRV back at 5 temperature has risen to 23.2 🙁 so much more work to be done. Perhaps start adding decorators' cap instead of the TRV head.

The flow temps are about as low as I can get them: 50c at -10c and 36c at 12c. I've been warned about poor performance with the Cosy 9 dropping the warm end below 36c. The 0c flow temp is 43c and dropping to 33c at 12c means the flow temp is 42.3c, a not particularly significant change. Given my wife is happy and the daily COPs are pretty good (SCOP since May is 3.84 with heating on mid-October) I'm not inclined to try and mess with it in terms of "always on, low and slow". Frankly, I'd just like to relax for a bit, ignore the heating if I can and get a life!

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