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Daikin Octopus installation update - I saw my first defrost. 😍😂

Lucia · 2025-01-03T13:27:38Z

Three months and two deep freezes later and I'm pretty happy with how my Daikin heat pump is running. It is now running on what Heat Geek's Adam Chapman calls 'Pure Weather Compensation' and Daikin call 'Leaving Water Temperature control' on a 'home made' design temperature of 38º @ -3º . Today it was -3 when I woke up and the house is a comfortable 22º. I'm fairly sure it will cope with 37º @ -3º if not 36º. For those who didn't see my original post when choosing an installer it's here. I chose Octopus for cost and because as soon as I met the technical team (as opposed to the nice heat loss surveyor) I was very impressed with their keenness and understanding of heat pumps. I argued unsuccessfully against the Octopus 50º design temperature and then lobbied hard for radiator upgrades that weren't originally specified. I learned as much as I could, mostly from the experts in this very forum, and in my head designed for a 40º flow temperature with my radiator lobbying. Just to recap my home is a bungalow of about 89sqm built into a hill with a big cellar (partially) on the ground floor and a garage with a utility room/space inside (freezer, washing machine, tumble dryer etc.,) both of which were excluded from the measuring & heat loss. Loft insulation 300mm and very patchy/holey cavity insulation. The 28sqm living room is effectively on the 1st floor and pretty exposed. The 180litre tank is in the cellar back-to-back with the 6kw Daikin heat pump. The hall is a square room used for play and workouts in the centre of the house and I argued against the MCS guideline of 18º for 21º. I also had one bedroom designed for 21º as it is used for an office. I started off using the Madoka as a room thermostat alongside weather compensation. I have no monitoring equipment except the Octopus app which tells me my electrical consumption and the flow temp/speed etc sensors on the MMI monitor. I found this combination of Madoka/WC erratic. My electricity use was, at times, up and down like a yo yo no matter how I tweaked the curve. What suited one OAT didn't suit another - the heat pump would switch on and off. Finally, a month after owning the heat pump I switched to LWT control and ditched the Madoka - it just no longer controls the pump. Houston we had lift off! This method is genius and Daikin seem to have designed this very well. I'm impressed. No ups and downs in the Octopus electricity consumption just super smooth sub 200-300w lines most of the time. No cycling. The heat pump never turns off. The flow rate is usually very low at around 7-9 litres pm except when it does defrosts and it shoots up to 29 litres. Recently I started experimenting with a small night time set back. If Daikin are very good at the tech, they are famously dire at writing manuals or offering access to information. There is nothing on how to programme a set-back on LWT control, zilch, nada, nix - bearing in mind room temperatures are not part of the equation. Eventually I discovered that you can tweak the overshoot number +/- 1º or whatever. This also very usefully permits testing of the 'design temperature' without restarting the heat pump. If it runs well at the room temperature you prefer on the chosen minus (or +) degree number you can programme the left side of the curve accordingly. Easy peasy!Oh, and even in the 'Big Freeze' it doesn't run the defrost very often and today I actually saw it (it's very quiet). 😁Radiator design things to note: I kept my trendy towel rail in the shower room and added my own designer radiator. It was really hard finding a small radiator with a high output for low temp. heating. Solution: Nordic Omega Aluminium 790mm x 660mm - Italian made, kicks out the heat and it's a very stylish 'designer radiator' with vertical convection fins on both ends. Everyone both designer and techie has admired it including Octopus. Sadly, no VAT reclaim for a self-install which is crap. When looking for radiators use an online calculator to convert from the standard 50º delta T - I converted to 20º delta T - which provides a rough capability estimate for a 40º flow temp according to HG. (It clearly works). Big beastie K3s 'disappear' (to a degree) if you paint them exactly the same colour as the walls. I use Tikkurila Optiva 3 (super matt paint) on the walls tinted to my chosen colour and Tikkurila Helmi 10 on the radiator and woodwork. Tikkurila is a Finnish brand, not cheap but cheaper than Little Greene etc., and tint-able to any colour. The numbers are the sheen levels and it is super tough and water-based. I knew my install team were good - the quality of workmanship is meticulous, they weren't threatened by female geekiness, they listened, they are heat pump evangelists, they worked hard and long hours but were easy going and great fun to have in the house for a week. Every single one of them has been promoted recently. To sum up..... ditch those thermostats - you really don't need them except as fairy wheels in ...

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RadWhisperer

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27/10/2025 10:44 pm

Posted by: @jamespa

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Is it possible there is air still trapped in the system. Mine took a month to clear and despite the presence of an auto bleed valve one radiator needed daily bleeding. Alternatively have you got an almost shut valve somewhere through which the water is being forced causing noise. Are all, or at least most, of your TRVs set to max so constantly open.

Flow through pipes should be close enough to silent not to matter so the noise is more likely to be a valve or bend or air or such like.

After installation the system did develop a noise in the volumizer and that turned out to be a bleed valve. Which when fixed caused a squeal in the balance pipe! Engineer was here so immediately knew what to adjust. In water heating mode there is no noise. Only when the two port switches to CH. I just checked the rads and everything was open apart from the lockshield in my bedroom which had a couple of turns on it. So I reckon that is another small improvement made thanks. No air in the rads.

Most of the noise comes from the outside pipes going up and over my bedroom and then down the other side to the downstairs rads. So I'm rather surrounded by pipes and susceptible to any noise in the system.

This post was modified 3 weeks ago 3 times by RadWhisperer

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JamesPa

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28/10/2025 8:46 am

Posted by: @radwhisperer

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Most of the noise comes from the outside pipes going up and over my bedroom and then down the other side to the downstairs rads. So I'm rather surrounded by pipes and susceptible to any noise in the system

ah - not the greatest routing. Is it possible to insulate and/or isolate the pumps from the structure?

4kW peak of solar PV since 2011; EV and a 1930s house which has been partially renovated to improve its efficiency. 7kW Vaillant heat pump.

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RadWhisperer

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28/10/2025 9:26 am

@jamespa Small mid-terrace so everything is is in closr proximity. Only thing I could do is try to swap the cheap plastic pipe clips for rubber isolating ones.

However I think that lockshield was contributing as it seem quieter when it turned on this morning. Just need a properly cold morning to hear it at it worst!

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JamesPa

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28/10/2025 10:19 am

Posted by: @radwhisperer

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However I think that lockshield was contributing as it seem quieter when it turned on this morning. Just need a properly cold morning to hear it at it worst!

Thats encouraging. As I say normal motion in pipework should be inaudible, its valves and bends that cause noise. Swept bends are better than elbows incidentally, but more trouble for the plumber.

4kW peak of solar PV since 2011; EV and a 1930s house which has been partially renovated to improve its efficiency. 7kW Vaillant heat pump.

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RadWhisperer

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28/10/2025 1:57 pm

Posted by: @jamespa

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Thats encouraging. As I say normal motion in pipework should be inaudible, its valves and bends that cause noise. Swept bends are better than elbows incidentally, but more trouble for the plumber.

My MMI is in the loft but I checked the pump flow rate when running the DHW cycle and it was 25 l/h and I could hardly tell it was running. So now I know where to look for any further noise reductions (if even required) cheers.

👍

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