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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bimbleuk

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20/10/2025 5:30 pm

Posted by: @jancold

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@bimbleuk That is interesting. Can you tell me where you found that setting on the MMI please?

Enable installer mode - 5678

Enter the Space Heating/Cooling menu

Enter Pump Operation Mode - Select Continuous or Sample (default)
Enter Pump Limit - Select 60%/70%/80%/90% Pump Limit During Sample

Be careful to only change the pump sample speed from that menu. Expert advice should be sought first before making changes to avoid incorrect pump operation of course.

When still in Weather Dependent mode + Thermostat you don't see the pump sample mode as a selection. I think it was demand or continuous.

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