Hi, quick question for those of you who have had your 9kW Daikin units swapped for the 8kW - roughly how long did the physical unit swap itself take?
Our 9kW was installed with the MMI & Madoka controls; so rather assuming the work involved is “just” a case of disconnecting the 9kW wiring & pipework and then fitting the 8kW in its place?
Presumably the existing controls are re-used with no other changes?
Waiting on dates for install at the moment but just want to get a better idea of the work involved.
Turns out after much deliberation that our 9kW was so early on in the installs that it was commissioned before the smaller 4-8kW units became available. As such Octopus are sticking by their original calculations/sizing but we’ve reached an agreement to part-fund replacing the unit.
Only a couple of hours. 3 guys onsite, two plumbers and an electrician.
New unit delivered the day before on a pallet. Old unit collect same day on the new units pallet.
Issues were concrete base for legs from the 11kW didn’t line up, so they got creative.
The primary flow and return are reversed on the 8 compared to the 11. They had to get creative.
On the upside, I did not need to add the new 8 to the Onecta app or the Onecta API. It’s all just moved over seamlessly.
My schedules came across to the new 8.
They did remove and check the magnetic filter.They also did do a purge and did a quick bleed of the rads as well once the replacement was in. They also checked he flow on the MMI and adjusted the abv for the reduced flow.
Cool! When did that happen? How long after install has it been between 11 and 8? I’m fighting the same battle. Yes, also keen to hear how it’s running compared to the 11.
@chrisg - can understand how we ended up with the 9kW here but the 11kW seems like a whole different step up in terms of oversizing if you’re now aiming for an 8kW.
How long have you had the system in for, and curious what the original heat loss calcs suggested vs reality?
It’s been in since late October 2024.
The survey indicated 9kw heat loss, 50c flow at -3c.
Reality during the cold snap in Jan (10th-12th) where were subzero for all three days and down to -5c overnight was 116kWh produced heat according to MMI (including DHW) but even if we take all that for space heating, it’s less than 5kw of heat loss. A flow temp of 37c at -3c is sufficient to maintain the house.
A Heat Punk calculation I did myself suggests 6kw heat loss at -5c.
Raised the issue with Octopus end of Nov beginning Dec.
Got nowhere with my install coordinator, main octopus heat pump support email etc.
Had to raise an official complaint via the form found here.
This triggered an engineer visit who was incredibly helpful. See suggested a re-survey.
The resurvey dropped my heat loss from 10kW down to 9.1kW, which meant the 11kW was the correct unit.
However, I have been collecting daily data since beginning of November using
The key for me was my local Octopus engineer (Jo) who new the right people to speak to and when presented with my data had no doubt the 11kW was oversized. But there were still lots of hoops to jump through and some pushback from octopus management. Jo also suggested I run the 11kW using the Octopus default settings so as not to provide an excuse along the lines of “its not working as you are not using our settings”.
This morning its looking like this as I start tweaking the curve, which the octopus default was still way too high
That cold snap certainly generated some useful metrics - was the trigger point for us trying to get a conversation re-started too.
Hard to accept the theory when you’ve got real-world examples demonstrating how your house and system behave, but still challenging to get the data reviewed.
Wow, that’s one heck of a difference. Fantastic to see! The idea of a system keeping the house warm with 246w rather 960w is quite the revelation all by itself really.
I’m guessing the performance data from HeatpumpMonitor.org for your system aligns with the heat demand figures you’ve calculated too?
Also found it extremely hard to get anywhere, similar timescales around our conversation from the looks of things with an official complaint being raised ironically at the instance of someone on the main customer services team.
Curiously we had a second survey conducted too, which seemed to be intended to find reasons to increase the original heat loss figure to help justify the 9kW.
Great to see the difference - looking forward to setting a date for our swap!
Starting to wonder how many customers with 9-16kW’s who monitor their system are actually happy with what it’s doing for them. Certainly raises questions about sizing…
I could probably get away with a 6kW here but have opted for the 8kW as they’re the same hardware & might as well keep the headroom; not expecting to need it though.
You are helping the masses (I hope) by opening Octopus’ and other installers eyes to the realities of heat loss!
I hope it means more homes get the right heatpumps from the getgo!
I have a feeling Matt’s eventually win helped Octopus not over size our property.
Part of them wanted to in the beginning, I pushed back and got them to put on an email that they’d downsize it is it was wrong.
They actually came with a 8kW and didn’t even tell me…
The cynic in me says the bean counters want oversize installs to make more in kW juice sales!
It’s their business model after all!
It’s an interesting problem isn’t it… on the one hand, fitting a 9-16kW Daikin rather than a 4-8kW means more energy will be used and therefore generates more revenue through energy sales. On the other… it generates more annoyed customers and probably those of us chasing down swaps cost them more in admin overhead, replacement unit costs & engineer time than they’d make from the additional energy cost.
I suppose the theory’s sound; fit a slightly too big heat pump and a customer’s house will be nearly guaranteed to be warm, resulting a happy customer. Just falls apart as Daikin’s model lineup forces the decision between large or small units, regardless of rating.
Haven’t seen many discussions about customers thinking they have oversized Cosy units so perhaps those can successfully modulate down to lower power levels whereas the Daikins can’t.
Seems to boil down to the surveys not always considering all aspects of the building materials, the design calcs having a safety margin included and the design team needing to ensure they satisfy everything needed.
The install team fit whatever they’re told to fit.
The Octopus service engineer told me that Octopus have taken note of my case. She also came round the day after the swap to check things out and is 100% behind my reasons to swap as was the original install engineer (now install trouble shooter) who also came back to do the swap.
Everyone from Octopus I spoke to was supportive and curious about my case. Nor has anyone from Octopus told me I am on my own now.
It took longer than hoped but it seems there are processes to go through, they are also extraordinarily busy.
because they made a lot of mistakes with over sizing , i still believe there are a lot of oversizing (arguably safe option ) knowing that only a single figure % will notice .
i bet they have a lot of 9 kw HP in a warehouse
Think that’s a really good point. Had a chat with someone earlier today who’s got an 11kW Daikin. Their house is a relatively recent build with decent levels of insulation. The unit cycles a fair bit but keeps everything warm without any fuss. Cost less than their oil boiler used to through Jan/Feb and they’re not bothered about chasing efficiency.
Would imagine a 6kW would work just as well
As for a warehouse, guess the replaced 9 & 11kW units get refurbished and used as spares / replacement / training kit but who knows!
