HughF

Ours were equally unhappy about the thought of 90mm in a 100mm cavity. We’re glad we went 150 and rockwool now, the thermal performance seems ‘good’ but it’s no passive house.

Is your builder any good? Pir in a cavity is a nightmare to get ‘good’… I’d go full-fill rockwool personally. Or blown bead.

If electricity wasn't 3.9 times the price of gas, it wouldn't matter. Stupid 'environmental levies'...

Probably, yes. They are paranoid about low flow errors and subsequent callbacks. Providing separation is an easy way to avoid this.

Grant have designed the Aerona3 to be a drop in replacement for an oil boiler running on S-plan. Completely the wrong way to fit a heat pump, but easy for installers. It's a shame as the Chofu unit they rebrand is quite decent.

Graham Hendra (he started freedom heatpumps, wrote the toolkit, and has been in the HVAC industry for his whole career) said that the number one issue with the early days of Daikin and Samsung installs (in the mid 2000's) was low flow errors. He decided hydraulic separation was the way to go to avoid all the flow rate issues, especially when everyone had TRVs on their rads. This has stuck.... I believe that now, he (like most of the industry) has come round to the idea of open loop (no hydraulic separation).

Not as far as I recall, it’s purely on the heating side of the 3 port…

Midea are supplied by freedom, freedom will have insisted on either PHX or LLH on all installs depending on year of install. They also run with external ‘stat and weather comp set to 55@-2 (if radiators) or 45@-2 (if UFH)…. This is all well documented in numerous YouTube videos by GH, by the tech docs floating around online, and by evidence of installs over on Mars’ ‘renewable heating hub’ forums. Lots of unhappy Midea owners over there.

Midea WC setup is part of the install process. It should have been setup. 55@-2, 37@15 are the defaults. Graham Hendra’s ‘Lizzie’ curve, named after his wife who complained the rads were always cold.

3kW immersion running 24/7 for 40 days (it’s nearly 40 days from December 7th - 20th Jan) would give nearly that usage. Backup heater in their LLH or buffer is running 24/7.

Midea wont be installed with a buffer. Plate or LLH depending on the year of install.

Bivalent systems are usually plumbed up with non return valves. The plate will be there to ensure warranty compliance with freedom heat pumps who supply midea here in the Uk. Sounds like your system is working though. 6000kWh/annum isn’t much. £1800/year on backstop rate.

Midea installer manual attached…. Nowhere in there can I find what the dhw hysteresis is set to by default. 1063-Midea-Installation-Manual-2021-for-web-FHP.pdf

The midea will say ‘on dhw’ in the middle when it is doing hot water reheat. I can’t find what the setpoint is for a dhw reheat in any of GH’s videos, but suspect it to be 10-12 degrees. When it’s heating radiators it will just say ‘on’ in the middle….

It’ll make about a grand on eBay, second hand…. You’d be better off spending the money on having it plumbed direct, ditch the plate heat exchanger and get the weather comp adjusted.

Midea, supplied by and plumbed according to freedom heatpumps instructions, which include the use of a plate heat exchanger. a couple of days replumbing this will make it much more efficient at heating the house…

‘Low on gas’ - what a load of horse shit…. Where do they find these people. As for it needing a service - that’s purely cleaning the filter ball or y-strainer. There’s nothing else to do that can affect performance. And people wonder why the industry has a bad name, did these people used to sell double glazing in the mid 90’s….. probably. You cannot check the charge on a monobloc like you would a regular hvac system (not a mini split) by monitoring the superheat, because they all have a refrigerant receiver built into the side of the compressor, the same as a mini split. The only way to verify the charge is to evacuate and refill off the scales, and no-one will do that this side of the pond. January was cold, of course you’ll see a worse COP….

Our whole house is running between £50-75 a week depending on how cold it is outside, that’s 115m2, heated to 22-22.5 24/7. Not unreasonable to have a £300/mo electric bill, especially if they’ve set her DD payment to cover the worst month. We’re on prepayment (reasons) so we don’t have to worry about paying the same amount every month so the energy co can pay their shareholders.

We did our rear extension, 3x5 on a building notice, no regs drawings or plans... Just made it up as we went along. We'll do the same with our side extension, settle on a contruction method (150 cavity, full fill) and get on with it.

Cheapest supplier so far is coming in at £236 but that's for a non-french (floating mullion)... Spreadsheet attached for info. https://docs.google.com/spreadsheets/d/19DsP9xARvOmH3sygbjOycDn70TVsht20168CWJIRDK8/edit?usp=sharing

It’s 100% a settings problem, it’s almost certainly running on the backup heater alone.

Yep, very sensible question. We can easily back calculate the electric costs for the year from this.

Air-air for the individual flats, and electric showers. Do you have 3 phase there? You might be able to get a decent 3 phase electric shower….

If the anti freeze valves are opening then the system is being turned off, or they are faulty. Daikin do like to use the backup heater and throttle the heat pump right back at the same time, a completely stupid scheme in my opinion. It sounds like you are trying heat your house on just the backup heater.

There are Two things that should always be designed out - hydraulic separation, and glycol…. Both the work of the devil.