PhilT

On mine there is no max ambient temp at which the unit turns off. It only turns off when target room temp at the central controller is exceeded by one degree, however that is transmitted from a room/rooms. This applies in all three modes; WC, Auto and target flow temp.

quote from a supposedly reputable manufacturer "...power consumption in standby mode should only be measured by use of a Watt hour meter to give a true figure, due to the nature of an inverter driven unit. Measuring current with a clamp meter and then calculating using P = V I pF will give higher readings than the system is actually consuming..." so to get a representative measurement you would need to switch absolutely everything off except the HP and watch your main meter reading over at least an hour.

It's a clever feature and seems to work well with my FTC6 and radiator setup but Mitsubishi advise it is not suitable for UFH. At least that's what I interpreted from their answer to my enquiry; "Auto adaption can only be used with Mitsubishi thermostats. UFH is generally used with third party thermostats so you will need to select the heating mode to fixed flow or weather compensation"

I do agree with you in principle but my supplier quoted the same price for Ecodan 8.5 and 11.2 models, and the databook suggests the older tech twin rotary compressor in the 8.5 is significantly less efficient at temperatures other than the 2degC midpoint. So If I was going for a smaller capacity model I would get one with a scroll compressor - either a smaller Samsung or Vaillant Arotherm Plus, costs permitting.

The 11.2 has a scroll compressor which gives a much flatter efficiency curve (COP vs ambient) than the twin rotary compressor in the 8.5, so better efficiency at very cold temps. Power delivery is constantly variable down to around 30% of full power so it can deal with low loads really well. Also I very much agree about the desirability of having the extra headroom for the really cold nights.

Mitsubishi Ecodan R32 (PUZ-WM112A). It's similar to most other latest brands/models using scroll compressors with R32 or R290 refrigerant. I was lucky to find an installer who really knew their stuff and did a fantastic job.

I reckon a SCOP of 4 to 5 is achievable for the latest models, well installed and set up. I just re-worked my numbers based on these latest costs (including daily fixed rates) and my ASHP is saving me £1,148 pa with no heat loss saving measures. Yes granted the old boiler was probably less than 80% (perhaps as low as 70%) efficient, but that is probably no different from the average uk household, still operating at crazy flow temps up in the 70s degC (the legal max is now 55degC). Even allowing for 70% efficiency I'm getting an implied SCOP of around 5.

The latest gen ashp models, if competently installed and set up, are much cheaper to run than the average gas boiler. At current rates mine is saving me c. £700 pa

Highly impressive. Samsung are at the cutting edge of energy saving gear. One of their latest full height fridge freezer models is claimed to run at an average power consumption of just under 0.3kWh per day!

"Louder" rather than "Loud" - it's all relative, only happening when it's very cold and everyone is indoors with the windows shut! You can barely hear 71dB from inside the house. Although it was unexpected based on the specs (and Youtube vids) it's really not a problem.

Yes it's somewhat confusing. Sound Power Level, also denoted by PWL, is different from Sound Pressure Level. Sound Power Level is the absolute level of sound power that an object radiates in all directions, i.e. the sound power GENERATED, in watts and decibels, whereas Sound Pressure Level is what is received by either the human ear or a measuring device such as a decibel meter. The LG is quoted at a sound power level of 63dB but I can't see a Sound Pressure Level quoted. The Ecodan is quoted as having a Sound Power Level of 60dB and a Sound Pressure Level of 47dB at one meter. This is for average temps, at which all the latest brands/models run at similar very quiet levels. That changes significantly when temps drop to a few degC and below - the fan and machinery work harder and get louder. I measured mine's Sound Pressure Level last year from an open window just under one meter to the right of the unit and got 53dB at 9degC, rising to 63dB at 4degC and 71dB at 0degC

PWL is "absolute" whereas SPL depends on distance from the source. Ecodan PWL is 60 with SPL 47dB @ 1m. All the leading brands are quiet at temps above 4degC. They all get much noisier below that (it's a muted "roar" rather than an unpleasant "noise") but the manufacturers don't quote those figures, at least I haven't been able to find any.

This is the text from the Copeland tech manual on their scroll compressors: http://www.hvacrinfo.com/cope_ae_bulletins/TAE1312.PDF (for those using resistive heaters the principal still applies) Crankcase Heat - Single Phase Crankcase heaters are not required on single phase compressors when the system charge is not over the 120% limit shown in Table 5. A crankcase heater is required for systems containing more than 120% of the compressor refrigerant charge limit listed in Table 5. This includes long line length systems where the extra charge will increase the standard factory charge above the 120% limit. Experience has shown that compressors may fill with liquid refrigerant under certain circumstances and system configurations, notably after longer off cycles when the compressor has cooled. This may cause excessive start up clearing noise or the compressor may lock up and trip on protector several times before starting. The addition of a crankcase heater will reduce customer noise and dimming light complaints since the compressor will no longer have to clear out liquid during start. "dimming lights complaints" lol. The above and table 5 imply that heat pump manufacturers may charge their circuit to more than 120% of the "charge limit" for reasons unknown but possibly efficiency gains? Lending weight to the hypothesis that Mitsubishi do on the models burning 40W for example, but LG don't - for example the model cited in an earlier reply which had effectively zero standby draw.

The tech blurb for Copeland scroll compressors says that some do and some don't; HPs with a coolant charge above a certain level need compressor heating to prevent the coolant compromising lubrication and start up. Sounds like LG and Mitsubishi have adopted different approaches; lower coolant charge/no compressor heating vs higher coolant charge + heating which would only make sense if higher coolant charge gives better efficiency

No to the first part but yes, my old heating method was horribly inefficient. My gas usage was 21,000kWh pa implying boiler efficiency of 76%. But even if EPC was overstated by 20% SCOP would still be well over 4.

I can't speak for the 3 phase models but the latest single phase 11.2kW model is keeping us cosy using only 3k kWh pa against an EPC heat loss calculation of 16k kWh pa. The standby draw is a small price to pay to achieve that level of efficiency. If you have another way of heating DHW you can switch it off in the summer

A clamp meter will give the wrong reading (see attachment from Mitsubishi). From the thread on Ecodan standby power consumption, there is some evidence, based on actual meter readings, that the resistive standby heating for single phase models draws around 40W on average, with a step change over/under 21degC. Standby Power Consumption (1).pdf

I recently looked into this myself for my Ecodan with conventional radiator circuit. Mitsubishi tech help told me:- "Auto adaption can only be used with Mitsubishi thermostats. UFH is generally used with third party thermostats so you will need to select the heating mode to fixed flow or weather compensation."

I have a service contract with my installer at £150pa and that pays for an annual service and safety check, extension of manufacturer's replacement warranty for 5 years, and unlimited phone technical support during working hours. Seems reasonable compared to what I got with my gas boiler.

Have you investigated the new Octopus heat pump offering? https://octopus.energy/get-a-heat-pump/?gclid=CjwKCAjwsfuYBhAZEiwA5a6CDMKI6dOagklOak9qTEMtWeoIzdw5SEUNo2MX8s0XkWoGUGdiK9bCGRoCFrsQAvD_BwE

Thanks! I hadn't been able to find a detailed explanation of this mode in any of the manuals. I also listened more carefully to one of Mitsubishi's own videos on YouTube ("Ecodan Heating Modes") which, at 2:20 briefly mentions the magic words "...auto adaptive..." and "...uses weather compensation in the background..." bingo! So the Ecodan does in fact have exactly the "smart" function I was looking for, as long as you are using its own compatible controller.

That would be great if true does anyone know how to set load compensation on the Ecodan controller?

Solar gain outside yes. The solar gain inside, which can be significant with a lot of glass/south facing etc. does not affect the WC curve - at least not on mine - it's a straight relationship between outside temp and flow temp. My system is well balanced but my preferred setup would be at 6am for the flow temp to be higher to get the room temp back up to my set level asap. As it approaches that set room temp I would like the HP to be smart and back off the flow temp to maintain room temp at my set level. Presently I have to do this manually by knocking a few degC off the flow temp once room temp has been reached. I don't want to lower the WC curve it would take too long in the morning to get the rooms up to temp. Like someone said, it would be good to have the WC curve on some kind of timer, like the temp timer, or, best of all, make the controller smart enough to reduce the flow temp as the room temp reaches the set level.

On my Ecodan the room stat rules even in WC mode. This is ok because sunny days warm the house more for a given outside temp, and WC mode is not smart enough to reduce the flow temp as the room reaches the desired temp and keep the HP efficiently ticking over bang on that room temp setting, which is a pity.

The latest leading brands/models are all very quiet at ambient temps above 3degC but below that sound levels start to rise from a whisper to a "roar", however you can barely hear it inside the house, and neighbours are indoors during the very cold periods anyway. The friend who recommended my ASHP had his installed just outside the back door of a 200 year old terraced cottage right up against a thin wood side fence. It has been going for over two years and he's had no noise issues with his neighbours