However it only makes sense if you are redoing a room
Indeed. My room with the greatest heat loss is the kitchen, with its three (or rather two and a half) solid stone outside walls, a good half of which is covered with fitted stuff, fitted kitchen, fitted cupboard and of course the huge 6ft long extremely heavy K3 rad, which will need very strong fastenings long enough to pass through the insulation to the solid wall. It's not that it is undoable, more that it is hugely disruptive, and so, as you say, only makes sense when redoing a room. At the moment, I have no plans to redo the kitchen, but who knows, if (when) a new owner takes over, they might want a new kitchen, and that would be the time to add internal insulation.
Midea 14kW (for now...) ASHP heating both building and DHW
@derek-m - yes, certainly an option, but I've always wondered how much benefit you get from wall reflectors, given they reflect back onto the radiator. I guess it reduces losses through the area of wall behind the radiator, but by how much, in say percentage terms? Then what is the total area behind the rads as a percentage of total external wall area? 10% of 10% is 1%...
In other news: I have found some open source Met Office data that has hourly air temp data (actually, it's every 5 mins or so, but a bit of jiggery pokery in a spreadsheet can make it hourly averages) for a location about 15 miles away from me, and plotted then again my twice daily (0800, 2000) kitchen temperature measurements. This is just a trial proof of concept plot for 1st to 5th April 2022 and I think it clearly shows the heating system fails to reach design temps when it is averaging about 2 to 3 degrees outside, left hand side of plot, room is around 2.5 degrees below design temp of 19 degrees, but can get to design temp when it is 10 degrees and a bit over degrees, right hand side of plot, room temp just gets up to 19 degrees ie design temp. I think what happens is when it's cold, the heat pump is running at max, but can't fully supply the demand, and so the room temp mirrors the outside temp ups and downs. You can just see the dips in room temp after the colder nights. The heat pump was on the standard Freedom curve weather comp mode at the time this data was collected, I plan to do a longer time series to include data from when the heat pump was running in fixed temp mode, but as it gets warmer, it is less likely we'll have colder spells that test the system.
Met office data from https://wow.metoffice.gov.uk/ You have to register (free) to access the data, a great source for geeks and nerds who like this sort of thing.
Midea 14kW (for now...) ASHP heating both building and DHW
@derek-m - yes, certainly an option, but I've always wondered how much benefit you get from wall reflectors, given they reflect back onto the radiator. I guess it reduces losses through the area of wall behind the radiator, but by how much, in say percentage terms? Then what is the total area behind the rads as a percentage of total external wall area? 10% of 10% is 1%...
In other news: I have found some open source Met Office data that has hourly air temp data (actually, it's every 5 mins or so, but a bit of jiggery pokery in a spreadsheet can make it hourly averages) for a location about 15 miles away from me, and plotted then again my twice daily (0800, 2000) kitchen temperature measurements. This is just a trial proof of concept plot for 1st to 5th April 2022 and I think it clearly shows the heating system fails to reach design temps when it is averaging about 2 to 3 degrees outside, left hand side of plot, room is around 2.5 degrees below design temp of 19 degrees, but can get to design temp when it is 10 degrees and a bit over degrees, right hand side of plot, room temp just gets up to 19 degrees ie design temp. I think what happens is when it's cold, the heat pump is running at max, but can't fully supply the demand, and so the room temp mirrors the outside temp ups and downs. You can just see the dips in room temp after the colder nights. The heat pump was on the standard Freedom curve weather comp mode at the time this data was collected, I plan to do a longer time series to include data from when the heat pump was running in fixed temp mode, but as it gets warmer, it is less likely we'll have colder spells that test the system.
Met office data from https://wow.metoffice.gov.uk/ You have to register (free) to access the data, a great source for geeks and nerds who like this sort of thing.
I'm sure Derek will chip in but wouldn't the radiators lose proportionately more heat through the walls than their area would suggest because the delta T between just behind the radiator and the wall will be a lot more than that between the rest of the room and the wall?
Useful data from the Met office; there is a station very near me so I'll have a look at that.
It definitely looks like your system isn't supplying enough heat at lower ambients. What exactly happens if an ASHP is underpowered? Does it just fail to meet its target LWT? Could you plot flow temps along with room and ambient temps? That might give some clue as to what is going on. I know it's a bit more complicated in your case with the primary and secondary flows.
I've read the whole thread with interest, some good discussion here.
For reference, the Midea rating specs are now quoted at A-2/W50 which is a good idea, and their detailed spec/cop sheet from their most recent price list also list the ratings and SCOPs at a good range of temperatures.
I just need to convince them to sell me one now 🙂
From the spec sheets (weights and dimensions), it looks like the 4&6 are the same unit, the 8&10 are the same unit, and as we know, the 12/14/16 are the same unit - all dipswitch controlled. I can see why the 16 is derated to 13 at -2 ambient, it's hard to get enough air through a single fan evaporator without excessive icing. You can also see how the units are dipswitch derated by the sound output, higher output, faster fan/compressor = more noise.
Off grid on the isle of purbeck
2.4kW solar, 15kWh Seplos Mason, Outback power systems 3kW inverter/charger, solid fuel heating with air/air for shoulder months, 10 acres of heathland/woods.
My wife’s house: 1946 3 bed end of terrace in Somerset, ASHP with rads + UFH, triple glazed, retrofit IWI in troublesome rooms, small rear extension.
Midea rating specs are now quoted at A-2/W50 which is a good idea
It certainly is, and interestingly, it clearly shows the model number nominal output (the number in the heat pump model name) is downright misleading. The MHC-V10 has an A2/W50 output of 8kW (20% less), the MHC-V12 has an output of 11kW (8% less) and the MHC-V16 has an output of 13kW (19% less). These are odd variations eg why is the V12 actual output only 8% less than nominal output, where as the other two are around 19-19% under-powered? It may have something to do with the fact the V12 and V16 are the same inside (same components), output is set by diddling dip switches (apparently).
I remain of the view that the heat pump industry deliberately misleads installers and customers by using model names that use numbers that bear little relation to the actual output at lower anbients ie when it matters. Freedom are to be congratulated for publishing A2/W50 data, but it is not headline data. Imagine the outcry if the car industry sold 100mph cars that only did 80mph (except going downhill with a following wind), or - this applies to the creative marketing on SCOPs - 50mpg cars that in practice only achieved 40mpg.
This dishonesty is, I suspect, a major, if not the dominant, cause of under-performing systems.
FWIW, I have found Freedom rather unhelpful, to say the least. Despite it being 2022, and the distinction between DIY and trade customers much blurred compared to past practices, Freedom have told me they are a B2B business, and have insisted I do everything through my installer. To me, this seems totally unnecessary: why do I need to relay my question through my installer, when I can just as easily in a sane world ask Freedom directly? You may have some interesting times ahead...
PS I've just noticed the second Freedom Midea table screen grab includes the unit weights, the V12 and V16 units being the same weight (and dimensions) adds credence to the possibility they are the same boxes inside and out, output is just set using dip switches. From the other weights/dimensions, it looks like the V4 and the V6 may be the same unit, likewise the V8 and V10. Hey ho... But why the hell don't they tell us this - it is a positive selling point (more flexibility)!
Midea 14kW (for now...) ASHP heating both building and DHW
Midea rating specs are now quoted at A-2/W50 which is a good idea
It certainly is, and interestingly, it clearly shows the model number nominal output (the number in the heat pump model name) is downright misleading. The MHC-V10 has an A2/W50 output of 8kW (20% less), the MHC-V12 has an output of 11kW (8% less) and the MHC-V16 has an output of 13kW (19% less). These are odd variations eg why is the V12 actual output only 8% less than nominal output, where as the other two are around 19-19% under-powered? It may have something to do with the fact the V12 and V16 are the same inside (same components), output is set by diddling dip switches (apparently).
I remain of the view that the heat pump industry deliberately misleads installers and customers by using model names that use numbers that bear little relation to the actual output at lower anbients ie when it matters. Freedom are to be congratulated for publishing A2/W50 data, but it is not headline data. Imagine the outcry if the car industry sold 100mph cars that only did 80mph (except going downhill with a following wind), or - this applies to the creative marketing on SCOPs - 50mpg cars that in practice only achieved 40mpg.
This dishonesty is, I suspect, a major, if not the dominant, cause of under-performing systems.
FWIW, I have found Freedom rather unhelpful, to say the least. Despite it being 2022, and the distinction between DIY and trade customers much blurred compared to past practices, Freedom have told me they are a B2B business, and have insisted I do everything through my installer. To me, this seems totally unnecessary: why do I need to relay my question through my installer, when I can just as easily in a sane world ask Freedom directly? You may have some interesting times ahead...
PS I've just noticed the second Freedom Midea table screen grab includes the unit weights, the V12 and V16 units being the same weight (and dimensions) adds credence to the possibility they are the same boxes inside and out, output is just set using dip switches. From the other weights/dimensions, it looks like the V4 and the V6 may be the same unit, likewise the V8 and V10. Hey ho... But why the hell don't they tell us this - it is a positive selling point (more flexibility)!
I am the funding provider, purchaser, designer and installer - if they won't sell to me then I'll just buy something else from someone who will. Cool Energy are currently on the list (they're helpful as heck on the email), as are LG (because the Therma V units seem a really good price).
Shame, because the Midea unit looks pretty decent from Graham's videos and what I've seen of the controller. I also feel slightly bad about getting hold of their latest edition of the spreadsheet (I just asked by email), using it to design my system, then not spending a penny with them.
The LG Therma V looks like it has a nice controller, that *might* (from what I can figure out) also support load compensation.
Off grid on the isle of purbeck
2.4kW solar, 15kWh Seplos Mason, Outback power systems 3kW inverter/charger, solid fuel heating with air/air for shoulder months, 10 acres of heathland/woods.
My wife’s house: 1946 3 bed end of terrace in Somerset, ASHP with rads + UFH, triple glazed, retrofit IWI in troublesome rooms, small rear extension.
Midea rating specs are now quoted at A-2/W50 which is a good idea
It certainly is, and interestingly, it clearly shows the model number nominal output (the number in the heat pump model name) is downright misleading. The MHC-V10 has an A2/W50 output of 8kW (20% less), the MHC-V12 has an output of 11kW (8% less) and the MHC-V16 has an output of 13kW (19% less). These are odd variations eg why is the V12 actual output only 8% less than nominal output, where as the other two are around 19-19% under-powered? It may have something to do with the fact the V12 and V16 are the same inside (same components), output is set by diddling dip switches (apparently).
I remain of the view that the heat pump industry deliberately misleads installers and customers by using model names that use numbers that bear little relation to the actual output at lower anbients ie when it matters. Freedom are to be congratulated for publishing A2/W50 data, but it is not headline data. Imagine the outcry if the car industry sold 100mph cars that only did 80mph (except going downhill with a following wind), or - this applies to the creative marketing on SCOPs - 50mpg cars that in practice only achieved 40mpg.
This dishonesty is, I suspect, a major, if not the dominant, cause of under-performing systems.
FWIW, I have found Freedom rather unhelpful, to say the least. Despite it being 2022, and the distinction between DIY and trade customers much blurred compared to past practices, Freedom have told me they are a B2B business, and have insisted I do everything through my installer. To me, this seems totally unnecessary: why do I need to relay my question through my installer, when I can just as easily in a sane world ask Freedom directly? You may have some interesting times ahead...
PS I've just noticed the second Freedom Midea table screen grab includes the unit weights, the V12 and V16 units being the same weight (and dimensions) adds credence to the possibility they are the same boxes inside and out, output is just set using dip switches. From the other weights/dimensions, it looks like the V4 and the V6 may be the same unit, likewise the V8 and V10. Hey ho... But why the hell don't they tell us this - it is a positive selling point (more flexibility)!
I'm sure you're aware that the TUV produce Technical Report documents in relation to the EN14825 testing - these have independent test results at various temperatures. I'm sure this is available for the Midea units as well. I attach the one from the Cool Energy 9kW inverter unit for your perusal/information, just so you can see what sort of things they test for.
Off grid on the isle of purbeck
2.4kW solar, 15kWh Seplos Mason, Outback power systems 3kW inverter/charger, solid fuel heating with air/air for shoulder months, 10 acres of heathland/woods.
My wife’s house: 1946 3 bed end of terrace in Somerset, ASHP with rads + UFH, triple glazed, retrofit IWI in troublesome rooms, small rear extension.
The ratings are also shown in their published price list now, which is transparent, I guess...
Off grid on the isle of purbeck
2.4kW solar, 15kWh Seplos Mason, Outback power systems 3kW inverter/charger, solid fuel heating with air/air for shoulder months, 10 acres of heathland/woods.
My wife’s house: 1946 3 bed end of terrace in Somerset, ASHP with rads + UFH, triple glazed, retrofit IWI in troublesome rooms, small rear extension.
@hughf - it also shows they charge £246.35 for flipping a few dip switches!
Well, if we’re going to get onto the topic of overpriced heat pumps 😂 after all it’s just a fridge really
Off grid on the isle of purbeck
2.4kW solar, 15kWh Seplos Mason, Outback power systems 3kW inverter/charger, solid fuel heating with air/air for shoulder months, 10 acres of heathland/woods.
My wife’s house: 1946 3 bed end of terrace in Somerset, ASHP with rads + UFH, triple glazed, retrofit IWI in troublesome rooms, small rear extension.
Another way of looking at the small differential is that it supports the idea they are the same units, the small differential is just there to make them appear different. Have to agree, they are very expensive fridges. At the least they should provide indoor on demand ice dispensers.
Midea 14kW (for now...) ASHP heating both building and DHW
Thinking about installing a heat pump but unsure where to start? Already have one but it’s not performing as expected? Or are you locked in a frustrating dispute with an installer or manufacturer? We’re here to help.
