@bretix intelligent is just for EV. You can get GO without one. No one actually asks
12kW Midea ASHP - 8.4kw solar - 29kWh batteries
262m2 house in Hampshire
Current weather compensation: 47@-2 and 31@17
My current performance can be found - HERE
Heat pump calculator spreadsheet - HERE
Your complaint should actually be against Midea and Freedom, since the data clearly shows that a 14kW labelled heat pump, cannot deliver 14kW of heat energy when it is required to do so.
Did you find out how much efficiency you are losing due to the installation of the PHE?
My understanding as a non-lawyer is that as I don't have a contract with Freedom or Midea (for Midea heat pumps in the UK, Freedom are in effect Midea), I have no comeback against them (no contract so can't be a breach of contract). I think a better and ultimately more useful for other people approach is naming and shaming, and of course the RHH doesn't an excellent job doing this, but the problem is audience, many of us are preaching to the converted. The politicians don't care one iota, all they want is ticked boxes, all heat pumps fed and ready to fly, and Freedom are delighted to oblige. For the average punter, as others have observed, there is information asymmetry so huge it can, to coin a phrase, be seen from space. It's a rigged market through and through. Trading Standards won't stand a chance, and MCS, as has been recorded many many times on this forum, are useless and toothless. What's missing is media interest, and I am not sure how to go about generating that. Human interest stories first and foremost of course, but most journalism in this country is but a shadow of its former self. Where are the great investigative stories of the past from the Sunday Times these days?
The PHE (in)efficiency remains an unknown, because we don't know enough about it, and can't measure the things that would allow a valid calculation of efficiency, but I don't think it is that great at the moment, based on crude primary in secondary out temperature measurements. Nor do I think it, strictly speaking, loses anything, it is more like a resistance to transfer, or a bottleneck in the system that restricts flow of heat/energy. One constant problem with heating system design is we calculate radiator sizes based on in effect mean radiator temps, and then focus on and monitor LWT. All the manufacturers tables do this, the output tables are for heat pump LWT, not what actually turns up at the rads. We design the rads to be say 50 degrees, set the pump to deliver a LWT of 50 degrees, and then ignore the fact the rads will probably only be 40 degrees.
Back in the real world, it was -4 for most of last night, and this morning my kitchen was 15.5 degrees, 3.5 degrees below the design temp of 19 degrees. As we don't know what the heat curve does outside its set parameters (mine are currently -2 and 15), ie does it extrapolate the same gradient beyond these points, or does it flat line, I am going to use a -4 set point (55@-4). That said, I doubt it'll make any difference, at no point when observed over the last 24 hours has the LWT reported by the Midea controller reached its set temperature. With ambients around -2 to -4, the LWT has been around 49 to 50. It should be (at least) 53 (current setting is 53@-2).
The other thing I have noticed is that during the cold weather, the LWT/RWT gap has widened. In milder weather, it is normally 5 degrees, which is as I understand it where it should be. Over the last couple of days it has been 8 degrees, but I am not sure what this tells us. I am not sure the answer is obvious.
Midea 14kW (for now...) ASHP heating both building and DHW
@kev-m - here's the text from the post that wouldn't allow me to post the file:
I've extracted and tidied up the Midea 14 and 16kW data from the Engineering Data handbook, and it looks like the 16kW unit can deliver the necessary heat, but at a cost. At 0 degrees ambient, 55 degrees LWT (needed whatever the unit to have the rads emit enough heat), the 14kW unit delivers 11599W at a COP of 2.27 using 5099W input, the numbers for the 16kW unit are 12643W out at a COP of 2.4 using 5278W input. At -5 ambient, the difference is greater, see attached file. My heat loss at -2, you may recall, is 12.4kW.
All these figures are from the 'max' rows, I've never seen a way of setting 'max', 'norm' and 'min' capacity level, and so have assumed the unit maxes itself out when it needs to.
I tried plotting the data, but it looked like an unholy mess and added nothing to the raw figures.
You also asked "Were potential losses from the PHE factored into the calculations?" - I don't know for sure, but I suspect not (see also above in my previous reply to @derek-m).
From the point of view of 'naming and shaming' you could try e-mailing the various newspapers etc. to see if any would be interested in your case.
From the research I have carried out on PHE's, it would appear that it would be normal for the water temperature in the secondary circuit, to be 5C lower than that in the primary circuit. Whilst this should not be a major problem with a gas or oil fired boiler, it can have quite a detrimental affect with an ASHP. If as you have stated, the water coming from the heat pump is 50C, then the temperature of the water going to the heat emitters could be in the region of 45C, which means the heat energy output from the heat emitters is much reduced, hence their failure to bring your kitchen up to the desired temperature. I will forward the e-mail I received from your PHE manufacturer so that you may be able to obtain more details.
The fact that your heat pump cannot achieve the required LWT does appear to indicate that it is under powered for the job. The only options that I can suggest is to lower your heat loss, or replace your heat pump with one that can produce its specified energy output.
I think that the forum has now explored all the available options, you therefore must decide which may work best for you.
@kev-m - here's the text from the post that wouldn't allow me to post the file:
I've extracted and tidied up the Midea 14 and 16kW data from the Engineering Data handbook, and it looks like the 16kW unit can deliver the necessary heat, but at a cost. At 0 degrees ambient, 55 degrees LWT (needed whatever the unit to have the rads emit enough heat), the 14kW unit delivers 11599W at a COP of 2.27 using 5099W input, the numbers for the 16kW unit are 12643W out at a COP of 2.4 using 5278W input. At -5 ambient, the difference is greater, see attached file. My heat loss at -2, you may recall, is 12.4kW.
All these figures are from the 'max' rows, I've never seen a way of setting 'max', 'norm' and 'min' capacity level, and so have assumed the unit maxes itself out when it needs to.
I tried plotting the data, but it looked like an unholy mess and added nothing to the raw figures.
You also asked "Were potential losses from the PHE factored into the calculations?" - I don't know for sure, but I suspect not (see also above in my previous reply to @derek-m).
I thought the COP would be better with the bigger output at these high demands and it is. If the COP stays at 2.4 then the 16kW should deliver 12.4kW with 5167W input, which is very close to what the 14kW needs to deliver 11.6. I'm assuming the ASHP has a variable output and isn't 3 speed - I might be wrong.
The only difference between the mideas is the fan and compressor speed…. Run both faster, get more heat out.
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.
From the research I have carried out on PHE's, it would appear that it would be normal for the water temperature in the secondary circuit, to be 5C lower than that in the primary circuit. Whilst this should not be a major problem with a gas or oil fired boiler, it can have quite a detrimental affect with an ASHP. If as you have stated, the water coming from the heat pump is 50C, then the temperature of the water going to the heat emitters could be in the region of 45C, which means the heat energy output from the heat emitters is much reduced, hence their failure to bring your kitchen up to the desired temperature.
I am sure this is a factor, and as I have said, I don't think Headroom Heat Pumps factor this in, they just assume PHEs (and LLHs) have 100% heat transfer, ie the system is designed as if they weren't there (that's why they are called Headroom Heat Pumps, everything has loads of headroom). It's only later, in the Installation manual, that the PHE/LLH appears, usually but not always along with the warranty warning. The other system factor is the heat pump output is inadequate in cold weather, see below.
I still have reservations about removing the PHE, it is likely to be irreversible if it happens, so I need to be really sure I want to do it, and furthermore it won't invalidate my warranty. The other potential game changer is the secondary glazing. It is still work in progress, it is slow work because the frames are awkward to work on, and I'm probably giving myself lead poisoning, as the paint is at least 40 years old, and some of it probably much older. With the cold weather, it has been much easier to identify draughts by feel (the icy cold blast is much easier to identify that warmer air in milder weather), and these draughts are not trivial. The worst offending windows are irregular cast iron lattice casements in irregular oak frames, very pretty to look at especially with the old float glass, but leaky as a sieve, and no easy way to seal them directly. For starters, the rebates are too small. Once the oak frames are levelled - there is often a step between adjacent timbers, and many of the joints are held together with large wooden pegs which are proud of the surface, and decorated - the secondary glazing, held in place by magnetic strip all round the edges, will create a seal, and should substantially reduce if not effectively stop draughts.
Putting all this together, I am going to focus on getting the secondary glazing done, and see how much difference that makes. I don't think it is any coincidence that the room that struggles most is the kitchen, which is triple aspect with three windows, only one of which is currently secondary glazed.
I think that the forum has now explored all the available options, you therefore must decide which may work best for you.
Derek, I hope that doesn't mean you are getting fed up. I know from past posts you have felt this before - you do all your input, and then we punters ignore it. I would just like to reassure you that I have found your, and that from the other many wonderful people on this forum, extremely helpful, and absolutely in no way have your efforts been wasted. You have all greatly increased my understanding of how ASHP systems work, and helped my greatly in deciding what I do and don't do.
PS the link in your second post above isn't appearing as a link for me, Mars has my email address, he might be kind enough to give it to you so you can email the PHE email to me. The email may help me to decide.
I thought the COP would be better with the bigger output at these high demands and it is. If the COP stays at 2.4 then the 16kW should deliver 12.4kW with 5167W input, which is very close to what the 14kW needs to deliver 11.6. I'm assuming the ASHP has a variable output and isn't 3 speed - I might be wrong.
The only difference between the mideas is the fan and compressor speed…. Run both faster, get more heat out.
Interesting, I hadn't looked at it that way round, ie calculating the necessary power input from the COP to get 12.4kW. Continuously variable, rather than three fixed steps, makes sense, isn't that the sort of flexibility inverter controlled units give you? It should also be possible to monitor energy use, I have three places I can do that, external meter, on the Midea controller itself, and on the app, though as @batalto has shown, the rounding errors mean the app will probably not be accurate enough. I may well flip the switches tomorrow. Tonight looks like it is going to be very cold again, like last night, but the forecast up to a week ahead shows below zero at night every night, and even all day on some days.
Midea 14kW (for now...) ASHP heating both building and DHW
Unless it is an RNI that is glued to the exchanger you can remove the thermal insulation from it. The nameplate is on the front cover where the 4 connections are.
If you want to make selections on your own or check different duty point for a particular unit, feel free to register at www.cairo.hexonic.com. This is our selection tool. When the registration process is complete and you click the verification link received in an email, mail me again so I can push it a little bit to grant you access to the selection modules.
From the research I have carried out on PHE's, it would appear that it would be normal for the water temperature in the secondary circuit, to be 5C lower than that in the primary circuit. Whilst this should not be a major problem with a gas or oil fired boiler, it can have quite a detrimental affect with an ASHP. If as you have stated, the water coming from the heat pump is 50C, then the temperature of the water going to the heat emitters could be in the region of 45C, which means the heat energy output from the heat emitters is much reduced, hence their failure to bring your kitchen up to the desired temperature.
I am sure this is a factor, and as I have said, I don't think Headroom Heat Pumps factor this in, they just assume PHEs (and LLHs) have 100% heat transfer, ie the system is designed as if they weren't there (that's why they are called Headroom Heat Pumps, everything has loads of headroom). It's only later, in the Installation manual, that the PHE/LLH appears, usually but not always along with the warranty warning. The other system factor is the heat pump output is inadequate in cold weather, see below.
I still have reservations about removing the PHE, it is likely to be irreversible if it happens, so I need to be really sure I want to do it, and furthermore it won't invalidate my warranty. The other potential game changer is the secondary glazing. It is still work in progress, it is slow work because the frames are awkward to work on, and I'm probably giving myself lead poisoning, as the paint is at least 40 years old, and some of it probably much older. With the cold weather, it has been much easier to identify draughts by feel (the icy cold blast is much easier to identify that warmer air in milder weather), and these draughts are not trivial. The worst offending windows are irregular cast iron lattice casements in irregular oak frames, very pretty to look at especially with the old float glass, but leaky as a sieve, and no easy way to seal them directly. For starters, the rebates are too small. Once the oak frames are levelled - there is often a step between adjacent timbers, and many of the joints are held together with large wooden pegs which are proud of the surface, and decorated - the secondary glazing, held in place by magnetic strip all round the edges, will create a seal, and should substantially reduce if not effectively stop draughts.
Putting all this together, I am going to focus on getting the secondary glazing done, and see how much difference that makes. I don't think it is any coincidence that the room that struggles most is the kitchen, which is triple aspect with three windows, only one of which is currently secondary glazed.
I think that the forum has now explored all the available options, you therefore must decide which may work best for you.
Derek, I hope that doesn't mean you are getting fed up. I know from past posts you have felt this before - you do all your input, and then we punters ignore it. I would just like to reassure you that I have found your, and that from the other many wonderful people on this forum, extremely helpful, and absolutely in no way have your efforts been wasted. You have all greatly increased my understanding of how ASHP systems work, and helped my greatly in deciding what I do and don't do.
PS the link in your second post above isn't appearing as a link for me, Mars has my email address, he might be kind enough to give it to you so you can email the PHE email to me. The email may help me to decide.
I thought the COP would be better with the bigger output at these high demands and it is. If the COP stays at 2.4 then the 16kW should deliver 12.4kW with 5167W input, which is very close to what the 14kW needs to deliver 11.6. I'm assuming the ASHP has a variable output and isn't 3 speed - I might be wrong.
The only difference between the mideas is the fan and compressor speed…. Run both faster, get more heat out.
Interesting, I hadn't looked at it that way round, ie calculating the necessary power input from the COP to get 12.4kW. Continuously variable, rather than three fixed steps, makes sense, isn't that the sort of flexibility inverter controlled units give you? It should also be possible to monitor energy use, I have three places I can do that, external meter, on the Midea controller itself, and on the app, though as @batalto has shown, the rounding errors mean the app will probably not be accurate enough. I may well flip the switches tomorrow. Tonight looks like it is going to be very cold again, like last night, but the forecast up to a week ahead shows below zero at night every night, and even all day on some days.
MCS is aware of the overbadging practice. See page 15 of the link. Maybe they should be stopping this rather than just pointing it out. But no matter, all installers will have read the attached and will practically know it off by heart.
And then they bury it in page 15 of a 98 page document. What planet are these idiots on?
This is the relevant paragraph, with my emphasis added:
For instance, the standard rating condition for ASHPs used to be air at 7° C and water flow at 35° C. However, in practice they may be required to produce water at approximately 55° C with design ambient temperatures of circa -2° C. At these latter conditions the output of many heat pumps could be as little as 60% of the output at ‘standard’ (nominal) rating. For example a 13kW ASHP may provide 13kW of heat at 7° C and 35° C flow temperature but it is unlikely to do this at an air temperature of -2° C and water flow at 55° C. The actual output could be as little as 7-9kW and hence, if relied upon for the design of the system, it will be vastly under-sized incurring the cost of expensive supplementary heating and/or lead to issues of poor comfort.
This is so important it should be on the front cover of the document. Even that isn't enough, it should be on billboards across the country, and in prime time public information broadcasts on TV. Or just legislate to make calling a dumper truck a Ferrari illegal.
But what do MCS do? Bury it on page 15 of a 98 page document. Utterly incompetent and incapable, they should be disbanded. But it won't happen, because no one cares one jot about the consumer. We are the mere fodder for Freedom Heat Pumps to make millions, Midea to make trillions, and give ministers warm feelings of boxes ticked and targets met.
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.
