Hi @cathoderay

From what I have read, you are perfectly correct that the performance of the MCS organisation itself, leaves a great deal to be desired, as it also would appear do many of its accredited installers. 🙄 

It is unfortunate that a Midea unit was chosen for your installation, since the actual maximum heat output of their units begins to fall below the specified value, as the reducing outdoor air temperature approaches 0C. The specified output from a similar sized Mitsubishi Ecodan is stated to be maintained down to an outdoor air temperature of -10C. See attached spreadsheet.

The major weakness with ASHP's, is the fact that the calorific value their main energy source, the outside air, is not constant, and in fact reduces during the conditions when it is most needed. This is the primary reason why the heat output and efficiency of an ASHP falls off a cliff as the outdoor air temperature falls below zero.

At least in the UK there are not that many days when the outdoor air temperature is at zero or below throughout the whole day, and most days there is a temperature variation of 5C or more between the lowest and the highest temperature. One thing that you could do in your situation is to take advantage of this temperature variation, by boosting the indoor temperature during the warmer outdoor air temperatures, and hence use the thermal mass of your home to help support your heat pump during the colder periods of the day.

It also may be a good idea to purchase a simple fan heater to help supplement your heating system should we have a particularly cold spell.

@batalto cool can you crack this one open for me its called mcs031, some cells are protected its really annoying, im trying to automate it.

@grahamh - Ask and yee shall receive

@cathoderay 

No manufacturer or distributor will ever tell you that the units can be adjusted for capacity but its always been the case, they just rev limit them with software. its easy when you know how, its always in the manual somewhere.

I'm no longer at Freedom haven't been for a year or so but i think you have an old version of the heat loss produced before the final data was sent in by midea but i cant remember its been so long, anyhow here is the info on the 14 from the data book

I disagree with the comments re a Mitsi, in my opinion mitsi is a very average unit, its the Vauxhall Astra of heat pumps but impossible to purchase at the moment. You are much better off with a Midea. 

good luck with it

it will do you proud

@batalto legend thanks, thats perfect

Posted by: @grahamh

@cathoderay 

No manufacturer or distributor will ever tell you that the units can be adjusted for capacity but its always been the case, they just rev limit them with software. its easy when you know how, its always in the manual somewhere.

I'm no longer at Freedom haven't been for a year or so but i think you have an old version of the heat loss produced before the final data was sent in by midea but i cant remember its been so long, anyhow here is the info on the 14 from the data book

I disagree with the comments re a Mitsi, in my opinion mitsi is a very average unit, its the Vauxhall Astra of heat pumps but impossible to purchase at the moment. You are much better off with a Midea. 

 

good luck with it

it will do you proud

Since I don't have either a Midea or Mitsubishi heat pump I cannot comment in detail on their performance. All I can do is compare the published performance data, which from a heat output perspective would indicate that the Midea unit is inferior to the Mitsubishi unit. Since I am not involved within the ASHP industry, I don't have any particular allegiance to any particular manufacturer, so try to assess each based solely upon the data available.

If, as it was stated, it is so simple to change a 14kW Midea unit into a 16kW unit, I find it hard to believe that it was not done in this case.

@grahamh - I've not been able to find anything in the manual yet, but no rush, need to see if there is a problem at low ambients before fixing it. Haven't looked inside the unit itself, to damp outside today, don't want to get water inside it.

All the pre-installation calcs were done using v2.4 of the spreadsheet, a legacy from how long it took for everything to happen. The handover to me after installation version (and so I think the one that went to MCS) was v3.28. It looks as though the hidden Midea data (the Heat pump capacity tables) are unchanged, all that has been changed is the option to select the 14kW unit has been added to v3.28. In both versions, for example, the 14kW Midea output at 0 degrees ambient/55 degree flow is 12.4kW, compared to 11.6kW (11599W) as shown in your screen grab, my original post chart, and @derek-m's spreadsheet, all of which use data from the same Midea publication, which does not appear to have made it into even Freedom's latest version of the spreadsheet. The unfortunate thing is that the heat loss here is 12.3kW, which lies in between those two outputs, 12.4 is a marginal MCS pass (output > loss), 11.6 is a definite fail (output < loss).

I'm sure the Midea is basically a sound unit, it is just a pity so much of the documentation is completely the opposite, not to mention also almost impossible to find, except in dedicated forums like this one. I also ended binding myself to the Midea unit at the beginning of the process by putting it in the Listed Building and Planning applications, because of its low profile (I don't think there are any other UK available low profile units in the same output range).

@derek-m - I agree about Freedom not up-rating the unit, see previous post.      

Reviewing the entire history of this installation to date, I think the key points can be summarised as follows:

All the design calculations were done using v2.4 of Freedom's Heat Pump Tool Kit. This came about because the original quote was done in Feb 2021, and presumably v2.4 was the current version then. There was then the long delay caused one way or another by the LAD grant process and their preferred installer, until I reverted to my original installer in very late December 2021, and we just picked up where we left off, still using the same spreadsheet. The proposed heat pump was the Midea 16kW unit (the spreadsheet only had 12 and 16kW Midea options, so a 14kW unit wasn't considered, and the 12kW unit was too small), and the spreadsheet showed it was a clear MCS pass (shorthand for could supply 100% or more of the heat needed at design conditions, ie MCE room temps and ambient temp).

Only days before the installation was due to start on 31st Jan this year, it became apparent Freedom had no Midea 16kw units (there had been a rush on them because of the Mitsubishi supply chain failure), but they did have a 14kW unit, so the obvious question was: would this be OK? It still wasn't available as a drop down choice in the Freedom heat pump tool kit, but by unlocking the spreadsheet, it became apparent there was Midea 14kW data, and so a 14kW choice was added to the heat pump selection drop down box. This done, selecting the 14kW unit showed a marginal MCS pass (can supply 101% of the heat demand at design conditions). 

The problem was the Midea data in the Freedom Heat Pump Tool Kit was significantly wrong. We knew it wasn't gold standard from notes in the spreadsheet, but at the same time it was there, and there was no reason to suppose it was a long way out. The only other Midea data available at the time, the A7/W35 etc data, rang no alarm bells. Given it was a 14kW Midea unit or no ASHP at all (planning constraints plus the LAD funding deadline of 31st March), and the Freedom and Midea data suggested the unit would be OK, we did the obvious thing, and went ahead with the 14kW unit.

It was only after the unit had been installed that I came across this forum, and so in due course Midea's own full capacity (output) data, which shows the 14kW unit was a clear MCS fail. At warmer flow temps (needed because of the design constraints) and design ambient temps, Freedom's heat pump tool kit had the output as ~12.4kW, while Midea's own data showed it to be ~11.3kW, a full kW less at the most critical heating condition, when the heat loss was ~12.3kW.

So much for the theory. It's possible even Midea's own data is wrong (done in lab conditions, dieselgate, whatever) and of course the heat loss calcs are only ever an estimate. The only way of knowing what will happen in the real world is to wait until it happens in the real world, ie wait until we have a spell of cold weather, and see how the unit performs.

In the meantime, I think it would be extremely useful, not just to me, but to others with larger Midea units (eg someone with a definitely oversize 16kW unit might want to try running it at 14kW to see if savings can be made), to get confirmation that the units are in fact the same hardware, and the output is set in software/dip switches or by some other means that can be changed, and if so, details of how to make those changes. @grahamh, perhaps you can help us out here?

cathodeRay         

@cathoderay flicking the dipswitches so a 16 becomes a 14 or 12 just changes the max output. All the switch does is limits the max output of the unit and max rpm of the compressor. 

changing the capacity down will save money but will leave you cold, but so will switching the unit off at the mains. i dont recommend it 

instructions are inside the cover of the unit top right of the wiring diagram. dip switches only work when the power is off. 

if there are any issues with sizing I would be straight onto the installer / designer ask them to confirm that the unit is ok. its a part of mcs to hit the required heat loss.

in the bad old days every manual under the sun was on freedoms web site for download, if its not now ask your installer to get the data for you, freedom will send it to the installer if they ask for it.

hope this helps

@derek-m all good points but since almost no one reads the instructions they dont know the capacities can be changed. 

No manufacturer will ever tell you you can do it either, why would they? Rebadging the same units means you can have a big range which is an industry obsession. 

its common in most industries, in the car world you can buy a car with or without cruise control, all of them have it but if you take the option they activate the software (for a fee) if you dont they dont. 

a look under the bonnet or lid confirms that the units are identical, or a look in the spare parts list. something dullards like me like to do. 

For ref from the MCS database: The Mitsi 14kW scop at 50c is 3.3 the Midea 3.59. not surprising the Midea is a much newer unit. 

Hi @cathoderay

It is my understanding that the published performance data provided by manufacturers, is actually obtain by testing carried out at independent test facilities, and performed to specified international standards. I would therefore be more likely to believe such data as against data provided by any supplier or installer.

@grahamh - yes, that helps, I will have a look inside the unit when it is less damp outside and see if I can make sense of things. Presumably if a 16kW unit can be downrated to 14kW, then a 14kW unit can be uprated to a 16kW unit.

My installer leaves today for Australia for six weeks (one of the many constraints that put pressure on to have things happen fast, which they did, thank heavens) and in any event I need to wait for a cold spell to determine real world actual performance. The MCS fail is more complicated, because it is a definite fail, but at the same time, it is only on paper, and I am reluctant to start what could be a long and complicated process if real world experience shows it isn't necessary. That said, if an upgrade is needed, I very much hope it will simply be a matter of flicking switches, not swapping entire units. In passing, I remember my installer remarking at the time the 16kW unit was unavailable, and we had to substitute a 14kW unit, there was very little saving in price, which fits with them being the same hardware (but with a minor 'for show' price differential to make it look as though they have a bigger range).  

Given my installer is now unavailable for some time, I very much hope freedom will have the good grace to talk directly to me.

@derek-m - "I would therefore be more likely to believe such data" - yes, I am of the same mind, which is why I say the unit is an MCS fail when the manufacturer's data is used.