I had aircon in my old house - standard split system with indoor units on the wall. It worked well. Summer or winter, extreme hot or cold, I was able to ensure bedroom and office stayed well controlled and comfortable. Not once could it not cope.
For the new house I put some money aside to invest in an even more serious aircon, ducted, with a lossnay and for fresh air as well. We are directly on the A40 with no vents in windows, so needed. It is far from cheap (A lot of houses in wales are probably cheaper than this installation!). I was keen, and happy, to pay "top dollar" for a "proper" system. This is my retirement, my comfort, I deserve this!
As I have said on twitter, that it is Major Cooling & Heating that are doing this. They were recommended, and have been in business some time.
They are nice, and friendly, and do seem reasonably competent on the face of it. So we ordered the system and it is installed. It took some time. It involved a lot of work we had to do with help from my son-in-law/sparky.
But it is not right, sorry. I do feel a tad sorry for them - as it looks like they took all the room sizes, and so on, and contacted their suppliers that recommended a Mitsubishi system with Lossnay and GUG. It was installed, then the issues started.
There are two big issues.
1. It cannot read the room temperature from the controller. This is the controller that comes with it, which they says is not even a "standard spare part" as it is specially for the GUG, yet it has a thermistor in it, and has a setting to use the controller temperature, which it accepts. This fooled us as clearly it was not using the controller, freezer spray made that really easy to demonstrate!
2. It does not seem to be powerful enough.
The first point is pretty much a show stopper. We have two rooms on each of two systems, and may want to run one or the other or both. The fact we want to cool the "secondary" room was important as my wife and her sister when using the guest room, have very different ideas on a "comfortable temperature"! We do accept that if we are running both rooms at once, then they are not separately controllable - we know that. That was not actually a problem for us. For the "one or the other" we actually put motorised vents to each room and switched the controllers in each room so only one was connected. Simple, or so we thought. But apparently, even though it has at thermistor and a setting, it can only read the "return air flow", which only comes from one room! Not impossible to fix with more vents and more motorised vents in the pipes for the return air flow, but for one room this meant removing wardrobes, and plaster board and trunking a vent in the wall and lots of work (which we paid for separately) and may now need doing for the "return air" if we do that. Not good. Not impossible to fix.
Even so, we now know that this also means much more careful placement of the vents in the rooms else the feed air just runs along the ceiling to the return vent and thinks all is well and the room is warm. This meant changes to vents, and lots of testing. Getting the airflow matters way more if the temperature sensor is not the controller, put where we want it.
The second point is, frankly, a bigger concern. It got to over 28℃ in my office last summer. So a system that can cool even that one room to 21℃ is needed. I was clear I wanted an "over spec'd" system if necessary to do that. But as it is not the height of summer I have no way to test that. All I can test is heating. Well the system says it can do 28℃ heating. So let's try!
The answer is a solid "nope", by several degrees. One system managed one room (not the two rooms and en-suites it should do, just the one) up to 25℃ after some hours. The other much the same 24℃. Yes, it works for 20℃ and so is actually fine for now, but if it cannot cope with heating many degrees now, how will it cope with cooling many degrees, as many as 7℃, in summer?
At the end of the day this gives me zero confidence the system has enough "oomph" to cool my office in the summer at all.
Can I help? Well, I am. I have invested in more test equipment, calibrated sensors, etc. I have tried everything even moving and changing vents. We had the vents all changed to larger size at the start when it was apparent it would not cope. I am doing everything I can to make this work if at all possible. But no luck.
I am now putting in several sensors in one room at 0.5m height intervals to see if the air circulation and heat distribution is somehow a factor. But even so, the basics of "not enough oomph" is pretty clear.
So next step is down to Major Cooling & Heating to see if they have an answer, changes to the system, an alternative system, or a refund. We will see how good they are.