2022-06-02

New air-con, part 6

Well, well, well... I am impressed with 4 Seasons. They have only gone and sorted it.

This is the huge difference between this install and the previous Mitsubishi install from a different company. The customer service to get to the bottom of the problem and fix things.

Firstly, they did discuss this "anti-freeze" mode with Daikin, and whilst we all agreed that turning the fan down was silly, their point, which is very valid, is that it should not be happening at all. The refrigerant should not be getting so cold in the first place - this is a fault condition. That is what needs fixing.

Naturally I leapt to the conclusion that the issue was air-flow. But I was wrong. It seems the advice from Daikin at this point was right - they said to check the refrigerant. Well, pressures had been checked several times. But they suggested there was too little refrigerant. Indeed they suggested (counter intuitively) that we would see these lower temperatures if there was not enough refrigerant. That seems crazy, obviously.

Well, the installer, and I, were rather baffled, but the only thing that basically makes sense is that the system is (over) compensating for the lack of refrigerant, and that is how it ends up colder. And, of course, at the same time, it is unable to carry the heat away properly, so does not work as well.

The symptoms were pretty simple, when cooling, the refrigerant quickly goes down to as low as -10C, which it manages for a few minutes, and then the anti-freeze mode kicks in, and everything stops for 10 minutes, and overall things are not working well.

Now, the refrigerant is settling around 5C with no problem, and cool air is coming out, and the room is quickly cooling. It is not going negative at all, not even getting below 4C. It varies, and I have seen 5C to 8C, but that is "sane".

So what did we fix?

The fix was to completely drain down the system and refill it - simple as that. The big clue was that only 0.9kg of R32 came out. It should have had around 2.5kg. So he emptied, vac'd, and refilled. What I had not appreciated is that these systems come pre-filled for installation, so it seems that somehow it must have come without the right amount - some must have leaked in transit (not good). But the only real test he can do is pressures, and they were fine, so no clue that there was not the required amount of R32.

I'll add some graphs once we have a couple of days running to confirm. But I am sat here on a warm sunny day in a nice cool office. To say that I am over the moon is putting it mildly.

Side effects

A small side effect is that my Daikin wifi modules have way more monitoring and reporting and graphing now. I did loads of work to try and find what was actually happening, turning in to a seriously useful tool.

Next job is the new controller to work with it for when people want manual control but doing a better job than the normal Daikin controller.

Another small side effect is that my previous very tight temp control is now a little less tight as the effect of cooling (or heating) is much more and continues longer, so some level of predictive processing may be needed to manage tighter temp control. Should be pretty easy.

5 comments:

  1. Its not really counter-intutive as to why the temperature reduces with reduced pressure.

    Its common sense. The pipes have less refrigerant in them so therefore cannot conduct heat as efficiently. This will result in the refrigerant getting too cold and hence the pump shuts down.

    For a similar reason this is why people should buy fridges/freezers rated for <10C ambient if you want them in a garage/shed.

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  2. I am not sure it is that counter-intuitive. With no refrigerant the inside unit would not get cold at all. It is by operation of the refrigerant that it gets cool at all. So intuitively, less refrigerant would mean less effectiveness, and hence less cooling. I appreciate that there is technicality about the way it works, but the intuitive operation suggests it should not work as well and hence not cool as much.

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  3. Imagine its water you're pumping round and there's a coolant section.

    What happens when you reduce the flowrate of the water?

    1) the coolant section starts to freeze - ie build up ice;

    2) the rest of the pipework heats up causing erratic temps in the area designed to be cooled.

    Its pretty much that simple - both temperature flow sensors will be next to the cooler and they'll both show low temps so the system will try to warm by shutting down. There are generally good reasons for having the sensors positioned like this - your case being a classic example.

    Similar thing happens with freezers not rated for <10C ambient temps - for the reason that they don't have the specified refrigerant in them for those temps.

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  4. It is all to do with pressures of the refrigerant, if there is less refrigerant it evaporates more quickly resulting in bigger drops of temperature. The evaporator starts to produce ice if it drops enough, but this only happens on the first lengths of the evaporator as the refrigerant quickly runs out and the remaining evaporator coil isn't chilled. Overall the system has less heat moving capacity, just what it does have is concentrated in a small area where it gets very cold.

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  5. This is exactly the droids I was looking for; I just got a Daikin system installed and the COTS options are pretty subpar. Daikin's you've mentioned; there's also Airzone which is much better designed but still doesn't support TLS and also would cost me €650 for four.

    Unfortunately, the buck converter is out of stock everywhere so I'll have to look for alternate parts or respin the board if I want to build some.

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