New air-con, part 5

After the fiasco of the previous air-con install, I was pleased with the new one, as you can see, and especially that I can make my WiFi controllers.

However, this month, as we have got warmer, I have run in to an issue. It was gradual, kicking in some afternoons. Initially it was something that fooled my temperature control, causing it to flip to heating and back to cooling...

I made the controller a bit more reactive, and fixed the flipping to heating, which was good, but still, in the afternoons, things were not right.

Will all this, over night was OK, mostly, but not always. After a while I realised the clue was in the power traces. Basically, after a while the unit switches in to a mode where it cycles, around 11 minutes on, and 11 minutes off, and a low fan when off too.

This is not enough to keep my office cool, and as we go on, it is getting worse and worse. It always starts the day OK for some minutes, but can go in to this mode right away after that.

This is crazy. I tried all sorts. I thought maybe it is the "econo" mode, which apparent limits cooling when below a certain temperature. I even fudged the temperature (replacing thermistor with a resistor) to test this, but no joy.

After a lot of testing for a couple of weeks, I have found it. It is an "anti freeze" mode. This is what they say (when you know what to google). Needless to say that Daikin support did not work this out for us.

What is especially annoying is that when it is pending 10 minutes with "thermostat off", it also puts the fan in what is shows as "LL" mode, i.e. slower than "L". Well, if it want to avoid the coil freezing you would think it should keep the fan at "H", but that is not what happens.

So now we know what it is, well what can I do?

For a start, I can try and pre-empt the anti-freeze logic, but that does not really solve the problem of why it is freezing the first place. It would have helped a lot if Daikin could have simply said "that looks like anti-freeze kicking in" when asked. Indeed, a fault/indicator on the controller or controller app would have helped so we knew the problem.

Even so, a way better outcome than previous air-con install, and some hope it will be "just working" soon.

Update: Clearly air-flow is the issue, but by preempting the anti-freeze I can keep it on full fan more and so have a slightly improved performance for now.

Part 6


  1. Not to want to state the bleeding obvious... but have you tried just increasing the internal fan speed to increase the temperature of the internal coils?

    1. Yeh, fan on max, and field setting for what max fan means is on max. Installers looking in to it.

  2. As a youthful refrigeration apprentice I was always told there should never be ice anywhere on an AC plant, and if there was then it was a sign of a problem.
    Perhaps it's just under-charged (i.e. leaking), that's always a reasonable first guess...

    1. Pretty sure it is airflow. Gas pressures all rechecked yesterday.

  3. That seems very bizarre. If the coil is too cold, it should just stop the compressor while leaving the fan running until the coil warms up (I even had a cheapo £200 standalone unit which managed to do this, despite otherwise having no thermostatic control at all). I see no reason at all to mess with the thermostat or the fan speed.

  4. If the evaporator coil is freezing then the air must be coming out very cold at that point, can you measure the air temperature as it leaves the unit, see if it is really getting that cold, i.e. a few degrees above freezing? I think going into auto defrost is a fault, it can't really be frozen on the indoor units in cooling mode unless the internal temperature is down to around freezing. Typically there is just too much warm air going over the evaporators that they could ever get chance to become cold enough to freeze.

    1. Indeed, this has to be an airflow issue. It claims 1400RPM on the fans, but does not feel like a lot of air coming out. I need to find my air-flow meter.

  5. are you the only person in Wales using air con?


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