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Help with Daikin split unit (basic operation seems inefficient)

Hi all,

I have moved into a new condo with two FXAQ24MVJU units. I need some help from experts understanding what the deal is with these, because *I can't find anything online, including the sparse manuals on Daikin's site*. Thanks in advance!

So first of all the two units came with one BRC4C156 remote control for the two units. The FXAQ units don't have a temperature display, just a small panel on the right side with basically one button (the entire thing turns on and off). Only the remote has a temperature display, but it's set by you. There no way to see the thermostat of the unit.

I am having a lot of trouble using these units as heat pumps. It's only just starting to get a bit cold here (around 45-50 outside). It's going to get a lot colder.

My question to you is, where do I find the user facing operations manuals for these? How do I tell whether they were set up correctly? This is a rental (previously sales units but converted to rentals) and the details and people involved are all history.

For example, I have left the unit in 'heater' mode, and the fan continually runs blowing normal / cold air. If I set the temperature for 80 degrees, when my room is about 65 or such, the heater will turn on, and hot air will come out, but that will last only a minute or two before it blows normal/cold air again (you can hear the heat pump turn off). It's literally a minute or two. Sure, it heats up .. but I thought these things reached peak efficiency after 10 minutes of continuous heat pump blowing.

Is there something wrong with the thermostat? or does that sound normal?

Next - I want it to blow heat at a steady rate, and then turn off the fan when it reaches the desired temperature. I don't want the fan to always blow. Why would a heating unit continuously blow not hot air when its heat pump is turned off? Doesn't just wear down the fan -- and my wallet, because of the electricity costs?

Also – how do I use one remote (BRC4C156) for two units? It's a mystery to me how this place was set up. It came as a surprise – after lease signing.

Was something missing in the installation of the unit? or is the above setup normal?



  • TonyS
    TonyS Member Posts: 849
    Not familiar with Daiken

    But I sell quite a few Samsung and Comfort star units.

    If the unit is blowing room air before it has satisfied the setting, chances are good you have a low charge. Most units do not have a low pressure switch and will continue to run. The only safety is a hi temp thermistor on the compressor and I have found they will run and run without overtemping even with 0 charge. On HEAT mode the units blower will shut down when satisfied but will first modulate down to the lowest possible point before shutting down. This is the whole concept of modulating inverters- to replace just what is being lost.

    Heat pumps have gotten a bad name because they were originally sized to the cooling load. Heating load is usually 2 to 3 times greater depending where you live. Inverter mini splits do not suffer from this disadvantage because they can be sized to the heat load and they will modulate down for proper dehumidification and cooling in the summer. I have a Samsung Vivace on my first floor, it achieves a COP of 2 at 17 degrees. Thats half the price of resistance. The air is always toasty warm, everyone stands in front of it when they come in from a freezing night. It will shut down at 5 degrees outdoor ambient which is hardly ever reached southeast PA.

    In cooling mode, the indoor fan will run continuously, this is because the temperature sensing bulb is in the unit, this is why you can put your remote in a drawer after setting the temperature, it flashes the wall unit and in order to receive a accurate reading must keep the air circulating... indoor blower motor uses 33 watts.

    Comfort star allows you to use the remote as the thermostat with their follow me feature. This feature works well for units mounted on high walls or cathedral ceilings although in this mode, just like the old Sanyos the remote must stay within eyeshot of the unit. You cannot use gauges on a mini, you must weigh in the charge. I would start there, inproper flares and procedures have left many of these units with leaks.

    Good Luck

  • Lots of technical data available to you

    I'm surprised that you are having problems finding literature. You might have gone to the corporate website, but you want to be at the North American site.

    Daikin is one of the few manufacturers that makes all of their literature available to everyone!

    Simply visit their website:

    You can access all of the installation and operation manuals for their entire product line. No secret handshakes, no passwords.

    Good luck!
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