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We had a Daikin ductless system installed as a replacment for our old system that finally died. We have 4 total units inside the house, with 1 in each of the 3 upstairs bedrooms and a larger 18K BTU unit on the main floor. Its a small townhouse.

I have had a few weeks to observe how the units operate. Each upstairs unit gets each bedroom to temp and cycles off. Each of them will cycle back on and run briefly to keep the room at the temp they are set for. The main floor unit never cycles off. It runs constantly - even when it has reached the target temp.

Is this normal or could there be a problem with the main floor unit? I have also closed off all the old vents and filled in the floor register with insulation to reduce any potential air leakage.

The model number for the unit in question is CTXG18QVJUW. I have also turned of the unit for a couple hours and turned it back on - still same issue. I even had the HVAC installer come back and put in a WiFi module on this particular unit, so I could monitor it another way and when I use the app it says the temp is higher than what it is set for and the unit is still running.

I appreciate any and all input. Thank you!

Windward
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  • Sounds like an issue with the temperature sensor unit, or the "computer" that "listens" to it, but doesn't do the right thing (most likely the former). Without knowing models/makes, hard to tell what type of sensor is in use, and how it actuates the on/off of the AC. Sorry to be so simple, but have you tried to turn it off (completely, for several minutes), then back on again? Have you placed any hygrometers/thermometers in the room to trust the temps? If the sensor is acting funny (ie. stuck, or providing false readings), this could explain the issue. – stevieb Jan 19 '19 at 21:23
  • Thanks stevieb. The model number for the unit in question is CTXG18QVJUW. I have also turned of the unit for a couple hours and turned it back on - still same issue. I even had the HVAC installer come back and put in a WiFi module on this particular unit, so I could monitor it another way and when I use the app it says the temp is higher than what it is set for and the unit is still running. – Windward Jan 19 '19 at 21:25
  • Then it may be a communication break between the "brain" and the sensor itself. I'm not much more help beyond that, so I'd advise to edit your question with the further details you've provided here in comments, lest someone else has had this same issue. – stevieb Jan 19 '19 at 21:31
  • It almost sounds like it's a simple relay issue or something. All the best, I hope you get it sorted. By what you've already done (by having your HVAC guy come back and investigate), sounds like you're on your way. – stevieb Jan 19 '19 at 21:33
  • Could it be that the unit is modulating to control temp instead of cycling on/off? – ThreePhaseEel Jan 19 '19 at 22:14
  • @ThreePhaseEel - I'm not sure. If it did that I would assume that the temp wouldn't change. Right now, I have the unit set at 65 and the upstairs units set at 67. The WiFi app, which is only on the unit I have an issue with, says the main floor temp is 72 and it as still running. – Windward Jan 20 '19 at 14:43
  • @Windward -- what is the temperature trend for that zone...? – ThreePhaseEel Jan 20 '19 at 15:16
  • @ThreePhaseEel -- when the old, traditional system was installed, I'd set the thermostat to 67 and it held just fine. The system would cycle maybe 3 times an hour. With the ductless, the upstairs holds at whatever temp I set the units on, the main level unit never turns off, it runs 24/7. – Windward Jan 20 '19 at 17:29

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