Forcing an inverter split system to run at its lowest output power

[liamg]

Hello,

I need to run an inverter type (DAIKIN) split system on a solar/battery powered DC/AC inverter. Unfortunately, the DC/AC inverter is only rated at 1kW and the A/C system is a 18000BTUs one.

I don't need the A/C full power anyway and I can't upgrade the inverter for now neither.

Do you know of any clean (no major hacks of the unit internals) solution to achieve that? I thought of replacing the indoor unit (or the remote) thermistor with a potentiometer, to simulate a fake (manual adjusted) room temperature, closer to the unit setpoint.

Anyway, I don't know if the unit "brain" (MCU) will wait for ever in that lowest output power state to reach the setpoint temperature.

Do you guys know what's the actual algorithm of the internal MCU in such a situation? Or any other way to take over the compressor control?

Thanks in advance for any clue.

[FaultCode]

What is the model number of your unit, 18,000btu does not tell us the electrical rating of the unit.

[Edit]Looking at Daikin data I think you may have something like an FTXS unit and reading the manual you could use the ECONO function to set an upper frequency limit, or try the QUIET mode which also holds things back.

Service manual here if you want http://bit.ly/2sctxMw

[liamg]

Thanks a lot for your support, @FaultCode!

Sorry, I forgot to mention: it's a FTX50GV / RX50GV combo. Can you provide a link for its Service Manual, too?

Btw, I don't have the "ECONO" option on my remote control (just the "QUIET" one). Is there a way to lock/set the maximum output power by using some secret/service procedure?

[liamg]

I've read on the product page (https://www.daikin.eu/en_us/products/FTX-GV.html) that it supports wired remote control, centralised control and ECONO mode (decreases power consumption so that other appliances that need large power consumption can be used).

Anyway, I see no "ECONO" button on my infrared remote control. Is there any jumpers inside the unit or something?

Does anyone have the Daikin FTX50GV(RX50GV) service manual, please?

[liamg]

Still didn't find the Daikin FTX50GV(RX50GV) service manual. :( Any help, please?

[frank]

Still didn't find the Daikin FTX50GV(RX50GV) service manual. :( Any help, please?
All you have to do is follow Faultcode's link http://www.daikinac.com/content/assets/DOC/ServiceManuals/SiUS091133-FTXS-LFDXS-L-Inverter-Pair-Service-Manual.pdf

[liamg]

I still prefer the right service manual (that's it, the FTX not FTXS) as I don't know what features are missing from my unit (the "ECONO" mode being the most obvious one).

Do you know how to limit the upper frequency of the compressor?

[frank]

I still prefer the right service manual (that's it, the FTX not FTXS) as I don't know what features are missing from my unit (the "ECONO" mode being the most obvious one).

Do you know how to limit the upper frequency of the compressor?

There is little difference between the FTX and the FTXS.

I've only been designing, installing and repairing Daikin systems for 30 years and never found a way to do what you require the system to do so maybe I'm not the best person to ask :rolleyes:

Joking aside, have you considered asking Daikin directly if it is possible?

[scoobydo]

Does the system have thermistors on the pipes? Was this what you was eluding to by fooling the unit into a different duty cycle?

[liamg]

@frank:

It should be doable but the service manual aren't of great help though.. I need a mode detailed schematics.

Anyway, seems like the compressor power (frequency) depends on the actual speed of the internal unit fan hence a rough output power limitation could be accomplished by setting this to "QUIET" (lowest fan step).

Anyway, the "ECONO" mode of FTXS explicitly sets an upper limit on compressor power (but, like I've just said, FTX doesn't have such a feature).


@scoobydo:

I've made no changes for now; I'm still trying to find a "clean"/reversible solution..