Daikin rooftop defrost problems

[gramcor]

I have five Daikin rooftop model UATYP 560AY1 with same problem :
in winter , in HEATING mode , defrost program is too short and ice cover the condensers .
( all the rooftops are mounted in same conditions )
If i change sensor positions on condensor , the defrosting period is the same .
I want to increase the defrost time ( if is possible...) , but i don't have technical manual for PCB .
Please help me with some informations ....

Thanks in advance

[install monkey]

you need to comfirm the correct gas charge- or compare running pressures with the 4 normal units,also clean condenser coils can affect systems

[gramcor]

Daikin technicians checked all parameters, all is normal , but did not have a technical solution. When increase the humidity at temperatures below 5 degrees C, ice accumulates progressively on condenser. PCB has a fixed duration of deicing, which reduces with the temperature measured by the sensor.

[al]

You should be able to change the defrost frequency, i think it's a jumper wire? Alternatively if all else is ok, fit a timeclock, knock out indoor fan and connect to 4 way valve.

al

[install monkey]

dip switch 1-8 doesn't allow for changing defrost duration, is there an economiser on the unit or a manual fresh air damper on it?