Mitsi City Multi

[SatPro]

Hi,

We are having problem with a Mitsi PURY-P250YMF-B city multi. The customers are running the system in heating and after a few days the condensing coil tuns into a huge block of ice.

Obviously the system seems to be struggling with going into defrost/not defrosting long enough. The system has had its refrigerant (R407c) reclaimed, the system pressure tested and then the correct refrigerant weighed back into the system.

Anyone have any ideas as to why the system would be doing this?

[nike123]

Did you checked thermistors of outdoor unit?
They are responsible for guiding system.

[Thermatech]

Perhaps the RV is not always changing over to cool mode for the defrost. Sticking RV ?
Its energized for heat mode so pull the RV connector on the circuit board to de energize the solenoid & it should instantly change over to cool mode & fill the outdoor coil with hot gas.

The outdoor unit monitors the TH7 coil temp sensor & after 50 mins if its below -8 deg C then it will start deforst.
Then during defost it monitors TH5 coil temp & discharge pressure.
If the discharge pressure is >10bar & TH5 is > +8 deg C after 4 mins of defrost then defrost will be complete.

So important to confirm the TH7 & TH5 temp sensor data is correct.
For instance if the TH7 has failed or reading incorrect temp & is always reading higher than -8 deg C the outdoor unit will not ever start a defrost.
If TH5 is reading a few deg C high then the unit might do 4 mins defrost only & finish defrost because TH5 reports +8 deg C but the coil has not completely defrosted & the actual temp at TH5 is still lower than +8.

You can read the data of the temp sensors at the outdoor circuit board using the SW1 dips & service manual.

Check hot gas flow during defrost to ensure no incorrect bypass to suction & correct gas flow through the check valve block & solenoid valve block through into the outdoor coil.

You can fine tune the defrost with some options at the outdoor circuit board dips.
For instance you can change the end defrost temp at TH5 from +8 to +15 deg C.

[gasman]

is it freezing up in side of the cabnit on the acumlater

[IPASA]

Hi Sat Pro, please let that the systema turn of and restart 3 times (this is going to take less than an our), and we are going to get a error code, and we can be more certain about what is the origin of your problem, because we can have serveral options of problems.

When you install, you use nitrogen while you sold ?... you charge the gas according to the design ?... you charge correctly the gas (liquid or gas) ?... if you make all this correctly the problem is goin to be of the equipment if not, you can have somthing wrong when you install.

How many time have this systema operatin, is new or have some time installed ?

Best Regards,

IPASA