Hello members,
I'm an improver refigeration engineer but have been thrown on to an interesting air conditioning problem and I'm hoping someone may have an idea or suggestion to help me solve this fault...

I went to a site which has numerous City Multi Mitsubishi Electric COOLING only A/C units. On the faulty system, in one particular room a ceiling mounted cassette is showing a 1500 fault code which technical have informed me is an overcharge error. This system is piped to another two a/c units in another room (one is a cassette/ the other wall mounted). When one unit is running the unit cools fine, but when all three run the error occurs on either controller.

I have tried to power down all outdoor and indoor units and re-activate, still the fault occured. I noticed a TH1 thermistor was not in it's holder on the discharge line (someone previous must have removed it), I placed it back into position. Also, I found a note on the outdoor unit saying 1kg removed! The system runs on R407c.

Another call has come in because the staff are complaining it's too hot, I hope someone might be able to help me...I'm thinking about removing the gas, and recharging (will try to measure the pipe lengths and make a calculation to charge accurately) but I've been told by staff at the site this has been done before. I hope for any recommendations you guys might have.

Kind Regards,

Neil the PIE MAN

P.S It's PUY - P200 YMF - C [OUTDOOR]
PLFY - P8OVAM-A [INDOOR]