Mitsubishi Mr. Slim question

[qctech]

Hi all, I got a question maybe someone could shed some light on for me. I installed a 18,000 btu Mr. Slim AC unit in my Living Room about 8 years ago(sorry its not the garage). I installed it myself brought it down to vacumm and charged it as it was precharged and was good for up to 50 ft of line. Well i was way under that and the unit has worked excellent. I would like to check it and possible top it off if needed. I do not have any literature on it and was wondering if any one has done this and what kind of pressures and how to charge it? Thanks in advance and sorry for being long winded.


Anthony

 

[rickairmedic]

Anthony my first question would be what is in it R-22 or 410A as that will make a differance on presssures ( 410A runs at higher pressures than R-22 ) . Also unless your joints are bad there shouldnt be a need to top it off refrigerant doesnt dissapate over time it would have to leake out somewhere.


Rick

 

[qctech]

Hi Rick, It has R-22 in it I forgot to mention that. The reason I am concerned is that it seems to be short cycling when its not that hot out. Is that normal?
Ive been an auto and equipment mechanic for 18 yrs and my experience with ac has been only with vehicles and I belive this sysytem operates a bit different. If i am correct its a capillary system it operates on.

Anthony

 

[rickairmedic]

Anthony with R-22 I usually go for 65-72 PSI on the suction side ( larger tube ) depending on which brand I am working on . I dont have alot of experiance with the Mitsubishi but would say if you are at 65 PSI you should be ok. 410A is also more of a pain due to the fact the charge has to be calculated with tight tolerances . R-22 is much more foregiving .


Rick

 

[qctech]

Thanks Rick, in the event it does need to be charged, does it go in as a liquid or a gas? And I dont remember if I have to open a valve before charging.

 

[bazar01]

Thanks Rick, in the event it does need to be charged, does it go in as a liquid or a gas? And I dont remember if I have to open a valve before charging.

If not familiar with the system, it may well be worth it to leave it to the professionals. Work safe!

For reference, units have charts for superheat, subcooling, outdoor temp and return air temp located behind the electrical section cover.

 

[rickairmedic]

Anthony you want to charge it as a gas on the blue side of the guages . I am not sure what type of king valve is on the Mitsubishi myself so I am not sure if you have to open it or not . The easiest way to tell is to hook your guges up to it . The blue hose is Low pressure suction line ( the larger line and the red hose goes to the Liquid line . Once you hook up the guages if you done get any pressure readings then it will most likely have a king valve you will have to open to get a reading and charge the unit . The king valves with a flat brass cap on them wont need to be opened but if the valve next to where you hook up the hose isnt flat but flat with a cylinder in the middle thats one you will have to open to get a reading and charge the unit . You dont want to add alot of freon at a time . Start the system and let it run for 10 minutes then see where your charge is if you are between 65 and 72 PSI on the low side its fine if not then add some freon and let it settle and continue doing this till you get a reading in that area . I would also add make sure its at least 70* or warmer before trying to check and charge it as it will be easier this way without having to teach you super heat and other calculations you dont really need .


Rick

 

[qctech]

Thank you Rick!

Anthony