fujitsu cassette AOT54RPA3L

[savoc]

Hi guys having troubles with the above unit. Whats sucks about this job it it is 3 hour drive and scissor lift hire is required to access the unit. The customer said they have always have had trouble and has never worked (commercial site). Suction 325 kpa, liquid 1025 kpa. air off 5 degrees. air on 24 degress ambient around 25. Reclaimed gas and weighed in correct gas charge (new refrigerant) measured pipe run as well. what appears to be happening is flood back. the pipe work from the suction valve to the accumulator to the compressor is fully frosted. coils are clean and filter is clean. no frosting from suction pipe connection on cassette. switched a/c to heating and same thing happen accumulator fully frosted all the way back to the compressor.
when unit is powered up i can hear the eev working. (i assume its working) i checked the resistances of the valve and all is in range. checked senors as well all in range. So what could cause flood back on heating and cooling? is the electronic expansion valve suck? faulty outdoor board? and also blew nitrogen threw pipe work thinking there was a blockage. Someone out there must have a idea?

[Tayters]

Suction pressure in cooling is about -5*C so a tad low but not excessive. Would need superheat readings as well to confirm if it is actually flooding back. If it is flooding back then consider perhaps too little load on system, overcharged with R22, pipe run too short, pipe sizes wrong (3/8 + 3/4), fan running too slow.
If on the other hand you have a low pressure fault then look for partial blockage in drier (by condensor outlet) or more likely in strainer after EEV, service vlave not open all the way, kink in pipework somewhere.

[savoc]

Thanks for the reply. the pipe run is about 23 meters and i added the correct amount. 50 grams per meter after 7.5 meters. as recommend by tech support. You got me thinking now about to little load. i did have the a/c set to 18 degrees to keep it running out side temp was only about 24.(customer was complaining that they were freezing) the pipes are not kinked i traced them all the back to the cassette. i did check the little strainer by touch test and couldn't feel any difference in temp/diff. whats got me is that it does the same in heat and cool mode. On heat the discharge was around 2000kpa. The job is out in the country and we need to hire a scissor lift to get access and the cost is going to get very high. So on the next trip i need to get it right. do you think i should just replace the valve and strainer? i am just really stuck on this one, i bet in the end it will be something really basic.

[Tayters]

Is that extra charge correct? Here's the spec from the service manual, infers precharged to 20m so for your 23m charge is 3.85kg total.

Hard to say about the strainers blocking. I've seen them blocked but not enough to create frosting afterwards - just a low suction pressure. The lack of service ports make it hard to confirm so if in doubt need chopping out and inspecting or fitting your own access ports. From your description it would apppear the superheat is low rather than high in which case this would mean there is no restriction in the system but this would need confirming with temp readings.

[Tayters]

For the mouthorgan unit with the same outdoor (ABY54...) then the manual is a bit clearer:

Additional gas charge is not necessary with pipe length up to 20 m (for 45R, 54A, 54R types), and 7.5 m (for 30A, 30R types).

[savoc]

Thanks for the info. tech support may have giving me the wrong information. going by the info you supplied im 700grams over charged. do you think the charge is the same for a cassette and ducted?

[Tayters]

I think that outdoor goes with a cassette (AUT54RLB3W) or mouthorgan (ABT54RBA3W).
The charge should be the same for both.

Cheers,
Andy.

[savoc]

Hi posted a question about a week ago. the problem is flood back to the compressor on cooling and on heating mode. the accumulator turns white and when look under the compressor blanket, the compressor is white as well. Weighed in correct charge, washed indoor and out door coils. have slightly low suction pressure have high t/d across coil. air on 23 air off 8. when i turn a/c on i can here the electronic tx valve ticking. sensors and coil readings all in range. I am thinking the t.x is stuck or the out door board is faulty and not responding to the pipe thermistors. has anyone got any idea how to test and check the electronic t.x valve. i dont think its the strainers as i have no temperature drop across them. there must be a fujitsu expert out there!!!

[Taaz1275]

Savoc,
i'm looking thru the forum for any assistance with the problem that Im facing with a similar unit doing the same things as your unit you worked on here ...the unit im working on is AOT90RPA3L.....flooding back...I've ordered the outdoor thermisters, the electronic expansion valve coil and the expansion valve as well which Im going to replace once I receive the parts ....im interested to know from you what eventually turned out to be the problem to your unit, it would greatly assist me and bring more light into the picture.

[Taaz1275]

Savoc,

Im interested to know of how did things turn out,here I am facing the same problem with a similar unit and Im still in doubt as not being so sure of the diagnosis that I have come up with,..I am suspicious of the electronic expansion valve being faulty and in saying so, stuck in the open position reason for the flooding back to the compressor.I suspect other contributing factors like the input signals from the outdoor thermisters that determines the output result which in this case is the position of the needle valve in the expansion valve,...anyway, I've reached the point now where I've ordered the outdoor thermisters, the expansion coil and valve and will have them replaced upon receiving them parts....Im interested to hear and learn from you of what eventuated out of your experience with the AOT54RPA3L...your help will be greatly appreciated.