Small 1/2ton R22 marine A/C problem

[marco59]

Hi all,
I am bench testing a Cruisair marine A/C,7000 Btu,R22,RGA5480EXC Tecumseh compressor,water cooled coaxial condenser.
I got it for free as scrap unit,I repaired a leak,removing the 4 way valve for the reverse cycle and recharged by weight (10 Oz)
I arranged a "bench test" to read both suction and discharge pressures,change the load on evaporator with warm air and/or vary the fan speed,vary the condensing temperature changing the water flow,read the compressor current and both inlet /outlet air temp.
It seems to "works" but...I observed some "strange" things:
as I had a too low suction pressure,55 psi,and both suction & discharge press. does not rise as espected increasing the load on evaporator (only the superheat have increased).The superheath was almost correct,about 15F.
I then tried to slowly rise the condensing pressure at the "nominal value" for summer sea water temperature but only the discharge pressure increased,the suction rised only a little (1-2 psi) and when I got around 230 psi the suction pressure began quickly to descend at less than 30 psi.The compressor current has increased as espected,and little or no cold at all air output.
Any explaination?
What others tests could I do to check it?
I also observed that at compressor starting the suction pressure stays very low (15-20 psi) for a long time,let says 3 to 5 minutes...is it normal?
Sorry for bad English language.
Ciao from Italy
Marco

[Brian_UK]

What sort of expansion device is the system using?

[marco59]

Hi,
sorry to forgot to mention it.
It is capillary tube,and it is rather short,just 8 inch
Marco

[nike123]

Make all measurments and than post data here!
http://www.refrigeration-engineer.co...30&postcount=1

[Magoo]

Sounds like you have a blocked capillary and or drier, more than likely moisture blocking outlet of capillary, Start again and change filter drier and evacuate system several time.