weak compressor or blockage system

[kefah]

Hi
i got split ac unit
classic type
24000 BTU
rotary compressor
capillary tube system
R22 refrigerant
it had leak due to damage suction line pipe
so i replaced

made deep vacuum
charged system by weight
i installed the system

after 1 hour of operation discharge line iced
and suction pressure was 35 psi
and no cool

current for the system is 13
and draw amperage was 9 amp
voltage was 215 volt

then what i did
i thought my weight charge was non correct
so i added more refrigerant
suction press reached 65 psi
and amp draw reached 13
which rise gradually until it reached 15 so compressor overloaded
is that blockage or bad compressor

[Airsteve]

Hi Kefah
Have you tried a pump down test on the compressor?
As far as a blockage is concerned checking Superheat and Subccoling will assist in diagnosing.

[kefah]

i did this to charge outdoor unit only by weight
i closed the discharge and attched manifold to suction
and started compressor
when system sucked 1.900 kg as in name plate
i closed suction line
and switched off unit


ok if pump down done then i have blockage and compressor ok??

[Airsteve]

The basic health checks would be compressor pump down to 0psi. If you can achieve this then the compressor is most likely ok.
Superheat (aim for 6k as you would already know)
Sub cooling (if high then blockage, check capillary, blocked drier etc)
Also check non condensables. Assuming fans, coils etc are clean and working ok. You mentioned you replaced the suction line. Was it an identical size? How did the original one fail?

[al]

Kefah

Your compressor sounds ok, if it wasnt pumping properly then your liquid line wouldnt be iced up, sounds like the drier might be blocked.

recover your gas and change the drier, flush some nitrogen through the outdoor and indoor units in case of capillary blockage and vacuum and recharge.

[nike123]

There is no driers in most split system AC units!
Only filter!

If compressor curent is 80% or less than on nameplate, compressor is probably inefficient! But that is case only if everything else is fine.

Check my blog entry:
http://www.refrigeration-engineer.co...ling-scenarios

"discharge line" in split system is part of evaporator , since it is after capillary. It is filed with gas-liquid mixture of certain "quality". Mixture is present because of pressure drop in capillary and phase change of refrigerant occurred by heat energy spent to cool down liquid refrigerant to saturation temperature of refrigerant at that point (phase change energy). That doesn't necessary mean that you have any restriction.

First check air flow across evaporator with air flow meter, and if evaporator is clean from any dirt. Than charge by weight.
Than measure compressor current at max fan speed. If current is within 80-100% then measure superheat.

Low room temperature and low humidity and low air flow can be cause of smaller diameter pipe icing as well as evaporator icing.

Quality could be found and understood by looking at Pressure Enthalpy Chart for that refrigerant.

[nike123]

Superheat (aim for 6k as you would already know)

Superheat with capillary tube as expansion device is variable and not constant!
Therefore, charging by weight is easiest and only secure way to properly charge system and to eliminate improper charge as probable cause!

[kefah]

evap is clean
room is very hot
charged by weight
fan speed is max and ok

[nike123]

But that doesn't mean that air flow is correct. You should measure it to be sure.
Than check for supply pipe collapsing at bends and (filter-drier, if present) blockage by moisture (heat portion of pipe where it start icing by hot gun).

From your first post, and if we asume that above is correct, than we have this scenario:
MILD RESTRICTION (factory charge) = High superheat. Low suction pressure, indoor TD & current draw. Normal to high subcooling. Normal to low head pressure

[kefah]

thank u all
for very useful info
80% its blockage in filter or capillary

[nike123]

Could be moisture, vax or oxidation if brazed without nitrogen.
Check with hot gun at point where icing start, but only after proper charging by weight.
If cappilary is cold to touch at beginig, than it is filter blockage!

[kefah]

ok
i will check then reply u