sizeing coil

[wilt]

Hi,
Could anyone help me with regards to sizeing condensor coils to evaporator coils?Ive been told rule of thumb is the condensor coil should match that of the evaporator coil,or near as damn it?
My problem is the unit i have has one of those aluminium slimline condensors and the system has two evaporator coils of the copper tube style larger than the condensor put together.It has only a small reciever tank of about 1/2kg refrigerant mass so these unit are operating undercharged and if the sight glass is full the system wont pump down.Could this affect its performance ability & also cause LP problems when at -20 degrees C,its running on R404
Its piped from the condensor to the first evap inline then tee off to the next evap, the liquid pipe is about 1/4 id with a run of 3 metres.
Any advice appreciated

[chemi-cool]

The right coil should discharge the heat from the evaporator and the compressor so it will always be larger then the evaporator regardless of the material its made of.

[wilt]

thanx for your reply chemi-cool.So the possibilty of an inbalance of my condensor to evaporator ratio is out?could this cause me LPcut outs when fridge is at -20 degrees C and oil return to the compressor? as im getting around 7psi suction which is close to the suction LP setting.

regards

[Magoo]

You say you are getting LP cutouts close to LP settings, is that a typo error, do you mean HP cutouts, clixon cutouts.
The scales on LP switches are a guide never accurate, test and setup with set of gauges to be totally accurate

[wilt]

Hi Magoo.
The problem is that this system has a small condensor & very small reciever on the refrigerant labelling plate it has a charge of 1.1kg of r 404a. The system it self in the evaporator section which is made up of 2 evaporators larger than the condensor 1 for frozen & 1 for chill, so in order to run this system ive added 300grammes extra, any more than this & the system is unable to pump down,Now the sightglass is flashing indicating a undercharge,when the system has been running and nearly down to set point any excessive rpm on the compressor makes it drop to LP cut out which is 2psi(this is a directdrive transport fridge system by the way).so if i add refrigerant let say another 600grammes & add an ambient of +25 to say +27degrees C in our best british summer its going to start having head pressure problems,so is the condensor too small?
the condensor is of the aluminium hi efficient heat dissipitation micro coils.
regards