Subcooling query

Hey guys just a quick query about
Subcooling. If a unit say for example a small tx fed fridge we're to be overcharged the subcooling would increase and back up into to the condensor and the reduce
Volume of the condensor thus heat rejection area will cause a higher pressure. What i can't seem to grasp is if a unit we're to be partially undercharged, with less refrigerant passing through the coil why would not the refrigerant also be subcooled not bubbling away in the sight glass? With the lower ambient i can't understand it would not also subcool with ease. Just trying to get a better understanding! Thanks

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Subcooled liquid is liquid colder than the saturation temperature.
The saturation temp is dictated by airflow over the cond, the size of the cond,
the size and speed of the comp and the size of the expansion valve.

Free subcooling will always be at a temp greater than the ambient, so
on most correctly sized air cooled systems the subcooling will only be at
about 4 to 6 deg's lower than the condensing temp (saturation temp).

So if the cond was big enough or oversized, it could supply subcooled liquid to the valve
but if there was not enough refrigerant you would see a level inside the sightglass (bubbles if
the sight glass was situated in the vertical position).

The trouble is bubbles or a level of liquid inside the sightglass does not automatically
mean the system is short of gas, it will be a good indicator that the system is short,
but if the condenser is dirty then it will not condense correctly.

You need correct subcoolings and superheat settings but that is not the only indication
and futher tests need to be done.

coolrunnings

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