Service Port - Suction Line Pressure

I have an ducted split unit (1.5TR) installed in the bed room. The unit was not cooling adequately. Our AC maintenance technician went near the condensing unit, connected his refrigerant manifold to the service port of the suction line, and the other end of the line to open air and sprayed away (refrigerant/oil??) and kept monitoring the manifold gauges. After spaying out for some time, the cooling became back to normal.

I asked him what is being evacuated from the system, for which his response was excess oil! My doubt here is, since suction line is under negative pressure when the system is running, how is it spraying out? Shouldn't it be sucking in as in the case of refrigerant charging? Also, what is the probability of oil reducing the cooling efficiency of the unit.

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This is so wrong in so many ways.
Your technical guy needs to go back to school and learn what is correct.
Your knowledge is also wrong, the low side is not in a vacuum it would be
at 5 bar, 6 bar, 7 bar or maybe even higher so there would be ample pressure
to vent even though that is absolutely the wrong thing to do.

In the EU that would potentially lead to a criminal conviction. Bad practice and
ignorance at it's worst.

By the way ask your technical guy what he thinks the oil is for??

Rob

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As it’s an ac unit the suction would be in positive pressure , if it was negative pressure you would have a freezer and the evaporator would be a block of ice !! The question is where has the excessive oil come from as only the compressor oil charge should be in the system which will under normal circumstances will not cause a problem .

Quote:

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Originally Posted by Rob White

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This is so wrong in so many ways.
Your technical guy needs to go back to school and learn what is correct.
Your knowledge is also wrong, the low side is not in a vacuum it would be
at 5 bar, 6 bar, 7 bar or maybe even higher so there would be ample pressure
to vent.

In the EU that would potentially lead to a criminal conviction. Bad practice and
ignorance at it's worst.

By the way ask your technical guy what he thinks the oil is for??

Rob

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They are here only to fix the issue... least bothered about regulations . I was also surprised to see him venting the thing to the atmosphere! But the unit is cooling now.. probably with no oil in the compressor! These ACs are under a 'contract' so, they fix it if its gets broken, so we are not questioning them!

What do you think? How did his solution work anyway??

Quote:

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Originally Posted by Rob White

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Your knowledge is also wrong, the low side is not in a vacuum it would be
at 5 bar, 6 bar, 7 bar or maybe even higher so there would be ample pressure
to vent.


Rob

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Yeah my mind was not working in terms of gauge pressure :-)

Quote:

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Originally Posted by Glenn Moore

As it’s an ac unit the suction would be in positive pressure , if it was negative pressure you would have a freezer and the evaporator would be a block of ice !! The question is where has the excessive oil come from as only the compressor oil charge should be in the system which will under normal circumstances will not cause a problem .

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probably the oil was trapped in the vertical risers of the refrigerant pipe??

The only reason that the oil was being sprayed out was that the oil travels around the system with the refrigerant and if you open a valve fast enough and open enough you will spray oil with the refrigerant.

Unit was possibly overcharged with refrigerant by the same fools some time ago.

Quote:

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Originally Posted by Brian_UK

Unit was possibly overcharged with refrigerant by the same fools some time ago.

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Sure enough, the air conditioner was refilled with a coolant.
At the same time, it was possible to remove excess amount of refrigerant neater, without throwing oil into the atmosphere.
It was better to collect all the gas with the help of the refrigerant evacuation station, then refuel at the rate.