split AC suction line cold & liquid frostiong sweating ?

[todd86]

Had some one ask me to take a look at a split ac unit the had set up the had brought the unit used & was pumped down with r410a refrigerant. It had lowside pressure of 15 bar when unit was started low side pressure began to raise very fast whilst liquid line frosted & suction was really cool the unit was blowing cold air the unit was admittedly shut down.

But the liquid line frosting suggest restriction why is the suction really cold is this due over charge?

[The Viking]

When you say liquid line, are you looking at the pipework between the outdoor unit and the indoor unit?

:cool:

[todd86]

Hi viking thanks 4 the reply yes the lines connecting the indoor & out door 1/4 & 1/2 inch.

[The Viking]

Then you are not looking at a liquid line.
On a modern split the expansion device is in the outdoor unit and the only true liquid line is therefore inside the outdoor unit.
As you say that the suction pressure increased when the compressor started, is this a heatpump by any chance?

:cool:

[kefah]

i think low ***** charge

[todd86]

Hi yes it is a heat pump.

[The Viking]

So if you have a gauge connected to the service port on the larger valve on the outside of the outdoor unit and the pressure increases when the compressor starts then the system is operating in heating mode. This could either be because heat mode is selected or because a relay or the 4port valve is stuck.

That you also got frost on the intermediate (smaller) pipe indicates that you got other issues as well.
Perhaps this system got dirt in it?

:cool:

[todd86]

Thaks again for the reply so as larger connecting pipe feels really cool & the expansion pipe is frosting sweating defiantly a issue with to much charge as their wasn't much of a run on the pipes?

[The Viking]

Unlikely that what you describe would be an over charge issue, normally any split can operate with the factory charge in even with the shortest of pipe run.

I somehow get the feeling that you not have much experience of working on AC units, perhaps it is time to call someone in?

:cool:

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