R134a Help!!

Got a little test rig coldroom at work to train on.

Supervisor asked me to do home work :)

I got to find out what to set the HP and LP up at

Would any one know? the refrigerant is 134a :)
He told me to keep in mind its a pump down system


Thanks

I'd set the hp switch for 60-65c condensing temperatue, you will need to convert this to a pressure with a slide rule or pt chart.
The lp setting would depend on the design temperature of the cold room and the type of compressor.
For a recip comp, i'd set the cut out at 2 or 3psi for a scroll it would possibly be higher.
For the cut in you need to convert the design temperature of the room e.g. 12c into a pressure with you slide rule pt chart and make the cut in a few psi lower, maybe 5 or 10 psi.
What you want it a nice wide differential to stop short cycling with a high enough cut out that it doesn't go into a vacuum and a low enough cut in that it will cut back in. If the cut in is too high the tev can limit the suction pressure to below the cut in pressure and you unit won't start till the room is too warm. This is more of an issue with pumpdown cut out.

Jon :)

Quote:

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Originally Posted by monkey spanners

I'd set the hp switch for 60-65c condensing temperatue, you will need to convert this to a pressure with a slide rule or pt chart.
The lp setting would depend on the design temperature of the cold room and the type of compressor.
For a recip comp, i'd set the cut out at 2 or 3psi for a scroll it would possibly be higher.
For the cut in you need to convert the design temperature of the room e.g. 12c into a pressure with you slide rule pt chart and make the cut in a few psi lower, maybe 5 or 10 psi.
What you want it a nice wide differential to stop short cycling with a high enough cut out that it doesn't go into a vacuum and a low enough cut in that it will cut back in. If the cut in is too high the tev can limit the suction pressure to below the cut in pressure and you unit won't start till the room is too warm. This is more of an issue with pumpdown cut out.

Jon :)

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All quality info but you've put a monkey spanner in the works, Deano will never fit all that on the palm of his hand :):D:D

Quote:

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Originally Posted by VRVIII

All quality info but you've put a monkey spanner in the works, Deano will never fit all that on the palm of his hand :):D:D

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Get bigger hands Deano :D:D:D

lots of space on the reverse side of a p/t chart