View Full Version : Question about walk-ins
Inches of Mercury
04-25-2007, 08:31 PM
This would be about freezers and coolers.
How would you know what "normal" pressures would be for a typical unit? Sure I can calculate superheat/subcooling, but if I walk up to a low-temp unit is there a certain range I should expect?
Maybe this is a stupid question...
04-25-2007, 08:36 PM
but refrigerant type, box temperature, ambient temperature, etc... are very big factors in determining an answer to your question.
04-25-2007, 08:45 PM
first what is desired box temp
subtract design TD (10 for freezer, 7 to 25 for coolre depending on app)
convert answer to pressure
ex: R22 35 deg cooler at 10 TD
using your PT chart:
R22 convert to 25 to 48.8 psig DONE easy
R134A convert 25 to 22.1 psig
(25 is proper suction temperature)
to find all the desired TD's get Heatcraft Engineering Manual
checkpage 21 and page 23
no one should be in refrig business with this type of maunual
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