Question related to HVACR- what is your normal saturated condensing tempteture should be during low ambient or what tempteture it should not fall bellow, I heard 85 to 105F I want to understand low ambient head pressure control properly what is that magic number it should not fall bellow also one refrigeration tech was telling me you will want a 70 degree F liquid temp going to your TXV for better operation can you explain this a little in detailed way so I dont have ask others thank you.. Thank you.
Hello, Thank you for your question. When it comes to low ambient head pressure control, the main focus is to ensure that we are getting the correct pressure drop across our metering device for it to operate correctly. Typically, a minimum of 100 psi or more. Take for example a unit operating on r22. Head pressure 175psi/93f saturated condensing temp. Suction pressure 75 psi/ 44f saturated evaporating temp. These are typical numbers for an ac unit or water chiller using r22. The difference between the two pressures is 100 psi, this is the drop required for effective operation of the Txv. Any refrigeration system that goes below 55f or 12c ambient temp may require a form of head pressure control. Fan cycling controls, condenser flooding or even refrigerant operated airflow control dampers. Typically they try and control the saturated condensing temp above 85f. This is a minimum number because most normal efficiency condensers run with a 30f TD across them. For example if the ambient is 55f and my heat load is constant then I would be looking at a saturated condensing temp of 85f on a normal efficiency unit. R22 at 85f is 155 psi condensing, R22 at 32f evaporating is 57 psi still 100 psi differential. Have a play with a pressure enthalpy chart to get a better feel for this. Cheers
Excellent video! Thank you!!
Thanks mate, my pleasure.
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Question related to HVACR- what is your normal saturated condensing tempteture should be during low ambient or what tempteture it should not fall bellow, I heard 85 to 105F
I want to understand low ambient head pressure control properly what is that magic number it should not fall bellow also one refrigeration tech was telling me you will want a 70 degree F liquid temp going to your TXV for better operation can you explain this a little in detailed way so I dont have ask others thank you..
Thank you.
Hello,
Thank you for your question.
When it comes to low ambient head pressure control, the main focus is to ensure that we are getting the correct pressure drop across our metering device for it to operate correctly. Typically, a minimum of 100 psi or more.
Take for example a unit operating on r22. Head pressure 175psi/93f saturated condensing temp.
Suction pressure 75 psi/ 44f saturated evaporating temp.
These are typical numbers for an ac unit or water chiller using r22.
The difference between the two pressures is 100 psi, this is the drop required for effective operation of the Txv.
Any refrigeration system that goes below 55f or 12c ambient temp may require a form of head pressure control. Fan cycling controls, condenser flooding or even refrigerant operated airflow control dampers. Typically they try and control the saturated condensing temp above 85f. This is a minimum number because most normal efficiency condensers run with a 30f TD across them. For example if the ambient is 55f and my heat load is constant then I would be looking at a saturated condensing temp of 85f on a normal efficiency unit.
R22 at 85f is 155 psi condensing,
R22 at 32f evaporating is 57 psi still 100 psi differential.
Have a play with a pressure enthalpy chart to get a better feel for this.
Cheers