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Low air flow

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johnjohn89
johnjohn89 Member Posts: 100
in A-C, Heat Pumps & Refrigeration
Does low airflow cause high superheat?What I understand is low air flow cause low superheat because less heat pick up evaporator coil low suction pressure! But
Someone said low air flow can cause high superheat I don’t get that? And why? 

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  • pecmsg
    pecmsg Member Posts: 4,845
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    X-Valve or Piston?
    lowering the air flow with an x-valve “shouldn’t” change the SH. The valve will compensate within it limits. 
    PIATON: lowering the air flow WLL lower the SH. 
    RPKIronmanGW
  • pedmec
    pedmec Member Posts: 973
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    if you have a piston type metering device you have several areas of concern affecting your superheat. the main one is the load on the evaporator. if you reduce the load (airflow) then your load on the evaporator is reduced and your superheat is reduced. if you have an extremely hot day outside the resulting increase in head pressure with further reduce the super heat as the increase in head pressure will cause a greater differential on the low side and you will flood the evaporator even further.

    this is why all r22 condensers use to come with charging charts under the cover to show the relationship between low side and high side pressures on piston type metering devices.

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