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Extremely high head and suction pressures

Originally had the same conditions above and came to the conclusion that the evap coil had blockage (we tried several times to clear it) and then removed all the refrigerant, swapped out the evap coil (used nitrogen while brazing), did a pressure test and vacuum test, and recharged with new refrigerant -- note: evap coil uses a piston metering device and we reinstalled the same one -- during the beginning of the recharging process the pressures and temps seemed to be ok but then the hissing noise at the condenser (bypass) started and after a few minutes the head pressure climbed way up and the suction did not follow -- but after we shut off the unit the head remained high and the suction followed -- after a few more minutes the head pressure dropped and the suction pressure remained high -- if the unit is powered back on then the cycle repeats itself -- so we're not sure what to check from here -- I suspected the condensing unit filter/dryer but the temps on either side of the device are not drastic

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  • dochoa838 Aug 14, 2008

    american standard model # wch024b100aa heat pump. starts ok then my head pressure go's real high and my low side go's down then it comes back down and repeats it's self till it trip over load. could it be my txvs or reversing valve going bad?

  • b_neilson Dec 12, 2013

    a restriction to refrigerant flow, faulty txv, plugged screen located at the txv inlet, possibly kinked liquid line.

  • Anonymous Mar 23, 2014

    replacing air conditioning condensing unit, where do i locate the piston metering device

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Disconnect the blower and turn on the ac.see if the coil frosts evenly.when you had the system open,you should have changed the liquid line drier.

Posted on Jul 29, 2008

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65 PSI TO 70 PSI IS THE SAME SUCTION PRESSURE FOR ALL TON SPLIT AC OR THERE IS DIFFERENT SUCTION PRESSURE IN ON CONDITION?


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Hello, typiccally with noncondensables in the system your head pressure would be alot higher. 175 is pretty low high side pressure. Usually coils will freeze due to either low airflow or low refrigersmt charge not becuase of non condensables. I would get a second opinion from a differant company.

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1 Answer

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Before you start checking pressures, you need to make sure that the unit is clean inside and out. You also need to know what the ambient temp is outside so you know what the pressures should read. Without this information, your info is useless to me. You need to know what your saturation temp is to determine if the head pressure is too high or too low. If the outside unit is dirty, you will have a high head pressure and low suction pressure. If the inside is dirty, you will have a high suction and a normal to low head. My advice to you is to clean first and then start checking temps and pressures. Otherwise you are spinning your wheels.

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1 Answer

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