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  1. #1
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    Effects of capillary tube plugged

    Since one flows the other if cap tube is plugged would pressures be the same lower than normal on both sides or would you see something more like higher pressure on high side and lower than normal on lowside

  2. #2
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    Higher head and lower suction. A restriction in a cap tube would not allow proper flow, so head pressure would rise due to lack of flow and the evaporator coil would be starved, hence lower suction.

  3. #3
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    Lower than normal head, low suction. If its over charged your head would be higher and your suction low

  4. #4
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    Quote Originally Posted by CoolShowers View Post
    Higher head and lower suction. A restriction in a cap tube would not allow proper flow, so head pressure would rise due to lack of flow and the evaporator coil would be starved, hence lower suction.
    I was thinking that as well but if cap is plugged than how could you see higher head pressure if suction is low?than not much is going to come out high side due to starves evap Wish that was true with banks putting in low money yet getting higher return.

  5. #5
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    I was thinking higher head because more refrigerant would be in the condensing coil and less in the evaporator. Refrigerant has to be somewhere!

  6. #6
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    This is what I found. Temp would be higher but com pressure can only compress what the evap can supply. So how can you have higher pressure of low side is supplying comp with hardly any refer? Symptoms with restricted metering device low condensing head pressure and low amp draw and low evap pressure. If amps are low comp is not working hard so no way could you have higher head pressure.

  7. #7
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    Until joe schmo goes and adds a bunch of refrigerant because he's not happy with low suction. Then you get a higher head

    Sent from my SGH-T999L using Tapatalk 2

  8. #8
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    Yeah, after thinking it through more, there'd be low suction, normal head, but fairly high sub-cool indicating sitting refrigerant.

  9. #9
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    Quote Originally Posted by hvac wiz 79 View Post
    Until joe schmo goes and adds a bunch of refrigerant because he's not happy with low suction. Then you get a higher head

    Sent from my SGH-T999L using Tapatalk 2
    On that note let me ask this. What happens when refrigerant is added to the low side with a restricted cap tube. What happens to the low side pressure

  10. #10
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    Suction remains low but the head and subcooling go up. Subcooling would of been normal to low prior. now this is where you would expect anyone seeing these readings to stop and realize something isn't right ...

    Sent from my SGH-T999L using Tapatalk 2

  11. #11
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    Since most cap tube coils are on older sub 10seer equipment with small condensors it would be conceivable to see higher liquid line pressure with no additional freon. If its a higher seer unit with larger condensor to store the additional refrig that used to be in evap you will see lower head.

  12. #12
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    Quote Originally Posted by hvac wiz 79 View Post
    Suction remains low but the head and subcooling go up. Subcooling would of been normal to low prior. now this is where you would expect anyone seeing these readings to stop and realize something isn't right ...

    Sent from my SGH-T999L using Tapatalk 2
    I was reading on Supcos website and they are showing with a too much restriction that excessive pressure would be seen. And they are also stating if refer is added to a system with a restricted cap tube that pressure on suction will increase as refer pressure is coming from cylinder and it is past the restriction as you would see lower pressure due to restriction so pressure would rise due to no restriction from cylinder

  13. #13
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    A restricted cap tube will give symptoms of low high side pressure, low suction pressure, high sub cooling, and high superheat. Compressor Amp draw would also be low. If you think about it head pressure is a product if the work being done by the compressor. If its not pumping anything or very little then it's doing little work .. Also if there's little to no refrigerant getting to the evaporator then there's no heat being absorbed to have rejected in the condenser.
    This is why you cannot accurately diagnose a cap tube system as being low in charge based on pressures alone. You need to look at the whole picture by measuring sun cooling, super heat, comp Amp draw, and operating pressures.

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