# high head pressure low suction



## tcbaker72 (Jun 30, 2009)

I just wanted to pick every ones brain i could. I am working on trane condensor and have high head pressure and low suction pressure. It was 90+ out today and I dumped r-22 into the system and no matter what I did I could not get the suction line to sweat and the superheat never dropped below about 20 degrees. my head pressure was around 285 and the suction around 55. I am thinking it may have a missing piston or the compressor. I would love some feedback


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## hvaclover (Oct 2, 2008)

Need more info. Tonnage of unit. How much refrigerant did you put in?
Why do you think you need a sweaty suction line? That depends solely on the the dew point of the air.

Why do you think its the compressor. Are you a tech?


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## tcbaker72 (Jun 30, 2009)

yes i am a tech and the dew point does matter. I was working on another model that was the exact same and was able to get the suction line to sweat. the evaporator is clean aswell as the filters. the sytem is a three ton unit with matching evap. the thing i was concerned about was the superheat. 8-10 is standard and the suction pressure should have been around 60-65 according to the manufacturers paper work with a head pressure of 270-275.


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## Plumber101 (Feb 25, 2009)

Have you washed out the condenser coils?


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## tcbaker72 (Jun 30, 2009)

no i did not but that was only because they looked clean


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## Plumber101 (Feb 25, 2009)

Looks and Is clean are two different things.

Had one yesterday pushing 300 hi washed coils brought it down to 225.

There are many things that push up hi pressure but the most common that I see is dirty condenser coil and a high heat load

Wash it and see what happens..what is 10 mins


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## tcbaker72 (Jun 30, 2009)

thanks for the advice. iwill try it tomorrow


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## 30yrhvactech (Jun 30, 2009)

The first rule I learned 30 something years ago. If the unit runs, grab a hose and clean the condenser. You would be amazed by the amount of customers who sweep the junk off the fins and try to tell you that they cleaned it.


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## hvaclover (Oct 2, 2008)

55psig and 285 head after you added gas... by this i am assuming you mean enough so that it should have affected the back press. 

With that high a super heat and and hi head that is probably a partial restriction.

Dirty condenser would give you much higher lo side.

How was the amp draw?


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## beenthere (Oct 11, 2008)

Why do so many get hung up on only looking at SH on a fixed metering device system.

Always chck your SH and SC on both fixed metering device systems, and TXV systems.

It will lead you to the problem.


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## psilliman001 (Sep 1, 2007)

*partial restriction*



hvaclover said:


> 55psig and 285 head after you added gas... by this i am assuming you mean enough so that it should have affected the back press.
> 
> With that high a super heat and and hi head that is probably a partial restriction.
> 
> ...


 doesen't take much to plug that little piston i've taken chips of valves , solder balls , & debris from poor brazing practices , easy to check & repair.........Jack:yes::yes:


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## hvaclover (Oct 2, 2008)

*high head pressure low suction..

in my day we would call that the perfect date!:icon_redface:
*


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## hvaclover (Oct 2, 2008)

psilliman001 said:


> doesen't take much to plug that little piston i've taken chips of valves , solder balls , & debris from poor brazing practices , easy to check & repair.........Jack:yes::yes:



Man that ones hits a nerve!

I totally agree with you, a filter drier in near the evap would eliminate most of that.


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