Original message
| jbmendoza
 |  "a/c short cycling"
, posted Thu 5 Jan 03:10  
i have a 10 toner split type air con, the problem is it always tripping on the low pressure switch, no matter how i charge it the pressure always go down to 20 psig thus triggering the low pressure switch, but whe i measure the liquid line just above the filter drier the pressure is around 200 to 230 psig, i have normal current pressure on my high side is 200 psig, is this a sign of loss compression or a blocked TXV? please comment thanks
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Replies:
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| cesarin78801
| "Re(1):a/c short cycling" , posted Thu 5 Jan 20:25
when asking a question about an oparating a/c with a problem you need all the info like
ambient temp,,indoor temp,,,suction line temp,,,,liquid line temp.,,,also suction line presure and head pressure to get a better answer,,
but it might be txv not metering properly or stuck in the close possition or low refrigerant charge depending on the subcooling you are getting
remmember i said "subcooling not superheat"get your sub cooling right,,,,,, and then check your superheat
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| | jbmendoza
| "Re(2):a/c short cycling" , posted Fri 6 Jan 19:58
thanks you sir, what is your prefered range or criteria of subcooling for a 5 to 10 tons split type air con, sir is there i way i can make it run continously just to check other parameters, i adjust (backseated) the TXV 7 full turn but the unit is still pumping down to 20 psig then tripping on the LPS. by the way my unit has two evaporator,.. im waiting for your replay sir thanks
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| | fitter597
| "Re(3):a/c short cycling" , posted Fri 6 Jan 22:26
subcooling depending on the machine would be between 15 and 30 degree's. Big Trane 50 ton and above want 15 degrees,on a 10 ton it should tell you in the service panel what they are looking for. make sure you don't have any dampers closed in the system, like if you have outdoor air damper and return, exhaust. make sure the belt is on right and not to loose, make sure the evaperator isn't plugged with dirt, if all that checks out ok, then i would change the TXV.
"We Do It Right The First Time"
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| | jbmendoza
| "Re(4):a/c short cycling" , posted Sat 7 Jan 02:48
thanks a lot fit, im relieved i thougth its a loss compression, i had a broken compressor last year i dont want to happen it again, thanks all of you guys more power!
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| | chiller guy
| "Re(5):a/c short cycling" , posted Sat 7 Jan 09:14
If the compressor was shot I doubt you could pump the unit down. Am I to understand that you are feeding two evaporators with one expansion valve? Have you checked the drier for restriction/ pressure drop?
All refrigerants are safe - All refrigerant are dangerous. The difference is YOU !!!
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| | jbmendoza
| "Re(6):a/c short cycling" , posted Sat 7 Jan 10:34
sir it has both txv on each evaporator, i clean and loosen the tension of the spring on the TXV, then run the unit, my sub cooling is 9.93 celcius (head press converted to P/T chart minus liquid line temp) outdoor temp 24 celcius, suction line is 14 psig, head press is 170 psig, sir what this mean? i ran the unit for 5 min and the compressor becomes hot than normal.
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| | jbmendoza
| "Re(7):a/c short cycling" , posted Sat 7 Jan 10:38
sir by the way i pull out the drier and blow air on it on the direction of arrow i felt there is some resistance butn when i blow on the opposite side its quite smooth is it obstructed?
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| | Mikey78
| "Re(8):a/c short cycling" , posted Wed 15 Mar 07:46
a shot in the dark but is the suction line prperly sized for the pumping capacity?
Canadian Eh?
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