high head pressure low suction

 
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Old 06-29-2009, 09:23 PM   #1
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high head pressure low suction


i am working on a trane condensor when I arrived at the job site I found the eveporator frozen solid. I thawed it out replaced the filters and cheked the coil it was fairly clean. I then found the pressure at around 45 psi on the suction and 185psi on the head. it was 90+ degrees out so I proceeded to add some refridgerant to the system and raised the head pressure to around 285 but could not get the suction above 50 psi. the superheat never fell below 18 degrees. I am thinking I have the wrong or missing piston or the compressor is not working properly. any ideas would help

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Old 06-29-2009, 10:28 PM   #2
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Re: high head pressure low suction


Need to know the sub cooling but it sounds like you are stacking up refrigerant in the condenser and the orifice is plugged. You may be over charged now. If you were missing it you would be running a high suction not low. Are you sure it is not a TXV?
High head is normaly dirty condenser or substantilly over charged.
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Old 06-29-2009, 10:35 PM   #3
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Re: high head pressure low suction


ya its a piston not a txv but i think you are right about the over charge that is what concerned me and prompted me to post this.
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Old 06-29-2009, 11:04 PM   #4
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Re: high head pressure low suction


even with piston type/ still need subcool,
all trane systems have a check valve/ could be inop!
most trane systems never get cleaned very well cuz the panels are a pain! sounds like a double issue, john's right on it.
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Old 06-29-2009, 11:04 PM   #5
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Re: high head pressure low suction


1)I would wash the condensor.

2)You don't know how much freon you have in now so you may want to remove it and weigh it back in with a scale. Lot less aggravation that way and then you have a good reference point to work with.
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Old 06-29-2009, 11:19 PM   #6
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Re: high head pressure low suction


after you recover, flush system w/nitro - then after you calc. for lineset and factory charge, clean outdoor coil and watch as the head presure drops, if not suction will flutter and the check valve needs replaced!
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Old 06-30-2009, 10:03 PM   #7
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Re: high head pressure low suction


Quote:
Originally Posted by supercool View Post
after you recover, flush system w/nitro - then after you calc. for lineset and factory charge, clean outdoor coil and watch as the head presure drops, if not suction will flutter and the check valve needs replaced!
Ok What check valve?
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Old 07-01-2009, 10:27 PM   #8
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Re: high head pressure low suction


It probably has a partial restriction and now you have overcharged it. I would start at the filter drier. Trane usually has a factory copper filter drier installed. Look for temp drop across it.
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Old 07-02-2009, 12:01 AM   #9
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Re: high head pressure low suction


I agree with the filter/drier being a probable cause, but if you are still getting a solid line of liquid through the filter/drier, you may not be able to tell a difference in temperature. Your system subcooling will however tip you off to a partially blocked filter/drier.
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Old 07-02-2009, 01:27 PM   #10
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Re: high head pressure low suction


Quote:
Originally Posted by supercool View Post
even with piston type/ still need subcool,
all trane systems have a check valve/ could be inop!
most trane systems never get cleaned very well cuz the panels are a pain! sounds like a double issue, john's right on it.

I find it easier to pull the fan and spray in cleaner from the inside of a Trane condenser. You don't always have the room to pull off the outer panels.
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Old 07-03-2009, 12:28 AM   #11
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Re: high head pressure low suction


Most Tranes dont get cleaned very well because of patented "Spine Fin " coils which are superior to Everyone elses coils because Blah Blah Blah.
tc if its over charged, who did it and why.
Checking temp accros the filter is a great diagnostic tip but should be done in the first few minutes of running befor the whole line gets cold. with the numbers you put up it sure looks like a liquid line restriction but you are on the front line.
back to basics. start fresh. Verify the complaint. listen to the customer!!!!!! he may tell you all you need to know.
I see it has been a few days? have you found anything yet?
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Old 07-03-2009, 01:52 PM   #12
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Re: high head pressure low suction


I believe I remember seeing posts about cleaning Trane/A-S spline fin coils using a blow torch. This is a public service post by someone who does not sell Trane or A-S
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Old 07-03-2009, 05:31 PM   #13
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Re: high head pressure low suction


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Originally Posted by RoBoTeq View Post
I believe I remember seeing posts about cleaning Trane/A-S spline fin coils using a blow torch. This is a public service post by someone who does not sell Trane or A-S

Lucky no HO tried it a blew his face off in the process, the lawsuit could have been real bad.
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Old 07-04-2009, 02:36 AM   #14
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Re: high head pressure low suction


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Lucky no HO tried it a blew his face off in the process, the lawsuit could have been real bad.
We could use a few incidences like that to keep HOs from buying direct from contractors selling on the Internet.
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Old 07-04-2009, 11:59 AM   #15
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Re: high head pressure low suction


Quote:
Originally Posted by tcbaker72 View Post
i am working on a trane condensor when I arrived at the job site I found the eveporator frozen solid. I thawed it out replaced the filters and cheked the coil it was fairly clean. I then found the pressure at around 45 psi on the suction and 185psi on the head. it was 90+ degrees out so I proceeded to add some refridgerant to the system and raised the head pressure to around 285 but could not get the suction above 50 psi. the superheat never fell below 18 degrees. I am thinking I have the wrong or missing piston or the compressor is not working properly. any ideas would help
I had the same problem on a 5 ton Trane package unit.

Non condensible's will cause this, pull the charge, remove and replace the drier, pull a vacuum to less than 450 Microns and make sure it holds, recharge the system and it should take care of the problem.
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Old 07-04-2009, 03:54 PM   #16
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Re: high head pressure low suction


Quote:
Originally Posted by bwalley View Post
I had the same problem on a 5 ton Trane package unit.

Non condensible's will cause this, pull the charge, remove and replace the drier, pull a vacuum to less than 450 Microns and make sure it holds, recharge the system and it should take care of the problem.
And if the OEM filter/drier is on the inside of the unit, replace it with a piece of tubing and install a new filter/drier in the liquid line between the service valve and the indoor coil.
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Old 07-06-2009, 01:33 AM   #17
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Re: high head pressure low suction


I agree with the last 2 posts but what check valve are the others talking about? I have never seen a check valve in a split system or any other refer sys. unless 1 condenser serving multiple evaps.
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Old 07-06-2009, 08:17 AM   #18
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Re: high head pressure low suction


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Originally Posted by hvactech View Post
I agree with the last 2 posts but what check valve are the others talking about? I have never seen a check valve in a split system or any other refer sys. unless 1 condenser serving multiple evaps.
They are talking about the F.C.C.V.
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Old 07-06-2009, 04:22 PM   #19
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Re: high head pressure low suction


Quote:
Originally Posted by hvactech View Post
I agree with the last 2 posts but what check valve are the others talking about? I have never seen a check valve in a split system or any other refer sys. unless 1 condenser serving multiple evaps.
Carrier used to require a solenoid valve be installed in the liquid line close to the coil for bleed type TXV systems. Could this be what is being referred to?
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Old 07-06-2009, 04:30 PM   #20
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Re: high head pressure low suction


Quote:
Originally Posted by RoBoTeq View Post
Carrier used to require a solenoid valve be installed in the liquid line close to the coil for bleed type TXV systems. Could this be what is being referred to?
This is a Trane system that is being discussed.
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