Original message
| Brant
 |  "TXV valve?"
, posted Wed 3 Sep 16:10  
We have several Trane 30 ton units with split 15 ton compressors and five of them act as if there is an expansion valve problem, (ie; Hunting when starting, low suction\high head, vacuum on suction side and high head) condensor coils have been split and cleaned, but I cannot find expansion valves on them.
Trane Model #TCH300B400GA
Any sugestions??
Thanks,
Brant
From Booger Holler TN
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Replies:
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| Xenos
Webmaster 
| "Re(1):TXV valve?" , posted Wed 3 Sep 16:51
Wow this is a tough one, and I may be way out on a limb here but if I am not mistaken those evaporators have several orifices as in like 15 each. Where the liquid header is, each branch has a orifice. I am actually thinking that maybe the crimping that holds them in place may have let a go on a couple or for some reason they are getting plugged up. Find each one and look for any frost at it. Also check the subclooling right before them and make sure you have at least 10 degrees as any vapor will really mess them up since each one is really small.
I do get a bit confused with the high head issue though. Low suction so no load is being picked up, why the high head with no work being done. Ok I’m thinking out loud but there’s something to this. Sub cooling should lead you in the right direction, though maybe overcharged and flooding but then the vacuum problem.
Nope the first one is where I would start, check sub cooling and check those restrictors.
Xenos.
The best way to escape a problem is to solve it.
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| | Brant
| "Re(2):TXV valve?" , posted Wed 3 Sep 23:16
No frost or ice on evaporators, in fact with only one of the compressors running there is not much cooling going on at all. I know the one showing an actual vacuum on the suction side indicates a complete restriction such as a failed TXV, can dryers cause the same symptoms? Most of the ones reading low suction are reading around 35 lbs. PSIG with 300+ on high side. I tried bleeding off high and low sides for possible air in system, but comes back to original readings with charge. All are at 40 lbs or less and are not cooling??
From Booger Holler TN
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| | melaman
| "Re(3):TXV valve?" , posted Thu 4 Sep 19:26
Yes dryers can cause the same symptoms, you will be able to note it by a temperature difference across the drier.
What is the entering liquid temperature and pressures?
Pareto's Law
If a group of tasks are arranged in order of their priority 80% of the value come from the top 20% of the list.
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| | airworxhvac
| "Re(4):TXV valve?" , posted Fri 5 Sep 22:18
need subcooling and superheat for a correct answere. unit probably has orfice metering devises in header just before evap coil.
His grace is sufficient.
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| | melaman
| "Re(4):TXV valve?" , posted Thu 4 Sep 19:32
The reason why I would like to know the temp and pressure of the liquid line is because your system is acting like it is severely over charged
Pareto's Law
If a group of tasks are arranged in order of their priority 80% of the value come from the top 20% of the list.
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| | Brant
| "Re(2):TXV valve?" , posted Wed 3 Sep 23:17
ALSO these units are only 2 years old.
From Booger Holler TN
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| | Xenos
Webmaster
| "Re(3):TXV valve?" , posted Sun 7 Sep 12:57
I have been away sine Thursday and have pondered your question many times. I do think you have a restriction somewhere. And the over charge is just a result of it. I would really be interested in your pressure and temperatures you are getting on the liquid and suction line.
Xenos.
The best way to escape a problem is to solve it.
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