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    ebnsena5813's Avatar
    ebnsena5813 Posts: 4, Reputation: 1
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    #1

    Mar 17, 2013, 03:32 PM
    free hvac questions and answers
    We have air cooling York chiller model YCHA 110, it has two systems with two reciprocating compressors, syst #1 = 60 ton, syst#2 =40 ton, when the chiller is running, after 5 minuites, compressor #1 tripping by oil pressure switch off due to liquid flooded in the suction line, also after 10 minuites the second compressor tripping by the same way due to same reason, we replaced the two thermostatic expansion valves, we adjusted superheat at 10 f, we retubed the cooler but the same problem is happened.
    kindly help.
    hvac1000's Avatar
    hvac1000 Posts: 14,540, Reputation: 435
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    #2

    Mar 17, 2013, 05:59 PM
    From here it looks like the liquid refrigerant coming back from the evaporator is the problem. Usually by the time the liquid refrigerant has passed through the evaporator it has turned into a vapor. If this is left to cause damage the liquid refrigerant will eventually wash out the oil in the compressor and we all know what that causes.

    You need to find out the air flowing into the evaporator temperature and the air flowing out of the evaporator temperature. If the temperature is to low or not enough between in and out then there is a problem at this point in the system.

    I usually mention checking other things first because a system that has worked well for years should not be having this kind of problem unless something was changed or adjusted improperly.
    ebnsena5813's Avatar
    ebnsena5813 Posts: 4, Reputation: 1
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    #3

    Mar 18, 2013, 01:21 PM
    Thanks hvac1000, herewith the operation condition measured parameters :
    water flowing through the evaporator, T in = 48.2 f, Tout = 54 f, air flowing through the condenser, T in = 94 f, Tout = 115 f, suction pressure = 60 psi, discharge pressure = 275 psi, I hope you will find something in this operation data and grant me your assistance.
    regards
    hvac1000's Avatar
    hvac1000 Posts: 14,540, Reputation: 435
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    #4

    Mar 18, 2013, 02:15 PM
    It seems the spread here ( T in = 48.2 f, Tout = 54 f,) is quite low. You only have 6.2 degrees of spread or TD= Total Differential on your evaporator setup. Setting that aside for a minute. I believe what I am seeing here is a situation where the evaporator is not allowing, or capable of, or being held back from the heat removal process. This type of situation will cause the same experience you are having now which liquid refrigerant going back to the condenser when it should almost all be a vapor. The temperature tells the tail since the TD is not up to specs.
    I need to know what type/number of refrigerant you are using AND what has changed on this system before this problem started since it must have run well for some time in the past. NOTE: This is only an example. Years ago I had a similar problem and was called into try ans figure out what was causing the problem. I found out 2 weeks before the factory management was talked into replacing there air filters with a new style that would really trap more dirt. Well the filters really did trap more dirt BUT they would plug up real fast also and since the air could not go across the coils fast enough the system would trip on the safety's. The sad part is that I talked the company to contact the new filter supplier and when they showed up to replace the filters I asked them when was the last time they were out to change them. The filter change guy said they had just installed the new filter system 2 weeks ago and was surprised they were plugged up so soon. Needless to say I had them leave a few of the filters out and we started and ran the system. It worked well and all was back to normal so I told the filter contractors they better be changing the filters about every week to 10 days. The company spent some big bucks for me to be there and figure it out but as simple as the solution was they themselves could not come up with the fix.

    Send refrigerant type/number
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    ebnsena5813 Posts: 4, Reputation: 1
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    #5

    Mar 18, 2013, 02:21 PM
    For correction : super heat adjusted 12 degree celsius.
    ebnsena5813's Avatar
    ebnsena5813 Posts: 4, Reputation: 1
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    #6

    Mar 18, 2013, 02:31 PM
    Freon 22

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