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Thread: thermal valve

  1. #1
    Join Date
    Feb 2005
    Posts
    9
    First I would like to thank you in advance.

    I have a complete 5 tons (from what I heard) gas heat system. My outdoor model is TTN060C100D0.

    I had problem and called a service man out. He said that my thermal valve was bad. It was connected on the outside of my coil above my gas heater. I agreed to have it replaced. After he had replaced it., he gave me the old valve and shooked the bulb and told me it was bad. I could hear and feel something was loose inside the bulb.

    The valve he replaced was not exact like the one he took out. It was a bigger valve. The valve number I could read was SVE-4-CP100. But there was one small line he DID NOT connect like the old valve. The old valve had a 1/4 inch line connected to it from the big freon line. I asked him but his reply was "the old valve was external equalizer, and the new valve was internal equalizer". The unit runs cool but not as well as It used to. Thus, I have some questions to ask:

    Question 1: What does that 1/4 inch line on my old valve do?

    Question 2: when the bulb on the valve make noise like I described, that means the valve is bad? Because the new valve make no noise when I shook the bulb.

    Question 3: On my new valve, the number 4 is for my tonnage? whereas I have 5 tons right?? And the CP100, what does it mean?



  2. #2
    The 1\4 inch line that was in the suction line probably near where the bulb was strapped on is the external equalizer line. It allows the TXV to reference the suction line which is the pipe leaving the indoor coil for a pressure reading, the reason for this is to compensate for a pressure drop through the coil,in which a non-externally equalized TXV will not. The ( non external ) will reference the pressure at its outlet which is the entering side of the coil. You will always have better control with an externally equlized bulb. Although it should not change the capacity of the TXV, in general if given the choice of choosing a smaller or larger TXV for the system the standard practice is to use the smaller one.

    As far as the thing making noise, who knows? that is not a normal procedure for testing a bulb, there is nothing inside the bulb but a lttle freon. If it made noise I would be surprised and condemn it also.

    The three questions you are asking are not the ones that you should be asking , try posting what the original problem was with all available information,




  3. #3
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,358
    SVE-4-CP100 is a Sporlan 4 ton expansion valve with external equalization for R22 or R407A applications. CP100 is the thermostatic charge of the bulb.

    Your new valve appears to be internally equalized. An externally equalized valve will allow better superheat control as it accounts for the pressure drop through the evaporator.

    For you as a homeowner, this technical info means little. For the technician that serviced your system, it means everything. First of all would be why he replaced the expansion valve initially. They are often blamed for being the culprit when other outstanding factors are actually the problem, such as a technician that blames the TXV rather than having a thorough understanding of refrigeration theory and application.

    Your loss of cooling performance should be investigated. It could have several causes, not necessarily TXV related.

    I also have to chime in with Eddy...what was the original complaint that led to having your expansion valve replaced?
    • Electricity makes refrigeration happen.
    • Refrigeration makes the HVAC psychrometric process happen.
    • HVAC pyschrometrics is what makes indoor human comfort happen...IF the ducts AND the building envelope cooperate.


    A building is NOT beautiful unless it is also comfortable.

  4. #4
    Join Date
    Feb 2005
    Posts
    9
    My appology to my service man. He did show me that the low pressure went down to zero when the unit run. He said that the valve was not opening. But your answere was not too clear.

    So my new valve SVE-4-CP100 needs to have the tube connected
    or not connected will not efffect my cooling?

    Thanks

  5. #5
    If it is not an externally equalized TXV it does not need to be connected to the suction line.

  6. #6
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,358
    Originally posted by gnauq
    My appology to my service man. He did show me that the low pressure went down to zero when the unit run. He said that the valve was not opening. But your answere was not too clear.

    So my new valve SVE-4-CP100 needs to have the tube connected
    or not connected will not efffect my cooling?

    Thanks
    Okay...this is where I wasn't sure. I should have stuck with my initial instinct and asked you if the SVE-4-CP100 was your NEW valve. Apparently, it is. If so, the "E" in SVE stands for "externally equalized". Which means that if this is your NEW valve, the technician did not connect the external equalizing line for your NEW valve, which should have such a line installed, if indeed SVE-4-CP100 is your NEW valve.
    • Electricity makes refrigeration happen.
    • Refrigeration makes the HVAC psychrometric process happen.
    • HVAC pyschrometrics is what makes indoor human comfort happen...IF the ducts AND the building envelope cooperate.


    A building is NOT beautiful unless it is also comfortable.

  7. #7
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,320
    It needs to be connected, it an external equalizer valve, it needs the suction line pressure reference to work properly.
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    How many times must one fix something before it is fixed?

  8. #8
    Join Date
    Apr 2002
    Location
    Dallas, TX
    Posts
    2,987
    Originally posted by gnauq
    The valve number I could read was SVE-4-CP100. But there was one small line he DID NOT connect like the old valve. The old valve had a 1/4 inch line connected to it from the big freon line. I asked him but his reply was "the old valve was external equalizer, and the new valve was internal equalizer".
    If the new valve is a SVE-4-CP100, the valve is externally equalized and it will have three connections: inlet, outlet, and equalizer. The equalizer connection will be 1/4". If that connection is open, the valve will simply stay wide open and will not regulate. If the connection was soldered shut, valve operation will be erratic, and will likely starve much of the time.

    Originally posted by gnauq

    Question 2: when the bulb on the valve make noise like I described, that means the valve is bad? Because the new valve make no noise when I shook the bulb.
    A rattling sound from the sensing bulb is not indicative of anything.

    Originally posted by gnauq

    Question 3: On my new valve, the number 4 is for my tonnage? whereas I have 5 tons right?? And the CP100, what does it mean?
    The SVE-4-CP100 is nominally rating of 4.5 tons, and it will handle a 5 ton a/c system. The 'CP100' indicates the valve uses an R-22 a/c thermostatic charge. I do not have any problems with your serviceman's valve selection. The installation worries me though.

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