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  1. #14
    Join Date
    Dec 2012
    Location
    Illinois
    Posts
    403
    "" Do Not Memorize what you do - Always know Why you are doing it; understand the basic nuts & bolts of it. So that when it becomes necessary to innovate - you know what can and cannot be tolerated""

    Thats a golden nugget of wisdom PHM!!

    IMPRESSIVE!!

  2. #15
    Join Date
    Dec 2013
    Posts
    34
    Question 1 - the power head is the only opening force on the expansion valve . If it fails the valve will slam closed so you will have a low suction and high superheat. If the valve is stuck open then it's probably not your power head it's something in the valve. Of course everything I said is only true if you have eliminated the possibility of there being moisture in the system which can freeze in the valve and cause symptoms of a stuck open or restricted valve.


    Question 2- sporlan has published
    That one full turn is approx. 4 degrees so 1 quarter turn is 1 degree




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  3. #16
    Join Date
    Dec 2013
    Posts
    34
    Question 3 - if you mount vertically because you don't have another option mount it with cap tubes facing up

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  4. #17
    Join Date
    Jun 2013
    Location
    Central Florida
    Posts
    731
    Quote Originally Posted by nchvac View Post
    I installed a Sporlan TEV today that was adjustable. This particular installation was for an A/C unit, but being most Residential A/C TEVs are not adjustable, I thought it a waste of time to ask the following questions.
    My first question is how do you know when a replaceable power head has failed versus a failure in the other components of the TEV, or in other words when do you know for sure that the powerhead is the issue.

    My second question is: Sporlan shows in their paperwork that in order to adjust you turn one way for up and one for down, but they don't tell how many turns or fraction of a turn = one degree.

    Did I say two? I meant 3 questions. They also showed that they don't allow a Vertical bulb placement. I see vertical placement all of the time and this particular install had no horizontal placement option and the bulb had to be placed after the equalizer tube. Valve held 15 degrees superheat at the coil out of the box even with this misapplication. What was supposed to happen that they don't want a vertical placement and bulb after the equalizer tube?
    www.emersonclimate.com/Documents/FlowControls/pdf/2004FC-141%20R7.pdf

    EMERSON CLIMATE TECHNOLOGIES
    TECHNICAL HELP GUIDE 2013
    Page 4.

    To compensate for an excessive pressure drop through an evaporator, the TXV must be externally equalized. The equalizer line should be connected to the suction line at the evaporator outlet, past the remote bulb location so that the true evaporator outlet pressure is exerted beneath the TXV diaphragm.

    If I remember correctly, 1/4 turn = 1 degree.


    "Real men don’t use instructions, son; besides, this is just the manufacturer’s opinion on how to put this together." -Tim Taylor
    JUST A LITTLE CLOSER AND THE LITTER BOX IS ALL MINE!

  5. #18
    Join Date
    May 2003
    Location
    Utah
    Posts
    743
    A couple of thoughts:

    There is no magic number of turns per degree of superheat that works for all valves. For example, there are nearly twice the number of turns from fully open to fully closed in a G valve as compared to a balanced ported valve. In addition, there are a lot of factors that could change the amount of superheat/turn from application...distributor sizing (which affects the amount of available pressure drop across the TEV port...which in turn affects the valve capacity), the liquid temperature, which again affects TEV capacity,....

    It's a much better practice to measure the superheat and adjust the valve as needed rather relying on opening/closing the valve a certain amount of turns to hopefully get a predetermined amount of SH change.

    The reason for mounting the bulb on the horizontal is to eliminate it from sering temperature fluctuations seen every time the trap fills enough to burp a volume of oil up the riser.

    If you need to install the bulb on the vertical, the capillary should be at the top of the bulb to prevent the charge from leaving the bulb. But...the way the bulbs are constructed, the charge should never drain out of the bulb anyway...when looking at the bulb with the capillary at the bottom, the end of that capillary inside the bulb will extend up beyond the bottom of the bulb about 1/4". There's no way for the charge to completely drain out of the bulb...plus, the charge will want to migrate to the coldest location anyway....which ought to be the bulb. I have heard from many technicians of control issues when the bulb was installed on the vertical with the bulb pointing down...and after reversing the bulb the valve started controlling fine.

    Regarding the amount of pressure drop cross the TEV port: The rating condition for the valve is at a 40* Evap temp, 100* liquid temp and 100 lb pressure drop across the valve port. This is where the 100 lb drop comes from. The valve doesn't really care what the pressure drop is (within reason). where you can have problems is when the valve is selected based on a certain pressure drop...say 150 lbs. when you experience less pressure drop, the valve capacity is reduced. At some point, if the pressure drop continues to reduce, the valve capacity will become less than required. That's the only limiting factor in how low the pressure drop can go...it becomes problematic if it causes the valve capacity to become less than what is required to properly refrigerate the evaporator and maintain required SH under varying load conditions.

  6. #19
    Join Date
    Mar 2008
    Posts
    257
    In addition some field notes, clean bright and tight. These days were working with smaller suction lines in supermarket most important to get good contact/max surface contact and very tight about two o'clock. Something that works well is insulation over the bulb. Less return air influence on the exterior 97% of the bulb during recovery after defrost and high load pull down . There is a patented superheat sensor that changes the ratio of surface area of the bulb. I would also say on the question of vertical mount that the bulb should be as far possible beyond the last pass of the evaporator, so often I see the bulb in the correct vertical orientation but two passes up from the outlet of the evaporator. I go out of my way to provide a horizontal suction line at the exit of the evaporator.

  7. #20
    Join Date
    Aug 2009
    Location
    Maine
    Posts
    3,716
    So what is going to happen as we change to electronic expansion valves?

  8. #21
    Join Date
    Oct 2012
    Location
    Wisconsin
    Posts
    4,439
    Quote Originally Posted by lytning View Post
    So what is going to happen as we change to electronic expansion valves?
    There are temperature sensors, and usually pressure transducer(s) as well. They will maintain their superheat without need for adjustment, unless there is a system problem or sensor issue.

    If you want to change the superheat, you do it via a computer or controller.

  9. #22
    Join Date
    Aug 2009
    Location
    Maine
    Posts
    3,716
    Yes that is what I thought, I think it is coming sooner rather than later for walk ins and probably some reach ins.
    Quote Originally Posted by Mike19 View Post
    There are temperature sensors, and usually pressure transducer(s) as well. They will maintain their superheat without need for adjustment, unless there is a system problem or sensor issue.

    If you want to change the superheat, you do it via a computer or controller.

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