problem with control enviromental cabinet

Discussion in 'General Electronics Chat' started by AHMARAFAH, Oct 28, 2006.

  1. AHMARAFAH

    Thread Starter Member

    Jul 11, 2006
    20
    0
    Hello all,
    It sounds like some body can do favor for me , posting investigation and clarification the solution of the problem indicated below:
    (the valve which control the cooling process stays open when it should be off this cause that system continuing cooling far the setting point)
    i check if the cause is mechanical problem or electrical issue but i still confused and not reaching to the solution.
    thanks in advance
    looking to hearing good news
     
  2. Papabravo

    Expert

    Feb 24, 2006
    10,145
    1,791
    From what little information you have provided I seriously doubt that any meaningful help will be forthcoming. Let's start with what the valve controls and what kind of actuator is being used. Then we can move on to what controls the actuator. At that point we might be able to offer useful suggestions.
     
  3. Dave

    Retired Moderator

    Nov 17, 2003
    6,960
    144
    For a start, can we get a schmatic or diagram of the system? I am struggling to see exactly is being asked here.

    Dave
     
  4. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    Hi,

    Have you been able to check the thermostat? If it has failed such that it always calls for cooling, then the valve and such are no longer suspect.

    Turn the thermostat up and see if the colling compressor/chill water valve shuts off.
     
  5. AHMARAFAH

    Thread Starter Member

    Jul 11, 2006
    20
    0
    thank you for your time and help .
    it is controlled enviromental chamber based on microprocessor controller which controls the cooling system and the humidity system.
    the cooling system uses liquid co2 tank with DIP tube .
    the humidification system is ultrasonic humidifier .
    the problem exists in the cooling system.
    the prober cooling system act as follow:

    the valve is open continuously and the co2 feeds the chamber continuously until reach the required set point .
    when the chamber reach the required setting point temperature the microprocessor provides the solenoid valve pulses of power that is sufficient only fo maintain the set point.
    according to these pulses the valve close and open and the co2 feeding into the chamber in plulses not continuous.
    the problem is: the valve is open continuously even if the chamber reaches the required temberature and the microprocessor provides tthe pulses for the solenoid valve .
     
  6. Syed

    New Member

    Dec 5, 2005
    6
    0
    We assume that controller is ok and so are the connecting wires.
    Confirm the operation of solenoid valve by listening the tuck-tuck sound on pulses if area is noisy place your hand around the valve and pulsation can be felt easily. If controller indicates pulsed out-put but no physical pulsations at the valve, check out-put from cabinet to the valve. If not pulsed but continous check the cabinet circuitry. If getting required pulsed out-put check as below.
    If your valve is N.Closed type (which most probably it is), there are chances of stucking in open position or some thing is stuck in its seat.

    Good luck
     
  7. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    Hi,

    By all means, take the valve apart and check the seat - even a tiny bit of crud will hold it open. Just to be sure, though, put a meter on the leads and see that the valve does not have voltage on it continuously.
     
  8. AHMARAFAH

    Thread Starter Member

    Jul 11, 2006
    20
    0
    Many thanks to you i investigate what you advise me to do and i found that:
    1-The solenoid valve is ok.as,i hear the tuck-tuck sound.
    2-We carry out the procedure of cleaning the valve stem to make sure that nothing is stuck in its seat.
    also,i want to clear that the valve is still open.although,we turn off the microprocessor.
    looking for your seriously help

     
  9. Syed

    New Member

    Dec 5, 2005
    6
    0
    Hello, AHMARAFAH

    If you can listen the operating sound of the solenoid valve, it confirms that your control system is ok and so is the actuation system of your solenoid valve. A properly working solenoid valve must block the flow completely on de-energizing, if it is normally closed type. Normally open type will block on energizing. If it is not allowing / blocking with the supply on / off the best option would be to replace it with a new one. (I always prefer to test even new components before installation)

    Regards,
    Syed
     
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