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Zone Valve

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Art Pittaway
Art Pittaway Member Posts: 230
in THE MAIN WALL
Is the pressure drop excessive, and is the valve sized correctly for the flow. Valves get a bad rap, when everyone does system sizing it's, "Go to the next size larger", coils, pumps, boilers, and the valve. Your three ways may be running at an almost closed position on one side or the other, and a high pressure drop will make any valve howl.
Johnson usually does good work, and has good equipment, recheck the P/D and size. Our Erie 1/2" zone valves have 3 Cv's available, and 4 Cv's sizes for 3/4" size. And time after time the largest Cv get's ordered.

Good luck, Art

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  • Mike Lundstrom
    Mike Lundstrom Member Posts: 10
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    Zone Valve

    I work for a school division doing maintenance on mechanical systems. One problem keeps haunting me. I have a Johnson Contols pneumatic zone valve that whistles at a certain position in it's stroke. I have replaced the valve and the noise continued. This building is equipped with a DDC controlled 3 way valve to regulate the water temperature in the building so I don't have to squeeze the flow too much when it's warmer out. This problem also recently has popped up in other buildings. Anybody got some wisdom to share?
    Thank You
  • Tom Anderson
    Tom Anderson Member Posts: 40
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    Many many times I have come across control valves installed backwards.... a sure fire way to make them screech. Check the installations.

    Agree with other comment... you also may have too much pressure across the supply and return lines. Solution may involve adjusting the discharge valve on the pump.

    Note also heating hot water for coils.... most important factor in getting heat out of a coil is temperature of your fluid... not water flow rate through the coil. So, throttling pump flow will reduce differential pressure and total flow... but heating systems are not highly sensitive to flow rates. And it is probably over designed to begin with.

    Also make sure you have enough static pressure at pump suction...... a low static water pressure in your loop increases the likelyhood of cavitation across the valves, which is the real cause of your screeching noise.


    Thomas E. Anderson
    President
    Cx Associates, Ltd.
    Building Commissioning Specialists
    http://www.cx-assoc.com
    933 Road 101
    Jeffersonville, Vermont 05464 USA
    hvac@cx-assoc.com
    Tel: 802-644-5616 Fax: 802-644-6797

  • RB_2
    RB_2 Member Posts: 272
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    I agree with all the above - some other thoughts

    Without having all the details general considerations would be given to the overall system items which can be adjusted such as mass flow rate, available differential pressure, static pressure and fluid temperatures. If manipulating these system items (mechanically, pneumatically or electronically) fail to provide a solution then if possible try adjusting some of the same parameters at the valve itself, failing this, consider the actual components which are the valve Cv, valve characteristics including cone shape, actuator stroke and speed.

    Note: Adjusting the static pressure upwards is a solution for cavitation but have the expansion tank resized prior to implementing this procedure.

    rb











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