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TRIAC PCB has blown component- please identify.

Discussion in 'Troubleshooting and Repair' started by LesW, Sep 21, 2019.

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  1. LesW

    LesW

    4
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    Sep 21, 2019
    B18487F4-DB25-4499-9937-0FA3ABA68F7C.jpeg A0E2D5A9-13FE-4CE8-BDED-1C2352C7B5F1.jpeg I have a motor control PCB from a ground source heat pump that has a visibly blown component. I would like it identified and to now how it would effect the boards performance as a whole.
    I have very limited electronics knowledge. The component is marked z1 on the PCB. The board controls a 230v ac pump.

    Picture to follow. I have made an attempt at a circuit diagram.
     
  2. Minder

    Minder

    2,922
    615
    Apr 24, 2015
    VDR - Voltage Dependent Resistor, for suppression, often when they do their job, they are sacrificed in the process!
    The circuit should work without it for trial purposes.
    M.
     
  3. LesW

    LesW

    4
    0
    Sep 21, 2019
    It still runs the motor. Should we replace the resistor, and can you suggest the component. We can’t find a replacement PCB.
     
  4. Minder

    Minder

    2,922
    615
    Apr 24, 2015
    I use 275L40, look up the Littlefuse VDR spec sheet, it shows operating voltage and Joule value, in the example the Joule rate is 40.
    Available on DigiKey
    M.
     
    Last edited: Sep 29, 2019
  5. LesW

    LesW

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    0
    Sep 21, 2019
    Replaced the variresistor with Z250F 275v 65 joules rating. The new component started over heating almost immediately power was applied. Is it likely we have other damaged components on this board. The mains voltage here is 245volts.
     
  6. Harald Kapp

    Harald Kapp Moderator Moderator

    9,668
    2,019
    Nov 17, 2011
    This type is rated for 230 V mains only, see here. Unfortunately no datasheet there :(
    Mains voltage is typically +-10 % at the least, use +-20 % for worst case. This means your mains can actually reach up to 294 V. The varistor should withstand this voltage without becoming conductive. You also have to take into account worst case tolerances and temperature degradation of the varistor. I suggest you use a min. 320 VRMS varistor.
     
  7. LesW

    LesW

    4
    0
    Sep 21, 2019
    Thanks for the timely response.. We are exploring a step down transformer to reduce the main to 220 volts as this heat pump is Italian in origin and is built fo continental voltage levels.
     
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