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Relay contact protection.

Discussion in 'The Projects Forum' started by martian, Sep 5, 2008.

  1. martian

    Thread Starter New Member

    Sep 5, 2008
    Hi All.
    I'm doing a small job at my inlaws, who have a lovely big garden, this is lit partly by a few 100 watt bulkheads, but mainly by 2x150 watt and 2x250 watt metal halide lamps.
    I sugested that they would be better off on a timer system, and that I would help him, he really isn't mechanicaly inclined so I'm in the process of building him a cheap timer box, and have gone for a 30 amp 240v relay, (the price difference between 15 20 and 30a relays was so small I thought I'd over engineer it), but I've been reading up and it seems the inductive kick at switchoff from these type of lights is quite big, so I was wondering what was the best way to help protect the relay contacts, (I dont want it to burn out after six months and look a chump). would a Metal Oxide Varistor be suitable, seeing they are so cheap, or would you suggest a different method?
  2. mik3

    Senior Member

    Feb 4, 2008
    You can you a varistor (transient suppressor) with a voltage rating of about 500-600 volts in parallel with the lamps to suppress this kickback voltage.