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Switchboard surge supressor

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  1. #1
    Join Date
    Nov 2010

    Default Switchboard surge supressor

    Just about to get the sparky in to wire up a new pump and drive - looking to get him to rip out all the old gear and put in new main switch, breakers etc. into a 12 pole DIN rail unit.

    Part of the install will be surge supressors (MOV type) and there's the option to get ones with signalling contacts to indicate when the MOV has died and needs replacing.

    The question is, how are you meant to interface to these contacts? Can you run a 24v loop through them and out to some kind of interface, or do you need to maintain isolation and not have random wires running out from behind the housing?

  2. #2
    Senior Member
    Join Date
    May 2010


    I don't know about your specific brand and setup but in the past I have always either used 240v signaling you can get din mount sirens and lights or used 240v output from whatever control gear your using be that a motor overload or say a surge arrestor out to a 240 to 24 relay in a separate enclosure like a two pole din enclosure or general enclosure rather than having low voltage in the consumer board.
    Plus it's a convenient place to hide a small transformer

  3. #3
    Join Date
    Nov 2010


    I haven't actually selected the units yet, but they'll most likely be a Clipsal 970RMT
    Search Results - Clipsal.com

    I have similar Hager units installed on another board, but never got around to doing anything with the Aux contacts as it wasn't clear what was the appropriate way to interface to them. This time I wanted to sort out something when everything is being installed. The 240v relay idea sounds good - the 240v can be wired in series through the 3 sets of NC aux contacts such that it's holding the relay open, when one arrestor drops out, so does the relay and I can use the appropriate contacts for whatever 24v signalling.

    All that said, reading the instructions for that particular surge supressor, it seems there may be some complications regarding upstream fusing - I'm upgrading a 50 year old pump shed with its own transformer that's had multiple generations and combinations of different kinds of pumps - the new setup will be much simpler (single pump running off a VSD), but I suspect there'll be a bit of head scratching between me and the sparky making sure the surge protection is set up correctly.

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