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Has my SPD tripped?

Chris Pearson

I may be being a bit thick, but ...

... how do I know if my SPD is still functioning?

The same might be said of an RCD, but of course we all check them six monthly so we could check the little indicator in the SPD at the same time.

However, if the RCD has tripped, we know about it 'cos the lights go off. If the SPD has exceeded its useful life, we know nothing. The one which I shall be installing at home has a switch for an indicator or buzzer, but that wouldn't be much use for a CU at the back of the hall cupboard/under the stairs/in the garage.

I am left thinking that if SPDs should be fitted, there should also be an effective alarm system. Do you agree?

Parents

  • Sorry, I clearly hadn't read your post properly!

    I suppose compared to the potential life-saving RCD a failed SPD generally only poses a risk to property. So if we can live with a broken RCD for up to (say) six months (if usual guidance is followed) I reckon in most situation a broken SPD could pose tolerable risks for a similar time.  If you want something more, then as you say, there are ones with switching contacts available so it's a simple matter to rig one up to a remote visual or audible alarm - which  of course could be positioned in a much more noticeable location than the CU. Some means of temporarily silencing the alarm might be a good idea though - otherwise it could end up like so many smoke alarms and be tampered with to remove the nuisance by those that don't have the ability to properly fix the underlying problem.

       - Andy.

  • in reply to AJJewsbury

    SPDs are often (usually, always?) installed with an MCB, as SPDs tend to fail short circuit.  So if the alarm goes off, turn off the MCB and the problem goes away.

  • in reply to Simon Barker

    not always, with or without MCB (Wylex for example) sometimes the flag drop and alarm contact is purely mechanical, more or less a one-time fuse link that when broken by the SPD failing low resistance pops the fuse, and in turn releases a spring that operates the alarm switch. It then rather depends what circuit the alarm is on,

    Mike.

Reply
  • in reply to Simon Barker

    not always, with or without MCB (Wylex for example) sometimes the flag drop and alarm contact is purely mechanical, more or less a one-time fuse link that when broken by the SPD failing low resistance pops the fuse, and in turn releases a spring that operates the alarm switch. It then rather depends what circuit the alarm is on,

    Mike.

Children
  • in reply to mapj1
    mapj1 said:
    It then rather depends what circuit the alarm is on,

    Quite so! I have been contemplating how to connect my alarm lamp. Clearly, the circuit must be protected. So I thought connect to the lighting circuit where the DB is situated. If the lighting there has tripped, then clearly action must be taken. If it has not, then the alarm will flash. Without doubt, the alarm circuit cannot be the SPD circuit.

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