PIR unit failures

[Robin]

Hello UK.d-i-y world. Glad I found this group, all seems very useful.

My question:

I've recently moved to a new house that has loads of outdoor PIRs - connected to typical looking external lighting (i.e. Halogen floodlights).

The problem is most of the b*ggers don't work. The PIRs are getting power, but the lights don't come on.

The obvious thing is the bulbs, but on the few I've changed so far, this hasn't fixed the problem. i.e. the problem has been with the PIR switch, not the bulb.

How common is this? Is there a limited lifetime for PIR units? (I guess most of mine are >10 years old).

Any advice appreciated.

- Robin

[Dave Plowman (News)]

They're usually a solid state switch - and like a dimmer can blow when a bulb fails. Unfortunately solid state components can burn out quicker than a fuse or circuit breaker can operate when presented with an overload - and a failing bulb sometimes shorts out for a moment.

Some better PIRs have a mechanical relay to switch the load and will prevent this type of failure.

[Huge]

In the 15 years we've lived in this house, all the external PIRs have failed and been replaced. So, yes they do have a limited lifespan & > 10 years is doing quite well.

[chrisj.doran]

The very first one I got from Maplin circa 1980 at about =A330 lasted 20 years and would probably still be going except that the lens got brittle and I put a finger through it. It had an internal fuse which often blew with the lamp. It may be worth looking for fuses in yours.

Later I added cheaper ones but seemed to be for ever replacing them. In the last 5-10 years I've switched to the ones which have the PIR hung off the bottom of the lamp, and these last longer, as well as being cheaper than separates.

As I've said here before, what I used to do was to throw the dead PIR in a corner with the intent of finding a round toit to repair it (they were expensive then). When the next one died, I tried the last dead'un and found it had recovered. The only explanation I could come up with was that the problem was damp ingress and a few months indoors had dried it out. With less holes for interconnections, I guess the integral units are better sealed. But it may simply be that the manufacturers are making them better.

The biggest problem I have nowadays is rusting screws. I grease them if I can find some grease at the strategic moment.

Chris

[Andrew Gabriel]

I fitted a couple for someone else about 10 years ago. They are separate PIRs controlling lamps which were already there. Neither has failed. They both have relays in them, so a bulb shorting isn't going to blow the triac.

I've also got a dirt cheap indoor 12V one which I waterproofed and fitted outdoors about 20 years ago. That's still working fine, although the mains switching and timing logic part is done indoors.

[The Medway Handyman]

How would you tell which have a relay? It never seems to be mentioned in the description. Just been looking at the TLC site & the specs all mention range, detection angle etc - but none mention relays. Is price a guide?

[The Medway Handyman]

Dreadfully unreliable. I change loads of them for customers. If I can I get the customer to buy the light to avoid any comeback.

[Owain]

They click.

Owain

[Dave Plowman (News)]

You can usually tell by the load spec. If it states *no* CFLs then it doesn't have a relay. Other than that listen for a click when it operates.

[Robin]

Many thanks for all the useful answers.

- Robin

[Dave Plowman (News)]

Just to add it would also have a neutral present.

[The Medway Handyman]

Thanks, but I meant how can you tell when buying or recommending one - you can't hear a click in a brochure :-)