help with external PIRs

[RichardGD]

I am hoping someone can help with problems with external PIRs tripping. The wiring has been in place for years with no problems until the last few weeks. I have a fused spur from ring main (tripswitch is on the main box) to outside switch and from this there are cables going in different directions to a PIR and light on one side and another PIR and 2 lights on other side. There is a switched live connecting the 2 sides so each PIR can switch on all the lights (connecting the L1 sides of the PIRs with all lights). I have checked each light and bulbs work ok, I then assumed that a PIR was faulty so bought a new one and connected to each in turn, but this made no difference. Yesterday, I decided to simplify the wiring and disconnected the switched live where it joins in the main switchbox, so in effect I had 2 separate circuits ( I could not quite understand this connection as if both PIRs switch on it seemed to me that live was sort of flowing in both directions, but clearly this had always worked). Anyway, setting the PIRs to work in daylight, all worked just fine. Activated the PIR many times - lights on and no tripping. Reset the PIRs to dark, and as soon as I tested one set of the lights later, they came on briefly and tripped like before. I am stumped!! How can the circuit work ok in the afternooon and then later trip when the only thing that has changed is that is has got dark and setting changed on PIR?! This must be some sort of intermittent fault? Does anyone have any ideas? The only thing that changed some time before the rash of tripping is that I moved one PIR a bit higher on the wall - changing the cable in the process - but this is wired exactly the same and I have double checked that wiring is all ok (it anyway worked in the day!). Thanks for any help you could give

 

[securespark]

What is tripping?

Is there anything switched on (on the same circuit) later after dark that is not switched on in daylight hours?

This could mean your lights coming on overloads the device.

 

[RichardGD]

the main trip switch for the whole house is tripping. Nothing else is on the circuits with the PIRs and lights - although this is run off one of the house ring mains, not a lighting circuit