Outside PiR unit causing other light to flicker

[Murphy]

I've tried to fit an outside PiR security light by cutting into the lighting radial circuit but when connected it causes the cloakroom tube to flicker. I've taken a direct connection and not used a FCU in between is this the problem?

 

[brown-nought]

Could be a bad connection. When does the tube flicker, all the time?, only when the outside light is on etc?

Do you have a switch on the outside light? It should have a method of isolation.

 

[Murphy]

Flickers all the time and seems to be as a result of pulsing from the sensor. ie the neutral is returning a on off live state. The tube comes on as normal via it's own switch. Haven't fitted a switch to the security light as it a dusk to dawn/motion sensor device but obviously could very easily.

 

[dingbat]

If you had fitted a switch then you could easily isolate the PIR lamp to see if it was actually causing the problem.

Security lights are best fitted via a fused spur from your ring circuit. Or better yet, on their own circuit from the CU.

 

[Lectrician]

It's not a switch cable you have 'chopped' into is it??

 

[pegasus]

Ref brown-nought's response.....

If an isolator were fitted alongside the PIR does it need to be double pole?

 

[Murphy]

It's not a switch cable you have 'chopped' into is it??

I'm beginning to think it must be, as I've now fitted a switched FCU (which does indeed make life easier for isolating the light!) and tried it with an ordinary lamp unit = same problem.

 

[andy]

Ref brown-nought's response.....

If an isolator were fitted alongside the PIR does it need to be double pole?

an isolator is designed to break both phase and neutral to allow someone to safely work on a circuit.

short answer: yes, it should be double pole

 

[pegasus]

Why is it that you can work on a lighting circuit (or power circuit) when you only rely on the mcb being turned off at the consumer unit?

In this situation, you have only broken one pole.

What am I missing?

 

[andy]

an MCB isint an isolator. if only using a MCB, your susposed to disconnect the neutral and live from inside the CU. altho no1 does

 

[plugwash]

some MCBs are single pole isolating switches

single pole isolation isn't idea but its all you get from pulling out a service fuse....

single pole isolation is safe PROVIDED the neutral stays intact. The risk of neutral brakage at the supply entry point is minimal (otherwise PME wouldn't have ever been allowed) elsewhere in the install it may not be depending on how things have been done