LED light blowing fuse Fitted my

[gazdkw82]

Fitted my parents a little 10w LED PIR light over the front door to help them see the steps.

took a fuse spur from a ring socket with a 3A fuse. 2.5 T+E from socket to switch, 1.5 T+E from switch to JB.

it worked fine for about 5 mins then turned off. I thought it was the settings so played around with it but nothing.

I checked for voltage in the JB that is just above the light. No voltage.

Voltage is fine going into the switch but not going out the switch so it had to be the fuse.

Changed fuse for another 3A which blew instantly. Changed then to a 5A and blew again but light did light up for a second.

This struck me as odd because 3A should be more than enough. Anyway I changed it to 13A and now there is defo voltage from the switch to the light as Iv checked the JB which is fine so now looks like the light itself has had it.

what could be causing this? Iv checked all connections with my voltage tester and doesn't seem to be any L-N short.

Am am I missing something?

 

[Pete999]

Why 2.5 from spur to switch? Have you checked all connections? by the sound of it you have taken a L and N to the light switch for you to be able to check voltage at the switch.

 

[Richard Burns]

I would suggest that you were unlucky and had a faulty light fitting.
A 10W LED may take a reasonably high inrush current on starting, perhaps up to 1A with a very short term peak above this and this should not cause a 3A fuse to blow.

Once you had fused down to 3A then a 1mm² cable would be suitable for this use as the maximum current is 3A and no normal installation method will reduce the current carrying capacity of a 1mm² cable below this level.

Since the system remains "operational" with a 13 A fuse (even if the light does not work) this would indicate that there was not an error in wiring that caused a short as a 13A fuse would still go (though the 32A MCB may go first on a short circuit).
However it is possible that a wiring error has now burnt out and so no longer occurs.
If you have a clamp meter then it may be worth checking if you are still drawing current on the cable from the FCU just in case there is an error.

However overall I would expect a fault in the light.
Take it back and get a new one.

 

[gazdkw82]

Why 2.5 from spur to switch? Have you checked all connections? by the sound of it you have taken a L and N to the light switch for you to be able to check voltage at the switch.

I thought it was standard to always spur from a socket with the same CSA conductors as the Conductors feeding the socket? From the FCU you can then use what CSA conductor is suitable?

 

[Pete999]

I thought it was standard to always spur from a socket with the same CSA conductors as the Conductors feeding the socket? From the FCU you can then use what CSA conductor is suitable?

It does but your post said 2.5 from socket to switch, I must have misunderstood your post are you using the FCU as the light switch?

 

[gazdkw82]

It does but your post said 2.5 from socket to switch, I must have misunderstood your post are you using the FCU as the light switch?

Yeh. My dad wanted a way to turn it off if he wanted

 

[telectrix]

you can use 2.5mm from socket to FCU . less chance of a poor connection in the socket, or 1.5mm as the fuse in the FCU will protect the cable before it.

 

[gazdkw82]

you can use 2.5mm from socket to FCU . less chance of a poor connection in the socket, or 1.5mm as the fuse in the FCU will protect the cable before it.

Very true. I did debate using 1.5 from socket to switch but I just remembered it was best practice to keep CSA the same in/out sockets.

tbh the run is only about 1metre so it's not like it would have been a massive cost difference