RCD Question

[Steve T]

Hi Guys,

Just a quick question i have an RCD on a submain board and if i turn off all the MCB's and then turn on the RCD and then turn the MCB's on one at a time they all come on.

Now if i have them all off again and i switch the lighting circuit MCB on with only one 100 watt lamp turned on and then try to turn on the RCD it trips out.

but if the light is turned off when i turn the RCD on it goes on fine.

If i then turn the light on its still fine.

This happens with all the lights in this building.

Now is this common? is it due to the rush of current going to an active circuit or is this showing that there is a potential fault looming.

Thanks
Steve

 

[ban-all-sheds]

Now is this common?

Yup.

is it due to the rush of current going to an active circuit or is this showing that there is a potential fault looming.

Neither.

In the 2nd scenario the RCD isn't tripping, it's just refusing to turn on. It's very common for RCDs not to turn on when there is any load present.

 

[Steve T]

cool thanks for that!