RCD tripping

[rustynails]

Hi all,

On a ground floor ring main protected by a 30amp bs3036 rewirable fuse the owner has reported the 100ma rcd trips out on any occasion where her bathroom extractor fan is on at the fused spur and she tries to use the Hoover.

After looking at her bathroom extractor fan, I've seen that it's being supplied off the ring main via a fused spur with a 13amp fuse and switched from the lighting circuit. So it has live and neutral from the FCU in 2.5mm then a live 1.5mm connected from a ceiling rose connected to the lighting circuit. Two earths are connected in a choc box inside the fan casing and the 1.5mm neutral is not connected.

She says that it doesn't trip if the FCU is in the closed position, it only trips in the open position with the Hoover.

Any ideas what could be causing this?

 

[tony mc]

A bit lost with the details.

If the FCU is closed it does not trip but trips when the fan is on! Then you say it trips when the FCU is in the open position. !

The RCD is detecting 50mA or more of leakage so I think the test equipment needs to come out and further info is required.

The fan set up needs sorting with the borrowed neutral from another circuit.

Is the RCD protecting the entire installation or just the ring ! I would imagine its the entire!

Have any tests been carried out ?

 

[Octopus]

Which circuits are the 100mA RCD protecting?

 

[telectrix]

sort the fan out first. then, with all items disconnectred, IR test and RCD test.

 

[sedgy34]

Could be just the fan at fault here and a different neutral

Doh is the rcd the main switch

 

[Guitarist]

Did you say that 2 earths are connected but a neutral isn't?
Sorry, but a bit confused....

 

[rustynails]

A bit lost with the details.

If the FCU is closed it does not trip but trips when the fan is on! Then you say it trips when the FCU is in the open position. !

Oops my fault, the FCU is in the closed (on) position when the RCD that protects the entire TT installation trips.

It has no effect on the power if it's in the open (off) position.

Sort the fan out first

Probably best that it go on the lighting circuit, with a 3 pole fan isolator and 30ma rcd.

But in the mean time I guess I need to inspect the wiring a little closer.

 

[rich.250]

If the Rcd protects the whole installation, I'd say if it's only when the double pole fcu is turned on it must be either the cabling from here to the fan, or the fan. N-E I'd guess.

 

[sedgy34]

Does the fcu have a neon light on it??

 

[oldtimer]

Have you check what type of fcu ie single pole or double if old then its a single pole so the earth and neutral is not broken I had a problem like this until I realised that a fixed electric fire was fed from a sp fcu and it had a neutral to earth fault

 

[rustynails]

It turned out to be a neutral to earth fault caused by a nail that had be driven through the skirting board into the cable and stayed put for 26 years tripping the elcb everytime the circuit was overloaded.

 

[Guitarist]

Now that was a long fault-finding timescale.... Thanks for letting us know mate

 

[GLENNSPARK]

Could be just the fan at fault here and a different neutral

Doh is the rcd the main switch

BS3036 board....what do you think sedg..eh?.....
for christs sake.....