Electrics tripping

[Taylortwocities]

Right, as you say.

Let us take a step back and look at the string. If I understand it, you have the following:

Seat > plug with 13A fuse > FCU with 13A fuse > cable to consumer unit > 40A MCB > 30mA RCD

When things go bang, if I understand you correctly, all of the fuses and the MCB and RCD blow or trip, is that correct?
There must be quite a big fault to blow a 40A MCB as well as the 13A ones.

Firstly, please confirm that my assumption above is correct.

Then, Please find the instructions for the bidet seat and find out what size fuse there should be in the plug.

(Thoughts) I'm not sure why there is a need for a plug&socket and an FCU, but there's no sense used, sometimes.

 

[m0t]

Everything blows/trips except the fuse in the plug attached to the seat.

The instructions on the seat don't specify a fuse size only a wattage (1500w) which I calculate means 7.5amp. There's a 13 amp fuse in the plug.

 

[undistilled]

Motte, You will probably need an Insulation resistance tester to find out what/where the problems is.

 

[stillp]

If it's tripping a B40 MCB I'd expect there to be some visible signs of shorting.

 

[Taylortwocities]

If the fuse in the plug does not ever pop, but the one in the FCU does, then I would suspect a fault in either the socket or the FCU, or the fixed wiring between the two.
A fault that big will leave signs of sparking/ arcing.
but I fear that is not something that can be diagnosed over the Internet.

 

[JohnW2]

Motte, You will probably need an Insulation resistance tester to find out what/where the problems is.

If it's tripping a B40 MCB, the fault impedance is going to be far to low for an IR tester to be much use (if it worked at all) - a 'low resistance' ('continuity') meter would probably be more appropriate!

Kind Regards, John

 

[winston1]

If it's tripping a B40 MCB, the fault impedance is going to be far to low for an IR tester to be much use (if it worked at all) - a 'low resistance' ('continuity') meter would probably be more appropriate!

Kind Regards, John

But maybe only low at 240 volts. At 3v or whatever it may show OC.

 

[stillp]

It's an intermittent fault, so testing, whether IR or continuity, is unlikely to find it. A visual examination, perhaps including some dismantling, is more likely to succeed.

Was this bidet seat made for the UK market, or is it from ebay?

 

[JohnW2]

But maybe only low at 240 volts. At 3v or whatever it may show OC.

Yes, that's possible - but one can't really win with many IR testers. For example, my MFT reduces the test voltage to whatever extent is necessary to limit the test current to 1mA - which would be under 5mV if the fault impedance (at 230/240V) were low enough for a B40 to operate.

Kind Regards, John

 

[JohnW2]

It's an intermittent fault, so testing, whether IR or continuity, is unlikely to find it. A visual examination, perhaps including some dismantling, is more likely to succeed.

It seems a bit odd. I would not really have expected that a fault in the device which caused a B40 to operate would normally leave the device operational.

Kind Regards, John

 

[EFLImpudence]

If the fuse in the plug does not ever pop, but the one in the FCU does, then I would suspect a fault in either the socket or the FCU, or the fixed wiring between the two.
A fault that big will leave signs of sparking/ arcing.

 

[stillp]

Maybe an intermittent fault in the wiring between the FCU and the socket, as suggested by TTC at 7:01.

 

[JohnW2]

Maybe an intermittent fault in the wiring between the FCU and the socket, as suggested by TTC at 7:01.

Yes, you're both right. I was thinking only about the loads, not the installation.

Kind Regards, John

 

[m0t]

Is there a likely cause of a wiring fault like this?

As a layman I can't quite wrap my head around how a fault could develop along a bit of cable, I'd always assumed that the faults would develop in the connections?

 

[JohnW2]

As a layman I can't quite wrap my head around how a fault could develop along a bit of cable, I'd always assumed that the faults would develop in the connections?

Yes, it's very much more likely to be connections.

Faults in the cable itself are mainly due to trauma - nails, screws, trapped under floorboards, gnawing rodents, located too close to something very hot etc. etc. I think that faults arising 'spontaneously' in 'modern' (last 50 years!) cables are incredibly rare.

Kind Regards, John