MCB trips when turned on AND RCD trips too

[Zeddd]

Hi All

Has a strange issue.

Was ironing upstairs and all the electrics were tripped. I reset the RCD and switched everything back on and upstairs is working all fine.

Strangely though, the downstairs conservatory sockets are no longer working.

The MCB that controls the conservatory sockets immediately trips when I try to turn it on, and it then immediately also trips the RCD.

The conservatory MCB is linked to 3 internal sockets (never used) and also one a spurred off external socket (used very occasionally) AND underfloor heating.

Never had any issues at all until the iron upstairs tripped everything up.

Could it be that the MCB is now somehow faulty from the ironing incident? And that is why the RCD trips immediately when turning it on?

Many Thanks

 

[DetlefSchmitz]

The iron may be a red herring.

 

[conny]

The iron may be a red herring.

No, it's definitely an iron. It's distinctly shaped like an iron.
A red herring looks like a fish.

 

[Zeddd]

The irons gone in the bin as I know that was faulty. But is it possible that the fact that the iron tripped the entire house that it’s somehow damaged the MCB for the conservatory in the process? Or is that wishful thinking.

My next point of call is the outdoor socket - as this is quite close to the conservatory guttering. I don’t have a leaky gutter that I am aware of, but thinking maybe in heavy weather it fell onto the outdoor socket and damaged it?

 

[conny]

@Zeddd, unplug everything on the affected MCB circuit and see if you can reset it. Turn the RCD on first. If the MCB resets start plugging the appliances back in, one by one. If it trips then unplug the appliance that tripped it, reset again and carry on putting the other appliances in to their respective sockets. If the MCB stays on, plug a different appliance into the socket that caused the trip. It it trips again, you may have something wrong with that particular socket.

 

[Zeddd]

The thing is nothing is plugged in. We don’t use interior sockets at all. The exterior one has nothing plugged in either.

The underfloor I removed the fuse from it so this should have turned it off?

 

[Zeddd]

Removing a fuse (are you sure it was a fuse?) still leaves the neutral connected.

The underfloor heating has a fused spur. It’s this fuse I removed.

 

[JohnD]

The underfloor heating has a fused spur.

With a switch, or without?

An outdoor socket, in rainy weather, should be viewed with great suspicion. As should outdoor lighting. I don't suppose it has an indoor DP isolator?

 

[Zeddd]

With a switch, or without?

An outdoor socket, in rainy weather, should be viewed with great suspicion. As should outdoor lighting. I don't suppose it has an indoor DP isolator?

The underfloor heating is unswiched. It’s one of those that you need to pop the fuse out using a screwdriver if that makes sense.

If it is the outdoor socket. I can try isolate it from the rest of the circuit easily as this is spurred off. So I can disconnect the spur wires from the socket it’s spurred from.

I’m not too sure how I would go about isolating the underfloor heating though.

 

[JohnD]

I’m not too sure how I would go about isolating the underfloor heating though.

Remove the FCU and replace it with an SFCU

https://www.tlc-direct.co.uk/tcl/search?query=fcu

 

[Zeddd]

Remove the FCU and replace it with an SFCU

https://www.tlc-direct.co.uk/tcl/search?query=fcu

Oh I see. It already has a unswitched FCU. So wouldn’t taking the fuse out of that act the same as a SFCU?

 

[EFLImpudence]

No. The switch will also disconnect the Neutral.

 

[Zeddd]

So I removed the outdoor socket (which was wet a little on the outside but dry inside as it is a sealed unit).

I removed the cables from the socket and left them exposed.

Then tried to reset the MCB. But it still would not go up and still took out the RCD.

Can I be confident that the outdoor socket is not the culprit then?

I have reconnected it for now, while I look further.

It’s either:

The 3 x indoor sockets (but no appliances are plugged into these at all)

Or

The underfloor heating

Or

MCB is faulty?

God I hope it’s not the underfloor that’s faulty as I have no idea what the rectification plan would be!

 

[Harry Bloomfield]

Oh I see. It already has a unswitched FCU. So wouldn’t taking the fuse out of that act the same as a SFCU?

Yes, unless it was a double pole SFCU. Always best to have a double pole isolator, on anything which goes outdoors, because there is a higher probability of faults - which need to be isolated.

 

[terryplumb]

Are the conservatory light/s also wired from the circuit protected by the MCB that trips ?