Curious fault after recent move

[Stuart27]

Hi All

Let me start by saying I have my 2365 level 3 but never worked in the industry so my knowledge is limited.

My partner and I recently purchased and moved in to our first home

Since moving in we've had a strange electrical issue and I'd appreciate some advice about what could be causing it, or things I could check. I'd love to be in a position to just get somebody out to figure it out but I've recently been made redundant so can't really afford to do that right now.

So the issue is this.. every now and then, maybe once or twice a week, the main breaker will trip on the cu, either whilst the shower is being used or soon afterwards

The curious part about this is that when it happens, the main breaker doesn't want to come back on. I have to turn off each mcb, then put the main breaker on, then each circuit in turn. Everything comes back on fine (even the shower) except the ring supplying the kitchen and upstairs bedroom, which causes the main breaker to trip again. I have to leave the ring off for 30 minutes to an hour before it'll come back on without tripping the main breaker.

The bathroom is directly over the kitchen so my thinking is it's probably water ingres on the ring and it won't come back on until it's dried out, but I can't find any evidence of it and most of the time we can use the shower without issue, its only occasionally this will happen but at 5am when I'm trying to shower and get ready for work and the whole house trips out, setting off the house alarm aswell, it's more than a little frustrating.

Also there is no rcd protection at the board, is this a big issue? I know they're recommended and I intend to replace the board when I can but how urgent is it to get them in?

Thanks for taking the time to read this, apologies if its missed out any relevant information

 

[Rockingit]

Please define 'main breaker' for us. The main isolator switch on a DB of any sort is completely passive, there is nothing inside it that does anything than operate as a manual switch.

Probably a photo will help.

 

[UNG]

So I'm assuming you have checked for any obvious water leaks under the shower / bath that may be getting into a junction box concealed under the floor

 

[Stuart27]

Please define 'main breaker' for us. The main isolator switch on a DB of any sort is completely passive, there is nothing inside it that does anything than operate as a manual switch.

Probably a photo will help.

Yeah so when this happens, the mcbs don't trip, only the main isolator on the board turns off. I'll post a photo of the board when I'm home

So I'm assuming you have checked for any obvious water leaks under the shower / bath that may be getting into a junction box concealed under the floor

Yep nothing under the bath. There has been a leak previously, known by the damp stain on the kitchen ceiling, but we resealed the bath and shower after moving in

 

[LewisM]

Sounds like the main rcd is tripping I've seen this a few times where there is a low IR between cables on one of the circuits but takes a while to really breakdown and cause a fault

 

[LewisM]

Sounds like the main rcd is tripping I've seen this a few times where there is a low IR between cables on one of the circuits but takes a while to really breakdown and cause a fault

I remember one which was rather strange where there was a fault on the outside lighting circuit very low L-E N-E resistance but not a dead short, it would trip the rcd for that side (split load board) so the homeowner just switched off the MCB and it wouldn't trip the RCD however after running the shower for a while the RCD would trip, the shower was on the other RCD which was unaffected turns out there was a hole where the cables for the shower and outside lighting went through that was extremely tight and the power when the shower was running would be induced into the light circuit and cause the rcd to trip due to N-E fault the fault turned out to be a outside light junction box full of water.

 

[pc1966]

As above, sounds like the main breaker is an RCD so anything making enough leakage will cause it to trip. Unfortunately these days even a perfectly sound installation can get close to that due to accumulated leakage from all of the electronic devices plugged in.

To find and fix the problem you just need to be systematic, but you will also need access to some test equipment (and hopefully the knowledge to use them safely).

Your property ought to have an EICR already, if not (or if poor quality) you ought to consider doing the basic inspection of checking the global IR at 250V first (so main breaker off and L+N to E, ideally off a MCB just in case...) and if low then systematically check each circuit.

Other thing to do is check the leackage with a suitable clamp ammeter over the L & N tails and then try each circuit it turn and observe what happens. If your total is above 9mA, which is possible even without faults, then your only solution is to look at a new CU with ideally RCBO for each circuit, or at the very least dual RCDs to try and keep the per-RCD amount below any risk of false trips.

 

[timhoward]

As others have said, the starting point is "what is tripping"

every now and then, maybe once or twice a week, the main breaker will trip on the cu

Also there is no rcd protection at the board, is this a big issue?

As you sure that the main switch on the board isn't an RCD?

Assuming this turns out be an RCD then IR testing is needed, as it could be the shower driving current through a N-E fault on another circuit.

 

[snowhead]

The symptoms appear to point to a leak associated with the shower causing the tripping, but could be coincidence.
However it may not be the shower tray leaking, it could be in the waste pipe away from the shower and or the water could be running down the kitchen wall into the back of a socket.

 

[UNG]

I think without doubt the proper test equipment needs to be deployed to have any chance of identifying what is causing the problem tripping

 

[James]

Without any test equipment, I would start by checking light fittings in the room below the shower, if there is any leak, it will often find its way into the lights of the room below.

 

[brianmoooore]

Establishing whether there actually is RCD protection is the first thing! Pic of CU required.
There's a massive difference between the potential danger of a fault that trips a RCD and one that trips a RCD, especially if a shower is in the equation.

 

[James]

Establishing whether there actually is RCD protection is the first thing! Pic of CU required.
There's a massive difference between the potential danger of a fault that trips a RCD and one that trips a RCD MCB, especially if a shower is in the equation.

Corrected that for you!

 

[brianmoooore]

OOps! OOps again! and again!

 

[pc1966]

OOps! OOps again! and again!

Sounds like a cross between Dick Dastardly and Brittany Spears!

Drat, drat and double drat! <twiddles moustache>