Water ingress into old wylex concumer unit

[sivoodoo]

Hi all,

Customer called me out to investigate a very loud bang at the fuse board, customer had not plugged anything in or switched anything on, he says it just went bang!!

Ive been asked to write a report for an insurance company regarding a massive water leak that has soaked the old wylex wooden backed consumer unit.
It appears to have been leaking for some time as the wooden back to the wylex board is soaked and rotten.


On removeing the cover of the board I found one leg of a ring main blown apart 3 inches up from where it connects into the fuse carrier.

Insulation resistance was non existent at 0.08Mohms between L and E and 0.05 between L and N. Nothing plugged in double checked!

1. Would water ingress cause this?
2. Why didnt the fuse blow? (No suppliers earth, but bonding to gas and water present Zs at board was good. Ze poor at 700).

Thank you.

 

[Marvo]

If you can attach a photo it might help decide on why the fuse didn't blow. Moisture would cause all the symptoms you describe. First thing to do is to fix the leak or if that's not an option then relocate the CU. The IR readings should improve as the CU dries out and apart from the obvious arc flash damage it may well be salvageable.

 

[Paul.M]

2. Water has traveled down the cable and shorted out the circuit before the fuse wire. It's only a small distance from the neutral bar or earth bar (MET) to the top of the 3036 fuse carrier. If the back board is soaked and rotten obviously it needs replacing asap and don't re-energize the board. The cu itself needs replacing and maybe relocating if this leak is prone to happen again.

 

[malcolmsanford]

View attachment flood_advice.pdf


Though this deals mainly with flooding it is also a good guide as to what to do with water damaged equipment.

With no supplier earth you seem to have a few issues here.

 

[sivoodoo]

Thanks, ive carried out a full PIR and the house needs a rewire, the customer was wondering how much of this he could have on the insurance.

 

[Paul.M]

Thanks, ive carried out a full PIR and the house needs a rewire, the customer was wondering how much of this he could have on the insurance.

The c/u change plus anything else that is associated with an up to current regs c/u change, bonding, tails size. You may even have a fighting chance of putting the case to them about a RCD would nuisance trip the existing wiring and needs rewired, long shot but worth a go? Also any cables damaged by water needs replacing so that could be the majority of the house.