Main fuse irregularly blows, why?

[dishman]

So what, in theory, could make mains fuses pop on separate services?

On the three phase, the two times it happened there in the past it was two different fuses.

Other than earthing points, and the actual supply, would there be any other common factors that means a fault on one could also be replicated on the other? Or a fault on one could cause a fuse to pop on the other?

 

[dishman]

Would requesting a service head test by the DNO be a potential option? Or requesting some kind of voltage monitoring?

If a common factor on the consumer side is the earthing points, I may ask an electrician to recheck all the earth connections.

I can also get them to check the supply cable to the flat consumer unit as @flameport suggested.

Are there any other avenues I should explore? Otherwise I'm at a loss as to why this happens.

 

[Scally-Ho]

To my eyes that 3ph isolator does not look fully engaged in the upright /on position, even allowing for wear etc.

 

[Harry Bloomfield]

To my eyes that 3ph isolator does not look fully engaged in the upright /on position, even allowing for wear etc.

They had a spring to enure rapid opening and closing. Even new, and properly engaged, the handle could be set like that.

 

[Scally-Ho]

They had a spring to enure rapid opening and closing. Even new, and properly engaged, the handle could be set like that.

In all of my years, I've never seen one that far down when engaged in the closed position, but maybe I didn't take much notice.

 

[Elsa TLC]

This was always the case with my wife.

I dont know what I did, but doesn't blow at all now.

 

[Harry Bloomfield]

I dont know what I did, but doesn't blow at all now.

Did you try resetting the MCB?

 

[Elsa TLC]

Did you try resetting the MCB?

This could be the reason. She always said I pushed the wrong buttons

 

[Scally-Ho]

This could be the reason. She always said I pushed the wrong buttons

That's often the problem when the screwdriver is not of the long-reach type

 

[Murdochcat]

So it’s happened twice - same phase or different ones?

 

[Elsa TLC]

That's often the problem when the screwdriver is not of the long-reach type

These days I would get my gas leak detecter out to see if it was safe before the screwdriver come out again.

 

[dishman]

So it’s happened twice - same phase or different ones?

It's happened maybe three or four times, at random, in the past 4-5 years. Twice on the flat side ( I think), and maybe twice on the 3 phase side, a different fuse each time on the three phase side.

 

[ericmark]

There is really nothing to add, except to test, an EICR has been done, but one does not know how well it was done. So what can one measure to give some pointers? Zero cost to user first, so IHD (in home display) part of the smart meter install, it should give some clues as to what is using high power, the app on the phone, this may also give some pointers, one of my clamp-on meters does have a maximum setting, the old cheap yellow one, and add items together, if I look at my house, with two instant showers, two cookers, surprised it has never ruptured the 60 amps fuse. I can see what I am using day to day, but only because I have solar panels, if something else used 1:30 am to 2 am it would be very easy to rupture the fuse, 60–16 = 44 amps, have a shower at same time, plus washing machine running, and there well over the 60 amps.

 

[Harry Bloomfield]

It's happened maybe three or four times, at random, in the past 4-5 years. Twice on the flat side ( I think), and maybe twice on the 3 phase side, a different fuse each time on the three phase side.

I agree with Eric's conclusion, I think we are all as mystified as you are.

 

[dishman]

Assuming I monitor as per above to see if anything can be gleaned.

Is there still the potential that there is some kind of damage on the supply side which could be causing this?