Fire at fuse board

sligono1

Twice this has happened over an 18 month period the trip for the electric shower has gone up in smoke electrician came out and replace the trip all was fine but this morn shower stopped and same thing again.
Why is this happening

Sleeper12

Most likely the cable wasn't screwed in tight enough. Though it could have been a bad trip switch

Sometimes I wonder what is tight enough. I have had the odd shower where a year or two later the connection block starts to melt. I swing out of it when I tighten them. I've seen some melt 7 or 8 years after being installed.

2011

sligono1 wrote: »

Twice this has happened over an 18 month period the trip for the electric shower has gone up in smoke electrician came out and replace the trip all was fine but this morn shower stopped and same thing again.
Why is this happening

I'm going to state the obvious here: This is serious. You could have lost your home or worse. If you have been using the same electrician if I were you I would seriously consider selecting a different electrician.

So why did it happen?

An instantaneous shower is generally the largest electrical load in most domestic installations. A 9.5 kW shower will draw a current of over 40 amps.

The heat generated at any point in an electrical circuit is a function of just two things:
1) The square of the current (and typically this type of shower draws the largest current within the installation)
2) The resistance at that point.

energy, watts = (I^2) x R

So what does this mean?
The current is something that you can't change, if the shower were to draw less than it's design current it would not function properly. So to prevent the distribution board from overheating it is important to ensure that there are no high resistances within it. Obviously your board has at least one high resistance point, this could be a connection that was not properly tightened, a faulty component or an undersized conductor.

Doe this make sense?

The best course of action might be to replace the entire board depending on the extent of the damage.

Dardania

I had a problem where dust was falling from the ceiling into the top of the breakers, and wih normal loosening of the cable connections, worked it's way in.

Could be something to look at in addition to checking that everything is tight enough. If there's resistance between the breaker and the cable, heat happens.
Also, get an electrician to check whether all the other connections are tight enough - if the same electrician worked on the rest of the installation, you might be more exposed to risk due to their shoddy practices.

kramer1

Cable could be to small , over heating at the terminal s , most likely loose connections but happening twice so close together is peculiar