wiring problem & replacing fuses

[dfitz]

Hi,

I have a house about 40 years old which still has the original fuse board/wired fuses.

We had a problem with a bedroom light not working and had an electrician come and fix it. Turned out to be that the previous owners had put in loft flooring and it had been laid over the top of the lighting wiring and when we (thankfully, only very occasionally) went into the loft, walked on the flooring which in turn pressed onto the cables and eventually broke the wires. What caused me to be totally freaked, was that the wires were scorched and the fibreglass was also black, where the wires were being crushed!!! now I am terrified that the wiring will catch fire, in the places where it still works but has been under the flooring?? I can't afford to have the electrician come back and rewire, but he suggested that we change our old wired fuses for the new trip style ones. Our old wired fuses never blew. I've been looking online but can't see what I need (can't remember what the electrician called them)

Someone has said that these trip fuses won't help as they protect against excessive current being drawn. I thought that they would trip if there was a broken wire/overheating in wires etc??

Can anyone help please?

I'm scared my house is going to catch fire

 

[bongos]

Unfortunately when the house was built it will have had the circuits designed to the cable runs that were present at the time.

If there is now loft insulation/flooring covering the cable then they should have been de-rated and protected accordingly (this means that the maximum operating current of the cable would have been reduced). There are alot of posts on this site at the moment in relation to people having loft insulation installed and wanting to know if their cables are safe running through the insulation.

It sounds like your cables are running on top of the loft insualtion so this may have already been taken account of but as the flooring is now over the top there is no way for air to keep the cables cool. It is possible that the cable scorched the fibreglass as a result of it becoming damaged from being walked on or it may have happened because it became overheated.

MCB's are protection from overcurrent. Installation of RCD's may help if there is a situation where there is earth leakage but if the circuit is damaged and is still running within the tolerances of a 30mA RCD then there is still a risk of fire. Also this work would involve a new consumer unit which will not be cheap.

The only real answer is to get an electrician out to inspect/test your cables to make sure that they have not been damaged from overheating and that the exisitng cable runs are safe.

 

[ban-all-sheds]

You need to lift all the flooring and inspect the cables for damage.

You say you can't afford to have the electrician come back and rewire, but how much would a fire cost you?

If the cables are damaged then the only solution is to replace them - fiddling around with changing the CU is not the answer, but you don't have to use an electrician to replace cables....

 

[JohnD]

they are called MCBs

A pound to a penny your old consumer unit (fuseboard) is a Wylex Standard in brown or Cream. MCBs to fit these are readily available, about £7 new but there are millions of second-hand ones about in good order for about half that.

they will be much easier and quicker to reset than changing a fuse, but are not going to cure your existing problem. They have the advantage that no-one is going replace a blown fuse by stuffing in a higher-rated bit of fusewire, or a nail or something, causing added danger

They are supposed to be fitted by a qualified electrician but they can be plugged in like your old fuses, but needing a screwdriver to change the plastic shield, and I estimate that approximately 100% of them are fitted without documentation by householders and handymen.

BTW cables for lighting circuits are very lightly loaded and will not overheat if covered with insulation. However Immersion Heater and electric Shower cables are loaded near their limit, and are likely to overheat if covered, especially as they may be operated for prolonged periods at full load.