How To Replace And Fix A Fuse

August 30, 2013 - By davidhogben

fixing a fuseSome time or another we all have to deal with a blown fuse and it is very common to hear someone say:  “I might not know much about electrics but I do know how to change a fuse”.

Well, that may well be a true statement in most cases but it does not take into account the fundamental fact that the fuse blew for a reason.  Of course, with modern fuseboxes (now called consumer units) the fuse doesn’t blow, it is the circuit breaker that trips although the end result is the same i.e. loss of power to the circuit concerned.

There are two ways in which the fuse tends to blow: the first is a slow overload and the second is a dead short.  Again, both situations produce the same end result and it is an important part of the diagnostic process to determine which one caused the power loss.

People often see a blown fuse as a nuisance but in fact, the device is merely doing its job in protecting against fire or electric shock.  Having said that, there are conditions which could be construed as nuisance tripping and I shall mention these later.

Fuse Overload

The slow overload is usually caused simply by having too much equipment connected to the circuit so over a period of time although the fuse does not go off with a bang – it slowly melts as it is trying to deal with too much current and eventually fails.  The quick overload is where the fuse is faced with a sudden surge in current, for example if a live cable is cut or a piece of equipment suffers a short circuit.  Anyone who has heard an old rewireable fuse gooff bang will be in no doubt as to which type of overload was which.

The nuisance tripping mentioned above occurs when a fuse blows or a circuit breaker trips as a consequence of a non-fault situation, usually when a light bulb goes or more rarely, when an old motor in a fridge, for example, starts up.  The fuse or circuit breaker sees a very short-lived high current which it interprets as a fault and reacts accordingly.

So if you are satisfied that there is a known reason why the fuse has blown, then it should be safe to re-energise the circuit by mending the fuse or resetting the miniature circuit breaker.

It is important that a rewireable fuse is only repaired using proper fuse wire of the correct current rating; many times we have seen bits of copper wire taken from electrical cable used and this is, to say the least, a dangerous practice because then high currents can flow in the event of a fault but the circuit may not disconnect, leading to the possibility of fire.

The actual method of rewiring a fuse can be learned from any DIY book; suffice it to say that unless you are absolutely confident that you can do it properly and safely (and also taking account the points mentioned earlier) then you should leave it to a qualified electrician such as Electricians in Richmond.  It comes as a nasty surprise when you plug a mended fuse back in to a circuit where the fault has not been cleared and does little for someone of a nervous disposition.

As ever, Sky Electrical and Electricians Twickenham is on the end of a phone to give advice or offer assistance so if you are in any doubt as to whether or not you are happy mending a fuse when your lights have gone (as the song goes) then give us a call on 020 8894 1799 or click here.

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