A ‘TRIP’ AROUND YOUR FUSE BOX
Notes on the correct usage of automatic circuit breakers
There are three main components of a modern fuse box.
a) The individual circuit breakers (MCB’s)
b) The main circuit breaker(s)
c) The RCD (also known as ELCB , GFI or Memsar Pechat in Hebrew)
a) The individual circuit breakers are replacements for the old wired fuses. They are provided on a per-circuit basis. 16 amps and 10 amps being the most common with 6 , 20 and 25 amps less so. If an individual circuit overloads or shorts, this breaker is the first line of defence. If it trips, try and find the cause. If it’s hot, then there is an overload. Turn something off in the house, wait a few minutes and then gently raise it to restore power to the circuit.
b) Where a flat has single phase there will be one main circuit breaker. In new buildings it will be 40 amps , in older buildings 25 amps and in even older buildings 20 amps.
Where three-phase power has been provided, there will be three main circuit breakers, usually joined together with a bar. This bar ensures that if one phase trips , all three go out. This is designed to protect certain 3-phase equipment from being damaged.The main circuit breaker will trip if the total load from all the individual circuits exceeds it’s rating (+ tolerance) or possibly if one of the individual circuits goes short circuit.
If the main breaker trips, and is hot to the touch, turn off some heavy power appliance(s) and wait for five minutes. Restore power as follows: Lower all the individual breakers and then raise the main breaker. Now raise all the individual breakers until all the power is restored. (This ensures that you don’t blow the Electric Company’s main fuse)
If after raising all the breakers and restoring the RCD, you still have no power, then either there is a power outage (UK: Power Cut) or the Electric Company’s fuse has blown. Call the Electric Company and try and pursuade them to come out ! They are more likely to respond if other flats in your building are also affected.
c) The RCD is about twice to three times the size of an MCB (minature circuit breaker). It’s purpose is to protect against electrocution , not against overloads or shorts.
(for more detailed information see separate information sheet on RCD’s)
Customer
: Hello is that the electrician ?Listen, the new circuit breakers that you just
put in keep tripping. The old fuses never blew !
EDS
: Ah ! thats because someone had already replaced theold fuses with coffin nails which meant that instead of
the old fuses protecting the house wiring, the wiring was
protecting the fuses !
Customer
: But it worked and I could run the washing machine at thesame time as the dryer, the dishwasher, the stove and all
the room heaters !!!
Can’t you put a ‘stronger’ circuit breaker in the box ?
EDS:
Maybe you should have kept the old fuses and replaced allthe wiring instead !
Look, for safety the fuses or circuit breakers MUST be
weaker than the wire in it’s circuit. That way if there’s
a problem, the fuse will go before the wire starts burning
or the the switch contact goes.
The thickness of the wiring determines the size of the
fuse that has to be installed.
There have been countlesss cases of fires in electrical
boxes caused by overloaded circuits or faulty fuses.
Customer
: So what can I do with my washing machine and dryer ?EDS
: In new flats that are wired correctly, each device willhave it’s own correctly rated breaker.
In old houses you’ll probably have to run one machine
after another or install a new heavy duty circuit
from the main fuse-panel to one of the machines.
Also, dryers usually have a half-power setting.
(any resemblance to actual customers is purely coincidental !)
______________________________________________________________________
An information sheet from
EDS ENGINEERING
Tel: 02 678 1627 Mobile 052 604388
November 1996 updated May 2001