What to look for
In many house-fault situations one or more RCDs will be fitted
and one has tripped. If you have a modern consumer unit it will
have one or two RCDs, that's the switches with an adjoining yellow
test button - sometimes the buttons are a different colour. MCBs replace old style fuses so there is one for each
circuit. Hopefully your board will be marked up to tell you what
each circuit is. Don't worry if this is not the case.
In all cases up is on and down is off.
The red switch is the main on/off switch - this should be up.
It can't 'trip' itself, it can only be turned on or off manually.
i.e. is down.
The chances are an RCD has tripped.
Now reset it by pushing it up. In some cases
you have to push down first and then up.
If everything is working then the chances are you just have a
blown light bulb. Check all bulbs and replace as necessary. If
you were trying to use an appliance when the power tripped then
there's a good possibility that the appliance is the cause of
the problem. Unplug it and put it to one side. If it's a toaster
or kettle the bin is probably the next stop for it. If it's a
washing machine, dryer or dish washer then check the appliances
service guide in the instruction book or book a repair.
then there is probably a fault on the
circuit. Most faults are caused by appliances or circuits that
supply something wet or that can get wet e.g. outside lights,
garden circuits or central heating. Unplug (not just switch off)
everything you can by pulling out plugs and in the case of items
such as central heating turning off the isolating switch, typically
a switch with a built in fuse. If the RCD will now reset plug
items back in one by until it trips again - now you will know
where the fault is. If you can't reset an RCD with all the MCBs
off (down) and all appliances unplugged then it's time to get
then there is a fault on that circuit.
Identify what the circuit is. If it feeds power sockets then unplug
all appliances before resetting the MCB. Then plug them back in
one by one until it trips again. Then you will know where the
problem is. If the MCB feeds lights then turn them all off before
resetting and try them one by one. The chances are a bulb has
There are a few variations on the above theme. Some older and
overhead supply installations will have a form of incoming RCD,
sometimes in a separate unit. Some installations will have an
integrated RCD and MCB for several circuits. The same principles
apply in these cases.
Finally please remember not to touch anything that could be live.
If something smells or looks burnt then do not use it. Don't take
anything apart unless you are qualified to do so. If you think
something is dangerous turn it off or turn off all power. Be safe!