My house is about 30 years old and has a six way + cooker consumer unit with
wired fuses. What would be an approximate cost to have this replaced with a
modern MCB unit. I realise that this is not a DIY job.
The lighting circuit is split - upstairs & downstairs, but the power circuit
is single, with a 30A fuse. I am worried in case I overload the power
circuit as I have added many extra sockets into the ring main. If I have a
new consumer unit installed, would it be possible to split the power circuit
into separate upstairs/downstairs circuits?
What reasons do you have for wanting to change it?
This is a question that comes up from time to time, and often there is a
assumption that a modern CU with MCBs is automatically "better". The
reality is often a bit more complex, as there are pros and cons to
At 30 years old there is a reasonable chance that there is not much
drastically wrong with your installation apart from a lack of outlets to
deal with modern usage patterns, and it sounds as if you have addressed
that already. You are unlikely to have rubber insulated cables in place
The ones to check would be the size of the earth wire in your power
circuit cables, since at one time only 1mm^2 wire was used for this, and
this does not really perform well enough with rewireable fuses. Also
look to see what RCD protection you have, since having this for most
power circuits can offer significant safety enhancements, and protection
of sockets that you use to power appliances outside is vital. Having
said that, see the mitigating nuisance trips and system design sections
I realise that this is not a DIY job.
What makes you say that?
You will find plenty of folks here who have DIYed this job.
It would... although you may find that a split of kitchen and rest of
house makes more sense, or even three circuits. Kitchens typically have
the largest concentrations of high current loads in a modern house.
Unless you routinely use fan heaters and the like the chances are the
rest of your loads are relatively small.
In article ,
John Rumm writes:
Agree here. I would carefully check a CU of that age for signs
of overheating due to deteriorating contacts, and retighten the
connections. Beware that unless you isolate the supply elsewhere,
there will be exposed live conductors inside a unit of that age,
and besides the obvious electric shock risk, there's a risk of
high energy arc flash burns if you end up shorting out the supply.
Yes, we were in exactly the same position so I did as John described.
I left the ring main completely alone but added extra circuits for the
kitchen appliances and utility room (where our washing machine and
dryer are located). More often than not, the load on the main ring
main will be a fraction of what it was designed for once you have done
this. I think the only thing plugged into our ring main now is about
four hundred chargers!
On Sun, 02 Dec 2007 02:53:39 GMT someone who may be "Terry D"
Personally I would consider replacing the wire fuses with HBC fuses
or MCBs. Before doing so I would make the appropriate calculations
and see what is available for the model of consumer unit before
deciding on the replacement. Replacing the wire fuses is a DIY job,
though some DIYers would be unable to make the appropriate
measurements and calculations.
I would only consider replacing a consumer unit of that age if it
was deteriorating or more ways were wanted.
Unless you are plugging high current appliances into those sockets
this is unlikely. However, as others have suggested, a separate
circuit for the kitchen and any utility area would be worth
considering, to separate washing machines, dishwashers and so on.
In article ,
Of course it's a DIY job - *if* you have the skills. Like anything else.
For a straight swop I'd guess at about 250 quid. To split the ring into
two would depend on the work involved. Get a few quotes.
Terry D explained on 02/12/2007 :
A new consumer unit would not help that much, apart from perhaps making
available extra circuits and the extra convenience of MCB's - your big
problem then is how to make use of them.
If the ring was wired as a single ring to cover the entire house, then
it will likely prove to be almost impossible to split up into two or
more ring circuits. The best/cheapest/quickest solution will probably
be to start again and install new circuits.
You can't overload a ring by adding extra outlets, you only overload by