Upgrade consumer unit

rock22

Helping a friend restore an old house has prompted me to look at upgrading my own electrical system. Sorry for all these questions but hope someone her can help.

My consumer unit contains a single pole mains switch, a 50A main fuse and then dedicated fuses for 2 light, 3 socket, and one heating circuit. There are no RCDs or MCBs fitted.
i was plainning to replace the main fuse with new 63A fused switch, replace the fuses with appropriate MCB's and protect the socket circuits with RCD. Perhaps i should protect all circuit with RCD's by fitting 2 RCD?

The system has been extended four times in the past, all by different electricians..
First, addition of transformer for a door bell. Wired into one of the light fuses i think. at least 30 yrs ago
Second; Outdoor to garage . A new consumer unit was fitted in the garage/workshop. Separate circuits are prrotected by RCD and MCBs. All wiring to garage was by underground armoured cable. Has been done about 20 yrs ago.
Third. Electric shower fitted about 4 yrs ago
Fourth: outdoor to patio area. ( This terminates in outdoor boxes. No lights or sockets fitted at moment. Fitted about 2 yrs ago.

While looking at the wiring I noticed
A, the power for the garage comes off the main switch and does not pass through the main fuse. Should it be rewired to pass throught the 63A fused switch when fitted.
B the shower unit has a separate RCD in a separate housing and is powered from the same take off as the garage. i.e. it too does not pass through the main fuse. Does an RCD alone give suficient protection?
C. The wiring for the patio is taken from a light fuse. SHould this not be taken fron cocket circuit and then protected by RCD when installed..

Sorry for all the questions. Additionally, should the oven be protected by RCD or is MCB onm its own enough.
I am assuming that upgrading from fuses to MCB's give me better protection, even on circuits without RCD's . is that the case?

Thanks for any help

2011

Hi rock22, before you go any further it is important that you understand the legal position on this:

Since the 1st of October 2013 it has been illegal for a non-Registered Electrical Contractor to carry out most electrical work in domestic premises. Refer to the Restricted Works Decision Paper published by the Commission of Energy Regulation (CER). As detailed in the above document “Minor electrical works” are exempt from this legislation. Further clarification on minor electrical works was obtained by email from CER can be seen here.

2011

As the legalities of surrounding this type of work have been clarified in my previous post I will try to advise.

rock22 wrote: »

My consumer unit contains a single pole mains switch, a 50A main fuse and then dedicated fuses for 2 light, 3 socket, and one heating circuit. There are no RCDs or MCBs fitted.

From this description replacing the distribution board would be a good start. However it is highly likely that the entire installation requires a rewire. The chance are your home is lacking in terms of numbers of circuits (there should be two for the kitchen alone), earthing / bonding and conductor sizes are unlikely to meet current regulations. It is also likely that in the interest of safety a number of other issues should be dealt with.

i was plainning to replace the main fuse with new 63A fused switch, replace the fuses with appropriate MCB's and protect the socket circuits with RCD. Perhaps i should protect all circuit with RCD's by fitting 2 RCD?

Apart from the legalities relating to this type of work it should only be carried out by a qualified electrician with suitable experience.

I would not protect everything with an RCD, it is unnecessary and is increases the chances of nuisance tripping. I do like the idea of an RCBO per socket circuit though. This is pretty much standard practice in industrial installations.

First, addition of transformer for a door bell. Wired into one of the light fuses i think. at least 30 yrs ago

There is nothing wrong with having a door bell transformer on a lighting circuit. However installing a DIN rail mounted transformer in a distribution board is a quite a neat solution.

Second; Outdoor to garage . A new consumer unit was fitted in the garage/workshop. Separate circuits are prrotected by RCD and MCBs. All wiring to garage was by underground armoured cable. Has been done about 20 yrs ago.

From your description this may be done properly. Impossible to tell without seeing it.

Third. Electric shower fitted about 4 yrs ago

What type of shower? If it is an instantaneous shower it should have a dedicated RCD & MCB (or RCBO).

While looking at the wiring I noticed
A, the power for the garage comes off the main switch and does not pass through the main fuse. Should it be rewired to pass throught the 63A fused switch when fitted.

In should be downstream of the main fuse and it should also have it's own fuse (or better still MCB). This can be resolved when the board is upgraded.

B the shower unit has a separate RCD in a separate housing and is powered from the same take off as the garage. i.e. it too does not pass through the main fuse.

Not good :eek:
Requires urgent attention.

Does an RCD alone give suficient protection?

No.
The RCD is not an overcorrect protective device.
An RCD provides supplementary protection only.
The cable could literally be on fire and a properly functioning RCD would not operate.

C. The wiring for the patio is taken from a light fuse. SHould this not be taken fron cocket circuit and then protected by RCD when installed..

A cooker circuit is for a cooker, not a patio
Patio lights should be fed from a lighting circuit, patio sockets should be fed from a socket circuit (sockets require RCD protection & outdoor sockets should have appropriate IP rating).
As a general guide determining whether a circuit requires RCD protection depends mainly on the type of load and to a lesser extent the ambient conditions.

Additionally, should the oven be protected by RCD or is MCB onm its own enough.

This would not be normal practice.

I am assuming that upgrading from fuses to MCB's give me better protection, even on circuits without RCD's . is that the case?

No.

My advice would be to get an experienced electrician to carry out a comprehensive survey. Then get three registered electrical contractors to quote for the work.

rock22

Thanks for such a detailed reply.
It looks like it is potentially a bigger job than i thought and may not offer better protection. Will probably leave well enough alone - except for shower. i will have electrician look at this.

2011

rock22 wrote: »

Thanks for such a detailed reply.
It looks like it is potentially a bigger job than i thought and may not offer better protection. Will probably leave well enough alone - except for shower. i will have electrician look at this.

The RCDs combined with MCBs will provide better protection.
There are a number of potentially dangerous issues with your present arrangement, so a new distribution board would make the installation safer.