Installing a new consumer Unit

[Chris123]

I plan to upgrade my current small consumer unit and install a larger one that will allow me to split the load and wire the lights/smoke detectors direct and not via the RCD as is currently the case. (The previous owner has wired everything through the RCD).

My current installation does not have a main switch other than the RCD one so how do I turn off the supply to install the new unit. Is is common practise to phone my supplier and ask for the supply to be turned off for 30 minutes. ??

Grateful for the advise of the experts.

Thanks

 

[Big_Spark]

This is a "normal" situation in the vast bulk of premises within the UK. When an electrician changes the Consumer Unit they disconnect the tails from the meter..the ones that connect the meter to the consumer unit, or they simply pull the main fuse to the property if it is easily accessible.

This is technically an offense, and the Electricity supply compnaies have always turned a blind eye to this practice. It is a simple enough matter to phone up on completion of the works and ask for an engineer to call in and re-seal the meter.

However I would never advocate a non-experienced nor qualified person doing this.

Many DIY sparks do this, and they do it perfectly safely, with the safest option simply being to pull the main fuse.

Regarding the splitting of circuits, thisd is a good idea, Lighting, fire and intruder alarms, and sockets likely to feed computer systems should not be fed from an RCD. There is nothing inherently wrong with this, but it is not desirable sue to the negative effects a trip could cause..like falling down stairs in the dark, being burgled because the alarm was off because your whatever tripped the RCD whilst you were out etc.

Split load boards are certainly one way of doing this, however the alternative, which may or may not be cheaper, is to use RCBO's on those circuits warranting protection from an RCD.

An RCBO is a protective device that incorporates the functions of the RCD and the MCB into one unit and sits in the place of an MCB within the normal board.

 

[Chris123]

Many thanks for the helpful and detailed answer. I will look at the cost of replacing the MCBs with RCBOs and removing the RCD as an alternative to the new consumer unit.

 

[ban-all-sheds]

Is is common practise to phone my supplier and ask for the supply to be turned off for 30 minutes. ??

No it is not. Nor is it uncommon practice. Nor is it almost-unheard-of practice.

What is common practice amongst professional electricians is to cut the seals on the main fuse and remove it. IMHO that is a very dubious practice, and for a DIY-er to attempt it would be utter madness.

The only way that you can turn off your supply is to first have the supplier come and fit an isolation switch between the meter and the CU. Then you can turn it off safely.

Are you also sure that you have the skills to replace the CU? Do you have the knowledge to choose the correct protective devices? Do you know what earthing system you have?

It's not quite the same as replacing a socket. There is absolutely no reason why a DIY-er should not be able to do it safely, but what I'm trying to say is that there may be more to it than you think there is.

 

[BR]

In relation to disconnection, the supply company will do so at your property, It is not a matter of the telephone operator pressing a few buttons and your supply if isolated! (maybe you knew this).

Is is probably fine to simply break the seal on the service head and pull out the main fuse as FWL has suggested. The supply company are very unlikely to make an issue out of it. If you ask one of the engineers themselves, i'm sure they would reseal if for you.

If you do not want to do this, it is possible to replace the board without disconnecting, provided you are careful.

 

[Big_Spark]

Ban, several time on this forum I have seen you mention the installation of an isolator being fitted by the Electricity Supplier BETWEEN the meter and the Consumer unit?

I am curious as to which company undertakes this action, as none within 100 miles of London do it that I am aware of, and for very good reason, they have no legal right to do so, so the only option would be to charge the consumer for this fitment.

Some of the newer meters, the electronic type have an isolator built into them, but I have never seen one of these fitted to a Domestic supply..I will agree this is a shame as it would make life a lot easier.

 

[Big_Spark]

If you do not want to do this, it is possible to replace the board without disconnecting, provided you are careful.

Are you serious in that comment!! That is the fastest way to recieve a potentially fatal shock and SHOULD NEVER be thought of or attempted by a professional, let alone a DIYer.

 

[BR]

What is common practice amongst professional electricians is to cut the seals on the main fuse and remove it. IMHO that is a very dubious practice, and for a DIY-er to attempt it would be utter madness.

I agree with you, it is common practice for professionals to do this, and they should of course reseal the cut-out. But speaking from the supply board end of things, it is a minor issue. Why do you think it would be "utter madness" for a diy-er to do this.

The purpose of sealing the unit is to prevent the householder bypassing the fuse (putting in a bit of cable). The seals on the meter are a separate issue and these should never be interfered with.

 

[BR]

If you do not want to do this, it is possible to replace the board without disconnecting, provided you are careful.

Are you serious in that comment!! That is the fastest way to recieve a potentially fatal shock and SHOULD NEVER be thought of or attempted by a professional, let alone a DIYer.

I'm going to have to start typing faster!
Do you not think you are overreacting a little here FWL, in my opinion if someone is capable of replacing a CU, this should not be difficult. Provided precautions are taken. I know i'm bending this a little, but what do you think the 1000v insulated screwdrivers, pliers knips etc. that are sitting in your toolbox are for?

I suppose it's like replacing a switch or socket without flicking the MCB on the board, in the professional business, we do it all the time, but this is a diy forum.....
I was going to start telling you about replacing an entire three phase CU (incl MCB's) in a hospital while maintaining supply to all circuits without interruption! but I don’t think I will

 

[breezer]

nver mind the debate, chris in short you can not do as you suggest (doesn't work like that) and it MUST be tested before connection.

I would strongly recomend you get an electrican in to do it for you

 

[ban-all-sheds]

Ban, several time on this forum I have seen you mention the installation of an isolator being fitted by the Electricity Supplier BETWEEN the meter and the Consumer unit?

I am curious as to which company undertakes this action, as none within 100 miles of London do it that I am aware of, and for very good reason, they have no legal right to do so, so the only option would be to charge the consumer for this fitment.

Some of the newer meters, the electronic type have an isolator built into them, but I have never seen one of these fitted to a Domestic supply..I will agree this is a shame as it would make life a lot easier.

Not just me - lots of people say that they have had this done, at their request, so "legal right" is irrelevant. Mind you, not all of them say (as I did not) that the supplier does it for free...

I need to get one fitted myself, and I'm within 100 miles of London, so I'll let you know.

 

[Millennium_Boy]

Never even think of trying to replace a fuse box, without cutting off the supply first, either by an isolation switch, or a modern Ampy Automation electronic meter, with it's integral isolation switch and positive contact indication unit.

If you short out the incoming supply, you will likely to cause an explosion, and whats more, endanger the supply to your neighbours too - the main service fuse is a "slow-blow type"!

 

[ban-all-sheds]

.. Why do you think it would be "utter madness" for a diy-er to do this..

And the PSSC of the incoming supply is.....?

I just think that the consequences of something going wrong are somewhat severe. Everybody must make their own informed decision about what is safe, what is not, what the risks are and what their levels of knowledge and skill are before deciding on a course of action. I would never advise a DIY-er to pull the main fuse, that's all.

I'm not sure I would advise another to do what I did when I replaced my CU either, but that's another story to be posted in a minute....

 

[BR]

Ban, several time on this forum I have seen you mention the installation of an isolator being fitted by the Electricity Supplier BETWEEN the meter and the Consumer unit?

I am curious as to which company undertakes this action, as none within 100 miles of London do it that I am aware of, and for very good reason, they have no legal right to do so, so the only option would be to charge the consumer for this fitment.

Some of the newer meters, the electronic type have an isolator built into them, but I have never seen one of these fitted to a Domestic supply..I will agree this is a shame as it would make life a lot easier.

Not just me - lots of people say that they have had this done, at their request, so "legal right" is irrelevant. Mind you, not all of them say (as I did not) that the supplier does it for free...

I need to get one fitted myself, and I'm within 100 miles of London, so I'll let you know.

The isolator has now been replaced (in Ireland anyway, and i believe many companies in Britain are doing likewise) with the meter, which incorporates the isolator.

 

[ban-all-sheds]

..If you do not want to do this, it is possible to replace the board without disconnecting, provided you are careful.

It might be possible. When I replaced mine I was fortunate in that there was already a service connector block in place, so that when disconnecting and reconnecting I was working with tails going into fixed terminals. I could see what I was doing, access was good, I had pukka 1000V tools, and I never at any stage had any live cables wafting about. And I was very careful.

It was my decision, and I would not "advise" anybody in the same position to do the same.

I didn't feel very relaxed about it though, and I'd much rather have an isolation switch.