Outdoor consumer unit

Postby Fatcockney » Wed Mar 30, 2011 12:09 pm

Hi I have an outdoor consumer unit fitted to the porch of a summer house (I moved in recently).

The consumer unit has a master switch and two individual switches within. One of these switches feeds external lighting & the summer house sockets. The other is vacant.

My issue is this: On the external wall is a two-gang waterproof switch. Only one switch is connected to cable. The cable runs into the summer house via a light fitting, then onto a light pull, then through the wall to an external light. AT NO POINT DOES IT CONNECT TO THE CONSUMER UNIT.

The light fitting inside, I have recently purchased and fitted. The previous owner removed the other one. Behind this light is a hole that goes into the consumer unit. I'm assuming that the owner removed the light and a direct connection to the consumer unit to make up the full circuit. Is that possible? Just seem a bit suspect to me?

None of the lights work (obviously) so my question is this....

Can I connect this light directly to the consumer unit safely to complete the circuit? OR Should I connect the consumer unit to the extwernal switch and loop the rest in from there??

I'm a failrly competent DIYer, but as this is external and there's water in the room, I'd prefer not to be all black and frazzled.

Appreciate the help
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Joined: Sun Jan 31, 2010 9:33 pm


Simply Build It

Postby ericmark » Wed Mar 30, 2011 5:08 pm

Although a WMDU (Weatherproof Main distribution unit) is common as a consumer unit weather proof versions are not too common. The norm is to make a box to house a standard consumer unit. A consumer unit is a type tested distribution unit and the type testing means as long as one follows manufactures instructions then there is no need for the person fitting the unit to declare that it has been designed to suit conditions it has all been done for him. To use not following manufactures instructions means it does need full paperwork to say how it has been designed and built to suit conditions.
This means the person doing the work will need to know what IP2X or IPXXB and IPXXD or IP4X mean and be sure it complies with these regulations.
It is unlikely any DIY person will be conversant enough with the regulations to know if it complies or not. And also he is unlikely to own the test equipment to test the RCD tripping times, Loop Impedance, High ohms at 500v or low ohms at 200ma required for the standard tests.
At £75 to even hire added to that the LABC charges of £100 plus it is unlikely to be cost effective even if you have all the knowledge to DIY.
I am not saying don't do it. I have found people who do know what they are doing and can do it safely but I am saying consider if it is really worth the effort in doing all the paperwork required by the Part P law?
I will guess the last owner did some DIY and realised that when selling the house he did not have the completion certificates required to sell the house with it all connected. Easy way out is to disconnect then no one can come back on him for any errors.
What I would suggest is to get an "Electrical Installation Condition Report" they were called "Periodic Inspection Report" that way you know your starting on a sound system. The things like loop impedance can be calculated but only if you know what it is at the origin.
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Postby Fatcockney » Thu Mar 31, 2011 9:22 am

So basically, this looks like a suspect installation and I should get a qualified response before proceeding?

Just for my own sanity though regarding the completion of the circuit.....

Is it possible that they wired the internal light direct to the unit to complete the circuit between the unit, ext switch, internal light & light pull switch? Would that have worked for them?
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Joined: Sun Jan 31, 2010 9:33 pm

Postby ericmark » Thu Mar 31, 2011 8:33 pm

There are 100's of ways that lights could be made to work both legal and following regulations and ways not sanctioned by the BS7671:2008.

This site does not permit pictures however neither do the guys preach over the top about what should not be done as DIY.

The method of vetting replies before they appear may seem slow but it does stop the righteous telling you what you should not do.

Going to one of the other sites not so well regulated you can post pictures and as a result you may get a better reply.

However get ready for the flack if they think you are going to do work in a garden without Part P.

Even in a house with a consumer unit the top must not have a hole which will allow a 1mm wire to enter and all other sides 12.5mm (finger thickness) is the limit for any hole. Where 20mm knock outs have been removed the hole must be filled with something not removable without a tool. That means rubber grommets are not good enough. The same applies where there are spaces not filled with MCB's.

Having said that it is still common to find a rubber grommet filling the hole or a plastic push in blank where all spaces are not filled with MCB's. And unless where children and play with the box in real terms it is not really a problem.

However to DIY in the garden means under Part P the LABC need to visit and inspect and the inspector may use common sense or he may follow the BS7671:2008 to the letter.

With the latter what looks safe may well fail so I am very careful when saying what will and will not pass.
Posts: 1133
Joined: Fri Oct 02, 2009 8:49 pm
Location: Mold, North Wales.

Postby Fatcockney » Fri Apr 01, 2011 5:49 pm

I really appreciate the time youve taken in the response. I'll be calling an electrician in. I think its for the best.
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Joined: Sun Jan 31, 2010 9:33 pm

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