ELECTRIC WIRING


Postby zzgeorgezz » Sat Aug 02, 2008 1:54 pm

hi there...i have knocked the walls down in 3 outbuildings to make a dining room....i have insulated the roof/loft above them and put a loft hatch in...and a large window in the wall lookin out into garden...I KNOW THE CONSUMER UNIT NEEDS REPLACING....i also want 4 double sockets in the (dining room) and 3 lights 2 of which will be on the wall....TO SAVE COSTcan i run my own cable from where the existin unit is which will go through wall into loft above (dining room)around outsid off loft to where sockets and lights are required then just just drop the cables down partially buried in the wall...which will be covered with plasterboard...CAN ANYONE HELP WITH THE REGULATIONS PLEASE...DO I NEED CONDUIT...WOT CABLE DO I USE FOR 4 DOUBLE SOCKETS...I KNOW SOCKETS NEED TO BE ATLEAST 450MM ABOVE FLOOR LEVEL ANY HELP MOST GRATEFULLY RECIEVED...I ALSO WANT TO RUN A POWER SUPPLY TO A SHOWER IN BATHROOM...MANY THANKS.....GEORGE.....
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Postby ericmark » Sat Aug 02, 2008 9:03 pm

OK to start with George go to projects and follow links to Part P. Once you have read this you will see some of what has to be done including the form filling.
Here is hard part for a registered spark under part p to sign the completion certificate he has to have designed, fitted and tested the installation and if part of the work has been done by a third party i.e. you then he can’t use his registered status and it has to go through the LABC (local authority building control) as a result it can end up costing more to DIY than get whole job done.
The new rules on where RCD’s are required are complex and in most cases we now fit them everywhere in which case 2.5mm for sockets on ring or 4mm for sockets on a radial and 1.5mm for lights in twin and earth is normal but for example if you did not want freezer on a RCD you could use cable to BS 8436 and mark to socket freezer only you could avoid using a RCD on freezer.
And the consumer unit could use RCBO’s or multi RCB’s and there are advantages and disadvantages with both.
I think the 450mm comes from the guide to 16th Edition which in turn got it from Part M and it seems either there were changes or they got it wrong. 400 mm to 1000mm above finished floor level for sockets switches are different think up to 1200mm and thermostat even higher and had someone followed the rules my wheel chair bound mother would not have been able to reach the thermostat. So some common sense required as well. You will find Part P with links from Part P the same with Part L.
Power to shower is best in 16mm cable although you can use smaller cable with smaller showers such a pain to up grade you may as well go for big stuff first time at least to isolator even if you use some smaller cable for last bit to shower where the shower will not take the bigger cable. Read instructions on shower as to breaker size normally around the 40 amp mark.
If you intend to run any cable outside remember UV and all outside cable is black do not run any grey twin and earth outside.
Once you have read Part P I expect you will have more questions if you are DIY’ing do take careful note of forms page 23 onwards and consider if you could fill these in yourself. There are forms without on line version written across them on IET website.
Eric
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Postby TOPSPARK » Sat Aug 02, 2008 11:24 pm

Hi george topspark here The advice i will give you is consult an electrician who is part p registered and explain the situation and see if he will consult with you on the job you are doing then with his input you could ask if you can run the cables and he can install the new mains board you need and second fix,then he can test and certify the job and register it with building control. Some info in other posts is too technical for diyERS to understand
regards
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Postby zzgeorgezz » Sun Aug 03, 2008 10:21 am

hi eric....
thanks for the quick reply..i havent gone through the part p yet completely....but from the current old consumer unit there is existing wiring going into the 'outhouses'...they are buildings connected to the house they are not phisically separate and have a roof and loft space over them....but the wiring is just tacked onto wall for the lights and there is only one single socket that went into one of the original 'rooms'...i read on one part of a site yesterday that it is acceptable...(or so i thought)...that original wiring on a single circiut maybe extended/modified without the aid of a compentant sparky...(so to speak)though it was advised it was best to have it checked after)so all i really wanted to do was extend the socket feed to 4 doubles...which will be tied into a new consumer box...and will require a 'ring main' i presume...as the socket in there is just one wire from the box it doesent have a return...and the lights iwas goin to move around to where i wanted them....to hide cables i was going to go in the loft and then down into the room...cut the wall out slightly so the wall can then be plasterboarded so it doesent interfear with cables...is it acceptable for me to do this...as i live in a little villiage and the cost of a spark to traval here to do all this aswell is going to get expencive...i need to know if cable needs conduit and all wiring will be visiable as it wont be boarded over till the sparky has been in...so on the socket cable can i just renew the wiring posistion plugs where i want then then return the circiut...so it is tied in then as a ring on a new box...all i want to do is the 'donkey work'....many thanks...george...
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Postby TOPSPARK » Sun Aug 03, 2008 1:12 pm

The cables can be protected by plastic or metal capping and then boarded over. Under the 17th edition wiring regulations they must be protected by an rcd, as you are changing your consumer unit then there is no problem so you dont have to use conduit as the capping mechanically protects the cables and is cheaper than conduit.
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Postby ericmark » Sun Aug 03, 2008 1:24 pm

If you are taking the supply from an existing ring main there is no real point in using a second consumer unit.
In the main you are not allowed new circuit from main consumer unit. Change the consumer it’s self, work in bathrooms, kitchens or gardens without Part P.
But to plan your wiring just to avoid Part P seems silly. And because of the new rules on RCD’s it would be very hard to avoid Part P work in an old house.
I don’t care if you don’t use Part P that is up to you but I would be wrong not to make you aware it existed.
It was until July unusual to use conduit in houses but with new rules maybe people will return to using it in future.
So long as all circuits are protected by RCD’s there is no real need for conduit and capping is only used to protect cables while they are being plastered.
As to doing donkey work for spark you really need to ask the spark that is going to do the work as I have already explained the rules if a spark is going to self certify for building controls are quite tight but you could of course go through the local authority building controls and then use the three signature forms. One for design, One for installation, and one for inspection and testing. You can still use a spark to do final bit inspection and testing and you can sign for design and installation.
What you need to decide is:-
a) Get spark to do the lot and let him do completion form.
b) Pay council and do some work yourself.
c) Break the law and hope no one notices when you come to sell or claim on insurance.
Forgetting about rules and regulations any electrical system can produce danger and it makes sense to check no mistakes have been made. The whole idea of Part P is the county council building control becomes responsible for site safety and need to ensure method statements and risk assessments are completed where required. They may require you to do your own method statement and risk assessment and inspection and testing but at the end of the day they are responsible for making sure it is done correctly and if they are not satisfied with your finding and reading they have to pay for it to be done. This is why I said read the Part P document it is not one way they have to do quite a lot to ensure everything is safe. Lets face it there is a big different between the £5 or so electricians need to pay for registration to the £70 or so you have to pay and the council are expected to do some work for that money.
Eric
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Postby zzgeorgezz » Sun Aug 03, 2008 5:10 pm

thanks topspark....it looks like that is way i have to go....i was just tryin to get it done in one hit so i dont have to pay for the bloke to come back again....but if i cut the walls out and notch it for the posistion of sockets i spose this would cut the time down....evevn if a sparky has to wire it in he still has to put the sockets where i want them....is this acceptable providing i dont exceed 50/60 metres of cable i believe is the max you can put in loop....i know from eric now i dont need cappin or conduit so it will just be a case of sparky layin cables...many thanks for your post...george....
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Postby zzgeorgezz » Sun Aug 03, 2008 5:17 pm

thanks eric....i was in no way goin to ignor part p...i just thought i had read enough to think it was ok for me to extend the original wiring...the socket in question was just a single feed...which thinkin bout may even be just a spur as it has no return....so i will have to get some quotes and negociate a deal of some sort so i can cut the labour cost to the one visit....many thanks for your post...george....
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Postby TOPSPARK » Mon Aug 04, 2008 6:34 pm

In respect a ring main can be 50 square metres and in that area you can have as many sockets on that circuit as you want but it sounds to me as though you wont be breaking the 50 square metres for the work you are doing or having done
regards
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Postby ericmark » Tue Aug 05, 2008 10:03 am

Hi George,
Glad to hear you following Part P do follow links and read yourself as you will find many people jump to conclusions rather than reading what it says. As to length of radial and Topspark says rule of thumb is 50 square meters and for Ring main 100 square meters but this is a rule of thumb and in many cases you will find it can’t cover anywhere near that much area. There are a number of limiting factors but volt drop seems in most cases to be the one which limits the most. For a 32 amp supply on a 2.5mm² ring main for power a maximum of 79 meters of cable can be used to keep within the 5% volt drop under the 17th Edition under the 16th Edition this was less with only 4% volt drop being allowed. There are other limiting factors like Earth Loop impedance and Neutral Loop impedance and ways to increase to distance like reducing MCB to 25 amp would allow 102 meters but I would think that could cause other problems. Where electricians have miss calculated how much cable they have used and have gone over limit reducing the MCB size will allow it to pass but not really something to plan for.
Eric
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