Advice for minor works

ianb89 · Jan 9, 2012

Hi to all!

Some advice please....

I am newly qualified sparky and i have just set up my own business and already been offered to do a loft conversion and an extention, which i haven't quoted for yet.

Before i set up i was a house basher so not much experience doing this kinda work

So this loft conversion requires extending the ring and lighting circuit. Would it be best to do a quick loop test on these 2 circuits?...to make sure that i'm not extending a circuit which could have a broken earth which would make testing at the end of the job a nightmare?

This of an obv question really but i want to know what other electricians do as i don't have experience doing minor works.

Thanks in advance.

Paul.M · Jan 9, 2012

Back to the ops question, would you tap into the existing ring and lighting circuit or install a db2?

GLENNSPARK · Jan 9, 2012

jase said:
that is why on a 2 storey house you put one on one side and one on the other so that there is always light on or around stairs if either side trips

ok Jase but i still think that pauls way of using a sub board is better as you have the diversity and you will need to ensure that you have 10% spare ways on the main c/u...so what if its fully loaded up then?.....and before you start about RCBOs then that would mean a high integrity board for the mainc/u and as you probably would find its a split load at best you would have to change it.....and thus would be inspecting and testing the whole install again....which may throw up other problems/issues that you can do without.....

jase · Jan 9, 2012

well that would be up to him, as for testing the existing ring to ee if it would be worth tapping into then by rights yes, would be worth doing IR R1+R2 and loop test before hand to see if it is suitable, you would also need to check the adequacy of the earthing and to make sure that any new wiring is covered by an RCD if required

Paul.M · Jan 9, 2012

We could do it either way, after all its only going to be a few sockets and two lights unless the customer puts in a bathroom with a shower.

Think the op needs to give us more info on what the customer wants to have installed.

On a personal note, i dont like tapping into existing circuits for loft conversions. Put it on its own db and everyone is happy. Well I am anyways

.

GLENNSPARK · Jan 9, 2012

jase said:
well that would be up to him, as for testing the existing ring to ee if it would be worth tapping into then by rights yes, would be worth doing IR R1+R2 and loop test before hand to see if it is suitable, you would also need to check the adequacy of the earthing and to make sure that any new wiring is covered by an RCD if required

well i know i would feel better if i had performed these tests and had some values i could note.....covering yourself and you should prove by both inspection and test that circuit/s that you either add to and/or alter are good for continued service and that anything you have done to those circuit/s is not going to have a detremental effect......

BlueToBits · Jan 10, 2012

ianb89
There is no standard 'formula' for this sort of work. There are often too many permutations and combinations to fully determine the best way of doing the job in the time you have on a quick site visit. You have to go with what you have got, use your experience to fill in the gaps, and be prepared to change your approach at any time. A quick loop and IR test may help, but will be irrelevant if the point of connection is under a laminated floor in a room with fitted furniture for example.

highspark · Jan 10, 2012

paul.m said:
Ian it sounds like your biting off more than you can chew for your first project. Loft conversion in my book = put a small 2 or 3 way dis board in the loft to keep it separate from the other house circuits and for safe isolation in the future. Work out the max demand for the loft (using diversity calcs) and feed it from its own supply, don't tap into the ring to feed it. If your unsure about doing this job pass it on to someone that has more experience and ask to work with them to learn. BTW its not a minor works cert if you install new circuits.

Is this a new thing putting CU's in lofts, twice I've read it now???? Is this to save on 5 meters of 2.5mm or something? Other than that i don't see any reason why to have a CU in a loft? Just keep everything together under one cupboard. My problem with putting a CU in a loft is the chances of other sparks going into the home isolating light & sockets for the whole installaton then getting a belt because its off a seperate supply is fairly high. By all means mark the original board and state there is a seperate CU but personally i wouldn't preference it or advise it.

Paul.M · Jan 10, 2012

As bluetobits said keep your options open.

Run two new circuits from existing board if you have a couple of spare ways.

Tap into first floor circuits but you could be opening a can of worms.

Isso switch from db1 to db2 clearly marked and accessible.

Each job is different, each building is different. It's down to us to design a safe, functional and cost effective system. Let's see which way the op goes.

ianb89 · Jan 10, 2012

Thanks for all the advice guys. Much appreciated.

Dave 85 · Jan 10, 2012

highspark said:
Is this a new thing putting CU's in lofts, twice I've read it now???? Is this to save on 5 meters of 2.5mm or something? Other than that i don't see any reason why to have a CU in a loft? Just keep everything together under one cupboard. My problem with putting a CU in a loft is the chances of other sparks going into the home isolating light & sockets for the whole installaton then getting a belt because its off a seperate supply is fairly high. By all means mark the original board and state there is a seperate CU but personally i wouldn't preference it or advise it.

That belt would be a valuable lesson to said sparky about safe isolation procedures, he would probably want to thank you for the free lesson.

highspark · Jan 11, 2012

Dave 85 said:
That belt would be a valuable lesson to said sparky about safe isolation procedures, he would probably want to thank you for the free lesson.

As I've said I just wouldn't preference doing what you have said to do in another thread, that being run a 16mm t&e into a loft supplying a sub-board supplying a ring shower and lighting circuit. Instead of upgrading current fuse board and taking circuits from new fuse board. In this case hitting 2 birds with one stone giving the whole house RCD protection. Also the 16mm cable would also have to be RCD protected unless you where running it surface mounted, in steel conduit (16mm cable remember) or buried 50mm deep in wall. 10mm is a bloody nightmare to run nevermind 16mm. It would be easier to keep everything at the origin!