wiring to a garage

[crosbie2000]

hi
Moved into a 1960's bungalow and there are many, many things wrong !!
Came home from a winter away and found no power in the garage
After checking fuses(both ends) and ringing the cable out I discovered a 2 red and 2 black core flex in rubber. you can imagine the state of it !. Crumbling and corroded, same for the distribution boards too!
anyway going to replace it all so can I use 4 mm pvc in a conduit or steel wire armoured. Garage is about 20 metres away from the house and can I bury it under soil or . . . ....
any advice would be great - I am an electrician by trade but not in the game for 10 years. Thanks in advance

Iain

 

[Taylortwocities]

Nothing has changed in 10 years.

You can't use PVC in plastic conduit, if thatis your thinking. you gotta use SWA. And it needs to be properly buried at least 450mm deep if under lawn/flower beds etc. With marker tape.

There is a decent picture on page 2 of this document
http://electrical.theiet.org/wiring-matters/40/appendix-4.cfm?type=pdf

 

[ericmark]

I would go for the SWA method. The supply to garage has been done many times but yours is slightly different as it already exists.

As to legal bit I know one is replied to replace like for like but personally I would consider improving was a better method and I would go for improvement. As to if I would tell LABC well of course I tell the police every time I exceed the speed limit so why not

Back to reality you must of course follow BS7671 not because it's required but it does mean your reasonably safe. So to start with the gauge of cable (How many mm's csa) must match the size of the supply MCB/Fuse.

What you want is if you hit with spade or have any other mishap the protective device will trip.

One of the big problems is move from fuse to MCB. The MCB has a very defined point at which the magnetic part will work. So unlike the fuse where some where near was good enough with the MCB the loop impedance is very important.

Also the earthing arrangements. It's not easy to assess if TT or the house earth is best. Even passive RCD in house or active RCD in garage.

I know you say your an electrician but I have met many an installation spark who for some reason things BS7671 does not apply to them and are still living in the dark ages. They seem to think if Tesla could do it why can't they? The fact that he died 7 January 1943 does not seem to matter!

 

[ban-all-sheds]

.. I know one is replied to replace like for like ..

JFC.

 

[crosbie2000]

Ta to all
I am going to do it right so I was just checking that SWA was the right way to go before doing it.
I'm replacing the 1960's fuses both ends with RCDs snd also installing an outdoor socket so I can plug my motorhome in.

thanks for the replies
regarding whata I can bury it under then.
I'm having 35 tons of earth excavated and it's a perfect opportunity to bury a swa cable under the stones before the driveway is laid.
stones will be about 300mm and a driveway on top. sounds ok to me but any contrarians out there ??

Iain

 

[ericmark]

Ta to all
I am going to do it right so I was just checking that SWA was the right way to go before doing it.
I'm replacing the 1960's fuses both ends with RCDs snd also installing an outdoor socket so I can plug my motorhome in.
Iain

Doing it right for a motorhome hit a problem with earthing. The problem is the regulations are written with the idea that you follow all the other regulations and the distance from your building to where the motorhome is parked can have a large affect as to what is done.

In the UK the ESQCR prohibit the use of a TN-C-S system for the supply to a caravan or similar construction.

OK in a caravan park you have at least 6 foot from any building to any caravan because of fire regulations so fitting a pillar with a 16A socket and a earth rod with TT supply is great.

But where my father-in-law parked his was within 3 foot of the house so one could touch extraneous-conductive-parts on both motorhome and house at the same time. So to have a different earthing method for both could be dangerous. Also as a semi-detached house his earthing needs to be same as next doors earthing which is why the DNO decide earthing method not you.

So once you break one rule or regulation likely you will also need to break another. It's a case of using skill and common sense with a risk assessment to decide on the best plan. Clearly this can't be done remote from the site it needs local knowledge.

You say you are an electrician so no need for me to explain about the difference between TT and TN-C-S or that of course TT does require RCD protection. You say RCD at source and destination clearly they would not be same size and you could use 100 mA and 30 mA but I really can't see the point I would just use 30 mA RCD at the source.

You say "do it right" so first step is to talk to LABC and see if they will accept your qualifications to do the work. They have accepted mine but refused my son even with a C&G 2391. I would also look at cost. It may be cheaper not to DIY with LABC charges. Clearly as an electrician you will have loop impedance tester and RCD tester etc. But they may want to see the calibration cert which could be a problem.

I know you will want to keep battery topped up on motorhome but I would think as solar panel would be far cheaper than connection to house mains supply. That's if you still want to "do it right"?

 

[ericmark]

.. I know one is replied to replace like for like ..

JFC.

Darned auto spell checker. I hadn't noticed what it had done. Clearly required not replied should have been the word.

 

[ban-all-sheds]

That's not the problem.

"Like for like" is.

 

[crosbie2000]

Gonna put a service duct in
Being dug out anyway
Makes a draw rope easy[/quote]

 

[ban-all-sheds]

Put in two so you can also run phone/data cables out there if ever needed.

 

[1john]

Two ducts he means, not ropes, although with two ducts you'll need two ropes!