garage supply

[leesparkykent]

The earthing arrangement might require the SWA to be on an RCD. What is the earthing arrangement?

 

[Manator]

@r.b most answers are a result in the way you have worded your question. To be honest, for myself it is very hard to grasp exactly what you want to know.

There have been some very good answers given, although they are a little cryptic, I presume to make you read up on the regulations and in the process learn a little more about being an electrician. For a start as an electrician you should never listen to anyone else, unless you have good reason to trust their advise. After taking that advise read up on it to make sure it is correct.

As a little exercise how would you deal with supplying a 63amp supply to an out building? It is still domestic,the cable used is 2core SWA, but would it need RCD protection? Installation method could be anything you choose, clipped direct to the fence, buried or free air along a catenary wire.

 

[r.b]

I Read a good section in the on site guide 7.2.5 its mentioning socket circuits and cables withouta metal covering need rcd an armoured has a metal cover  so an armoured doesnt need it.manator your post what a coincidence you mentioned 2 core i was going to give my mate the armoured to do the job a 2 core 4mm i have got ive had it in storage.i would prefer 3 core.manator i would say use the armour as an earth and it doesnt need rcd 

 

[Manator]

OK r.b, now you are thinking. However back to my little exercise,why would an armoured cable supplying 63amps not require RCD protection within a domestic property? (other examples exist but I am only dealing with the exercise stated)

 

[Andy™]

I Read a good section in the on site guide 7.2.5 its mentioning socket circuits and cables withouta metal covering need rcd an armoured has a metal cover  so an armoured doesnt need it.manator your post what a coincidence you mentioned 2 core i was going to give my mate the armoured to do the job a 2 core 4mm i have got ive had it in storage.i would prefer 3 core.manator i would say use the armour as an earth and it doesnt need rcd 

wow... done your own research and got your answer. well done. now just to do more of that in future. but just remember that the OSG is just a guide and contains a very small selection from the book, it will be in there in a lot more detail of which cables require which protection

 

[Sharpend]

Is that a compliment from you Andy :innocent  

 

[Essex1]

Wouldn't be much of an electricians forum if we all did not bother asking questions would it?

 

[r.b]

WHat about using an armour as the earth as i say ive happen to have 2 core armoured 4mm that i will be giving my mate to do the job i mean an earth is an earth isnt it just as long as its stated on test sheet (armour)  ideally yes 3 core is this perfectly fine with the 2 core i know i ask a lot of questions i mean yes it would save my mate money using this 2 core of mine but thats not the point if it needs the 3 core my mate will have to buy it got a sense its the 3 core option. I know which one id choose or run a separate 4mm earth even. With the armoured ?

 

[Andy™]

the armour is suitable as a CPC... so why go to the extra expense of an extra core? i rarely ever use a core as an earth, unless its there an not being used

 

[Essex1]

the armour is suitable as a CPC... so why go to the extra expense of an extra core? i rarely ever use a core as an earth, unless its there an not being used

Correction - in most cases it is acceptable to use the SWA as the CPC. Not all cases. 

Op - you will need to do cable calculations in order to determine if the SWA on your cable is suitable to be used as a CPC. 

 

[leesparkykent]

Are there any extraneous conductive parts that need bonding within the garage? If so the armour of the 4mm will not be adequate for the use of a combined CPC and bonding conductor.

 

[Andy™]

or TT it

 

[leesparkykent]

personally If there was an extraneous conductive part/s that required bonding I would install a 3 core SWA that's adequately sized for the bonding. Another option would be to install a separate conductor which would have to also be sized correctly due to burial under ground if that is your chosen installation method. You could TT it as mentioned above but Imo it would be the last option I would choose if you have a DNO provided earth that will more than likely have a better value than any TT arrangement you install.

 

[Andy™]

apart from DNO may not allow you to export an earth

 

[leesparkykent]

I wouldn't export the earth I would extend the equipotential zone to the garage.

 

[Essex1]

opcorn

 

[steptoe]

I wouldn't export the earth I would extend the equipotential zone to the garage.

Just who exactly from the DNO gave you that permission to change the definition of exporting an earth to calling it extending the EZ,?

You can only extend an EZ to an adjoining building, not half a mile down the road,  :shakehead

How big is this Faraday cage you are building that can surround the cable route and encompass the garage and dwelling without being broken?

Btw,

I have a rod with a Ze of 0.16

For those that are unable to understand Ra 

 

[leesparkykent]

bs7430

 

[Davethsparky]

Just who exactly from the DNO gave you that permission to change the definition of exporting an earth to calling it extending the EZ,?

You can only extend an EZ to an adjoining building, not half a mile down the road,  :shakehead

How big is this Faraday cage you are building that can surround the cable route and encompass the garage and dwelling without being broken?

Btw,

I have a rod with a Ze of 0.16

For those that are unable to understand Ra 

Do you mean an Ra of 0.16?

 

[steptoe]

Do you mean an Ra of 0.16?

No, I mean a Ze,

I did say that it was to help the folks that didn't understand Ra,

You can't measure Ra with a normal Ze loop tester, 

A lot of folks on here may not have a tester capable of doing an Ra test.