please could anybody help me with a job im pricing??? outbuilding needing earth rod.

[samg_4]

Im new to this forum so bare with me please guys. Right heres my question....

I have been asked to wire an outbuilding on a farm that is in the middile of nowere, the electricity company ( north west electricity) have sent a letter stating that i have to provide my own earth, so i presume that i will have to drive my own earth rod into the ground? i have never worked on a tt system before or ever had to drive an earth rod into the ground. please could anyone give me any advise on what i need to do? i have read 100Ma rcd has to be installed buy what would be the best way of doing this job??

any response would be great!! thanks again

 

[georges]

Re: please could anybody help me with a job im pricing??? outbuilding needing earth r

100ma rcd only required for metal cu . either cu split load with 2 30ma rcds or use rcbos for all circuits. and for earth rod find suitable spot and drive in extendable rod 1 meter lenghts 5/8 size or a single 1 meter 3/8 earth rod hope this is some use

 

[samg_4]

Re: please could anybody help me with a job im pricing??? outbuilding needing earth r

thanks for the help everything is of use at this stage. i have read my onsite guide and spoke to people at college but they have never done any work like this. All you guys on here seem pritty clued up i must have spent 4 hours reading everyones problems tonight haha.. another question?? would the 100ma rcd have to be in the electricity box in the field where the meter is? and then have my armoured going from 100ma rcd elclosure to my mains bored in the outbuilding?

 

[Deleted member 9648]

Re: please could anybody help me with a job im pricing??? outbuilding needing earth r

As your SWA will require earth fault protection a 100ma time delay RCD at the origin would be needed as it is unlikely that a TT will give you a low enough Zs for the overcurrent device to provide earth fault protection.

Alternatively you could follow Engineer54's advice and install multiple electrodes (making certain resistance areas dont overlap)to achieve a low enough Zs, and design the install to a higher standard than the totally meaningless requirements of Bs7671......if you take the second option I doubt your price will be competitive.

 

[Engineer54]

Re: please could anybody help me with a job im pricing??? outbuilding needing earth r

Still trying to be clever are we WirePuller?? haha!!!

 

[Deleted member 9648]

Re: please could anybody help me with a job im pricing??? outbuilding needing earth r

thanks for the help everything is of use at this stage. i have read my onsite guide and spoke to people at college but they have never done any work like this. All you guys on here seem pritty clued up i must have spent 4 hours reading everyones problems tonight haha.. another question?? would the 100ma rcd have to be in the electricity box in the field where the meter is? and then have my armoured going from 100ma rcd elclosure to my mains bored in the outbuilding?

Agricultural installations come under section 7 of the BRB,and are not covered by the OSG. Your SWA will require RCD protection as already stated for earth fault protection and fire protection...705.422.7....(max 300ma time delay)...with final circuits having differing RCD requirements....There are also many other requirements you may not be aware of for farm installs.
If you are designing and pricing an install in a farm building I would suggest you must refer to section 705 for yourself to ensure you are meeting the requirements. Hope this helps.

 

[malcolmsanford]

Re: please could anybody help me with a job im pricing??? outbuilding needing earth r

Wirepuller is spot on here, agriculture buildings, TT sytems and all this entails can be a complex installation for the most experienced of electrician, let alone by the sounds of things someone still learning at college.

As stated Section 705 is your guide in this but then you will need to to use various other parts of the regulations for fault protection, external influences etc etc..................personally I admire your confidence in taking this on, but I think a sensible approach to this would be to get a more experienced hand on board. I'm sure you'll appreciate there are a lot of good advicxe to be had on here, Wirepuller as started you in the right direction, but none of us are actually there and therfore it is impossible to advise you on a cost effective, safe design.