1st Job concerns

[Scotty]

Hi All,

I have just been to look at my first potential job since getting 17th Ed and Dom Installer qualificaion.
I need to install 2 outside lights and a garage ring main. The set up is a TT installation with a split load Hager board. My concerns and questions are as follows;

1) There is an rcd protecting the sockets, power shower and cooker but the lighting circuits have no rcd protection at all, the main switch is a straight 100 A DP. These should have rcd potection regardless for a TT, I would like some advice on the best way to resolve this, I though of adding a 63 or 80 A rcd and then moving the mcb's for the sockets and lighting to give some discrimination or adding a new circuit on a RCBO and letting the customer know the issue with the rcd protection.

2) The CU is on the outside wall in the garage so I intended to run the cable from the consumer unit up the garage wall and then out through the building in T & E and then to a box, I am not sure what is the best cable to use for the run to the 2 lights given the temperatures we get during the winter and the UV light degradation? (or should I use a different cable for the complete run back to the cu)

3) For the garage ring I will be installing in conduit for additional protection, what is the view generally on cable runs in garages regarding additional protection? i am thinking of s/w drops and boiler feeds etc.

I will be using this work for my assessment so your guidance would be much appreciated.

Thanks,
Scotty

 

[steviesparks]

Hi All,

I have just been to look at my first potential job since getting 17th Ed and Dom Installer qualificaion.
I need to install 2 outside lights and a garage ring main. The set up is a TT installation with a split load Hager board. My concerns and questions are as follows;

1) There is an rcd protecting the sockets, power shower and cooker but the lighting circuits have no rcd protection at all, the main switch is a straight 100 A DP. These should have rcd potection regardless for a TT, I would like some advice on the best way to resolve this, I though of adding a 63 or 80 A rcd and then moving the mcb's for the sockets and lighting to give some discrimination or adding a new circuit on a RCBO and letting the customer know the issue with the rcd protection.

2) The CU is on the outside wall in the garage so I intended to run the cable from the consumer unit up the garage wall and then out through the building in T & E and then to a box, I am not sure what is the best cable to use for the run to the 2 lights given the temperatures we get during the winter and the UV light degradation? (or should I use a different cable for the complete run back to the cu)

3) For the garage ring I will be installing in conduit for additional protection, what is the view generally on cable runs in garages regarding additional protection? i am thinking of s/w drops and boiler feeds etc.

I will be using this work for my assessment so your guidance would be much appreciated.

Thanks,
Scotty

My advice scotty don't have your assessment on a TT job, have you got an earth rod test meter? Like me then probably not, my advice.... keep it simple.

 

[David.]

hey

can i just ask whats an earth rod test meter about?? Ithought on TT installs you could just so a normal Ze test and this would confirm resistance to earth??

 

[cbw]

David, thats my belief also.....Ze in place of Ra,

certainly not running around the fields in this weather!!!

CBW

 

[slocm3105]

If you did this on your assessment i'm almost certain they would ask you to get out your earth electrode resistance tester and show them how you would test the resistance of the electrode. If you have GN3 have a read through that and see how the test is conducted. You will soon see why people have advised you against this .

 

[Scotty]

I remember reading up on this during the college course, I hoped it would be something I would not come across very often. Just a pain the first work I get offered is for a TT. Perhaps I should put this one on the back burner until I get acredited as per the advice here, the customer is smeone I know so they will probably wait as the job would be done at mates rates.

That aside, any help on my original questions would be great, the course I did gives you a good understanding of the regs but it is no substitue for experience and some tips for best practice would be invaluable.

Thank you to all who have taken the time to reply.

 

[A-Non-eMouse]

you dont have to have a earth electrode tester. you can do it with a loop impedence tester if the electrode under test is being used in conjunction with an rcd.

 

[Jason Smith]

Are the two outside lights going on the side of the garage ?

srry ! just re-read your message. From the back of the garage ring main (socket ) length of 2.5 to a 13 amp fused spur. Change fuse for a 3/5 amp. Label FS accordingly. From here run your lighting circuit calculating if you need 1.5 or 1 mil. I would go 1.5 as it just as easy to use as 1 mil.

 

[Golden_Boy]

David, thats my belief also.....Ze in place of Ra,

certainly not running around the fields in this weather!!!

CBW

What happens if the TT supply is in an urban area ( as I am ) with most of the " ground " being under 6 inches of concrete.. How does one then test the earth rod " properly " ??