Garage and summer house supply (tt or not)

[sidekick]

Proposed plan to supply from 32mcb on main csu in 4mm t/e approx 15m to outside wall into adaptable box -then 4mm 3 core swa to Garage approx 10m.
Inside garage - new csu rcd protected 16A x1 and 6A x1.
From 6A run 1.5 t/e to garage light and switch. From 16A run 2.5 t/e to 2g socket in garage. from socket 2.5 t/e to adaptable box at rear of garage and 2.5 3core swa 5m to summer house.
Adaptable box in summer house then run 2.5 t/e to 2g socket, from there 2.5 t/e to Switched FCU to suply light in 1.5 t/e. From first FCU 2.5 t/e run to second Switched FCU with 1.5 t/e to Adaptable box and then 1.5 3core swa 5m to supply garden lamp post.

Can anyone see any problems with this plan please. Also main house is TT and would i be best terminating earth at garage abd sinking its own earth rod making Garage a seperate TT.

 

[telectrix]

if the house is TT there is nothing to stop you adding another rod at the garage. it may even bring the Ze down on the house. i would check your possible loading and calculate volt drop as well. other than that, if your 4.0mm T/E from the CU to adaptable box is buried in wall, you will need a RCD or RCBO at the CU. this will do away with the need for RCD in ngarage, but, if there is a fault, it will trip in the house.

 

[sidekick]

if your 4.0mm T/E from the CU to adaptable box is buried in wall, you will need a RCD or RCBO at the CU. this will do away with the need for RCD in ngarage, but, if there is a fault, it will trip in the house.

The 32A mcb is on rcd protected board already and the 4mm t/e is under a suspended floor to the nearest air grate to the garage

 

[Engineer54]

As suggested, add another couple of rods to your TT system, it will indeed reduce your final Ze if then connected to your existing TT system. Just make sure they are driven deep, (not close to any building walls) and protect the cable to rod connections with purpose made ground boxes and with say amalgamating tape around the connections...

 

[telectrix]

if you are coming off an RCD in the house , then fitting another on the garage, you won't have discrimination, so in case of a fault. one or the other , or both, will trip. better to feed from non RCD section of house CU if you can, if not, leave out thr RCD in the garage.

 

[sidekick]

Thanks for the advice guys. Going to survey job on Monday so will have beter idea what I can and can't do then.