800fsbgang
Member
Im new to this forum and looking for some assurance i suppose ,im getting back into my sparky past, however not had a massive amount experience with TT earthing.
Ive done a job i wish to use for One my registration Jobs.Which is to run power to a garage approximately 10 metres away from The semi detached property.
The property is a semi detached which operates a PME Earthing, the outbuilding/garage is fairly old, and is made from concrete slabs,with reinforced wire mesh within the concrete side,it has a Metal frame supporting a metal roof.
due to the extraneous conductive parts, it is fair in my opinion not to export the present earth from the main property ,and a TT Earthing system will be adopted in the garage.
As follows:
Maximum demand for the Garage is no more than 4Kw which comprises of 2 x double sockets (1 of which a small freezer will be run constantly, and 2nd is an outdoor socket to which a lawnmower will be plug in occasionally ,the lighting 1 x 20 watt light, thats it.
so from the house, Ive run a 6mm 3 core SWA cable,Which is protected by a 16amp B type RCBO and earth the gland/sheath is earthed to the PME side.On top of the armoured at the Garage side I've measured a ZS of .40ohms with the reference earth.
on entering the garage, which runs into a 30ma RCD protected metal clad garage board, the gland is plastic, and the sheath has not been connected to the earth in any way.The earth core of the armoured is terminated in a Terminal block for measuring reference only.
The 2 circuits are a 1 x Type B 16 amp Circuit Breaker feeding the 2 x Sockets and the other a 1 x Type B 6 amp Circuit Breaker Feeding the lighting circuit.
Ive installed a TT earth electrode with 16mm earth csa back to the garage board met,and 10mm bonding to the metal roof/frame ,the area is clay soil with decent resistivity the RA measurement is 15.49ohms sub Station not a 100 metres away.
Ive taken a ZS measurement on the socket and 16.43 ohms measured. PFC is 14.9amps and PSC 501amps
Due to using a TT the maximum permissible ZS’s cant be met but theres 30ma RCD on the garage board to cover ADS .
If a L-E or L-N fault occurs then the 16amp B RCBO will disconnect the supply the house side, although it doesn't need to be an RCBO normal type would Suffice.
Would this be ok or have i missed anything, would you guys do anything difference?
I have not been able to do my 18th because the college closed down, have my 17th ,but doing in the next 3 weeks.
Kind regards
800fsbgang
Ive done a job i wish to use for One my registration Jobs.Which is to run power to a garage approximately 10 metres away from The semi detached property.
The property is a semi detached which operates a PME Earthing, the outbuilding/garage is fairly old, and is made from concrete slabs,with reinforced wire mesh within the concrete side,it has a Metal frame supporting a metal roof.
due to the extraneous conductive parts, it is fair in my opinion not to export the present earth from the main property ,and a TT Earthing system will be adopted in the garage.
As follows:
Maximum demand for the Garage is no more than 4Kw which comprises of 2 x double sockets (1 of which a small freezer will be run constantly, and 2nd is an outdoor socket to which a lawnmower will be plug in occasionally ,the lighting 1 x 20 watt light, thats it.
so from the house, Ive run a 6mm 3 core SWA cable,Which is protected by a 16amp B type RCBO and earth the gland/sheath is earthed to the PME side.On top of the armoured at the Garage side I've measured a ZS of .40ohms with the reference earth.
on entering the garage, which runs into a 30ma RCD protected metal clad garage board, the gland is plastic, and the sheath has not been connected to the earth in any way.The earth core of the armoured is terminated in a Terminal block for measuring reference only.
The 2 circuits are a 1 x Type B 16 amp Circuit Breaker feeding the 2 x Sockets and the other a 1 x Type B 6 amp Circuit Breaker Feeding the lighting circuit.
Ive installed a TT earth electrode with 16mm earth csa back to the garage board met,and 10mm bonding to the metal roof/frame ,the area is clay soil with decent resistivity the RA measurement is 15.49ohms sub Station not a 100 metres away.
Ive taken a ZS measurement on the socket and 16.43 ohms measured. PFC is 14.9amps and PSC 501amps
Due to using a TT the maximum permissible ZS’s cant be met but theres 30ma RCD on the garage board to cover ADS .
If a L-E or L-N fault occurs then the 16amp B RCBO will disconnect the supply the house side, although it doesn't need to be an RCBO normal type would Suffice.
Would this be ok or have i missed anything, would you guys do anything difference?
I have not been able to do my 18th because the college closed down, have my 17th ,but doing in the next 3 weeks.
Kind regards
800fsbgang
