DB2 (TT) trips DB1 TN-C-S

[Engineer54]

Thinking about it, in the summer I connected power to a DB in a brick built shed (about 5 metres from main house. Customer supplied all materials and I had to take the power source from an existing outside socket (customers preference). 3 core SWA provided so armour and copper core all earthed back to same (PME) earth point. No problem with that from my point of view but when supplying out buildings from which a person is stepping in, and out, potentially hanging on to something live, then my preferred, and standard procedure, is two core (cheaper) SWA, TT earth, and 30mA RCD fed from non-RCD MCB.

Haha, ...Classic!!

 

[Broken handle]

Thinking about it, in the summer I connected power to a DB in a brick built shed (about 5 metres from main house. Customer supplied all materials and I had to take the power source from an existing outside socket (customers preference). 3 core SWA provided so armour and copper core all earthed back to same (PME) earth point. No problem with that from my point of view but when supplying out buildings from which a person is stepping in, and out, potentially hanging on to something live, then my preferred, and standard procedure, is two core (cheaper) SWA, TT earth, and 30mA RCD fed from non-RCD MCB.

The only thing I insisted on adding was an FCU before the outside socket. I have ever since been surprised not to have received a call saying power to the shed had failed.

 

[Engineer54]

So when is an out building Not an out building then?? Just keep digging that hole!! lol!!

 

[Broken handle]

So when is an out building Not an out building then?? Just keep digging that hole!! lol!!

When it is inside.

 

[Broken handle]

So when is an out building Not an out building then?? Just keep digging that hole!! lol!!

I don't do that, customer has to get it sorted.

 

[Engineer54]

When it is inside.

Exactly, so now explain the difference between an out building 5 meters and 20m meters distant from main house?? lol!!

 

[Broken handle]

Exactly, so now explain the difference between an out building 5 meters and 20m meters distant from main house?? lol!!

15 metres, I think.

 

[Engineer54]

Ah, we have a clever bugger do we, ...it's a shame you're not as clever in you're role as an electrical tradesman, or in the care shown towards your'e customers. Seems it's all their fault, once you walk away from the job!!

 

[SPARTYKUS]

Thinking about it, in the summer I connected power to a DB in a brick built shed (about 5 metres from main house. Customer supplied all materials and I had to take the power source from an existing outside socket (customers preference). 3 core SWA provided so armour and copper core all earthed back to same (PME) earth point. No problem with that from my point of view but when supplying out buildings from which a person is stepping in, and out, potentially hanging on to something live, then my preferred, and standard procedure, is two core (cheaper) SWA, TT earth, and 30mA RCD fed from non-RCD MCB.

I think my point would be that providing as good an earth as possible is your primary protective measure, and for some reason you would not make use of a super low Ze available to you.

RCDs are unreliable, and do fail, but more importantly, they are supplementary. Not primary means.

especially if there is a wonderful earth available to use.....?

What am I missing?

 

[GLENNSPARK]

I think my point would be that providing as good an earth as possible is your primary protective measure, and for some reason you would not make use of a super low Ze available to you.

RCDs are unreliable, and do fail, but more importantly, they are supplementary. Not primary means.

especially if there is a wonderful earth available to use.....?

What am I missing?

not `especially` if theres a wonderful earth to use it is Sparty..

the earthing arrangements dictate whether a 30mA RCD is for additional..or fault protection

so theres no `especially` about it really..is there

 

[Engineer54]

not `especially` if theres a wonderful earth to use it is Sparty..

the earthing arrangements dictate whether a 30mA RCD is for additional..or fault protection

so theres no `especially` about it really..is there

Think he means when used within a TN system rather than a TT system, where in most cases in the UK, folk seem to be happy bunging in a short twig with 100 to 200 ohm Ra values...