TT Query? | on ElectriciansForums

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G

gottahugenoggin

Hi guys
Im currently at collage and new to this,so excuse me if this is a silly question or i dont use the correct terminology......so here goes.

I went to a friends house last night after another friend replaced a surface mount socket back box on the upstairs RFC.
He asked me to pop down with my MFT to check on something he wasn't sure about.
Given the chance to get my tester out,and gain some experience off i went.
His installation is a TT with no RCD protecting any of the circuits.
The RFC was on a 32A MCB wired in 2.5 T+E
The thing that concerns me is the fact that the Zs (measured on my MFT) for the RFC was (from what i can remember) was around 150 ohms giving a PEFC of 2A.

So how can disconnection times be met on a TT with no RCD when protected with a 32A MCB with a earth fault current of only 2A???

Am i missing something here or is it genuinely worrying unsafe situation?

What would be the best way forward from here? Would the best option be to fit an RCD to cover the full CU?

Bearing in mind im am not registered to carry out the work if needed,nor would i feel confident doing so.So am just asking advice to pass onto my friend.

If he chooses to get this sorted it will be by a registered sparky

Thanks in advance........Dave
 
A potentially dangerous situation which you have done well to identify,either convert to a TN system or install a 30ma RCD to cover all as a temp fix....I would not be concerned not being registered,you are obviously competant and this needs urgent attention if you cant get a registered spark in quickly.
 
Last edited by a moderator:
back in the days of the 16th, fitting a 100mA 0r a 30mA RCD front end was the way to achieve disconnection times on a TT system. nowadays, the preferred options are PME if available and/or a dual RCD or RCBO CU.
 
as wirepuller has just stated, you could split the tails and fit an up front RCD as a temporary fix. the installation would then be much safer.
 
Thanks for all the quick replies guys,ill get onto him now to sort it out asap.He said his friends a registered spark so ill speak to him directly to let him know the situation,thanks again.....Dave
 

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