TT RCD
- Thread starter Oxia
- Start date
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Yes you can - Is the 100mA RCD also the main switch for CU though?
It was the main switch but I was going to replace it with a 100A isolator.
Not only 'yes you can' (provided that all the final circuits are RCBO-protected) but, at least theoretically, 'yes you must' if (as is probably the case) they are SP RCBOs. An N-E fault on any of the final circuits won't be cleared by a SP RCBO, and therefore will 'take out' any up-front RCD, even if it's time-delayed, hence killing the entire installation - which is technically non-compliant with current regs.
Kind Regards, John
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Carry on then - You don't say what size the DNO fuse is but if its 100A you should upgrade your meter tails to 25mm ²?
Sorry but I should have said from the start this is a question about a TT'd shed from a TN-C-S Supplied house.
16mm 2 core XLPE feed.
Then hold everything I have said - since I am confused about your current set up.
Perhaps you could explain exactly what is the electrical set up you have now or plan to introduce? Include the devices at the home CU and those at the shed CU.
Also how you have connected one to the other - Split tails - Henley block maybe/hopefully.
From the house there is a 10mm twin and earth coming from our CU via a 50a MCB, this goes in to a sarel plastic enclosure (all this was there when we moved in)
From there we needed a run 60m away to our large shed to supply sockets and lights. We ran this in 2 core armoured protected by a double pole 32A MCB. and TT'd it at the shed end (at no point exporting the earth from the house)
Shed has 6 way consumer unit with 100ma rcd up front and all rcbo circuits.
Hope this helps?
I was advised that I should not export the earth from my house and to TT it at the shed. Plastic water pipes and timber frame.
Is that 50A MCB circuit protected by an RCD in the house CU? If so, your original question would obviously become a bit moot.
Kind Regards, John
The house has all RCBOs and the circuit in question is just an MCB
Fair enough. I take it that you mean 'all RCBOs' apart from this one MCB. In that case, the RCBOs in yoiu shed would obviously be effectively the same (functionally) as the up-front RCD in any TT system.
Kind Regards, John
Yes, All RCBOs exept one MCB. So I can do away with the RCD? I was told that I would need a 100 or 300ma RCD to protect from fire?
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