code query

[telectrix]

just done a EICR. good installation, approx. 10 years old. 16th ed.split board, lighting circuits non-RCD, on TT earthing. my query is this:
the Zs readings are high, due to the high Ze, insofar as , e.g. lighting circuits on 6A MCB each have a Zs higher than the max. permissible . should I C2 the high Zs readings, or give it a "pass" with a C3? your thoughts, gentlemen (and ladies).

 

[Dave OCD]

I'd C2 that Tel, unusual to find that as back then the split board on a TT install would generally have a 100ma protecting the lighting circuits. It's definitely potentially dangerous as any metal switch or light fitting could have a fair voltage appearing under fault conditions while the MCB thinks about tripping.

 

[HandySparks]

It's not possible to meet the disconnection times required, so definitely C2.

I see Dave has beaten me to it.

 

[Leesparkykent]

Code 2 for me also.

 

[bigspark17]

Is there a main switch s type rcd.? If so then NO code (depending on how high the result is) if no main switch rcd then i would be c2.

 

[telectrix]

I'd C2 that Tel, unusual to find that as back then the split board on a TT install would generally have a 100ma protecting the lighting circuits. It's definitely potentially dangerous as any metal switch or light fitting could have a fair voltage appearing under fault conditions while the MCB thinks about tripping.

yeah, i had to give a C2, if only to cover my back. a solution would be to replace the 2 6A MCBs with RCBOs. saves the cost of a new CU.

 

[telectrix]

thanks, lads, nice to have my thoughts confirmed. with a pefc of only 16A, those MCBs would be slow to trip.

 

[Hellmooth]

C2, would think they would have installed an RCD main switch.

 

[Octopus]

Do you think they will make any improvements?

 

[telectrix]

it's a landlord. he might go for the RCBO solution. i'll be back in a few days to replace a busted shower pull switch so i can give him a price. it's then up to him.

 

[bigspark17]

What else is on the non rcd side? Why not install main switch rcd s type instead of 2x rcbos?

 

[Dave OCD]

What else is on the non rcd side? Why not install main switch rcd s type instead of 2x rcbos?

You can't do an upgrade albeit an improvement that would still not comply with the current regs, after all there are bound to be bathroom lights & switch wires in walls at less than 50mm depth that now require 30ma ?!

 

[Risteard]

Is there a main switch s type rcd.? If so then NO code (depending on how high the result is) if no main switch rcd then i would be c2.

You MUST code missing 30mA additional protection where it is now required. But absolutely if there is no means of achieving earth fault protection then the installation has a potentially dangerous defect so C3 would be wholly inappropriate for that.

 

[telectrix]

What else is on the non rcd side? Why not install main switch rcd s type instead of 2x rcbos?

on the non-RCD side are 3 MCBs. 2 lights and 1 smokes. there's small reason to have 2 lighting circuits as its a 1 bed flat, all on 1 floor. i'm going to suggest 2 x 30mA RCBOs and maybe piggy back the smokes from 1 of the light circuits. this will also make the buried cables compliant and the lack of RCD protection for bathroom fan and lights ( shower is on RCD side, and supp bonding in place, so I gave that bit a C3 ).

 

[Midwest]

Would those RCBO's need to be DP or switched N. I only ask (and not trying to be clever) because of this debate some while ago;

TT systems and RCBO's - http://www.electriciansforums.co.uk/threads/tt-systems-and-rcbos.110727/