tt with no rcd

[plumberjohn]

Doing some work in a local shop. Shopkeeper had inspectio by council and fire officers,resulting in long list of things to fix.

I'been fitting key switches for testing the emergency lights, as well as a few other things.

He asked me to do a pir, but I dont think I'm competent yet. Agreed to have a look and point out any potential problems - all looks fairly good. Re wired and new cu 6 years ago.

However it's a tt system - I measured ze 50 ohm, so not bad- and it's a split load cu with 4 lighting circuits on non rcd side.

Is this ok? Comments please?

 

[Andy™]

so you have been doing work without checking the circuit is safe to modify.... wonder what your MWC says about 'condition of existing installation'

this was caused by a dead short L-E on a TT system. fault current was about 38A, enough to almost burn the place down, but not to blow fuse

this would have been prevented with an RCD

do you still think the shop wiring is 'safe'?

 

[plumberjohn]

Havn't finished yet or done the mwc, but I see what you mean.

The circuit checks out ok, earth continuity, polarity,zs etc all fine, but no rcd

 

[Andy™]

7671 requires all circuits on a TT system to be RCD protected. no exception.

this is basic stuff that you should be aware of

 

[m4tty]

Best get them rcd'd then mate

 

[Andy™]

and i hope the board isnt metallic

 

[plumberjohn]

Andy, didn' see all of your post. Just seen the pics!

No I don't think it's safe, and I think I would put an rcd in somehow, but i've said that I won't do the pir. Was just wondering what you would do?

 

[SPECIAL LOCATION]

I fail to see how your lighting circuits are meeting disconnection times and max permissible Zs without the use of an RCD???

Unless of course you are relying in the gas & water pipes to stay metal for the rest of the installations life??

None of the Zs table in my book are 50ohms+ without the use of RCDs'

Tried reading 411.5 ? 50 red book / 57 green book...?

Or try looking at the pictures in the on site guide..

pages 23 - 26 red pages 28 - 31 green...

 

[Andy™]

for a start, i wouldnt have done any work on the circuit unless RCD was to be installed. if RCD refused, walk.

 

[SPECIAL LOCATION]

[quote name='Andy

 

[plumberjohn]

No.board is wylex plastic. Would this have been compliant when installed under 16th edition?

 

[NozSpark]

So you've modified a fundamentally unsafe circuit and then left it that way:O

To be quite honest you shouldn't have re-energised the circuit without it having RCD protection, just get it done ASAP and take it as a learning experience.

 

[steptoe]

NO,

still required a 100mA front end, or similar,

what are the max Zs permitted to meet the disconnection times?

 

[NozSpark]

No.board is wylex plastic. Would this have been compliant when installed under 16th edition?

NO,

Think about it, you'll never meet the maximum Zs for any circuit with a Ze of 50ohms

 

[SPECIAL LOCATION]

[quote name='Andy

 

[Andy™]

No.board is wylex plastic. Would this have been compliant when installed under 16th edition?

no. and i doubt it would have been under 15th either. or 14th. and probably earlier (although it would have been ELCB that was required a long time ago)

 

[SPECIAL LOCATION]

No.board is wylex plastic. Would this have been compliant when installed under 16th edition?

headbangheadbang:red card

THINK....

how will you meet the fundamental principal of automatic disconnection of the supply before mr shopkeeper is brown bread?

 

[Andy™]

headbangheadbang:red cardTHINK....

how will you meet the fundamental principal of automatic disconnection of the supply before mr shopkeeper is brown bread?

you cant say things like that!

 

[SPECIAL LOCATION]

[quote name='Andy

 

[Evans Electric]

All the shopkeepers are brown where I live , except at ASDA .