Ring main too big??

[Boaky]

I recently tested a doctors surgery and found a number of ring mains
are too large. r1 1.9 rn 1.9 r2 2.7. Zs 1.47 supplied from a type 2 32 amp breaker
could anyone suggest how best to rectify this.
Dont really want involved with the remedials but don't usually refuse work.
any of u guys any suggestions

 

[Knobhead]

You’re just too practical Glenn. Far too easy.

 

[Farmelectrics]

32amp rcbo

 

[GLENNSPARK]

32amp rcbo

its the loading on the ring mate...

and whats the idea of using an RCD device to meet times on a TN?

not on my watch fella...

 

[Farmelectrics]

thought hes concerned about the high zs reading 20a breaker would be better but your not breaking any reqs installing an rcbo which would allow him a reading of 1667 ohms whats up with that

 

[Farmelectrics]

the op dosent mention loading on his opening page just the high zs readings

 

[Deleted member 72666]

A fresh supply of tin hats required!

 

[trev]

the op dosent mention loading on his opening page just the high zs readings

He mentions high readings on the end to ends mate, he then suggests that a 20 amp MCB wouldn't hold therefore the questions regarding loading came up

 

[GLENNSPARK]

thought hes concerned about the high zs reading 20a breaker would be better but your not breaking any reqs installing an rcbo which would allow him a reading of 1667 ohms whats up with that

we know what BS7671 says mate...

but its a load of crap...and needs sortin out....

its a really slovenly way to meet times....

and if the RCD/RCBO fails?

 

[trev]

thought hes concerned about the high zs reading 20a breaker would be better but your not breaking any reqs installing an rcbo which would allow him a reading of 1667 ohms whats up with that

So from that can we assume that you'd achieve 1667 ohms and be happy with that?

 

[Farmelectrics]

not saying id be happy trev would rather investigate but napit and others say in there brochuers that its acceptable to install rcbo to acheive zs readings what req does it break

 

[trev]

I'm not saying it breaks anything that could be used against you in a court, what I am saying is that if anyone seriously thinks that 1667 is an acceptable reading and would happily walk away from it without a second thought then they should not be part of our trade.
Further, Napit and the others don't make the rules.

 

[GLENNSPARK]

not saying id be happy trev would rather investigate but napit and others say in there brochuers that its acceptable to install rcbo to acheive zs readings what req does it break

the long & short of it is that you should never be having to rely on an RCD device on a well designed circuit coming of a TN

and whoever it is at Napit (the land of the plastic 2391)...wants to have a word with themselves....

it needs sortin out does that one in BS7671....

RCDs for fault...:yes

RCDs as a sole measure to meet times on a TN...:no

 

[GLENNSPARK]

So from that can we assume that you'd achieve 1667 ohms and be happy with that?

believe it or not Trev...its taught at college that its acceptable...

really poor....

 

[trev]

believe it or not Trev...its taught at college that its acceptable...

really poor....

Good grief!
Hang on a bit, isn't the 1667 only on TTs?

 

[GLENNSPARK]

Good grief!
Hang on a bit, isn't the 1667 only on TTs?

a typical scenareo given is that a cooker circuit`s value of loop is high..

then the class are asked for suggestions on how to `rectify` this...

using an RCD to meet times is one of the acceptable answers...

pulling in a parrallel G/Y is another...