DB protected by a 63amp RCCB

[pete555]

quick question i have come across a DB wich as recently been installed it is a 12way HAGAR DB with a 63amp RCCB as the isolator

my thought is that this should have been an isolator and RCBO,s fitted were required mainly to avoid problems from nuisance tripping am i right

 

[telectrix]

is it a 30mA or a 100mA delayed?

 

[pete555]

it,s 30 so no problem for final circuit but 12 ways off it seems alot

 

[Jay Sparks]

They should really be split over two/three rcds or better still, all on rcbo,s, to allow for discrimination

 

[Deleted member 26818]

Yes doesn't sound too clever.
Is there any explanation as to why it's been installed in such a manner?

 

[telectrix]

could be a TT system and cheapskate company.

 

[Marvo]

That's a pretty standard domestic installation where I live. If the global IR is okay and there's no history of nuisance tripping I wouldn't see it as a major problem.

 

[Engineer54]

Depending on what these 12 circuits are supplying, this arrangement could well be prone to nuisance tripping. Doesn't take that much of natural leakage on each of those circuits, to get very near to a typical tripping level of a 30mA RCD!!

 

[pete555]

The installation is a modular building pre wired by the company for a school

it supplies lighting and skts usual stuff but quite alot of IT

i raised the problem on the EICR as a code 3 bur the client thinks it is not a safety issue there probably right but this building is seperate to the main school and as no E/M lighting could be a H+S issue which to me is safety

 

[Marvo]

Hmmm, maybe the lack of E/M lighting would be a safety issue but I wouldn't see the RCD used as a main isolator to be a safety issue as such. Suppose it might be a gray area and worthy of a warning note if there's a lot of IT equipment which is notoriously leaky at the best of times.

 

[Jay Sparks]

The installation is a modular building pre wired by the company for a school

it supplies lighting and skts usual stuff but quite alot of IT

i raised the problem on the EICR as a code 3 bur the client thinks it is not a safety issue there probably right but this building is seperate to the main school and as no E/M lighting could be a H+S issue which to me is safety[/QUO

You shouldnt have more than 3 IT stations (PC, Printer etc) on one rcd because each IT station has an earth leakage of around 8mA, which should cause nuesance tripping.

Well, this is how I was always tought.

Jay

 

[pete555]

The installation is a modular building pre wired by the company for a school

it supplies lighting and skts usual stuff but quite alot of IT

i raised the problem on the EICR as a code 3 bur the client thinks it is not a safety issue there probably right but this building is seperate to the main school and as no E/M lighting could be a H+S issue which to me is safety[/QUO

You shouldnt have more than 3 IT stations (PC, Printer etc) on one rcd because each IT station has an earth leakage of around 8mA, which should cause the a tripping nuesance.

Jay

totally agree client local authority got no money to upgrade so make excuses

 

[Darkwood]

Had a local school up here with similar issue but much larger scale... submains 315amp was protected by 150mA monitors ...off the submains were many classrooms including offices and lighting and a few times a week after a company had upgraded 2 classrooms to IT suites half the school kept losing power.. i worked their often and knew the cause and told the caretaker before they did the job the error of their ways ....he had the company in and me in a meeting with the clark of jerks who had overviewed their work... i explained all that was needed was to take the monitors out as it was a swa submains supply it was on and all the sub-submains of this board had their own 30mA rcd front end....
Clark of jerks had to have too meetings with council before he agreed with me that they were not necessary at front end and due to changing earth leakage trends it was wise option..... 3weeks later before i could uncouple the leakage monitors a 30second job.....

I brought it up with clark of jerks prior to job mentioned it to the company doing the work and was blanked ... Karma is nice served in a hot cup !!!!!!! .... Their are the pen pushing interference squad and their are those on the front line who really know their job :smart:

 

[Darkwood]

Where IT classes are in schools i now always if possible have a locked built up fuse board with IS units for protection within the classroom these filter designed leakage and look for fault leakage so you still achieve 30mA protection but can have 10 + stations per circuit as oppose to max 5-6 stations... never had an issue and OP had obviously come across a poor design and would be best to right a seperate report to be issued to local council or Electrical Clark of Works for the area.

 

[pete555]

is it all about money now and stuff our knowledge which they ask us for and then ignore it

i think it,s time to leave this poor country