design change

[daveygh]

Hi all i'll try to keep it brief

I'm working on a site that is using an existing gym and changing it to site offices. The building is having a new 400A supply bought in by EDF to feed new boards + existing power etc. The consultant has done his design on a TNC-S supply but EDF are saying that they wont supply an earth because it is only a temporary supply ( 5 years) and we have to put our own earth rod in, the original design had a 48 way tp&n board and all the sockets on rcbo's but lighting and security spurs etc on normal mcb's - should this board now have a 100ma rcd main switch as the supply is now TT?

there is also a heating board that all circuits are mcb's - should this now have an rcd main switch or individual rcbo's?

also the existing boards and mechanical panels that we are re-feeding haven't got rcd protection so will we need to change this? (they are fed off an existing 100A supply that will be made redundant once the new supply is in)

appreciate your imput

 

[sparkytim]

Most likely ALL circuitS will require Rcd protection, so it seems you will have to provide RCBOs or RCDs where only MCBs were specified on TNS.

 

[Evans Electric]

Since when has 5 years been a temporary supply :C Can't the engineer challenge them on that . I thought all commercial/ industrial supplies were TPN+E .

Also check the need for Rcbo /RCD for commercial premises whose elects are serviced by competent people.

 

[Andy™]

Since when has 5 years been a temporary supply :C Can't the engineer challenge them on that . I thought all commercial/ industrial supplies were TPN+E . Also check the need for Rcbo /RCD for commercial premises whose elects are serviced by competent people.

TT needs RCD'd regardless of competent person on site or not

 

[Evans Electric]

Ah yes, I meant if the supply was TN-S or TNC-S Andy . I don't understand why they class it as temporary . Is it a Builder's supply or what ?

 

[Andy™]

no idea why the 'temporary' part either

 

[daveygh]

thats what we cant understand - the offices are going to be in use by 100+ people for at least 5 years so i dont see it as temporary but that is the excuse that EDF have given

 

[wozz]

any excuse is good enough for the edf!

i thought TT 3ph supplies were a pain as the first enclosure has to be plastic.

 

[wozz]

out of interest which project is this?

 

[batty]

Not going to be easy to comply with 17th if you only have one RCD for whole site. Seems mad they won't provide earth.