Ze / PFC conundrum at factory

[Dunc88]

How did you get 40ka when if using nominal 230 volts
230volt/ 0.01=23000amps 23ka?

I divided 400v instead of 230v! well spotted!

 

[Ian1981]

I divided 400v instead of 230v! well spotted!

If it's 3 phase then it could be more like 40ka as you would do a pssc between live and neutral and double it or if your meter allows test between phases.

 

[Dunc88]

True, thanks for the help all. I'll be going back next week to finish off. One more thing (i'll try not to make it sound too confusing), i'm carrying out an installation cert (see the consumer unit layout below)
Consumer unit @ origin (4way tp) > (feeding) DB 1, & DB 2 (via 2x D63a mcbs)
-DB1 feeds new circuit 1 out of 2.
DB 2 > DB 3 & 4 (via C63a mcb) *this 4x16mm swa "piggy backs" in & out of DB3's main switch before entering DB4 (perfectly acceptable I presume but not something i've seen before?)
-DB3 feeds new circuit 2 of 2.
My main question is, with the continuation sheets I currently total 12 pages, this is because the only consumer unit I havent worked on is DB4, so I was hoping not to have to record any readings at this consumer unit & to make a note in comments instead saying "DB4 not tested" but in all honesty, because the supply from DB2 ends @ DB4 (piggy backed into main switch @ DB3) this is where I should record another ZS on a seperate continuation just to segregate the 2 boards, would you agree? If DB3 fed DB4 via a circuit breaker, could I then write on the circuit details of DB3;
Circuit details for new circuit installed & then
"all other circuits not tested"?
Sorry to ramble on!

 

[Wilko]

If I've understood correctly... it's a new supply to DB4 but no changes in DB4. If so, perhaps an update to the DB4 details showing the new Zdb ?

 

[westward10]

No way I would "piggy back" one board from another.

 

[Dunc88]

If I've understood correctly... it's a new supply to DB4 but no changes in DB4. If so, perhaps an update to the DB4 details showing the new Zdb ?

Yeah i'll go with that so you can see all consumer units are on certificates for the sake of the install, wont hurt for future reference either. I suppose in even bigger installations where there are multiple DB's not associated with one you are installing a new circuit in, it's acceptable not to include these in your installation cert providing the one worked on has certs right back to the origin?

 

[Dunc88]

No way I would "piggy back" one board from another.

I've asked a couple of people about this as it didnt look right to me & i'd never seen it before & they seemed to think it was perfectly acceptable. Seems a very lazy/odd way to do it as DB3 & 4 arent too far away from each other & DB3 has plenty of space in it! Frustrating coming across things like this that you havent had anything to do with but thats how it goes sometimes (/most the time!!)

 

[Risteard]

A type 2 bs 1361 for example has a typical ka rating of 33ka so I think it will.
Like I've said manufacturers should be consulted if back up protection is used

The 33kA is for the fuse - not what the distribution board assembly is conditionally rated to owing to Annex Zb (previously Annex Za).

 

[Ian1981]

The 33kA is for the fuse - not what the distribution board assembly is conditionally rated to owing to Annex Zb (previously Annex Za).

We are not talking about domestic installations
Were it's highly unlikely to see such fault currents