main switch question

[spark 68]

an mccb main switch then mcb's or mccb's feeding sub boards.

when the shower/sockets/lights trip it doesnt trip every other mcb does it, same thing

Depends on the magnitude of the fault on the sub-DB circuit Shanky, with MCBs you only get partial discrimination at best, as Davesparks pointed out earlier HRC fuses > MCBs provide better discrimination.

 

[shanky887614]

Depends on the magnitude of the fault on the sub-DB circuit Shanky, with MCBs you only get partial discrimination at best, as Davesparks pointed out earlier HRC fuses > MCBs provide better discrimination.

Depends on the magnitude of the fault on the sub-DB circuit Shanky, with MCBs you only get partial discrimination at best, as Davesparks pointed out earlier HRC fuses > MCBs provide better discrimination.

what im saying though is the intake would be into a mainswitch that wouldnt trip then wither mcb's,mccb's idealy for each board.

they are all split off from the same point so how can the others trip honestly.

if the supply to all three was fed from the same mcb etc i could understand where you are coming from

 

[spark 68]

what im saying though is the intake would be into a mainswitch that wouldnt trip then wither mcb's,mccb's idealy for each board.

they are all split off from the same point so how can the others trip honestly.

if the supply to all three was fed from the same mcb etc i could understand where you are coming from

I agree with you here ^^, I thought you were talking about feeding the sub-boards from an MCB, my bad :35: lol

 

[shanky887614]

I agree with you here ^^, I thought you were talking about feeding the sub-boards from an MCB, my bad :35: lol

no, meter - main switch - x3 mcb's/whatever

thats just asking for trouble

 

[davesparks]

fair enough but im sure you can still buy bs88 boards.

or mccb's

Yes BS88 boards are still available and have their place in installations. MEM excel boards spring to mind, but they don't have main switches so would put us back at square 1

 

[davesparks]

an mccb main switch then mcb's or mccb's feeding sub boards.

when the shower/sockets/lights trip it doesnt trip every other mcb does it, same thing

No it's not the same thing, you suggested installing a DB and feeding sub mains from MCBs in that DB.
That puts the final circuit MCBs on series with the distribution circuit MCB, this will may not discriminate in the event of a fault on the final circuit.

 

[spark 68]

No it's not the same thing, you suggested installing a DB and feeding sub mains from MCBs in that DB.
That puts the final circuit MCBs on series with the distribution circuit MCB, this will may not discriminate in the event of a fault on the final circuit.

That is what I thought I was replying to earlier, tis Friday night though

 

[davesparks]

You were indeed replying to that, it's post 9 where he said it.

 

[shanky887614]

i wouldn't use either i would use an rccb mainswitch like i was given and told to do on the last job XD

 

[paulthemagpie]

the installation is a 3 phase incoming, however only one the phases used which goes into a henly block then splits into 3.

so best practise would be to place the isolator before the henly block so the main switch covers the whole installtion.

oh and they reasons why the main switch cant be a RCD switch.

 

[Octopus]

the installation is a 3 phase incoming, however only one the phases used which goes into a henly block then splits into 3.

so best practise would be to place the isolator before the henly block so the main switch covers the whole installtion.

oh and they reasons why the main switch cant be a RCD switch.

Do you really need to ask this??

 

[paulthemagpie]

Do you really need to ask this??

do you realy need to ask that?

 

[Plonker 3]

Read 314.1 in the BGB then have a think why you shouldn't fit a RCD main switch on a TN system.

 

[Leesparkykent]

do you realy need to ask that?

Why not?

 

[paulthemagpie]

Read 314.1 in the BGB then have a think why you shouldn't fit a RCD main switch on a TN system.

potentially if we had nuisance triping it could be a killer for this type of business. so rcd protection as a main switch is a no no. RCBO protection for socket circuits is needed so only that circuit in question would disconnect instead of whole supply