Using MCB's in parallel to give local isolation

[FatBob]

This installation has a very old DNO metal fuse box with a hinged lid, which may or may not open in one piece.
The DNO's meter feeds 2 x 63A MCB's in a 2 slot CU.

Can I feed a Henley block with both line connections from the 2x63A MCB's, thus using it as a local isolation switch?
The 80-100A DNO fuse should blow before the combined MCB's operate, assuming the current is split equally, which is should be.
The Henley block can then feed a normal CU.

Bit unconventional, but trying to think out of the box whilst waiting for DNO to fit local isolation?

 

[RogertheBodger]

Are you sure the DNO seal on the main fuse is there?

I can see from here that it has fallen off.

 

[malcolmsanford]

An MCB and an isolator are two physically different things. Most MCB's aren't rated as isolators.

A BS 60898 here in the UK is rated for for isolation, and emergency and functional switches mate. Are they not recognised as such there in SA ?

 

[johnboy6083]

i would like to add that only a dp mcb can give proper isolation in a 1ph installation

 

[malcolmsanford]

i would like to add that only a dp mcb can give proper isolation in a 1ph installation

True mate if you wish to use it as in reg 537.1.4, for both a TN and TT system.

In a TN system an isolator only need to switch the LINE conductor if the neutral is deemd to be conected to a reliable earth at a suitably low impedance.

 

[FatBob]

True mate if you wish to use it as in reg 537.1.4, for both a TN and TT system.

In a TN system an isolator only need to switch the LINE conductor if the neutral is deemd to be conected to a reliable earth at a suitably low impedance.

537.1.4 A main switch .. shall interrupt both live conductors of a single-phase supply

 

[FatBob]

What about replacing the 2 MCB's with a Mains switch like this TLC hyphen Direct/Products/CM9100.html to feed into the new CU.



Thanks for all the feedback, it is appreciated.

 

[malcolmsanford]

537.1.4 A main switch .. shall interrupt both live conductors of a single-phase supply

"A main linked switch or link circuit breaker"

So you could have a double pole switch, a double pole RCD or a double MCB, agree most domestic CU have a double pole switch 100amp switch, but if you wanted to make a board and use a MCB then you can

 

[FatBob]

Thanks for all the replies. I went with 2 circuits, one off each MCB on the basis that anything else could lead to identification problems. Will change it when DNO eventually calls me back to arrange an isolator and upgrade of the metal fuse casing from the early 18th century.
Still waiting.......
Still waiting.......