mk mcb

[georges]

after some advice will new mk mcb fit in old mk Ln type 2 board ?

 

[D Skelton]

No, is the short answer. It will fit in the board, on the DIN rail and be in line with the rest, however you'll have to bodge the busbar. When I've fitted new MK breakers to old MK boards, I've chopped out the busbar prong where the new breaker is to sit and linked from the main switch to it using a short length of 16mm/25mm single core cable depending on the main fuse rating.

 

[johnboy6083]

As a side note, it doesnt have to be a 16/25mm cable, you can use the principle of backfusing to size the feed to the MCB. I ofetn have to do this, in old panels, if there is no busbar, and i need a new way creating. So if the MCB is a 32A, then id use at least 4mm2. To be honest i usually use a bit of 6mm if ive got it about. The next electrician should look at the board before he decides to lump a new breaker in and rely on your link.

 

[D Skelton]

As a side note, it doesnt have to be a 16/25mm cable, you can use the principle of backfusing to size the feed to the MCB.

I can see the idea there, I just don't like the idea of protecting a 4mm cable with a 100A main fuse. What happens if over time, the connection becomes loose for whatever reason, then that cable will start a fire long before the main fuse even realises what is going on! Whenever I change a CU I always carry out a free first check a year after installation and you'd be surprised how many times I've had to tighten really loose connections after only a year of use due to expansion/contraction of copper terminations when heated and cooled.

Like I said, I can see your logic, but I personally wouldn't feel comfortable doing it that way.

 

[somersetsparks]

As johnboy says, its common practise, I had a spark who failed al load of I&T 's on extractor fans spurred from ring in 1.0mm. They went 4' in mini trunk before being fused down - I passed them to the customers delight!

 

[georges]

As johnboy says, its common practise, I had a spark who failed al load of I&T 's on extractor fans spurred from ring in 1.0mm. They went 4' in mini trunk before being fused down - I passed them to the customers delight!

thanks for the advice much appreicated

 

[steveberry11]

MK used to make a retro fit kit for this problem. I think that these may not be made any more.

 

[georges]

thanks steveberry11 I will ask the question cos you never know

 

[PC Electrics]

I've got some MK LN59xx type MCBs, even a 32A LN RCBO!. PM if you want to trade.