IEC Lighting Panel

[timm333]

I am trying to find an IEC lighting panel with 125A 50kA incomer breaker; and 6-32A outgoing MCB's/RCBO's. But the maximum available incomer is 25KA.

Does anybody know an IEC ligting panel that has 50kA incomer?

 

[ScottyUK]

Merlin-Gerin's Isobar4 range of distribution boards will take an NS series MCCB as the incoming device, good for up to at least 80kA, perhaps 100kA. I'd be really surprised to see that fault level at a sub-distribution board. 50kA is more like what you'd find at the main switchgear - you don't need much cable to really calm things down on an LV system. The typical 35mm^2 or 50mm^2 feeder to a DB really does drop the fault level once it's a few metres long.


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If we learn from our mistakes I'm getting a great education!

 

[timm333]

Thanks ScottyUK, the problem is that Isobar-4c has a maximum conditional bus bar rating 25KA. How about I put a 50 kA BS HBC fuse on the supply side of the main breaker of Isobar-4c. In this way I can use 25kA bus bar with no problems. Please comment.

Also in USA we have lighting contactors up to 12 poles, which means that 12 lighting circuits fitted on one contactor. But I see that Schneider’s lighting contactors in UK have maximum 4 poles only. What is the common practice in UK, is it to use one separate contactor for each lighting circuit, or is it to use 4 lighting circuits on one contactor?

 

[ScottyUK]

Thatr's a slightly different question - you can get an incomer good for 50kA but the board itself is not braced for it!

I'll have a look in my catalogues but I'll be honest - I've not seen a pan assembly braced for 50kA. I'm not sure that the fuse will help - you need to find out what the conditional rating is based upon. My guess is that the type-tested combination of the MCB and MCCB is ok at 25kA because the MCCB contacts will start to lift a little under a heavy through fault and act to limit the fault current, thus affording a degree of protection to the downstream devices.

Lighting contactors frequently switch the incomer of a sub-distribution board.


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If we learn from our mistakes I'm getting a great education!

 

[FreddyNurk]

Merlin Gerin publish cascading tables to evaluate MCB / MCCB combinations, they also publish fuse / MCB and fuse MCCB combinations, though whether you'll get what you're looking for is another thing.

What is also worth considering is that your main board has a prospective fault in the range of 50kA and is probably rated at 1 sec duration. However, for most of those panel boards, they're rated at 25kA for 0.2 sec, which is a little bit different, particularly when you're more reliant on the breaker tripping in time.

Most MCCBs quote very fast trip times, but I'd still be cautious about it. ScottyUK probably has the right approach, see how far away you can mount the lighting panel and go from there.

Incidentally, Merlin Gerin probably isn't the only brand that offers such things, though I'm not familiar with whats offered outside Australia.