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woobster1
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What is the Reason For 16A Type B and 2A Type C MCB Tripping Simultaneously

10/30/2013 11:09 AM

What is the reason for a 16A type B and 2A type C tripping simultaneously. The circuit is 240v with 100m of 2.5mm² cable from 2A type C to where short circuit occurred. Cable length from 16A type B to 2A type B 4m of 6mm.² The 16A type B should be replaced with a type C ?

UK wiring reg graphs for disconnection times have been checked and they are certain it should not occur.

I believe its because maximum fault current occurs quicker in the 16A type B at the same time with maximum fault current in the 2A type C resulting in both tripping simultaneously.

My manager cannot understand why the fault would not occur if a 16A type C fitted.

Any suggestions of a better way of explaining it would be helpful.
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BIN95
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#1

Re: What is reason for 16A type B and 2A Type C MCB tripping simultaneously

10/30/2013 11:23 AM

Is the 2A circuit load part of the 16A circuit load? If so, what is the peak load currently going through the 16A? The results may be what your manager needs to see to convince him to upgrade to type c.

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PWSlack
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#2
In reply to #1

Re: What is reason for 16A type B and 2A Type C MCB tripping simultaneously

10/30/2013 11:30 AM

That would explain it, though the original poster would be better advised to look for the location of the short circuit and prevent its recurrence first. GA

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woobster1
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#4
In reply to #2

Re: What is reason for 16A type B and 2A Type C MCB tripping simultaneously

10/30/2013 2:54 PM

Retraining of technician involved to dead test before cutting cable.
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PWSlack
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#8
In reply to #4

Re: What is reason for 16A type B and 2A Type C MCB tripping simultaneously

10/31/2013 4:22 AM

...before the individual becomes eligible for a Darwin Award? Good idea. Also, have a Permit To Work system in place so that there is due rigour to the assurance of safety before carrying out all work.

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woobster1
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#3
In reply to #1

Re: What is reason for 16A type B and 2A Type C MCB tripping simultaneously

10/30/2013 2:52 PM

Peak load measured 9.5A
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TonyS
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#5

Re: What is the Reason For 16A Type B and 2A Type C MCB Tripping Simultaneously

10/30/2013 5:59 PM

Why is the 2A a type C?

BTW 100M of 2.5 will not meet UK regs for volt drop or disconnection time.

Time for a rethink.

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Wal
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#6

Re: What is the Reason For 16A Type B and 2A Type C MCB Tripping Simultaneously

10/31/2013 2:18 AM

One explanation here.

I think Google will be your best advocate and coach.

What's the ambient (cabinet) temperature at the 16A location?

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PeterKnauf
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#10
In reply to #6

Re: What is the Reason For 16A Type B and 2A Type C MCB Tripping Simultaneously

11/01/2013 2:28 AM

People like us are the objects of google. If we know something about the question, and we share them here, google will provide our answer to people. So, we should never say google has all the answers. Hope you dont take it in a pessimistic way. :)

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Wal
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#11
In reply to #10

Re: What is the Reason For 16A Type B and 2A Type C MCB Tripping Simultaneously

11/01/2013 3:33 AM

Not at all PK.

I totally dig what you are saying.

I wasn't trying to flick the OP off... I did throw in my two bob's worth as well.

The OP said or implied that he needs to convince his boss of what is required and probably even needs to get his own head around the problem too.

When educating my bosses (clients) I find that a third party citation(s) helps to get the point across (advocate) and also helps me to perform solo sanity checks (coach) as well.

Have a good weekend mate.

We've just created yet another object for Google.

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silverfox
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#7

Re: What is the Reason For 16A Type B and 2A Type C MCB Tripping Simultaneously

10/31/2013 3:45 AM

Although it looks as though they should discriminate it sounds as though one of the breakers might have gone off spec. I've seen 100A breakers coming out out at 70A on thermal and RCBOs where the RCBO part didn't work. Oddly enough the same manufacturer. Suggest renewing both MCBs with the same rating and type.
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raghun
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#9

Re: What is the Reason For 16A Type B and 2A Type C MCB Tripping Simultaneously

10/31/2013 12:39 PM

These MCBs have a limit current upto which the coordination is ensured. If the fault current happens to be more than the limit current, both the MCBs tend to operate for a fault downstream.

Vendors generally provide coordination tables for MCBs which will give more specific information.

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BIN95 (1); PeterKnauf (1); PWSlack (2); raghun (1); silverfox (1); TonyS (1); Wal (2); woobster1 (2)

Previous in Forum: How Can A PLC Reset The Actual Value Of An Absolute Encoder Of A Servomotor   Next in Forum: Alternator Voltage Frequency Change

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