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dineshpandit80
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Join Date: Mar 2009
Location: delhi india
Posts: 79
Good Answers: 2

mccb

03/16/2009 5:07 AM

hi all

i am using a 100 A mccb but requirment of 32A Mcb can any one tell me what will be it drawback
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JRaef
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United States - Member - New Member Engineering Fields - Power Engineering - New Member

Join Date: Sep 2006
Location: California, USA, where the Godless live next door to God.
Posts: 4665
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#1

Re: mccb

03/16/2009 5:33 AM

When your load current reaches 33A, whatever the 32A MCB was supposed to protect will begin to overheat, eventually catching on fire probably long before the 100A MCCB will trip.

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dineshpandit80
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Join Date: Mar 2009
Location: delhi india
Posts: 79
Good Answers: 2
#2
In reply to #1

Re: mccb

03/16/2009 5:42 AM

cant understand

i want to know can i use 100A mccb instead of 32A although i know load current is not more than 25A
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ramvinod
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Join Date: Jun 2007
Location: chennai,India
Posts: 592
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#3
In reply to #2

Re: mccb

03/16/2009 5:46 AM

You can use 100 A MCCB but this will not protect your devices for over load beyond 25 A.This MCCB will have normal thermal settings 0f 80-100%.Therefore for any current beyond 80 amps only this MCCB will trip and isolate the circuit.

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dineshpandit80
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Join Date: Mar 2009
Location: delhi india
Posts: 79
Good Answers: 2
#4
In reply to #3

Re: mccb

03/16/2009 6:29 AM

what will happen at time of short circuit . as i know current will be very large at time of short ckt
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PWSlack
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United Kingdom - Member - Indeterminate Engineering Fields - Control Engineering - New Member

Join Date: Jan 2007
Location: In the bothy, 7 chains down the line from Dodman's Lane level crossing, in the nation formerly known as Great Britain. Kettle's on.
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#5
In reply to #4

Re: mccb

03/16/2009 6:37 AM

Either the 25A device, or the cable feeding it (whichever has the lower rating), will go BANG!

Last out the building is a cissy...

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lyn
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Join Date: Oct 2008
Posts: 42355
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#6
In reply to #4

Re: mccb

03/16/2009 9:19 AM

You will then have the opportunity to design and install a proper circuit, assuming the building is still there.
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CJMcGill
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Join Date: Jul 2008
Location: SoCal USA
Posts: 556
Good Answers: 23
#7

Re: mccb

03/16/2009 6:34 PM

Actually, a short circuit might well trip the 100A MCCB, but there will be no protection from overloading and burning up the 25A load. CJM

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CJMcGill (1); dineshpandit80 (2); JRaef (1); lyn (1); PWSlack (1); ramvinod (1)

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