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Topic Title: BS 7671, IEC - Breaker and Cable Sizing
Topic Summary: IEC MCCB
Created On: 16 May 2018 11:58 AM
Status: Read Only
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 16 May 2018 11:58 AM
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Selk

Posts: 15
Joined: 21 April 2018

How to size the conductor & breaker for group of motors/mixed loads using IEC standards. (for example in NEC, the article 430.24 & 430.62 is used); I did a google search and all I could find is to use a type -2 co-ordination chart for single motors and I could not find anything for breaker sizing of feeders
 16 May 2018 12:50 PM
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AJJewsbury

Posts: 17169
Joined: 13 August 2003

BS 7671 doesn't specify any particular method for sizing distribution circuits - rather it's up to the designer to consider the design load (possibly thermal equivalent current), starting currents and duty cycles, diversity on so on - all according to the particular conditions of the installation. I'm sure some here could give you some rules of thumb, and some guidance documents provide some (often conservative) diversity values for some common domestic and commercial situations, but ultimately it's down to the designer's understanding of the installation, the load equipment and now it's likely to be used.
- Andy.
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