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 Topic Title: IEE Wiring Regulation - Grouping factor Topic Summary: Created On: 12 May 2013 06:28 AM Status: Post and Reply Linear : Threading : Single : Branch
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 12 May 2013 06:28 AM tonychu1 Posts: 2 Joined: 19 November 2012 Based on the IEE 17th Appendix 4 Table 4C1 Note1 Should Grouping Factor (no. of cct=2) be applied to a single phase circuit design with two identical single-core live & neutral conductors connected in parallel? Edited: 12 May 2013 at 06:37 AM by tonychu1 12 May 2013 08:21 AM aligarjon Posts: 3291 Joined: 09 September 2005 grouping is based on the number of circuits not conductors. Gary ------------------------- Specialised Subject. The Bleedin Obvious. John Cleese 12 May 2013 08:36 AM Christof Posts: 16 Joined: 20 April 2013 Originally posted by: tonychu1 Based on the IEE 17th Appendix 4 Table 4C1 Note1 Should Grouping Factor (no. of cct=2) be applied to a single phase circuit design with two identical single-core live & neutral conductors connected in parallel? Grouping factor's need to be applied for Parallel Cables. Chris 12 May 2013 05:43 PM ebee Posts: 5982 Joined: 02 December 2004 Originally posted by: aligarjon grouping is based on the number of circuits not conductors. Gary Surely not? ------------------------- Regards, Ebee (M I S P N)Knotted cables cause Lumpy Lektrik 13 May 2013 01:39 PM AJJewsbury Posts: 13134 Joined: 13 August 2003 Surely not? I would have thought it was - it's all down to heat - 2 sets of cables carrying 30A each will produce the same amount of heat whether they're connected to two 30A fuses or one 60A one. As I see it the phrase "one circuit" of singles in appendix 4 context is just a shorthand for whatever the arrangement of conductors you assumed when looking up the cable's tabulated CCC - e.g. two live conductors for a single phase circuit or three lines, or three lines plus one neutral, for a three-phase circuit. - Andy. 13 May 2013 01:49 PM OMS Posts: 20647 Joined: 23 March 2004 Perhaps a read through notes 3, 4 and 5 will clarify. Worth also a look at 2.3 et seq - particularly the note to 2.3.1 and 2.3.3 regards OMS ------------------------- Let the wind blow you, across a big floor. 13 May 2013 02:17 PM Parsley Posts: 1254 Joined: 04 November 2004 Note 5 of Table 4C1 "If a group consists of n single-core cables it may either be considered as n/2 circuits of two loaded conductors or n/3 circuits of three loaded conductors." Regards 13 May 2013 04:27 PM broadgage Posts: 1650 Joined: 07 August 2007 Originally posted by: aligarjon grouping is based on the number of circuits not conductors. Gary Can not agree. If cables are paralled then they will produce the same heat as they would on individual circuits and therefore both common sense and the intent of the regs would suggest that the same degree of de rating should be applied. I cant see that 4no cables in two paralel pairs would have a greater current carying capacity than the same 4 cables used for 2 seperated circuits. 13 May 2013 10:56 PM aligarjon Posts: 3291 Joined: 09 September 2005 rightly or wrongly i read the OP as a single circuit where the conductors had been double up to get a satisfactory csa so spreading the load equally down both sets of cables. From what you are saying, and i can understand where you are coming from, that would mean you would have to apply a grouping factor to a single 3 phase circuit wired in singles ? Gary ------------------------- Specialised Subject. The Bleedin Obvious. John Cleese 13 May 2013 11:05 PM OMS Posts: 20647 Joined: 23 March 2004 From what you are saying, and i can understand where you are coming from, that would mean you would have to apply a grouping factor to a single 3 phase circuit wired in singles ? How so ? - you'd select from the relevant column of 4D1A fo a 3 phase circuit - which is already derated compared to a single phase circuit. Ie you have 3/3 conductors using note 5 to table 4C1 = 1 so no grouping applied and use the 3 phase CCC If you were installing 2 conductors per phase on that 3 phase circuit, you use the three phase CCC x 2 and derate by 0.8 as it's now grouped. ie 6/3 = 2 circuits grouped applied to the three phase CCC Regards OMS ------------------------- Let the wind blow you, across a big floor. 13 May 2013 11:09 PM aligarjon Posts: 3291 Joined: 09 September 2005 Thanks OMS . as you can probably tell i only tend to do domestic works and do very little calculation work. thanks for the lesson. Gary ------------------------- Specialised Subject. The Bleedin Obvious. John Cleese 13 May 2013 11:13 PM OMS Posts: 20647 Joined: 23 March 2004 My pleasure - now go and decide if the two legs of a ring dropping down the wall are "grouped" Regards OMS ------------------------- Let the wind blow you, across a big floor. 13 May 2013 11:37 PM aligarjon Posts: 3291 Joined: 09 September 2005 i think thats where i got confused because i know they aren't. ------------------------- Specialised Subject. The Bleedin Obvious. John Cleese 14 May 2013 12:01 AM OMS Posts: 20647 Joined: 23 March 2004 Well, that's debatable actually, but yes, we don't treat it as grouped because of current sharing around a ring. For what it's worth, you probably wouldn't consider grouping of ring circuits until you had at least 3 RFC's running together Regards OMS ------------------------- Let the wind blow you, across a big floor.
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