APPENDIX 1: Correction Factors for Sizing of Cable Conductors (1) Correction factors for ambient temperature Table 1: Correction factors for ambient temperature Note: Ths table applies where the associated overcurrent protective device is intended to provide shor circuit protection only. Where the device is @ semi-enclosed fuse to BS3036 the table also apples wnere the device is intended to provide overload protection Type of insulation FOBELBINY Timbo Tempera fromperatwre| 25 | 0] 35 [a0 [as 50 [55 | oo | os | 70] 75] o0 | 5 | 00 [95 Tar (flexible cables | 60% |1.04] 1.0 fost }osz}o71| 058 | oat font) _} ____ } |__| _} |__| __} }__} |__| Sora prose] Love | OO Jt 10 fo ee fer fore ors post | 05 joel || | TN CR dO OO Tear ousng [ewe —[os] to oar osefosr/aer for [ors foreoorpas [ose [Oss Pvcrss'cigo"c [soe os [ore forrfosr| os Tremonotna | gi mae | ave fo ofalafoerfon]o=]or fos] es] os fon [em] | TOE [res] 0 [oss oes|or"| a7 | sv [aus [oat Mineral: cL | a — 156 [rez] 10 [oss |osz|oes| oss | 08 [ors| 07 [oes| os [os |oar| om [oasl ‘Table 2: Correction factors for ambient temperature where the overload protective device is a semi- enclosed fuse to BS3036 “Type of | Operating | “Ambient Temperature insulation emperature| 25.90/36 [40 [45 [50 [5560 | 65 [70 [75 [90 | @5 | 90 | 95 Rubber (flexible cables | 60°C —_|1.04| 1 [0.96 0.91 |0.87 [0.79 0.56) ony “General punted, | 7’ |1.03/1 las7/ospe1pa7 pss)oss| 04s Paper | 80" [02/1 [o97.s|092|o90 0er|oes| 076 omzloaa| | I I Rubber | as’ [s.02|¥ .97/095(0.99/0.01/o.08)0.06) 089 (071 0.58[0.41| I I Heat resisting | 65°C _[1.03/1 [097 0.94|0.91)047 0.e4|000| 0.76 072/0.68|049/ 049 | [ pvcresroro'c| “oor | | | | | || oes) I Thermoseting | gop "ene go’ |1.02/1 |o.98|0.95 0930.91 \0.89)0.7| 085 .72|0.9|058| 0.39 Mineral Bare and exposed to| 70° and exposed to) 70°C /1.03/1 /0.96)0.93/0.89/0.86|0.790.82| 0.42 covered Bare and rot || 495% exposed to | 05% |1.02|1 [0.9810.98|0.93/0.91)0.89|0.88| 084 foe2p.79|077| 064 055 043, touch Note :Correction factors for flexible cords and for 85°C or 150°C rubber insulated flexible cables are given in the relevant table of ‘current carrying capacity in BS 7671 “These factors are applicable only to ratings in columns 2 to 5 Table 1 of Appendix 2. WF S.GH. Electric Wire & Cable Co., Ltd, V2.0 1(2) Correction factors for groups of cables Table (3): Correction factors for groups of more than one circuit of single-core cables, or more than ‘one multicore cable Torecton Factor Reference Method of Installation (See Appendix7) Number of Creuls or Mulleore Cables 2 “[s(s[7 [ele lolz[ fey] 2 Enclosed (Metiod S oF 4) or bunched and elpped ° closed (Metnad 3 or 4) or bunched and cipped | 9 | 9.70 [a.68}0.60)9.670.54|0.82)0.50[0.48)0.45[0.43|0.41)0.39| 0.38 Single ayer Touching Das [ore [o7s[07s[o72 [072 [0.73 [0.70 clipped to a non- — metallic Spaced 0.96 | 0.99 |o.99}0.90}o.20]0.20}0.99/0.20]0.20]0.90|0.90/0.20)0.90] 0.90 surface,(Mathod ‘Single layer Touching 086 [oar fo.r7|o7a[or4lo7a|arajo72[071[07 multicore on a perforated matal cable tray, vertical oF Spaced 0.91 0.89 |o.sslo.s7)o.s7| hovizontal(Method ‘4 L || Sil layer sie Horizontal 0.90 [0.85 perforated metal TI cable tay, 5 touching(Method Verical 085 a1) = ‘Single layor mallcore touching on ladder supports Manet 0.8 [0.82 | 0 [o.79)o.78)0.7al0.7a)0.77| Notes to Tables (2) 1, The factors in the table are applicable to groups of cables of one size only. The value of currant derived from application of the appropriate factors is the maximum continuous current to be carried by any ofthe cables in the group 2. f-due to known operating conditions, a cable is expected to carry not more than 30% of ts grouped rating, it may be ignored for the purpose of obtaining the rating factor fr the rest ofthe group. 3. Whan cables having different conductor operating temperatures are grouped together, the current rating should be based upon the lowest operating temperature of any cable in the group. (3) Correction factors for cables enclosed in thermal insulating material For a cable installed in a thermally insulated wall or above a thermally insulated ceiling, the cable being in contact with a thermally conductive surface on one side, current carrying capacities are tabulated in Appendix 2, Method 4 of Appendix 3 being the appropriate Reference method. Fora single cable likely to be totally surrounded by thermally insulating material over a length of more than (0.5m, the current carrying capacity shall be taken, in the absence of more precise information, as 0.5 times the current carrying capacity for that cable clipped direct to a surface and open (Reference Method 1 of Appendix 3), Where a cable is to be totally surrounded by thermal insulation for less than 0.5 m the current carrying capacity of the cable shall be reduced appropriately depending on the size of cable, length in Table 4 are appropriate to conductor size up to 10 mmsq in thermal insulation having a thermal conductivity greater than 0.0625 WIK.m, ‘Table 4: Cable surrounded by thermal insulation Tength in insulation derating factor mm. 30, 0.89 7100, O81 200, 0.68 400 0.55 WH S.G.H. Electric Wire & Cable Co,, Ltd, V2.0(4) Correction factors for the type of protective devices protecting the cable ‘Table 5: Correction Factors of Type of Protective Devices Type of Protective Device ‘Semi-enclosed fuse to BS 3036 0725 5. Correction factors for cables installed in enclosed trenches Table 6: Correction factors for cable installed in enclosed trenches (Installation Methods 18, 19 and 20 for Appendix 3) The correction factors tabulated below relate to the disposition of cables illustrated in items 18 to 20 of Appendix 3 and are applicable to the current carrying capacities for installation methods 12 or 13 of Appendix 3.as given in the tables of Appendix 2: Correction Factors Installation Method 16 Installation Method 13 [nstallaton Method 20, [Conductorerose-sectonatarea [2 [2 JB __]Bsingle- [Bsingie- [f2engle-|'2 single- [ie single [24 angie lsingle- |single- |single- [single- feore core feore core feare core loore Jeore|eorefeore feables, 4 ables, or leabies, 8 |cables, 8 cables, 12\cabies, lcables, cables, [cabes, leabies, two-core [4 three-or two-core ftwo-core fwo-core ftwo-core lort'lor2lor2 ft wo- Jeables, or four-core feabies, or cables, or feabies, or leabies, or leee- |iwo- fires feore [3 twee- orfcabies [6 three-or [6 tnee-or [0 three-or|12 three- jor tour-Jcare for four- ables, flour-core four-core ftour-core four-core for four- lcore cables |eore ors feables lcabies feables cables foore Jcable lcabies |tvee- lcabies lr tour lcabies 4 092 | oa [or |oez| oes | oes | ove | om | o74 | 009 é 092 [ose [oes [oa | oes | oa2 | ove | 08 | o73 | 000 10 cet | oas [oss | os | oss | o8 | o74 | 078 | 072 | 006 6 091 [oar [oe [ove| oes | ove | o71 | ove | o7 | 00a 25 09 | 086 | oa2 | ore | oar | ove | osa | ove | o47 | 0.2 38 oa9 [oes fos: [o7s| o# | o74 | ons | o72 | 00 | 08 50 ae [oes [ore [ora | ove | ova | oss | om | oe | on 70 oa7 | 082 | ore |o72| or | o72 | os | o7 | 062 | 087 5 as [oar fore | or | os | o7 | os | 008 | 08 | 088 120 as | os | o7s|ose| o7s | oss | 061 | 066 | 058 | 083 160 oes | ova [ors [osr | o72 | or | 05a | 064 | 057 | om 185 a3 | o77 [ors [os| o7 | oss | 058 | 063 | 055 | 049 240 a2 [ove [ori [oes | ooo | oss | oss | on | 053 | 048 300 ai | ova [oes | os2| ose | ose | os | 080 | 082 | 048 400 0a [073 [oar | ose | os | os | 052 | os7 | 05 | oa ‘500 ove [072 [oss [ose| oo | ose | 051 | 056 | o4@ | 049 630 o77 | 071 [oss [056 | oss | os7 | 04a | os | o47 | ot * When cables having different conductor operating temperatures are grouped together the current rating should be based on the lowast operating temperature of any cable inthe group. WH S.G.H. Electric Wire & Cable Co,, Ltd, V2.0 3