.. :: Ghazala Cables

Current Ratings

There are three main installation conditions that affect the current rating of a cable as follows:

PERMISSIBLE CONTINUOUS LOADING OF INSULATED WIRES AND CABLES WITH AMBIENT TEMPERATURE UP TO 25°C ACCORDING TO VDE 0100

Nominal cross section	Group 1 One or more single-core wires e.g. NYA in conduit		Group 2 Multi-core wires e.g. non metallic sheathed cables, lead-sheathed cables, flat wires flexible cables		Group 3 Single-core wires installed free in air with a space of at least one diameter between wires as well as in switching and distribution stations
mm 2	A		A		A
	Copper	Aluminum	Copper	Aluminum	Copper	Aluminum
0.75	-	-	13	-	16	-
1	12	-	16	-	20	-
1.5	16	-	20	-	25	-
2.5	21	16	27	21	34	27
4	27	21	36	29	45	35
6	35	27	47	37	57	45
10	48	38	65	51	78	61
16	65	51	87	68	104	82
25	88	69	115	90	137	107
35	110	86	143	112	168	132
50	140	110	178	140	210	165
70	175	-	220	173	260	205
95	210	-	265	210	310	245
120	250	-	310	245	365	285
150	-	-	355	280	415	330

The permissible continuous loading for conductors of 0.5 mm 2 cross-section and for the uses foreseen by the VDE 0100 specifications is : 2A

RATING FACTOR FOR THE AMBIENT TEMPERATURE

PERMISSIBLE CONTINUOUS LOADING OF SINGLE-CORE SHEATHED AND UNSHEATHED CABLES WITH COPPER CONDUCTOR

Nominal Cross Section	Cables bunched and enclosed in conduits or trunking		Cables clipped direct to a surface or on a cable tray bunched and unenclosed		Cables in air

	Current rating	Current rating	Current rating	Current rating	Current rating	Current rating	Current rating
mm 2	A	A	A	A	A	A	A
1	14	12	17	16
1.5	17	14	21	20
2.5	24	21	30	26
4	32	29	40	36
6	41	37	50	45
10	56	52	68	61
16	74	66	90	81
25	97	88	118	106
35	119	106	145	130
50	145	125	175	160	195	195	170
70	185	160	220	200	240	240	210

L	= Distance between cables up to and including 185 mm 2 = 2d
*	Distance between the wall and the surface of the cable ³ 20 mm 2

PERMISSIBLE CONTINUOUS LOADING OF PVC SHEATHED FLAT TWIN AND MULTI-CORE CABLES WITH COPPER CONDUCTORS

(BS 6004)

Nominal Cross Section	Cables bunched and enclosed in conduits or trunking		Cables clipped direct to a surface or on a cable tray bunched and unenclosed
	One twin cable with or without earth-continuity conductor	One three -core cable with or without earth-continuity conductor	One twin cable with or without earth-continuity conductor	One three -core cable with or without earth-continuity conductor
	Current rating	Current rating	Current rating	Current rating
mm 2	A	A	A	A
1	14	12	16	13
1.5	17	16	20	17
2.5	24	21	28	24
4	32	29	36	32
6	40	36	46	40
10	53	49	64	54
16	70	62	85	72

PERMISSIBLE CONTINUOUS LOADING OF PVC SHEATHED TWIN AND MULTI-CORE CABLES WITH COPPER CONDUCTORS

(BS 6004)

Nominal Cross Section	Cables clipped direct to a surface or on a cable tray bunched and unenclosed		Cable in air *
	Twin-core cable	Three or four-core cable
	Current rating	Current rating	Current rating	Current rating
mm 2	A	A	A	A
25	94	82	114	96
35	116	96	139	122
50	140	125	170	145
70	175	155	215	190
* Distance between the wall and the surface of the cable Ê 20 mm

Protection Against Overload Current:

The two requirements which determine the sustained current rating required are:-

Current rating of cable should not be less than the nominal current setting of the device providing protection against, which in turn should not be less than the circuit current.

The overload protection should operate at not more than 1.45 times current rating and not be less than 1.38 times the fuse rating.