Chapter N

Characteristics of particular sources and loads


Other lamp technologies - choice of circuit breaker

From Electrical Installation Guide
HomeCharacteristics of particular sources and loadsLighting circuitsOther lamp technologies - choice of circuit breaker

For LED lamps, see LED lamps - choice of circuit breaker.

Fig. N72 below indicates the maximum number of lamps according to the circuit breaker rating, for C-curve circuit breakers

  • for B-curve circuit breakers, the number of lamps should be reduced by 50%,
  • for D-curve circuit breakers, the number of lamps should be increased by 50%.
Fig. N72 – Maximum number of lamps according to the circuit breaker rating and curve, for other technologies than LED
Products Circuit breaker (C curve)
Type of lamp 10 A 16 A 25 A 40 A 63 A
Standard incandescent lamps, LV halogen lamps, replacement mercury vapor lamps (without ballast)
40 W 28 46 70 140 207
60 W 23 36 55 103 152
75 W 29 31 46 80 121
100 W 15 23 33 60 88
ELV 12 or 24 V halogen lamps
Ferromagnetic transformer 20 W 11 19 27 50 75
50 W 8 12 19 33 51
75 W 7 10 14 27 43
100 W 5 8 10 22 33
Electronic transformer 20 W 47 74 108 220 333
50 W 19 31 47 92 137
75 W 15 24 34 64 94
100 W 12 20 26 51 73
Fluorescent tubes with starter and ferromagnetic ballast
1 tube without compensation[a] 15 W 16 26 37 85 121
18 W 16 26 37 85 121
20 W 16 26 37 85 121
36 W 15 24 34 72 108
40 W 15 24 34 72 108
58 W 9 15 21 43 68
65 W 9 15 21 43 68
80 W 8 12 19 36 58
115 W 6 9 12 24 38
1 tube with parallel compensation[b] 15 W 5 µF 11 19 24 48 72
18 W 5 µF 11 19 24 48 72
20 W 5 µF 11 19 24 48 72
36 W 5 µF 11 19 24 48 72
40 W 5 µF 11 19 24 48 72
58 W 7 µF 8 12 19 36 51
65 W 7 µF 8 12 19 36 51
80 W 7 µF 8 12 19 36 51
115 W 16 µF 4 7 9 17 24
2 or 4 tubes with series compensation 2 x 18 W 23 36 56 96 148
4 x 18 W 12 20 29 52 82
2 x 36 W 12 20 29 52 82
2 x 58 W 8 12 20 33 51
2 x 65 W 8 12 20 33 51
2 x 80 W 7 11 15 26 41
2 x 115 W 5 8 12 20 31
Fluorescent tubes with electronic ballast
1 or 2 tubes 18 W 56 90 134 268 402
36 W 28 46 70 142 213
58 W 19 31 45 90 134
2 x 18 W 27 44 67 134 201
2 x 36 W 16 24 37 72 108
2 x 58 W 9 15 23 46 70
Compact fluorescent lamps
External electronic ballast 5 W 158 251 399 810 Infrequent use
7 W 113 181 268 578
9 W 92 147 234 463
11 W 79 125 196 396
18 W 49 80 127 261
26 W 37 60 92 181
Integral electronic ballast (replacing incandescent lamps) 5 W 121 193 278 568 859
7 W 85 137 198 405 621
9 W 71 113 160 322 497
11 W 59 94 132 268 411
18 W 36 58 83 167 257
26 W 25 40 60 121 182
Low-pressure sodium vapor lamps with ferromagnetic ballast and external ignitor
Without compensation[a] 35 W 4 7 11 17 29
55 W 4 7 11 17 29
90 W 3 4 8 11 23
135 W 2 3 5 8 12
180 W 1 2 4 7 10
With parallel compensation[b] 35 W 20 µF 3 4 7 12 19
55 W 20 µF 3 4 7 12 19
90 W 26 µF 2 3 5 8 13
135 W 40 µF 1 2 3 5 9
180 W 45 µF 0 1 2 4 8
High-pressure sodium vapor lamps

Metal-iodide lamps

Ferromagnetic ballast with external ignitor, without compensation[a] 35 W 12 19 28 50 77
70 W 7 11 15 24 38
150 W 3 5 9 15 22
250 W 2 3 5 10 13
400 W 0 1 3 6 10
1000 W 0 0 1 2 3
Ferromagnetic ballast and external ignitor, with parallel compensation[b] 35 W 6 µF 14 17 26 43 70
70 W 12 µF 8 9 13 23 35
150 W 20 µF 5 6 9 14 21
250 W 32 µF 3 4 5 10 14
400 W 45 µF 2 3 4 7 9
1000 W 60 µF 0 1 2 4 7
2000 W 85 µF 0 0 1 2 3
Electronic ballast 35 W 15 24 38 82 123
70 W 11 18 29 61 92
150 W 6 9 14 31 48
  • High-pressure sodium vapor lamps: for the 10 A and 16 A B-curve ratings, the number of lamps should be reduced by 10% to limit unwanted magnetic tripping.
  1. ^ 1 2 3 Circuits with non-compensated ferromagnetic ballasts consume twice as much current for a given power output. This explains the small number of lamps in this configuration.
  2. ^ 1 2 3 The total capacitance of the power factor capacitors in parallel on a circuit limits the number of lamps that can be controlled by a contactor. The total downstream capacitance of a modular contactor of rating 16, 25, 40 or 63 A should not exceed 75, 100, 200 or 300 μF respectively. Allow for these limits to calculate the maximum acceptable number of lamps if the capacitance values are different from those in the table.
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