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MCB & RCBO – Technical Data
SHORT CIRCUIT CURRENT AS A MULTIPLE OF RATED CURRENT
OPERATING TIME IN SECONDS
2 HRS
1 HR
1,000
100
10
1.0
0.1
0.01
0.001
1
3
5
10
20
100
1,000
Type
B
Type
C
Type
D
BACK-UP PROTECTION
Back-up protection is required only if the prospective short circuit
current at the point of installation exceeds the breaking capacity of the
MCB.When providing back-up protection consideration must be given
to discrimination between the MCB and fuse.
DISCRIMINATION
It is desirable that the protective device nearest the fault should
operate first.The low energy let through of modern MCBs provides
better discrimination with HRC fuse back-up than is given by earlier
types of MCBs.
CONSUMER UNIT MCBs
Standards BS EN 60898-2 : 2006
Rated voltage (single pole) 240V
Tripping characteristics Type B,C
Short circuit rating 6kA
Reference calibration temperature 30°C
Terminal capacity – outgoing cable 0.75 to 25mm
2
CAT REF C CURVE RATING
NHXB06 NHXC06 6A
NHXB10 NHXC10 10A
NHXB16 NHXC16 16A
NHXB20 NHXC20 20A
NHXB32 NHXC32 32A
NHXB40 NHXC40 40A
NHXB50 NHXC50 50A
4x10
2
Prospective short circuit current Ip/A
Let-through I
2
t (amp
2
/sec)
10
3
6 8 10
3
2 3 4 6 10
4
8
I
n
=
2
3
4
6
8
10
4
2
3
4
6
8
10
5
40 A
32 A
25 A
20 A
16 A
10 A
6 A
50 A
40 A
35 A
32 A
63 A
80 A
100 A
125 A
BS88 FUSE 160A
2
1
1
HW = 0.01 sec
2
min melting pt (pre-arching)
eg I
n
=125A BS 88
max let-through I
2
t of MCB
eg 6A
4x10
2
Prospective short circuit current Ip/A
Let-through I
2
t (amp
2
/sec)
10
3
6 8 10
3
2 3 4 6 10
4
8
I
n
=
2
3
4
6
8
10
4
2
3
4
6
8
10
5
40 A
32 A
25 A
20 A
16 A
10 A
6 A
50 A
40 A
35 A
32 A
63 A
80 A
100 A
125 A
BS88 FUSE 160A
2
1
1
HW = 0.01 sec
2
min melt g pt (p e-arching)
eg I
n
=125A BS 88
max let-through I
2
t of MCB
eg 6A
1 1.5 2 3 4 5
3 5
6 8 10 15 20 30
0.01
0.02
0.04
0.06
0.1
0.2
0.4
0.6
1
2
4
6
10
20
40
1
2
4
6
10
20
40
60
120
Tripping time
Minutes
Seconds
1.13 1.45
7
Multiple of rated current
ac
NHX, NSB AND PSB DISTRIBUTION BOARD
MCBs
Standards BSEN 60898 -2: 2006
RatedVoltage 230/400Volts
Tripping characteristics Type B, C and D
Short circuit rating 6kA and 10kA
Reference calibration
temperature 30˚C
Terminal capacity -
outgoing cable 0.75 to 25mm
2
NHXSBS, NSBS & PSBS RCBO
(COMBINED MCB/RCD)
Standards BSEN 61009 -2: 1995
BSEN 61009 -1: 2004
RatedVoltage 230Volts -1 2004
SP or SP with switched neutral
Tripping characteristics NSBS=B,C PSBS=C
Short circuit rating 6kA and 10kA
Reference calibration
temperature 30˚C
Rated residual operating
current 30mA
Single module Type A
Two module Type AC
Terminal capacity - 0.5 to 16mm
2
outgoing cable
Unique live side busbar combi-terminal allows
connection of cable up to 25mm
2
Maximum neutral cable size 25mm
2