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TECHN I CAL DATA
RCBO s
215
SPECIFICATION
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RCBOs (MCB/RCD)
POLESTAR
LOADSTAR
●
Standards
BS4293/BS3871
BSEN61009
●
Short circuit breaking capacity 10kA
10
kA or 6kA
●
Current rating
6
to 40A
6
to 40A
●
MCB Type classification
C
C
●
RCD Type classification
AC
A
●
Rated voltage & frequency
240
V 50Hz
240
V 50Hz
●
RCD Tripping principle
Electromechanical
Electronic
●
Neutral configuration
Switched
Solid
●
Positive contact indication Yes
Yes
●
Loss of supply Neutral
Inherent
Via functional earth
circuit
APPLICATIONS
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RCBOs provide both earth fault and overcurrent protection. For commercial
and industrial applications a unit should be employed, utilising Type C
(5–10
I
n) classification of MCB. RCBOs, other MCB classifications available
to order.
Polestar and 2 module Loadstar RCBOs employ an electromechanical
operating principle.
Loadstar 1 module RCBOs employ an electronic operating principle
incorporating loss of supply neutral protection via a functional earth lead.
All RCBOs give a high level of protection to individual circuits whilst exhibiting
improved immunity to response caused by transients.
Two module switched neutral RCBOs have safety advantages over single
module RCBOs and are exclusively used in continental Europe.
ADVANTAGES OF SWITCHED NEUTRAL RCBOs
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If a neutral to earth fault occurs in a circuit fed via an RCBO with a solid
neutral which is backed up by an upstream selective RCD, the selectivity or
discrimination will be lost and the main RCD will also trip as it will still detect
the fault which has not been cleared.
The main requirements of RCD protection are:
•
Additional protection against direct contact with live parts
•
Protection against direct connection with live parts
•
Protection against fire in the case of a fault to earth
If a fault occurs between neutral and earth where a solid neutral RCBO is
protecting a circuit, the RCBO will trip. However, as previously stated, the
fault will still be in the circuit within the rest of the installation.
As the neutral will be common throughout the installation, it is possible that
current could still flow through the fault and lead to a fire hazard. This would
mean that the RCBO would not offer full protection against fire and therefore
does not comply with one of it’s main protection requirements.
Testing of outgoing circuits is easier with RCBOs incorporating a switched
neutral as an electrician does not have to disconnect terminals before testing.
BS7671 requires that the main switch to a TT earthed installation must have a
switched neutral.
INSTALLATION TESTING –
CAUTION
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As Single Module RCBOs employ electronic components they should
be disconnected when carrying out the following tests on the electrical
installation:
(
a) Earth fault loop impedance test
The load terminals should be disconnected if it is intended to parallel-out the
unit for test purposes.
It may incur damage if mains potential is maintained on the load terminals of
this unit after the trip mechanism has operated.
(
b) Insulation test
Whilst RCBOs can withstand the effects of normal insulation testers without
damage, false readings may be given on the test instrument. For this reason
it is recommended that the device is disconnected during this test.
RCBOs (MCB/RCDs) & RCDs – GENERAL
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IEC PUBLICATION 60479 CURVES WITH CRABTREE RCD CHARACTERISTICS SUPERIMPOSED
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TIME/CURRENT ZONES OF EFFECTS OF AC CURRENT (15–100Hz) ON PERSONS
Zone Physiological effects
1
Usually no reaction
4
In addition to the effects
effects.
of zone 3, probability of
ventricular fibrillation
2
Usually no harmful
increased up to 5%
physiological effects.
(
Curve C2) up to 50%
(
Curve C3) and above
3
Usually no organic
50%
beyond Curve C3.
damage to be expected.
Increasing with magnitude
Likelihood of muscular
and time, pathyphysio-
contraction and difficulty
logical effects such as
of breathing, reversible
cardiac arrest, breathing
disturbances of formation
arrest and heavy burns
and conduction of
may occur.
impulses in the heart, and
transient cardiac arrest
without ventricular
fibrillation increases with
current magnitude and
time.
10,000
5,000
2000
1000
500
200
100
50
20
10
0.1 0.2 0.3 0.5 1 2 3 5 10 20 30 50 100 200 300 500 1,000 2,000
10,000
5,000
3,000
Current in milliamperes (RMS)
100
mA
30
mA
Typical current
Limits due to body resistance
at 230V
1
2
3
4
a
b
c
1
c
2
c
3
IEC 60479
Time in milliseconds