INDO-C.PPT Merlin Gerin Square D Telemecanique
BTT/C-E.Tison-En-10/97
BTT-E.Tison-En-10/97
C
Risks of direct contact in normal conditions
Electrical risks in wet rooms
Separation of circuits
A direct contact = contact with a live conductor
More likely to occur in terminal distribution
lights:
generaly not qualified,
electrical danger
If current through people > 30 mA :
instaneous breaking
irreversible heart/fibrillation effect
IEC 479-1 gives relation between current magnitude / time duration through human body
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C
Curve C1 of IEC 479-1
Defines the current-magnitude / time-duration limits which must not be exceeded
A
B
C1
C2
C3
1 imperceptible
2 perceptible
C1: no heart fibrillation
1
2
3
4
1
2
3
4
mA
ms
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C
IEC 364 recommends use of 30 mA RCDs
protection as an efficient protective measure
Solution:
accessible cables
30 mA RCDs cover both type of protections
direct contact
indirect contact
Risks of direct contact in normal conditions
To improve continuity of power supply : maximum of 5 to 10 sockets or lights per 30 mA RCD
Addition of normal leakage currents of each load
(ex: 3,5 mA of leakage current is allowed for EMC filter in electronic appliance)
30 mA
30 mA
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C
Ex: bath room - shower room - wash basin room...
Danger of fatal electrical accident is higher than in other rooms
in case of immersed feet and wet hands, the resistance of the body falls down from 1500 to 700 ohms (about)
Floor and walls become more conductive due to water flowing down
Bath salts or soaps generally makes the water more conductive
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C
Concentration of electrical appliances
into water
People try to catch it out from water or to jump out of the basin
People grasp a tap or any metalic part to avoid sliping
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C
4 main measures
bbb
bb
b
Zone 0 only electrical aplliances specially intended for use in a bath tub are permitted.
Zone 1 only water heaters may be installed.
Zone 2 only the following may be installed.
4 Water heaters, luminaires and aplliances are Class II and are protected by a 30 mA.
Zone 3 all appliance protected by RCD
30 mA.
plan views
vertical cross-section
Zone 1
Zone 0
Zone 2
0,6 m
2,40 m
Zone 3
Zone 1
Zone 0
Zone 2
2,40 m
Zone 3
0,6 m
2,25 m
Zone 1
Zone 1
Zone 0
Zone 2
Zone 3
2,25 m
0,60 m
Zone 1
4 main measures
4 main measures
reduces the risk of indirect contact occurence
reinforced isolation
basic isolation
live part
Class II
4 main measures:
Despite all previous mandatory measures, fatal accident still may occur:
once in water, class II is useless
flowing water down on devices inhibits class II insulation
connection of portable class II appliances into socket may be risky
equipotential bonding does not remain secured after years
water pipes may be made with plastic
BTT-E.Tison-En-10/97
C
and continuity of power supply
Safety of end users
to avoid panic when no longer light in case of insulation fault on other circuit
to isolate part of installation under maintenance
Continuity of service of the installation
faulty circuit does not affect other circuits
to keep powered circuits with top priority
(ex: freezing rooms,...)
Conclusions
For safety reasons, it is advisable to dedicate a circuit for bath room with 30 mA RCD
RCD
End of part C