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RCD Type F | 25
FAQ - Frequently Ask Questions
Is it possible to realize selectivity with type F RCDs?
What about the coordination with MCBs?
The coordination and selectivity rules are common for Type
AC, A, A-APR and F RCDs. For an RCD type F, the first level
of selectivity can be realized with any RCD in selective version.
Selectivity is guaranteed thanks to the time delay and higher
sensitivity of the RCD upstream. For any detail regarding the
coordination, please refer to the System pro M compact
®
.
Why ABB proposes RCCB in four poles versions in
Type F, dedicated people protection for single phase
inverter lines?
An RCCB 4P can be used for the protection of single phase
lines, by wiring each line downstream the protection, earning
two modules inside the switchboard (4 modules instead of
6 modules with 3 x F202). Moreover, four poles RCCB are
commonly used upstream multiple single phase lines in certain
countries.
What happens if two loads with single phase inverters are
connected at the same time downstream a Type F RCD?
RCD Type F ensure people protection in the same way as
other types of RCD. The RCD, as prescribed by international
standard, must not trip when residual current value is below
0.5 Idn, can trip between 0.5…1 Idn and must trip from 1
x Idn onwards. Respecting those values, loads with and
without single phase inverters can be supplied, regardless
their number. This could be the case, for example in a house,
if a washing machine is running while the user switches-on a
hoover.
How many fluorescent bulbs and computers can be
connected simultaneously if a 30mA APR type RCD is
installed?
APR RCDs are characterized by their high resistance to line
overvoltages from atmospheric origin, grid interference and
leakage currents. One of the main factors concerning the
origin of leakage currents is the connection of numerous
computers and fluorescent bulbs with electronic ballast at
the same time. APR RCDs, thanks to their anti-interference
characteristics, reduce the risks of unwanted tripping,
significantly improving operational continuity for numerous
applications (offices, supermarkets, datacentres, schools etc.).
The most critical aspect for dimensioning lines supplying
fluorescent lights or computers is undoubtedly the interference
these devices emit. Today it is impossible to give exact
indications on how many bulbs and computers may be
connected, as this is variable and depends on the connected
load. Despite this, we can try, as we have done in the table
below, to give a general indication which can help facilitate
dimensioning of these lines.
Three-phase supply
N
Single phase circuits
RCD type N. of electronic ballasts N. of workstations
(computers / printers)
Standard 20 2
A-APR Type 50 5