25
Ensure adequate selectivity if the new RCD is installed
downstream of an existing circuit breaker. In order to
ensure complete selectivity of two residual current
devices connected in series, the fault current of
upstream RCD
A
must be at least 3 times as high as
that of RCD
F
used to protect the Vitovalor PT2.
Adjust the activation times of both RCDs connected in
series in such a way that the disconnection time of
RCD
F
is less than the shortest disconnection time
for RCD
A
. Both conditions ensure RCD
F
for the
Vitovalor PT2 responds earlier than upstream RCD
A
l in A
t in s
A
F
Fig. 14
Response characteristics of the residual cur-
rent devices
Preparing for installation
Notes on connecting to the mains supply
(cont.)
5853335
Installation