ABB ESP M1R Installation Instructions Manual page 16

(b) Protecting supplies going out of the building
The connection methods 3.5a (i to iii) are not suitable for
protecting a power distribution board which provides a
supply to outside the building - either to a separate
building or some other external load (eg site lighting).
To protect the equipment inside the building, from
transient overvoltages entering the board on the
outgoing feed, protection should be installed close to the
external load. See Figure 7.
Incoming
supply,
fused F
S
HRC switchfuse or MCCB
F where F < 0.5 F
SPD SPD S
Figure 8:
ESP unit installed on incoming
side of distribution board.
3.6 Isolation
It is good practice to be able to isolate or disconnect the
ESP unit from the supply. The supply to the entire
distribution board should not be switched off on many
computer power supplies and other critical loads.
3/9 | Installation instructions for mains wire-in protectors
Incoming
supply,
fused F
S
Figure 9:
Installation of ESP unit on first
outgoing way of distribution board.
HRC switchfuse or MCCB
F where F < 0.5 F
SPD SPD S