Surge protection for IT distribution networks
It is a Type 2 + 3 device, meaning it handles both main distribution board protection (Type 2) and fine protection for sensitive loads (Type 3) in a single unit. Rated for 230 V AC (+/- 10 %) at 50/60 Hz, it provides common-mode protection between line and PE with a maximum continuous operating voltage (Uc) of 460 V L/PE. This 2-pole arrester uses MOV technology and delivers a nominal discharge current (In) of 2.5 kA and a maximum discharge current (Imax) of 8 kA in common mode (L/PE). The voltage protection level (Up) is below 1.8 kV in Type 3 mode, which is sufficient to protect most downstream equipment with a 2.5 kV impulse withstand. The unit includes a remote signalling contact (1 C/O) rated at 0.25 A / 250 V AC for monitoring the arrester status from a PLC or building management system.
The A9L08221 clips onto a standard 35 mm DIN rail and occupies 4 x 9 mm pitches (36 mm width). The housing is white (RAL 9003) and stands 70 mm tall with a depth of 90 mm. Tunnel-type terminals on both top and bottom accept rigid conductors from 2.5 to 25 mm² or flexible conductors from 4 to 16 mm². For IT systems, the arrester must be installed between each live conductor and PE (no N-PE mode). The manufacturer specifies an associated upstream overcurrent protective device: either an iC60L circuit breaker (10 A, curve C, 25 kA Icu) or gG fuses (25 A / 15 kA or 80 A / 50 kA). The short-circuit withstand of the arrester itself is 5 kA at 415 V phase-to-phase.
Environmental and operational limits
Relative humidity range is 5 to 95 %. Maximum operating altitude is 2000 m. The temporary overvoltage (TOV) withstand is 337 V L/N for 5 seconds; in safe failure mode it withstands 1453 V L/PE for 200 ms. Ground residual current (Ipe) is 0.6 mA.