A modular surge protective device (SPD) protecting the mains supply against overvoltage caused by a lightning strike or a switching transient.
DEHN SE · surge protective device (SPD)
DEHN DEHNguard M / MP LED wall infrastructure
The supply of an outdoor LED wall placed at a high point (on a roof, on a pole) is particularly exposed to overvoltage induced by nearby lightning strikes and to mains switching transients — these can destroy driver ICs and power supplies alike if no suitable surge protective device (SPD) is built into the distribution cabinet. The DEHNguard M/MP family is one of DEHN's modular, rail-mounted surge protective devices, designed specifically to protect distribution networks inside buildings.
In practice, a well-designed LED wall distribution cabinet contains an SPD alongside the circuit breakers (overcurrent protection) and the residual current devices (RCD, shock protection) — these perform three complementary protective functions, and none of them substitutes for another.
Where the DEHN DEHNguard M / MP sits in an LED wall system
The SPD sits on the input side of the distribution cabinet, after the main circuit breaker and before the power supplies and control electronics, mounted on a DIN rail, and diverts the phases to protective earth in the event of an overvoltage. The protection only works if the cabinet's earthing is sound: the arrester diverts the overvoltage to earth, so a poor or needlessly long earthing conductor renders the whole investment ineffective. The data lines on the LED wall side (Cat6, fibre) require a separate data-line SPD — the mains arrester does not protect those.
WHEN IT IS THE RIGHT CHOICE
On the supply of an outdoor LED wall placed high up or with long cabling, where lightning-induced or switching overvoltage is a realistic risk.
WHAT TO WATCH OUT FOR
An SPD substitutes neither for the circuit breaker (overcurrent protection) nor for the residual current device (shock protection) — the complete distribution cabinet has to contain all three protective elements together, properly sized.
The DEHN DEHNguard M / MP in practice
The customer feels this in one situation only: after a summer thunderstorm the wall does not start, and the service replaces several power supplies and receiving cards at once — a bill typically many times the price of an SPD. The SPD has a wear element: a window on the front of the module indicates when the cartridge is spent, and this has to be inspected annually when the wall is maintained, because an exhausted arrester no longer protects while signalling nothing to the system. To settle with the electrician in advance: the required SPD type, the backup fuse, the earthing arrangement, and whether a data-line arrester is needed alongside the mains one.
Alternatives to the DEHN DEHNguard M / MP
For an indoor wall inside a building and placed low down, a Type 2 arrester on its own is enough. For an outdoor wall on a roof or a pole, or where there is a lightning protection system (LPS), a combined Type 1+2 arrester is needed at the supply and a Type 3 at the end point. Data lines need a separate Cat-line arrester. The deciding factor is not the price of the wall but the route: how much cable runs in the open, and how high up.
DEHN DEHNguard M / MP manual and datasheet
The documents live on the manufacturer's own site and open in a new window — so you always get the latest version. We do not copy or translate their contents.
Related signal transmission and mounting
LED wall infrastructure — but what does it go into?
On its own the DEHN DEHNguard M / MP is a component. With us it works inside these displays — design, manufacturing and installation included.
