5WG1568-1AB81 KNX Room Actuator 24 Channel 230V 10A Relay Outputs DIN Rail Mounted Actuator Module

The N 568/81 is a room actuator rather than a distribution board actuator, and the distinction is worth understanding before it is specified. Twenty-four relay outputs on a single rail-mounted device, each rated AC 230 V at 10 A with one relay contact per output, means a floor of fan coil units can be driven from one enclosure instead of a row of small actuators distributed across ceiling voids. Two of the outputs carry an additional DC 30 V rating — the detail that matters when the same device has to switch a 24 V or 30 V DC drive alongside the AC valve and damper motors that make up the rest of the load list.

The engineering questions around this device are thermal and architectural. Twenty-four relays in one housing dissipate heat, so the enclosure has to be ventilated, and the outputs that run continuously — such as valve actuators that stay energised in heating mode — should be grouped rather than scattered.

The load list has to be read as motor loads rather than as resistive ratings: a 10 A contact will switch a valve actuator for years and will not survive an unquenched inductive kick from a large damper motor unless the manufacturer's derating guidance is applied. The two DC outputs should be reserved for the drives that actually need DC rather than used as spare ways.

On the software side, the application program provides the channel objects, but the choice between switching, staircase timing and valve control per channel is a programming decision that should be documented channel by channel — because a twenty-four-way device with no channel schedule is a maintenance liability.

Room actuators of this size suit buildings with many identical terminal units:

• Hotels — fan coil valves and damper motors on a floor of guest rooms, where the load list is repetitive and the enclosure can sit in a riser.
• Office buildings — perimeter induction units or the terminal boxes of a chilled beam scheme.
• Hospitals — wards with a large number of valves that must be switched independently, where the plant room has no space for distributed actuators.
• Schools and laboratories — science benches and ventilation dampers, where a single enclosure per laboratory keeps the switching out of the teaching space.

In each case the alternative is a row of four- or eight-channel actuators, and the choice usually comes down to whether the enclosure has room for one device with a heat load or several devices with more wiring.