Relay Quality in a KNX Actuator

A good quality relay is a key role to ensure high reliability for switching actuators used in a KNX building automation system. EN60669-1: Switches for household and similar fixed electrical installations – General requirements is one of the standards to define the performance and endurance of the relay.

Part 19.1 of EN60669-1 specifies the normal operation of the relay which is intended to connect a rated load with costƟ =0.6 and the target is to meet at least 40000 number of operations.

The designation AX has established to a (capacitive) fluorescent lighting load. A test with 140 µF is the minimal requirement and should operate at least with 10000 number of operations. Actuator products from MEAN WELL are further tested to 220 µF on top of the basis of EN60669-1 part 19.2. Since the LED driver is not yet regulated in the EN60669-1. It is considered as a capacitive type of load due to the major circuitry design of the common LED driver. As result, part 19.2 can be applied to LED driver type of load for the relay in a KNX actuator.

Another standard EN 60947-4-1: Contractors and motor-starters – Electromechanical contactors and motor-starters are also referred in KNX actuator. The tests are defined to simulate typical applications, e.g. motor loads (industrial) or fluorescent lamps (residential). Specifications AC1 and AC3 are switching performance specifications which have become established in the industrial field.

The following designations in EN60947-4-1 are commonly used in KNX building automation:

AC1 – Non-inductive or slightly inductive loads, resistance furnaces (relates to switching of resistive loads, cos Ɵ = 0.8)

AC3 – Squirrel-cage motors: starting or switching off during running (relates to (inductive) motor load, cos Ɵ = 0.45)

AC5a – Switching of electric discharge lamps

AC5b – Switching of incandescent lamps

The above conditions should pass with at least 6000 number of operations.

In short, a well designed KNX actuator should subject to the corresponding standard depending on applications to ensure a long and stable operation with minimized maintenance and service.