JB 125C33, Decentralized Power Supply 160 mA, AC 110 – 277V

The JB 125C33 junction box mount decentralized power supply provides KNX Bus power for Gamma and TRA installations. The device mounts to, or in, USA 4-11/16” square deep junction box.

Power supply has integral choke to support KNX data telegrams. Bus short circuit protection includes visible operation status indicators. KNX S-Mode installations requires at least one power supply per line segment, main line, and backbone. A second power supply can be added to handle bus loads exceeding 160 mA. Maximum of two (2) JB 125C33 can be wired in parallel for 320 mA bus load. For larger KNX installations, DIN mount power supplies are available from Siemens Gamma.

Note: If two (2) power supplies are operated in parallel on one bus line and if the overload LED is lit on one power supply, then the bus configuration must be changed until the overload display disappears on all units. KNX TP (twisted pair) installation is “Free-Topology,” “T” taps are allowed.

The distance between any bus device and the closest power supply unit must not exceed 350 m (380 yds). The power supply has voltage and current regulation, therefore is short-circuit proof.

Short power disruptions can be bridged with a reserve interval of at least 100 ms.