Edition 50
March 2011

S406 & S407 power supplies and Syncro Earth Fault Monitoring

As part of our continual development process, the switched mode power supplies used in the Syncro, Syncro XT control panels and our boxed power supplies have been updated. This update was performed during 2010 and was necessary in order to meet the additional (amendment A1) requirements of the harmonised EN54-4 standard.

The S406 (5.25 Amp) and S407 (2.5 Amp) power supplies have the same physical size and appearance and are slightly larger than the previous ENS400 power supply.

The number and location of the diagnostic LED indicators is different to the ENS400, with the introduction of an “AC normal” and “DC out on” indicator – both of which should be illuminated under normal conditions. There is also a “Heartbeat” indicator which flashes slowly to indicate the onboard microprocessor is functioning correctly.

These new power supplies also monitor battery impedance and will indicate a battery disconnected fault in the event of high impedance in the charging circuit as well as if the batteries are disconnected. A 4-way DIP switch is provided to allow correct battery type selection.

One of the other main differences between these new power supplies and their predecessors is the addition of a fault relay and the removal of the individual fault output terminals. Fault outputs are only provided via the 14-way ribbon cable to the Syncro panel (or the RPSM2 board in the KD25000 series boxed power supplies).

One of the fault monitoring requirements of EN54-4 is to monitor for any leakage currents to earth. This is to protect the integrity of the fire detection system from cable faults. The Syncro system will continue to work as expected for a single earth fault. However, in the event of multiple earth faults, there would be current flow between circuits via earth and the results could cause a total failure of the fire system if a combination of positive to earth and negative to earth faults exist.
On the ENS400 it was possible to temporarily disable the earth monitoring by linking the “EF” terminal to the load “+ve” terminal. This would give time to investigate the earth fault but is not generally recommended, as the panel no longer conformed to the requirements of EN54-4 and had the increased risk of a total failure in the event of multiple faults.

This option is no longer available on the S406 / S407 power supplies. The fault outputs on the 14- way ribbon cable header are not current limited and are not designed to be directly connected to a 24 volt source – whether directly on the 14-way ribbon or through the remote PSU inputs on the Syncro S551 main loop board. Any attempt to link these fault outputs to a 24 volt source will result in damage to the power supply.

The Syncro and Syncro AS control panels have the facility to disable the earth fault monitoring via the Access Level 3 “Engineering Disablements” menu option. This will give a “General Disablement“ indication and is stored in the Event Log and will prevent nuisance fault events from intermittent earth faults whilst the fault is being remedied.

If using the Syncro panel with Zener Barriers, please consult with Kentec prior to ordering the control panel. 

For details of the S406 / S407 power supplies, refer to the K25000 series power supply manual

EN54-2 and EN54-4 Approval Certificate for Syncro / Syncro AS panels and boxed power supplies

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