Power supply unit – Noby UK Noby-420 2-Zone User Manual

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Noby-420 Installation & Programming Instructions Rev3

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Power Supply Unit

The Noby-420 has a 27volt regulated PSU, with a continuous current rating of 1.0A, and a 20 minute rating of 1.5A.
The PSU is designed to meet the internal standby power requirements of the Noby-420 and also to charge and
maintain the SLA standby battery in optimum condition. The battery standby time is dependant upon the overall
system current drawn, including any ancillary equipment connected to the Aux 24v. Also it is strongly
recommended that the continuous system standby current does not exceed 1.0A, because some ‘reserve’ PSU
current may at times be required to rapidly re-charge the battery (e.g. after an alarm condition or prolonged period
of mains loss).

The Noby-420 enclosure can accommodate two 12v/7Ahr SLAs connected in series. Care must be taken when
planning an installation that there is sufficient battery capacity to meet the relevant standards regarding battery
standby times.

Always ensure that the maximum current drawn in alarm does not exceed the 3.0A battery fuse limit (F4).

The PSU is monitored for :


Mains Absence

Power LED extinguishes when mains absent for more than 90
seconds and flashes once mains restored. Mains absence is
accompanied by an intermittent warning bleep every 16s


Low Voltage < 21v

PSU Fault LED continuously lit whilst voltage < 21v and flashes
when the voltage is restored to > 23v


Battery Capacity Test

PSU Fault LED flashes


Fuse F4 (Battery/Low Volts)

PSU Fault LED flashes


Fuse F1 (Aux 24v)

PSU Fault LED flashes

Note 1: PSU faults are accompanied by a fault tone signified by 4 rapid pips every 4 seconds.
Note 2: The Battery Capacity Test is performed immediately after a System Reset and thereafter at 12 hour