44 en | System composition PRAESENSA
2019.11 | V1.00 | Installation manual Bosch Security Systems B.V.
power supply modules, one for each amplifier and one for the system controller and switch.
The PoE load of the switch is not counted in the table as this power is already taken into
account for the call station, the power is in fact passed through the switch.
For the required UPS capacity, the calculation is based on 24h operation in quiescent mode,
which is in this case the idle mode of the amplifiers, and 0.5h operation in alarm mode for
which the full power consumption of the amplifiers is taken. It is clear that most of the UPS
capacity is needed to keep the system alive during the 24h in quiescent mode, the energy
consumption during the much shorter alarm mode is less. If this system would use the PRA-
MPS3 multifunction power supply, the amplifiers would be able to run in snooze mode during
these 24h and the total energy consumption and associated battery size would be much
lower.
This system requires a UPS that can deliver at least 4.3kWh of energy. Also, the UPS must be
capable of providing at least 823W of instantaneous power, so a 1kW UPS, with 5kWh of
energy stored in batteries seems to be a good choice. It depends on how the aging of the
batteries and Peukert’s law has been taken into account by the manufacturer of the UPS,
whether this 5kWh capacity is really sufficient or that 6kWh would be a better choice.
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