MEDEA Installation Manual
37
2 -
Design
2.1
Power supply and battery sizing
2.1.1
Calculating the total system consumption
Knowing the total power consumption of the system is essential for correctly sizing power supplies and
batteries. The calculation procedure is shown below:
•
List all the required devices with quantity and max. unit stand-by consumption (obtainable from the
data sheets). Then multiply quantity and consumption to obtain the subtotal for each type of device.
NOTE
: Magnetic contacts do not consume current.
•
Add up all subtotals to obtain the maximum rated power consumption of the system.
•
Calculate an expansion margin of 10% of the maximum nominal absorption for possible future
expansions.
•
Add up the maximum nominal consumption and the expansion margin to obtain the total system
consumption to be used for future sizing.
2.1.2
Battery sizing
The system must be sized to guarantee the minimum autonomy time required by EN 50131 in the event
of a mains failure compatibly with the chosen safety level.
Calculating the total system consumption as shown in the following table.
Safety
grade
EN 50131
Minimum autonomy to be
guaranteed
with no mains power
Max. allowed consumption
MEDEA /32
MEDEA /64 MEDEA /160
7.2 Ah battery
9 Ah battery
18 Ah battery
3
60 hours
non-feasible configuration
30 hours *
--
300 mA
600 mA
2
12 hours
600 mA
400 mA
1500 mA
Table 26 - Central unit battery autonomy
* Autonomy is only authorised if the absence of the mains power supply is notified to an alarm receiving
centre or other remote centre (see EN 50131-1 Clause 9.2).
Power for all internal circuits and devices is supplied by an internal switching power supply (PS type A). A
12 V lead-acid battery is to be used.
IMPORTANT
The batteries used must be of the VRLA (Valve Regulated Lead Acid) type, in an
enclosure with flammability class UL94V-1 or higher and comply with IEC 60896-21:2004, IEC
60896-22:204.
There are two solutions if the calculated consumption is higher than allowed:
a) Try to exclude the 10% expansion margin from the total consumption calculation. You can proceed if
within the limits but remember that any future expansion of the system will be less easy to implement.
b) Insert one or more additional power supplies into the system.
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