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Before You Begin
Power Availability
Before connecting any external devices to the
control unit, you must make sure that the control
unit can provide sufficient current to power the
system during a mains failure for the time required
to meet the appropriate standard.
EN51031-1 Grade 2 and PD6662 Grade 2 both
require 12 hours standby time.
Note: When calculating the average load during
the standby time period you must allow for at least
two periods in alarm. To take the worst case these
two periods of alarm should each be 15 minutes
long, the maximum permitted in EN50131-1
section 8.6.
The amount of current available from the control
unit depends on the size of battery fitted and its
health. The current taken by the control unit PCB,
communicator and keypads is given in Technical
Specifications – EN50131-6 Ratings on page 37.
The following calculation shows a simplified
example: in an alarm system with an Menvier30
control unit, two i-kp01 keypads, and 15 wired
PIRs the system takes the following total
quiescent current:
Device
Control unit PCB
15x PIRs at 15mA each
15 wired door contacts @2mA
each
2 x (wired expander @ 40mA
each)
4 x i-kp01 at 30mA each
(backlights off)
4 x Sirens (quiescent) at 25mA
each
During an alarm, these figures become:
Device
Control unit PCB
15 x PIRs at 15mA each
15 wired door contacts @2mA
each
2 x (wired expander)
4 x i-kp01 at 60mA each
(backlights off)
4 x Sirens (in alarm) at 400mA
each
The total amp hours required =
(0.615 A x 11.5h) + (2.255A x 0.5h) = 8.2Ah
Page 12
Current
100mA
225mA
30mA
40mA
120mA
100mA
Total
615mA
Current
120mA
225mA
30mA
40mA
240mA
1600mA
Total
2255mA
One new, fully charged,17Ah battery can provide
the charge required by the example system and
would meet the Grade 2 requirements.
Note: All current drawn from the Aux terminals
(12V) must be included in the overall calculation.
CAUTION: Ensure that the system does not
demand more than the maximum current available
from the control unit during an alarm, see page
37.
Bus Cabling Requirements
Cable Type
In general, the control unit requires standard 7/0.2
un-screened four core alarm cable for wiring the
bus.
For maximum performance in harsh environments
use twisted pair screened cable with a
characteristic impedance of 100-120ohms eg:
Belden 8132 or cable designed for RS485.
Use one pair for data lines A and B. Use the other
pair for 12V and 0V. For optimum performance
the voltage at the keypads and expanders should
be greater than 12V.
Screened cable may prove necessary if the
installation site has equipment that produces high
levels of R.F. (Radio Frequencies). For example,
welding equipment is known to produce a large
amount of radio interference. If screened cable is
required, you should keep to the following
guidelines:
1. Avoid earth loops by connecting the screen on
the cable to mains earth at the control unit but
nowhere else.
2. The continuity of the cable screen is most
important and screens MUST be continuous
along the full length of the cable.
3. Where the cable enters any metal enclosure,
ensure the screen is isolated from the case.
Cable Segregation
Segregate the bus cabling from any other wiring,
such as mains supply cables, telephone cables,
computer network cables and R.F. cables. Use
cable ties to keep cables separated.
Keep the bus cable clear of cables supplying
sounders, extension loudspeakers or any other
high current devices.
Cable Configuration and Length
You can connect up to 10 devices to the control
unit bus. You may connect the devices either in
daisy chain (serially), or in star (parallel)
configuration at the control unit connector.
Menvier30
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