Before You Begin
Menvier40/100
Page 12
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. PD6662 Grade
3 requires 12 hours (when the control unit is fitted
with an ATS4 communicator) including two
periods of 15 mins in alarm.
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 38.
The following calculation shows a simplified
example: in an alarm system with an i-Menvier40
control unit, two i-kp01 keypads, and 20 wired
PIRs the system takes the following total
quiescent current:
Device
Current
Control unit PCB
120mA
20 x PIRs at 15mA each
300mA
1 x (wired expander)
20mA
2 x i-kp01 at 30mA each
(backlights off)
60mA
Siren (quiescent)
25mA
Total
525mA
During an alarm, these figures become:
Device
Current
Control unit PCB
200mA
20 x PIRs at 15mA each
300mA
1 x (wired expander)
20mA
2 x i-kp01 at 60mA each
(backlights off)
120mA
Siren (in alarm)
400mA
Total
1040mA
The total amp hours required =
(0.525 A x 11.5h) + (1.040A x 0.5h) = 6.56Ah
Note that for Grade 3 this example assumes that
the communicator has its own power supply.
One new, fully charged, 7Ah battery can provide
the charge required by the example system and
would meet the PD6662 Grade 3 requirements.
Note: All current drawn from the Aux terminals
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
38.
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 cable with a characteristic
impedance of 100-120ohms eg: CAT5 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
not at the keypad or expander.
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 20 devices to the control
unit bus on a Menvier40, or 45 on a Menvier100.
You may connect the devices either in daisy chain
(serially), or in star (parallel) configuration at the
control unit connector.
