3
2. Installing the system via BUS
• For the connections use the twisted pair and sheathed ca-
ble VIMAR 01840.E (2 x 0.5 mm2). The wire pair distributes
both the power supply voltage (29 V d.c.) and the device
control signals.
• The devices do not have to be connected in any particular
order, maintaining the polarities indicated on the terminals.
• The voltage at each point of the bus must never fall below
20 V. In particular, check the points farthest from the pow-
er supply unit and the sections of cable where the load is
greater.
• The total current used by the various devices must not ex-
ceed the nominal current of the power supply unit. Make
sure that the current drawn by a device increases as the
power supply voltage decreases (for the consumption of
the device, please refer to its instructions booklet).
• A bus system must be supplied by 1 or 2 power supply
units and related chokes (diagram on page 4).
• Maximum bus cable length with 1 power supply unit:
250m.
• Maximum bus cable length with 2 power supply units: 500
m. For optimum load distribution, it is necessary to connect
the two power supply units to the two ends of the bus.
• For “star” bus connections, avoid creating branches of the
bus that are too long and have few devices; it is recom-
mended not to exceed lengths of 50m if the branch has
no more than one device and 100 m if there are no more
than 5 devices. The best case is when the branches have
devices distributed along the cable.
