Kentec
Addressable Control Panels –
400mA Loop Current
The desire for more addressable loop beacons
and sounders to be fitted on to each addressable
control panel detection loop circuit has resulted
in a market demand for higher current capacity
loop drive circuits.
Whilst
the ability to provide higher loop current
to drive sounders and beacons is useful, there
is a penalty in increasing the current capability
of the loop. As the loop current increases,
the effect of loop cable resistance, inductance
and capacitance on the panel to detector signalling
becomes more significant.
The
overall result of increased loop current is
a reduction in the maximum permissible cable
length for the detection loop.
Table
showing typical reduction in loop length with
increased loop current (1mm cable)
This
table shows that there is a balance between
loop loading and loop length. It is considered
better practice to provide many low volume
(low current) sounders evenly distributed
around a reasonable length loop, rather than
a smaller number of higher volume (higher
current) devices on a smaller loop.
If
there is a requirement to provide high loop
current over longer loop distances, then the
cable cross section area must be increased,
resulting in a more expensive installation
cost.
Using
400mA as the maximum available loop current,
the Kentec control panels offer sufficient
capacity to drive a reasonable number of devices
over an acceptable loop cable length.
Typically
the 400mA loop current is sufficient to fully
populate a loop with loop sounders at 85dB,
or to fit at least 50 sounder and loop beacon
combinations at 85dB.
For
full verification of loop designs, always
use the loop calculation applications, which
can be downloaded using the following links:-
Apollo loop calculator:
Hochiki loop calculator:
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