General Cabling Requirement; Cabling Requirement 4 To 20 Ma Current Loop - Crowcon Xgard Bright Bedienungsanleitung

NOTE: the mini USB socket is not intended for customer use, connecting this to a
computer is likely to damage both Xgard Bright and the computer.

3.5 General Cabling Requirement

Cabling to Xgard Bright must be in accordance with the recognised standards of the
appropriate authority in the country concerned and meet the electrical requirements of
the detector.
Suitable explosion proof glands must be used. Alternative cabling techniques, such as
steel conduit, may be acceptable provided appropriate standards are met.

3.6 Cabling Requirement 4 to 20 mA Current Loop

Fulfils the requirements for 4 to 20mA current loop and HART connections, allows for
connection and powering of accessory beacon or sounder subject to current consump-
tion, cable resistance and panel voltage. Current consumption should consider worst
case e.g. when the accessories are powered.
Beacon/
Sounder
Example Calculation 1
What is the longest cable for a bright to operate using point to point connection and
powering a sounder with 250mA current consumption. Use parameters of 1.5mm
where the controller has a guaranteed minimum output voltage of 18V.
This type of cable has resistance of 12.1Ω/km, therefore the there and back cable resist-
ance is 24.2. Xgard Bright has min voltage requirement of 10V.
The alarm 2 current for Xgard Bright (pellistor) is 95mA and the sounder output max
current is 0.25A, so a total current in alarm driving the sounder output is:
Max current = 0.25 + 0.095 = 0.345A.
18V = 10V + (0.345 x 24.2 x d), where d is distance in km
d = (18 – 10) / (0.345 x 24.2) = 0.958km
Example Calculation 2
As example calculation 1 but without the sounder.
Xgard Bright pellistor requires a dc supply of 10-30V, at max current in alarm 2 of 95mA.
Ensure there is a minimum of 10V at the detector, taking into account the voltage drop
18
Xgard Bright
Detector
Power +V
Signal
Power 0V
Xgard Bright
Control
Panel
2 cable,