Question: What resistance must have a current limiting resistor when connecting detectors SPD-3.0 to a 2-wire loop?
Answer: A current limiting resistor must issue the current from 8 to 30 mA for the normal operation of a detector in the “Fire” mode when the power voltage drops for detectors ≤ 8 V. Therefore for a direct current loop with the voltage 24 V the resistance value of the current limiting resistor must be within the limits of 560 Ω to 2 kΩ, the recommended value is 1,5 kΩ. For a direct current loop with the voltage 12 V the magnitude of resistance of the current limiting resistor must be within the limits of 150 Ω to 510 Ω. The recommended value is 390 Ω. A current limiting resistor may not be installed when connecting SPD-3.0 to A.C. loops, so as current limitations in the loop in the “Fire” mode are carried out by a control panel.
