Installation, Operation & Maintenance Parksafe Gas Detector
Rev: 11 0421
6
Wiring a Detector
Power and Modbus data are wired between detectors with the first connected
to a control panel DETECTOR CHAIN terminal. If using a shielded wire
(recommended) then connect the shield to [-] power terminals.
For MODBUS communications, a shielded cable is used.
The shielding can be of 2 types: braided [mesh of thin conducting wires]
or foil (consisting of a thin sheet of metal covering the twisted wires).
One example of such cable is BELDEN 3082A.
If you are encountering noise or irregular problems with a Modbus link,
the problem is likely related to grounding, incorrect shielding or wiring mains power next to Modbus wiring.
To ground the data cable, the shield should be connected to [-] of the chain terminals.
Reversing the [D+] and [D-] connections of any device can lead to the whole system to stop working owing to reverse
polarity found on the terminals.
The detector must be earthed/grounded for electrical safety and limit the effects of R/F & EMC interference!
Ensure the 120-ohm termination resistance switch is on at each end of a cable run!
Wiring a Detector Chain
Up to 16 Parksafe detectors can be connected, chained in a parallel ‘daisy chain’ method up to approx. 500 yards
from the panel depending on chain configuration, wire type for power and condition. Any other way may cause issues
or damage to the overall system. It is recommended that the cable of same color should be used to connect all [D+]
terminals together and similarly cable of same color to be used to connect all [D-] terminals together.
Split chain example from a Parksafe Control panel. Single chain example from the Parksafe Control Panel.
