Pentair Goyen Mecair FFA, Инструкция по установке и эксплуатации, Страница: 21 / 44

15 INSTALLATION AND OPERATION MANUAL – OWNER'S RECORD FFA MANUAL – FILTER FAILURE ALARM
Cables should be routed to avoid sources of large electromagnetic fields, such as heavy switching gear. Care taken
during the installation of the cables ensures a long, maintenance-free life and avoids possible damage to the control
unit and sensor.
In summary, the cabling should be installed such that:
•
Heavy vibration is minimized to prevent fatigue and failure.
•
It is not vulnerable to accidental damage.
•
It is away from sources of large electromagnetic fields (if possible).
See Connecting the Sensor on page 18 below for information on running the cables between the sensor and control
unit (signal cable and parallel earth cable).
6.2.4 Grounding the Sensor
For FFA sensors it is essential the sensor body is grounded to the stack wall. This is necessary for Ex safety.
In addition, poorly grounded sensors may pick up external noise producing false high readings. Ensure the
installation complies with the following guidelines:
•
The sensor may only be fitted to a metal duct or stack. If the stack is not metallic or you are concerned that the
stack may not provide a suitably earthed shield for the sensor, please contact Goyen | Mecair.
•
The grounding strap (or earth wire) provided must be connected to ensure the sensor body is securely grounded
to the metallic stack wall. The sensor is electrically grounded to the ductwork by the mechanical connection made
between the sensor and the socket and by the external grounding strap.
NOTE: The grounding strap must be connected between sensor enclosure and stack wall. Relying on the stack
connection only is not acceptable in hazardous areas!
•
When connecting the grounding strap between sensor enclosure and stack wall leave sufficient length so that the
sensor can be removed and placed on the ground or platform for maintenance without disconnecting.
•
For threaded connections: DO NOT PUT PTFE TAPE AROUND THE THREAD (as this can compromise the sensor
grounding connection)!
•
If necessary, remove excessive rust from the thread and socket and apply a copper-loaded grease.
Surge Protection (Safety Grounding Cable)
To reduce the likelihood of damage from nearby lightning strikes, or from electrical surges due to high-power
equipment, run an additional earth cable (or grounding cable) between the sensor and the power supply.
The additional earth cable should follow exactly the same path as the sensor cable so as to ensure the closest
possible electrical coupling between them. Preferably, and if feasible, the two cables should be twisted together
loosely as they are laid. Alternatively, they may be clipped together at regular intervals along their length.
At the sensor end, the earth cable should be bonded to the sensor enclosure body, or to a point on the stack
immediately adjacent to the sensor head, using a low-resistance screw termination. At the power supply, the
earth cable should be bonded to the same mains earth point as is used to connect the power supply safety
grounding strap.
CABLE LENGTH
GROUNDING WIRE
CONDUCTOR AREA (mm²)
0–3 m (0–10 ft) not required
3–10 m (10–33 ft) 4
10–30 m (33–100 ft) 6
30–100 m (100–330 ft) 10
Above 100 m (330 ft) 16
6.2.5 Running Cables between Sensor and Control Unit
CAUTION!
Do NOT route cables where they may be at risk from lightning damage (e.g. over exposed roofs).
•
To prevent water from entering the instrument, mount all instruments and accessories with the cable glands
facing downwards.
•
After inserting and connecting a cable, fasten the cable glands tightly onto the cable to form a seal. Leave a little
slack in the cores.
•
Cable sheathing must always penetrate the cable gland fully, and the gland must be fastened tightly to it.