Detcon FP-624C User Manual

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3.4.3.6 Calibration Level Adjustment

The Calibration level is adjustable from 10% to 90% LEL. The menu item appears as:

“CalLevel @ ##%”

3.4.3.7 Set Bridge Volts

For applications where the sensor is remotely mounted away from the sensor transmitter, the detector bridge voltage is

adjustable to compensate for differing wire resistances. The menu item appears as:

“SET BRIDGE VOLTS”

3.5 I

NSTALLATION

Optimum performance of ambient air/gas sensor devices is directly relative to proper location and installation practice.

3.5.1 Field Wiring Table (4-20 mA output)

Detcon Model FP-624C combustible gas sensor assemblies require three conductor connection between power sup-

plies and host electronic controllers. Wiring designators are + (DC), – (DC) , and mA (sensor signal). Maximum

single conductor resistance between sensor and controller is 10 ohms. Maximum wire size for termination in the

sensor assembly terminal board is 14 gauge.

AWG

Meters

Feet

240

800

360

1200

600

2000

900

3000

Note 1: This wiring table is based on stranded tinned copper wire and is designed to serve as a reference only.

Note 2:

Shielded cable may be required in installations where cable trays or conduit runs include high voltage

lines or other sources of induced interference.

Note 3:

The supply of power must be from an isolating source with over-current protection as follows:

AWG

Over-current Protection

AWG

Over-current Protection

10A

20A

25A

The RS-485 (if applicable) requires 24 gauge, two conductor, shielded, twisted pair cable between sensor and host

PC. Use Belden part number 9841. Two sets of terminals are located on the connector board to facilitate serial loop

wiring from sensor to sensor. Wiring designators are A & B (IN) and A & B (OUT).

3.5.2 Sensor Location

Selection of sensor location is critical to the overall safe performance of the product. Five factors play an important

role in selection of sensor locations:

(1) Density of the gas to be detected

(2) Most probable leak sources within the industrial process

(3) Ventilation or prevailing wind conditions

(4) Personnel exposure

(5) Accessibility for routine maintenance

Density - Placement of sensors relative to the density of the target gas is such that sensors for the detection of

heavier than air gases should be located within 2-4 feet of grade as these heavy gases will tend to settle in low lying

areas. For gases lighter than air, sensor placement should be 4-8 feet above grade in open areas or in pitched areas

of enclosed spaces.

Leak Sources - Most probable leak sources within an industrial process include f langes, valves, and tubing connec-

tions of the sealed type where seals may either fail or wear. Other leak sources are best determined by facility engi-

neers with experience in similar processes.

Model FP-624C Combustible Gas Sensor PG.8