Detcon FP-524D-HRT - Manual (Page 13)

Model FP-524D-HRT
FP-524D-HRT Instruction Manual Rev. 0.1 Page 9 of 48
NOTE: Any unused ports should be blocked with suitable ¾” male NPT plugs. Detcon
supplies one ¾” NPT male plug with each J-box enclosure. If connections are other than ¾”
NPT, use an appropriate male plug of like construction material.
2.6 Field Wiring
Detcon Model FP-524D-HRT combustible gas sensor assemblies require three conductor connections between
power supplies and host electronic controller’s 4-20mA / HART interface. A 250 ohm load resistor is needed
on the 4-20 mA line when it is not being used. Wiring designations are DC+, DC-, and MA (sensor signal).
The maximum wire length between sensor and 24VDC source is shown in the Table below. The maximum
wire size for termination in the Junction Box is 14 AWG.
Table 1 Wire Gauge vs. Distance
AWG Wire Dia. Meters Feet
Over-Current
Protection
22 0.723mm 700 2080 3A
20 0.812mm 1120 3350 5A
18 1.024mm 1750 5250 7A
16 1.291mm 2800 8400 10A
14 1.628mm 4480 13,440 20A
NOTE 1: Wiring table is based on stranded tinned copper wire and is designed to serve as a
reference only.
NOTE 2: Shielded cable is required for installations where cable trays or conduit runs include
high voltage lines or other possible sources of induced interference. Separate conduit runs are
highly recommended in these cases.
NOTE 3: The supply of power should be from an isolated source with over-current protection
as stipulated in table.
NOTE 4: A 250 ohm load resistor is needed on the 4-20 mA line when it is not being used.
Terminal Connections
CAUTION: Do not apply system power to the sensor until all wiring is properly terminated. Refer to
Section 2.7 Initial Start Up.