detcon inc. Model FP-424C 4-20 mA Combustible Gas Sensor (0-100% LEL) Operator’s Installation & Instruction Manual May 18, 2010 • Document #2243T • Version 3.8 CAUTION: FOR SAFETY REASONS THIS EQUIPMENT MUST BE OPERATED AND SERVICED BY QUALIFIED PERSONNEL ONLY. READ AND UNDERSTAND INSTRUCTION MANUAL COMPLETELY BEFORE OPERATING OR SERVICING. ATTENTION: POUR DES RAISONS DE SECURITE, CET EQUIPEMENT DOIT ETRE UTILISE ENTRETENU ET REPARE UNIQUEMENT PAR UN PERSONNEL QUALIFIE.
Table of Contents 1.0 Description 2.0 Principle of Operation 3.0 Application 4.0 Specifications 5.0 Installation 6.0 Start-up 7.0 Calibration 8.0 Fault Supervision 9.0 Trouble Shooting Guide 10.0 Spare Parts List 11.0 Warranty 12.0 Service Policy Detcon Model FP-424C Combustible Gas Sensor PG.
1.0 DESCRIPTION Detcon Model FP-424C combustible gas detection sensors are designed to monitor ambient air for combustible hydrocarbons in the lower explosive limit range (0-100% LEL). The sensor assembly consists of a plug in replaceable matched pair of catalytic beads mounted in a stainless steel housing, a 12-28 VDC 4-20 mA DC control transmitter, an explosion proof junction box, and a machine fitted rain shield. 1.
To Controller Terminals BLUE MA 4-20MA – + 24VDC YELLOW BLACK Sensor WHITE 1.4 Explosion Proof Enclosure The transmitter electronics are packaged in a cast aluminum explosion proof enclosure and given a baked epoxy paint finish. The explosion proof enclosure has 3/4” NPT female entry ports. The enclosure is fitted with a threaded cover. Electrical classification is Class I, Div. 1; Groups B, C, D. 1.
Compensator/Reference 2.7V R1 Zero Set Pot R2 Detector/Active Output 2.1 Characteristics The detector elements maintain good sensitivity to combustible hydrocarbons in air in the lower explosive limit range, as shown in the response curve illustration below. However, for gas concentrations above the LEL range, the bridge output decreases.
When calibrating with one gas (Cal Gas) and scale sensitivity is required for a different gas (Target Gas) use the following calculation to determine calibration adjustment requirements: Target Gas K-Factor/Cal Gas K-Factor x Cal Gas concentration = Required adjustment level. For example, when calibrating with 50% LEL methane when propane is the target gas: 1.81/1.00 x .5 = 90.5%. The sensor response is lower to propane than it is to methane.
4.0 SPECIFICATIONS Method of Detection Catalytic detector diffusion/adsorption Measurement Range 0-100% LEL (lower explosive limit) Accuracy/Repeatability ± 3% LEL in 0-50% LEL Range ± 5% LEL in 51-100% LEL Range Response/Clearing Time T50 <10 seconds; T90 <30 seconds Zero Drift < 5% per year Operating Temperature Range -40° to +167° F; -40° to +75°C Operating Humidity Range 0-100% RH (non-condensing) Output Linear 4-20 mA DC Input Voltage 11.5-28 VDC Power Consumption (maximum) < 2.
5.2 Remote Mount Considerations If the application requires that the sensor head be remotely mounted away from the transmitter, maximum line resistance should be 1/2 ohm. Use the wiring table below. AWG 20 18 16 14 Maximum Length (feet) 50 75 125 175 5.3 Sensor Location Selection of physical sensor location is critical to the overall safe performance of the product.
5.4 Local Electrical Codes Sensor and transmitter assemblies should be installed in accordance with all local electrical codes. Use appropriate conduit seals. Drains are required at the bottom of vertical conduit runs. The sensor assemblies are designed to meet NEC and CSA requirements for Class I; Groups B, C, D; Div. 1 environments. Note: An appropriate conduit seal must be located within 18" of the sensor assembly. Crouse Hinds type EYS2, EYD2 or equivalent are suitable for this purpose. 5.
d) Replace the plug-in transmitter module and the junction box cover. 5.6 Remote Mounting Applications Some sensor mounting applications require that the gas sensor head be remotely mounted away from the sensor transmitter. This is usually true in instances where the gas sensor head must be mounted in a location that is difficult to access. Such a location creates problems for maintenance and calibration activities.
Material Requirements * Digital volt meter * Jewelers type screwdriver a) Declassify the area around the sensor. b) Remove the junction box cover from the remote sensor enclosure (see figure 4). c) Using the digital volt/ohm meter, measure the bridge voltage at the remote sensor terminal connector board from the “White” terminal to the “Blue” terminal as shown in figure 4. Target voltage is 2.7 volts. d) At the transmitter, adjust the “VOLT” potentiometer (see figure #5) to achieve a reading of 2.7 vdc (±0.
ment and will, in most cases, not require significant adjustment on start up. However, Detcon recommends that a complete calibration test and adjustment be performed within 24 hours of installation. Refer to calibration instructions in later text. 7.0 CALIBRATION PROCEDURE 7.1 * * * * Material Requirements Digital volt meter Jewelers type screwdriver Detcon PN 943-000006-132 Threaded Calibration Adapter Span Gas 50% LEL methane in air at a controlled flow rate between 200 ml/min. 7.
8.0 FAULT SUPERVISION Model FP-424C sensors incorporate fault circuitry which monitors both the detector loop and the bridge voltage of the catalytic bead sensor element. Should one or both of the catalytic bead circuits become electrically “open” a Detector Fault condition will occur which will result in the illumination of the “DET FLT” LED located on the transmitter face plate. Should the bridge voltage drop below 1.
Unstable Output/ Sudden Spiking/Nuisance Alarms 1. Check condulet for accumulated water. 2. Check transmitter and Terminal PCB for abnormal corrosion. 3. Determine if problem correlates with condensation cycles. 4. Add/change Detcon condensation prevention packet PN 960-202200-000 (replace annually). 5. Check for unstable power supply. 6. Check for inadequate grounding. 7. If correlates with radio communications then use Detcon RFI filter accessory. 8.
11.0 WARRANTY Detcon, Inc., as manufacturer, warrants each new LEL plug-in detector (PN 370-201600-000), for a two year period under the conditions described as follows: The warranty period begins on the date of shipment to the original purchaser and ends two years thereafter. The sensor element is warranted to be free from defects in material and workmanship. Should any sensor fail to perform in accordance with published specifications within the warranty period, return the defective part to Detcon, Inc.
