FCL18-01 Series

Liquid Level Control Relay
Single Function — Empty Operation

Reliable single-function liquid level relay for automatic emptying control of tanks, sumps, and reservoirs. Adjustable sensitivity (5–100 kΩ) and safe low-voltage electrode operation — all in a compact 18mm DIN rail housing.

12–240V AC/DC Supply Empty (Drain) Function 2 Level Probes Sensitivity 5–100 kΩ Immediate Response DIN rail mount 18mm slim design 1×SPDT 16A Low-Voltage Electrodes IP40 Front
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FCL18-01 Liquid Level Control Relay
💧 Automatic Emptying Control Designed to automatically drain tanks, sumps, and reservoirs when the liquid reaches the set probe level.
⚡ Low-Voltage Electrodes Probes operate at max. AC 3.5V / <0.1mA — safe for conductive liquids and personnel, no risk of electrolysis.
🎚️ 5–100 kΩ Adjustable Sensitivity Fine-tune the probe response from 5 kΩ to 100 kΩ to suit different liquid conductivities and probe arrangements.
⚡ Immediate Relay Operation No time delay — the output relay closes or opens instantly when the liquid level triggers the probe threshold.
📏 18mm Ultra-Slim Design Seamlessly integrates with FCT18, FCP18, FCV18, and FCC18 series for a consistent panel layout.
🔧 1×10⁷ Mechanical Life Outstanding 1×10⁷ mechanical operations for reliable long-term service in pump control applications.

📋 Model & Ordering

Model Function Probe Levels Sensitivity Supply Voltage Datasheet
FCL18-01 Empty (Drain) 2 probes 5–100 kΩ adjustable 12–240V AC/DC 📄 Download PDF

💡 FCL18-01 is a dedicated Empty (Drain) function relay. When the liquid reaches the high-level probe, the output relay energizes immediately to start the pump. After the level drops below the low-level probe, the output de-energizes immediately to stop the pump. For multi-function versions (Empty & Fill selectable), choose FCL18-02. Probe set FCL-PB is sold separately.

⚙️ Technical Specifications

🔌 Supply

Supply TerminalsA1 – A2
Supply Voltage12–240V AC/DC
Power ConsumptionAC 3.5VA / DC 2.0W
Voltage Tolerance-15% ~ +10%

🛡️ Monitoring & Probes

FunctionEmpty (Drain)
Probe TerminalsS1 – S2 – C (Common)
Sensitivity Range5 kΩ – 100 kΩ
Electrode Voltagemax. AC 3.5V
Probe Current< 0.1 mA
Response TimeImmediate (no delay)

🔌 Output

Contact1 × SPDT
Rated Current16A @ 250V AC
Mechanical Life1×10⁷ operations
Electrical Life1×10⁵ operations

📐 Physical & Environmental

Dimensions18 × 90 × 64 mm
MountingDIN rail EN 60715
Protection DegreeIP40 (front) / IP10 (terminals)
Operating Temp.-20°C ~ +55°C
Storage Temp.-30°C ~ +70°C

📜 Standards & Certifications

ComplianceGB/T 14048.5, IEC 60947-5-1, EN 6812-1
Contact ConfigurationSPDT: 11(COM)-12(NC)-14(NO)
Pollution Degree2
Max. Cable SizeAWG 13–20 / 0.4 N·m

💡 Panel LED Indicators

LED Color Status Meaning
Un Green OFF Supply voltage not applied
Un Green ON Supply voltage applied
R Red OFF NC (11-12) contact closed (pump off)
R Red ON NO (11-14) contact closed (pump on)

📈 Function Diagram – Empty (Drain) Operation

FCL18-01 Empty Function Diagram

• The relay monitors the liquid level using conductive probes connected to terminals S1 (high level), S2 (low level), and C (common).
• When the liquid reaches the high-level probe S1, the output relay R closes immediately (NO contact 11-14 makes). The pump starts draining.
• When the liquid drops below the low-level probe S2, the output relay R opens immediately (NC contact 11-12 makes). The pump stops.
• The cycle repeats automatically as the tank refills. For single-probe operation, connect S1 and S2 together — the relay will start and stop at the same level.

🎬 See it in Action

🔧 Wiring & Terminal Layout

Terminal Identification

A1 — Supply L / + A2 — Supply N / - S1 — High Level Probe S2 — Low Level Probe C — Common (Ground/Reference) 11 — COM 12 — NC 14 — NO
⚠️ Safety Note: Keep the power supply disconnected during installation. The probe circuit operates at low voltage (max. 3.5V AC) but must be wired with appropriate insulation. Do not connect probe terminals to mains voltage.

Supply (A1–A2): 12–240V AC/DC.
Probes (S1, S2, C): S1 = start pump (high level), S2 = stop pump (low level), C = common reference. Suspend probes at appropriate heights in the tank. For single-level control, connect S1 and S2 together.
Output (11-12-14): SPDT 16A/250V AC, wire to pump contactor.

FCL18-01 Wiring and Terminal Layout Diagram

🛠️ Parameter Setting Guide

  1. Enter Parameter Setting Mode: Long-press the button until the LED flashes.
  2. Set Sensitivity (kΩ): Adjust the sensitivity threshold from 5 kΩ to 100 kΩ to match the conductivity of your liquid and probe configuration. Lower kΩ values are for more conductive liquids; higher values for less conductive ones.
  3. Confirm and Store: Long-press until LED stops flashing. The setting takes effect immediately — no power cycle required.

🏭 Typical Applications

💧 Sump & Pit Drainage
Automatically empties sumps, elevator pits, and underground collection tanks
🏠 Wastewater Management
Controls sewage ejector pumps in residential and commercial lift stations
🏭 Industrial Tanks
Maintains tank levels by draining process water or condensate at the high-level point
🌧️ Stormwater Control
Activates stormwater pumps when collection basins reach a preset level
🚰 Well & Borehole Dewatering
Controls submersible pumps to keep groundwater levels below foundations or excavations
🔧 Machine Coolant Systems
Drains coolant tanks when full to maintain proper circulation in CNC and machining centers

🔗 Related Products

Explore other liquid level relays in the FCL18 series:

FCL18-01 — Single Function Empty (Current Page) FCL18-02 — Multi-Function Fill & Empty

❓ Frequently Asked Questions

🔹 What is the probe sensitivity and how do I set it?
Sensitivity is adjustable from 5 kΩ to 100 kΩ. It determines the resistance threshold at which the relay detects liquid contact. For clean water, a setting around 10–20 kΩ typically works. For dirty or low-conductivity liquids, increase the value. Use the digital button to adjust.
🔹 Can I use a single probe instead of two?
Yes. Connect S1 and S2 together to a single probe. In this configuration, the pump will start when the liquid reaches the probe and stop when it drops below it immediately — there is no time delay.
🔹 Are the probes safe to use in conductive liquids?
Absolutely. The probe circuit operates at a maximum of AC 3.5V with less than 0.1 mA. This is intrinsically safe for personnel and prevents electrolysis or corrosion of the electrodes over time.
🔹 Can I use FCL18-01 to fill a tank instead of emptying it?
No. The FCL18-01 logic is fixed for empty/drain operation. To fill a tank (start pump on low level, stop on high level), you need the FCL18-02 multi-function model, which allows selection between Empty and Fill functions.
🔹 Does FCL18-01 have any timing delay?
No. The FCL18-01 reacts immediately when the liquid level reaches or drops below the probes. There is no adjustable or fixed time delay. This provides instant pump response for straightforward level control applications.
🔹 What is the mechanical life of the output contacts?
The relay has an outstanding mechanical life of 1×10⁷ operations. Electrical life is 1×10⁵ operations at rated 16A/250V AC. This provides excellent longevity for pump cycling applications.

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