Monitoring Relays for Industrial Protection & Automation

A monitoring relay continuously watches an electrical parameter (voltage, current, phase, liquid level, light) and trips its output contacts when a preset threshold is crossed. Unlike a circuit breaker (which protects against short circuits and overloads), monitoring relays protect against gradual abnormalities — overvoltage, undervoltage, phase loss, undercurrent, or dry running.

Fiicco monitoring relays include:

• FCV18 — Single-phase voltage relay (over & under voltage protection)
• FCC18 — Single-phase current relay (over & under current protection)
• FCL18 — Liquid level control relay
• FCB18 — Twilight (light) relay for outdoor lighting control

All Fiicco monitoring relays fit the same compact 90×18×64mm DIN-rail format and share 1×SPDT 16A output contacts.

This distinction applies to FCV18 and FCC18 models:

• Manual reset (-01 models): Once a fault is detected and the output trips, the relay stays latched in the fault state even after the fault clears. An operator must physically press the reset button on the front panel to restore normal operation. Use for: critical equipment where unexpected restart could cause damage or injury (compressors, pumps, industrial machinery).
• Auto reset (-02 models): Once the fault clears and normal conditions return, the output automatically resets to normal operation without manual intervention. Use for: non-critical loads, HVAC systems, general-purpose protection.

Both modes offer adjustable trip delay (0.1s–20s) to filter out brief transients.

The FCV18 monitors single-phase AC or DC voltage and disconnects the load when voltage goes outside the safe window you set (overvoltage or undervoltage).

Monitored voltage options (via DIP switch selection):

• AC 20–80V (suffix: A48 / D48)
• AC 165–260V (suffix: A220 / D220) — covers standard 220-240V mains
• AC 65–270V (suffix: A240 / D240) — wide AC range
• DC 9–18V (suffix: D12)
• DC 20–80V (suffix: D48)
• DC 65–270V (suffix: D240)

Supply voltage options: AC 230V, DC 24V, or AC/DC 12-240V (universal). Measurement accuracy: ±1% / ±1V. Adjustable trip delay: 0.1s–20s. LED indicators show power (green) and relay status (red).

The FCC18 monitors single-phase AC or DC current flowing through a connected load and trips when current exceeds (overcurrent) or drops below (undercurrent) the set threshold.

Four FCC18 variants, selectable via DIP switch:

• FCC18-01: Overcurrent protection — manual or auto reset
• FCC18-02: Over & under current protection — auto reset only
• FCC18-03: Undercurrent & overcurrent — manual reset
• FCC18-04: Over & under current — manual reset

Current ranges (AC and DC): 0.05–0.5A, 0.1–1A, 0.2–2A, 0.5–5A, 0.8–8A, 1.6–16A. Measurement accuracy: ±1%. Hysteresis (release margin): 5% above / 5% below threshold. Supply voltage: AC 230V, DC 24V, or AC/DC 12-240V.

The FCL18 controls pumps or valves to maintain liquid levels in tanks. It works with external electrodes (probe) immersed in the liquid. The relay monitors conductivity between electrodes and switches its output to fill or empty the tank accordingly.

FCL18-01: 2-level control (Min + Max probes) — one fill pump, one empty pump

FCL18-02: Selectable functions A–F:

• Function A: 2-level control — fills liquid between Min and Max
• Function B / C: 1-level control — fill liquid
• Function E: 1-level control — empty liquid
• Function D / F: 2-level control — empty liquid

Time delay (Tt): 0.1s–10s adjustable. Sensitivity: 5–100KΩ selectable. Probe is not included — use Fiicco FCL-PB probe (1.5m red, 2.5m white, 3.5m blue). The relay's 1×SPDT 16A output connects directly to pump contactors.

The FCB18 (twilight relay) automatically turns lights or equipment on at dusk and off at dawn based on ambient light level. It replaces manual timers for street lighting, billboards, signage, and outdoor area lighting.

Key features:

• Auto mode: Automatically detects sunset/sunrise via built-in light sensor (FCB-PB, 20cm cable included)
• Manual ON / Manual OFF: Override the automatic control for testing or manual operation
• Adjustable lux threshold: Set the exact light level at which the relay switches — from bright daylight to complete darkness
• Supply voltage: AC 230V, DC 24V, or AC/DC 12-240V

Unlike mechanical timers, the FCB18 automatically adjusts for seasonal changes in daylight hours without reprogramming.

Hysteresis (H) is the percentage window between the trip threshold and the release threshold. It prevents rapid on-off cycling near the setpoint.

For FCV18 voltage relays: If you set U> at 240V with H=20% (Function A), the relay trips when voltage reaches 240V. It does NOT release until voltage drops below 240V × (1-20%) = 192V. This 48V deadband prevents chattering near the threshold.

Trip delay (Tt) is the minimum time an abnormal condition must persist before the relay trips — filters out transient spikes. Adjustable from 0.1s to 20s.

Release delay (Tr) on FCC18: The minimum time normal conditions must persist before the relay releases from fault state — prevents rapid reset cycling. Also adjustable from 0.1s to 20s.

Yes. Fiicco monitoring relays (FCV18, FCC18, FCL18, FCB18) are designed for universal use on both 50Hz and 60Hz AC power systems. The relay's internal measurement circuit automatically adapts to the AC frequency it detects.

All models feature a wide input range:

• AC 230V (suffix: A) — standard European/Asian mains
• DC 24V (suffix: D) — low-voltage control circuits
• AC/DC 12-240V (suffix: W) — universal wide voltage, works globally

Voltage tolerance: -15% to +10% across all supply options. The universal (W) models are recommended for export since one part number covers 100-240V environments worldwide.

The FCL-PB probe (electrode set) uses three conductors:

• Red (1.5m) — typically the high-level (Max) electrode
• White (2.5m) — typically the low-level (Min) electrode
• Blue (3.5m) — reference/common electrode

Wiring to FCL18:

• Terminal S1: Connect the Max (or Level) probe wire
• Terminal S2: Connect the Min probe wire (not used in 1-level control)
• Terminal C: Connect the blue common reference electrode

The relay body (R terminal) must be immersed in the liquid as the sensing reference. For tanks deeper than probe lengths, use extension cables to extend probe wires to the appropriate levels.

Yes. The relay's 1×SPDT (Single Pole Double Throw) output contact can interface directly with PLC digital inputs or automation controllers.

Standard terminal layout:

• Terminals 11-14: Normally Open (NO) — closes when relay is energized (normal condition)
• Terminals 11-12: Normally Closed (NC) — opens when relay trips (fault condition)
• Terminals A1-A2: Power supply to the monitoring relay

For PLC digital input: connect the PLC input between 11 and 14 (NO). When the monitored parameter goes out of range, the relay de-energizes, 11-14 opens, and the PLC detects the fault. Cable size: AWG13-20 (0.4N·m torque).

Yes. All Fiicco monitoring relays carry the following international certifications and standards:

• CE — European market compliance
• EAC — Eurasian Economic Union (Russia, Kazakhstan, Belarus)
• RoHS — hazardous substance restrictions for EU and global markets

Manufacturing standards: GB/T 14048.5 and IEC60947-5-1. Protection degree: IP20. Pollution level: 2. Max installation altitude: ≤2200m. Operating temperature: -20°C to +60°C (storage: -40°C to +85°C).

Match the relay to the parameter you need to protect:

• Voltage fluctuations (sags, surges) → FCV18 single-phase voltage relay
• Motor current overload / underload → FCC18 single-phase current relay
• Pump tank overflow / dry-running → FCL18 liquid level relay
• Street lights / outdoor lighting auto control → FCB18 twilight relay

Then choose supply voltage (A=230V AC, D=24V DC, W=AC/DC 12-240V universal) and reset mode (-01 manual, -02 auto). All Fiicco monitoring relays share the same compact 18mm DIN-rail form factor and 1×SPDT 16A output contacts, so they can be mixed and matched in the same control panel.

Yes. Fiicco provides comprehensive OEM and ODM services for the complete monitoring relay range:

• Custom logo and brand labeling on products, housing, and packaging
• Custom voltage and current monitoring ranges
• Custom timing parameters (trip delay, release delay, hysteresis)
• Custom probe lengths and connector types for liquid level relays
• Volume pricing for large orders

With our own factory and 10+ years of manufacturing experience since 2013, we support both small custom runs and high-volume production. Contact us at fiicco.com/contact to discuss your requirements.