FCC18 Current Relays for Over & Under Current Protection

The FCC18 continuously monitors single-phase AC or DC current and trips its output contacts when current crosses your preset overcurrent (I>) or undercurrent (I<) thresholds. Unlike a circuit breaker (which trips on short circuits and sustained overloads), the FCC18 protects against gradual current abnormalities — overload, underload, phase loss, and dry running that can damage motors, pumps, and other equipment.

Key specifications:

• Monitored current: AC 0.05A–16A and DC 0.05A–16A (6 ranges each)
• Supply voltage: AC 230V, DC 24V, or AC/DC 12-240V (universal)
• Measurement accuracy: ±5% / ±0.1A
• Output: 1×SPDT 16A relay contacts
• Dimensions: 90×18×64mm DIN-rail mount
• Certifications: CE, EAC, RoHS, GB/T 14048.5, IEC60947-5-1

The FCC18 series covers four monitoring modes:

• FCC18-01 (Overcurrent): Trips when current exceeds the I> threshold. Supports manual or auto reset. Use for: motor overload protection, cable overload monitoring, equipment requiring overcurrent cutoff.
• FCC18-02 (Undercurrent): Trips when current falls below the I< threshold. Supports manual or auto reset. Use for: pump dry-run protection, conveyor belt break detection, compressed air system monitoring.
• FCC18-03 (Over & Under Current, Manual Reset): Monitors both overcurrent and undercurrent simultaneously. Must be manually reset after fault. Use for: critical equipment where unexpected restart could cause damage (deep well pumps, submersible pumps, industrial conveyors).
• FCC18-04 (Over & Under Current, Auto Reset): Same dual monitoring as FCC18-03 but automatically restores when current returns to normal window. Use for: HVAC systems, cooling pumps, general-purpose dual-threshold protection.

The difference is how the relay restores normal operation after a fault:

• Manual Reset: Once current crosses the threshold for longer than Tt, the relay trips and stays latched — even after current returns to normal. An operator must physically press the reset button on the front panel. Essential for critical equipment where unexpected restart could cause damage or injury (submersible pumps, large motors).
• Auto Reset: Once current returns to the normal window and stays there for the restore delay (Tr), the relay automatically closes its contacts again. No manual intervention needed. Use for: non-critical loads, HVAC systems, general-purpose protection.

Note: FCC18-03 uses manual reset only; FCC18-04 uses auto reset only. FCC18-01 and FCC18-02 offer a choice of manual or auto reset (set via DIP switch or button on the front panel).

The FCC18 uses front-face DIP switches and rotary dials for configuration:

Step 1 — Select monitored current range (DIP switches 1-2):

• A0.5 / D0.5: AC/DC 0.05A–0.5A
• A1 / D1: AC/DC 0.1A–1A
• A2 / D2: AC/DC 0.2A–2A
• A5 / D5: AC/DC 0.5A–5A
• A8 / D8: AC/DC 0.8A–8A
• A16 / D16: AC/DC 1.6A–16A

Step 2 — Set supply voltage (DIP switch 3): A (AC 230V), D (DC 24V), or W (AC/DC 12-240V universal).

Step 3 — Set thresholds with the I> (overcurrent) and I< (undercurrent) dials. Use the trip delay (Tt) dial to prevent nuisance tripping from brief inrush currents. The green LED shows power on; red LED shows relay tripped.

Yes. The FCC18 current relay is 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 — no manual frequency setting is needed.

Three supply voltage options are available:

• A: AC 230V — standard European and Asian mains
• D: DC 24V — low-voltage control circuits
• W: AC/DC 12-240V — universal wide voltage, covers 100-240V globally

Voltage tolerance: -15% to +10% across all supply options. The universal (W) models are recommended for export distributors since one part number covers all global mains voltages.

FCC18 has two terminal groups:

Power supply terminals (A1-A2): Connect to the supply voltage (AC L/N or DC +/-). This powers the relay's internal circuitry.

Current sensing input (IN-OUT): Connect the load's line conductor through the IN-OUT terminals. The relay measures current flowing through this conductor. For three-phase loads, connect one phase conductor through the FCC18 to monitor current draw.

Output contacts (11-14-12):

• 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)

Terminal specs: AWG13-20, stripping length 7mm, torque 0.4N·m. Mounting: DIN rail EN/IEC 60715.

Trip delay (Tt) is the minimum time (0.1s–20s, adjustable) that current must stay outside the set window before the relay trips. It prevents nuisance tripping from:

• Motor inrush current during startup
• Brief load fluctuations
• Pump pressure surges

Restore delay (Tr) applies only to FCC18-02 and FCC18-04 (auto reset models). After a fault clears, the relay waits Tr before automatically restoring output. This prevents rapid chattering when current hovers near the setpoint.

Setting guide: Use a longer Tt (5-20s) for motor loads with high startup current. Use a shorter Tt (0.1-2s) for pump dry-run detection where quick response is needed. For auto reset models, set Tr shorter than Tt to prevent deadlock.

Yes. The FCC18 is specifically well-suited for pump protection applications:

• FCC18-02 (Undercurrent): The most common choice for pump dry-run protection. Set I< slightly below the normal operating current of your pump. When the well runs dry or an airlock occurs, current drops, and the relay trips to stop the pump before damage.
• FCC18-03 (Over & Under, Manual Reset): Recommended for submersible pumps where unexpected restart could cause mechanical damage or flooding. Monitors both overcurrent (blockage) and undercurrent (dry run) simultaneously.

Tip: Set the undercurrent threshold (I<) at approximately 70-80% of the pump's normal operating current to allow for normal variations while catching genuine dry-run conditions. Set Tt at 3-10 seconds to accommodate brief startup current variations.

The FCC18 carries the following certifications for global market access:

• 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.

Environmental ratings:

• Protection degree: IP20
• Pollution level: 2
• Max installation altitude: ≤2200m
• Operating temperature: -20°C to +60°C
• Storage temperature: -40°C to +85°C
• Temperature coefficient: 0.05%/°C at 20°C

Yes. Fiicco provides comprehensive OEM and ODM services for the FCC18 current relay:

• Custom logo and brand labeling on the product housing, packaging, and documentation
• Custom current monitoring ranges beyond the standard 6 AC and 6 DC options
• Custom timing parameters (trip delay, restore delay ranges)
• Custom supply voltage options
• 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.