FCV18-02
Single-Phase Voltage · Over-voltage & Under-voltage Protection Relay
Precision Single-Phase Voltage Protection in 18mm
The FCV18-02 is a high-performance single-phase voltage monitoring relay providing reliable over-voltage and under-voltage protection in an ultra-compact 18mm DIN rail module. With AC/DC input support ranging from 12V to 240V, it covers virtually all single-phase voltage monitoring requirements.
Designed for industrial control panels, power distribution systems, and sensitive equipment protection, the FCV18-02 delivers ±1% measurement accuracy with adjustable trip thresholds, configurable time delay, and adjustable hysteresis for stable operation. The front-panel button interface enables fast, tool-free configuration.
Quick Specifications
Why Choose the FCV18-02?
Engineered for industrial reliability and precise single-phase voltage monitoring.
Over & Under Voltage Protection
Dual-function protection guards your equipment against both dangerous over-voltage and damaging under-voltage conditions with independently adjustable thresholds.
±1% Measurement Accuracy
Electronic voltage sensing circuit ensures stable, repeatable protection with minimal drift across temperature and load variations.
16A SPDT Output Relay
High-capacity SPDT output handles direct load switching. Mechanical life 10 million cycles, electrical life 100,000 cycles for long-term reliability.
Tool-Free Configuration
Four front-panel dials (U>, U<, Tt, H) allow fast, screwdriver-free setup. No programming or software tools required.
Adjustable Hysteresis
Configurable hysteresis (H) from 1% to 10% prevents relay chattering near the trip threshold, ensuring stable operation and extended relay life.
Protection Functions
Comprehensive monitoring of over-voltage and under-voltage fault conditions.
The FCV18-02 monitors both over-voltage and under-voltage conditions simultaneously. The diagram below illustrates the operating regions. The relay trips when the measured voltage exceeds the over-voltage threshold (U>) or drops below the under-voltage threshold (U<) and holds for the configured time delay (Tt).
The adjustable hysteresis (H) setting ensures stable operation by defining the difference between the trip threshold and the reset threshold. This prevents continuous relay chattering when the voltage hovers near the trip point.
1. Over-voltage Protection (U>)
When the measured voltage rises above the adjustable over-voltage threshold (U>), the relay initiates the configured time delay (Tt). After the delay elapses, the relay trips and opens/closes the output contact based on your wiring configuration. This protects connected equipment from dangerous overvoltage conditions caused by power surges, load rejection, or grid faults.
- Trip threshold: Fully adjustable via front panel dial (U>)
- Time delay: Tt setting prevents nuisance tripping from brief transients
- Reset: Automatic reset when voltage drops below U> × (1-H%)
2. Under-voltage Protection (U<)
When the measured voltage falls below the adjustable under-voltage threshold (U<), the relay initiates the configured time delay (Tt). After the delay elapses, the relay trips. This prevents equipment damage and malfunctions caused by sustained low-voltage conditions from brownouts, overloaded circuits, or loose connections.
- Trip threshold: Fully adjustable via front panel dial (U<)
- Time delay: Tt setting prevents nuisance tripping from brief voltage dips
- Reset: Automatic reset when voltage rises above U< × (1+H%)
Technical Specifications
FCV18-02 Series — Full electrical and mechanical specifications.
| Parameter | AC Models (A48 / A220 / A240) | DC Models (D12 / D48 / D240) |
|---|---|---|
| Voltage Type | Single-Phase AC | Single-Phase DC |
| Monitored Voltage Range | A48: 20-80V AC A220: 165-260V AC A240: 65-260V AC |
D12: 9-18V DC D48: 20-80V DC D240: 65-260V DC |
| Over-voltage Setting (U>) | Direct voltage value (set on dial) | |
| Under-voltage Setting (U<) | Direct voltage value (set on dial) | |
| Time Delay (Tt) | 0.1s ~ 30s (adjustable) | |
| Measurement Accuracy | ΔV < ±1% | |
| Temperature Coefficient | 0.05%/°C at 20°C | |
| Output Contact | 1 × SPDT (NO + NC) | |
| Rated Current | 16A / 250V AC | |
| Mechanical Life | 1 × 10⁷ operations | |
| Electrical Life | 1 × 10⁵ operations | |
| Ambient Temperature | -20°C to +60°C | |
| Mounting | 35mm DIN Rail (EN/IEC 60715) | |
| Dimensions (H × W × D) | 90 × 18 × 64 mm | |
| Weight | 68g | |
| IP Rating | IP20 | |
| Standards | GB/T 14048.5, IEC 60947-5-1, EN 61812-1 | |
* Storage temperature: -40°C to +85°C. Operating altitude: ≤2200m. Pollution level: 2.
Terminal Connections
SPDT relay output with screw-clamp terminals for fast, reliable wiring.
FCV18-02 — Single-Phase AC/DC Voltage Monitoring
- Always de-energize the panel before wiring
- Verify supply voltage matches the module rating before powering on
- Connect monitored voltage leads to the correct terminals (S1/S2 for AC, +/- for DC)
- Terminal 11 = Common, 12 = NC, 14 = NO — wire your load to the appropriate contact
- Use correct wire gauge for 16A load current (min. 1.5mm²)
- Tighten terminal screws to 0.4 N·m torque specification
- Stripping length: 7mm (AWG13-20)
Front Panel & Settings
Configure the FCV18-02 using four adjustment dials — no software or programming tools required.
| Parameter | Description | Setting Range |
|---|---|---|
U> |
Over-voltage Trip Threshold — voltage above which the relay trips | Model-specific, see ordering table |
U< |
Under-voltage Trip Threshold — voltage below which the relay trips | Model-specific, see ordering table |
Tt |
Time Delay before trip — the delay period before confirming a fault | Adjustable (model-specific steps) |
H |
Hysteresis — difference between trip and reset threshold to prevent chattering | 1% to 10% (adjustable) |
LED Indicator Panel
Un — Green LED
Lit = relay is powered on and monitoring the system
R — Red LED
Lit = NO contact (terminals 11-14) is closed, relay is energized
How to Set Parameters
- Enter setting mode: Press and hold the button until the LED starts flashing.
- Adjust dials: Set
U>,U<,Tt, andHto your desired values while the LED is flashing. - Confirm: Press and hold the button until the LED stops flashing to save your settings.
Note: The reset thresholds are calculated based on the hysteresis (H) setting: Over-voltage reset = U> × (1-H%) and Under-voltage reset = U< × (1+H%). For example, with U> = 250V and H = 2%, the relay resets when voltage drops below 245V (250V × 98%).
Models & Ordering
Choose the voltage monitoring range that matches your application.
| Model Code | Voltage Type | Monitoring Range | Typical Applications | Manual |
|---|---|---|---|---|
| FCV18-02-A48 | AC | AC 20-80V | 24V, 36V, 48V AC systems, industrial control circuits | PDF ↓ |
| FCV18-02-A220 | AC | AC 165-260V | 110V, 120V, 220V, 230V AC systems | PDF ↓ |
| FCV18-02-A240 | AC | AC 65-260V | Universal AC systems, wide range monitoring | PDF ↓ |
| FCV18-02-D12 | DC | DC 9-18V | 9V, 12V DC battery systems, telecom power | PDF ↓ |
| FCV18-02-D48 | DC | DC 20-80V | 24V, 36V, 48V DC systems, solar installations | PDF ↓ |
| FCV18-02-D240 | DC | DC 65-260V | 110V, 220V DC systems, industrial DC power | PDF ↓ |
FCV18 Family — Model Comparison
Compare the FCV18 series voltage relays to find the right protection configuration for your application.
| Model | Over-voltage | Under-voltage | Trip Setting | Time Delay | Phase Type | Reset Mode | Ideal For |
|---|---|---|---|---|---|---|---|
| FCV18-02 | U> direct set | U< direct set | Direct voltage value | 0.1~30s | Single-Phase AC & DC | Auto Reset | Unattended systems. Automatic restart after voltage returns to normal. |
| FCV18-01 | U> direct set | U< direct set | Direct voltage value | 0.1~30s | Single-Phase AC & DC | Manual Reset | Applications requiring manual reset. Trip latch ensures fault is acknowledged before restart. |
Configuration Examples
Real-world setting examples for common voltage systems.
FCV18-02-A48 — 24V AC System
| Over-voltage (U>) | 28V |
| Under-voltage (U<) | 20V |
| Time Delay (Tt) | 0.1s |
| Hysteresis (H) | 1% |
FCV18-02-A220 — 220V AC System
| Over-voltage (U>) | 240V |
| Under-voltage (U<) | 200V |
| Time Delay (Tt) | 1s |
| Hysteresis (H) | 2% |
FCV18-02-D12 — 12V DC System
| Over-voltage (U>) | 15V |
| Under-voltage (U<) | 10V |
| Time Delay (Tt) | 1s |
| Hysteresis (H) | 1% |
See It In Action
Watch the FCV18-02 product overview and demonstration.
Typical Applications
The FCV18-02 protects equipment across a wide range of industrial sectors.
Battery Systems
Protect 12V/24V/48V battery banks from over-charge and deep discharge damage.
Solar Installations
Monitor DC solar panel arrays and battery storage systems for voltage anomalies.
Power Distribution
Panel-level monitoring in LV switchgear and distribution boards.
Telecom Power
Protect telecom base station power systems and DC distribution equipment.
Industrial Control
Protect PLCs, sensors, and control circuits from voltage anomalies.
Ready to Order or Need More Details?
Download the full technical manual or contact the FIICCO team for pricing, samples, and OEM options.
Frequently Asked Questions
Common questions about the FCV18-02 single-phase voltage protection relay
The FCV18-02 series offers six models covering DC 9V to AC 270V: FCV18-02-A48 (AC 20-80V), FCV18-02-A220 (AC 165-260V), FCV18-02-A240 (AC 65-260V), FCV18-02-D12 (DC 9-18V), FCV18-02-D48 (DC 20-80V), and FCV18-02-D240 (DC 65-260V). All models accept AC/DC 12-240V supply voltage.
The AC models (A48, A220, A240) are designed for monitoring alternating current systems. The DC models (D12, D48, D240) are designed for monitoring direct current systems such as batteries, solar installations, and DC power supplies. All models can be powered by AC/DC 12-240V supply.
Hysteresis (H) defines the difference between the trip threshold and the reset threshold to prevent relay chattering. For over-voltage: relay trips at U> and resets when voltage drops below U> × (1-H%). For under-voltage: relay trips at U< and resets when voltage rises above U< × (1+H%). Example: With U> = 250V and H = 2%, the relay trips at 250V but only resets when voltage drops to 245V (250V × 98%). This ensures stable, reliable operation without rapid on/off cycling near the threshold.
The FCV18-02 has a single SPDT (single-pole double-throw) relay contact rated 16A/250V AC. Terminal 11 is the common, 12 is normally closed (NC), and 14 is normally open (NO). Wire your load between terminal 11 and terminal 14 for normally open operation — the circuit is energized when the relay trips.
No. The FCV18-02 is designed for single-phase voltage monitoring only. For three-phase systems, consider the FCP18 series (FCP18-01, FCP18-02, FCP18-03, FCP18-04, FCP18-05, FCP18-06) which are specifically designed for three-phase protection including phase sequence and asymmetry monitoring.
The FCV18-02 is certified to CE, RoHS, and meets the standards of IEC 60947-5-1, GB/T 14048.5, and EN 61812-1. This makes it suitable for industrial automation applications in Europe, Asia, and other global markets.
The time delay prevents nuisance tripping from brief voltage transients. For sensitive equipment, use shorter delays (0.1s-1s). For motor loads or systems with frequent voltage fluctuations, use longer delays (1s-10s) to filter out normal transients. Note: When set to 0.1s, the relay may continuously engage/disengage if voltage fluctuates near the threshold — it is recommended to set Tt to 1 second or more.
Yes. FIICCO provides OEM services including custom branding (logo, model number, color), tailored specifications, and custom packaging for orders of 100+ units. Factory-direct pricing ensures competitive costs for OEM customers. Contact us at info@fiicco.com with your requirements and quantity for a tailored quotation.