Collection: Level & Voltage Monitor Relays

A voltage monitor relay continuously measures the supply voltage and compares it against preset upper and lower thresholds. If the voltage goes outside these limits — due to overvoltage, undervoltage, or phase loss — the relay opens or closes its output contact to disconnect or alarm the protected load. They are essential for motor protection in three-phase systems. Explore our full Level & Voltage Monitor Relays range for available models.

A voltage monitor relay detects electrical conditions — overvoltage, undervoltage, phase loss, or phase sequence — and protects motors and equipment from electrical faults. A level monitor relay, by contrast, monitors the physical level of a liquid (water, oil, chemicals) in a tank or vessel using conductive probes or float inputs, and switches a pump or alarm accordingly. Many applications use both together. Browse our Level & Voltage Monitor Relays collection for models covering both functions.

Yes — level monitor relays are commonly used to automate pump operation. When the liquid level drops below a set point, the relay activates the pump; when the level reaches the upper set point, the pump is switched off. This eliminates manual monitoring and prevents both dry-running and overflow. For motor efficiency in pump systems, pair your relay with a Motor Run Capacitor.

Three-phase voltage monitor relays typically protect against overvoltage, undervoltage, phase loss (one or more phases missing), phase imbalance (unequal voltages across phases), and incorrect phase sequence (phases wired in the wrong order). Each of these conditions can cause motor overheating, reduced torque, or mechanical damage if undetected. Pair your relay with Motor Run Capacitors for a complete motor protection setup.

Most conductive-probe level monitor relays use a low-voltage sensing circuit: a common electrode (reference) is placed in the tank alongside one or two sensing electrodes at the desired low and high level positions. When the liquid bridges the circuit between the common and the sensing electrode, the relay detects conductivity and switches its output. Always follow the manufacturer's wiring diagram, and ensure probe materials are compatible with the liquid being monitored. Browse our Level & Voltage Monitor Relays for models with full wiring documentation.

Motor capacitors and monitor relays serve complementary roles in motor protection. Capacitors — including Motor Run Capacitors and Motor Start Capacitors — improve motor efficiency, power factor, and starting torque. Monitor relays, on the other hand, protect the motor from abnormal supply conditions. Together they form a robust protection and performance package for single-phase and three-phase motors.

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