Monitors

Monitoring relays watch for abnormal electrical conditions — over/under voltage, phase loss, motor overload, signal failure, ground fault — and trigger alarms or trip protective contacts. They sit between the control system and the equipment being monitored, providing early warning before a failure cascades.

Enicstra stocks monitoring relays from Allen-Bradley, Phoenix Contact, Crouzet, ICM Controls, Symcom, Bender, and other manufacturers. Coverage includes single-phase and three-phase voltage monitors, current-sensing relays, phase-sequence and phase-loss detectors, ground-fault monitors, and motor protection relays. Every unit is bench-tested for trip threshold accuracy and backed by our 12-month functional warranty.

Monitoring relays must be specified for the exact voltage, current range, and trip behavior of your circuit. If a specific monitor part number isn't shown, send the OEM code and the parameters being monitored. Most quote inquiries reply within 1–2 business days.

Subcategories

Relay Output Monitors

EDM relays and forced-guided contact monitors for safety-circuit feedback — current and obsolete in stock.

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Monitors

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Buying guide

Choosing Monitors components

Monitoring relays come in many specialized forms — voltage, current, frequency, phase, ground fault, motor — and each is tuned to a specific monitoring task. A general-purpose voltage monitor won't catch the unbalanced-phase condition that destroys a three-phase motor; a phase-sequence relay won't see a slow voltage drift.

Specifications to confirm before ordering:

Quantity being monitored (voltage, current, phase, frequency, ground fault, etc.)
Nominal value and trip thresholds (over, under, both)
System voltage and number of phases
Trip and reset behavior (manual reset, auto-reset, latching)
Output contact configuration (NO, NC, SPDT, DPDT)
Output rating for downstream contactor coil or PLC input
Delay/hysteresis settings to avoid nuisance tripping
Mounting style (DIN-rail, panel-mount, flush-mount)
Compliance markings (UL 508, CE, CSA)

Common monitor types and applications:

Voltage monitor (single-phase): protects sensitive loads from over/under voltage on 120/240 VAC
Three-phase voltage and phase monitor: protects three-phase motors from phase loss, reversal, and unbalance
Current sensing relay: alarms on motor overload, no-load (broken belt), or jammed conditions
Ground-fault monitor: detects insulation leakage in motor circuits and isolated control systems
Frequency monitor: protects loads where generator or VFD frequency excursions matter

For motor protection, a current-sensing monitor with adjustable trip class is usually the right starting point — overload relays in modern motor starters handle most cases.

Related categories Frequently asked questions

Can you supply discontinued ICM, Symcom, or Crouzet monitors?

Yes — legacy monitoring relays from these specialized manufacturers are common requests, particularly older ICM and Symcom motor protection units. Send the model number for a quote.

Voltage monitor vs phase monitor — what's the difference?

A voltage monitor watches a single nominal voltage value and trips on excursions. A phase monitor specifically watches three-phase systems for phase loss, phase reversal, and phase unbalance — failure modes a simple voltage monitor won't catch reliably.

Do monitors handle their own load switching?

No — monitoring relays have small output contacts (typically 5–10 A) intended to drive a contactor coil or PLC input. They don't switch motor loads directly. Pair the monitor with an appropriately sized contactor for load disconnection.

How do I avoid nuisance tripping?

Use a monitor with adjustable trip delay and hysteresis settings. For brief voltage dips that don't matter to your equipment, set the delay to 1–2 seconds. For sensitive electronics, set tighter thresholds with shorter delays.

Are these new, surplus, or used?

Most stock is new-old-stock — unused, often in original packaging. Some legacy monitors come from tested system removals. Each product page lists condition where known.