Single Phase Voltage Relays RN-111M & RN-113 for Commercial & Retail Protection

When the Grid Misbehaves, Your Commercial Equipment Pays the Price

Ask any refrigeration technician servicing commercial cold rooms across India and they will tell you the same story: the compressor did not fail because of a mechanical fault. It failed because the supply voltage sagged to 170 V at 11 PM on a summer night — and stayed there for forty minutes while the motor windings quietly cooked. The compressor was never tripped. There was no protection device watching the supply. There was just a circuit breaker waiting for a short-circuit that never came.

Single-phase commercial loads — cold storage units, CCTV NVR systems, point-of-sale terminals, commercial split ACs, and small passenger or goods lifts — share a common vulnerability. They are designed to operate within a specific voltage window (typically 200–240 V for most equipment). Below that window, motors draw excess current and overheat. Above it, capacitors, MOSFETs and compressor windings fail prematurely. A plain MCB or MCCB offers zero protection against either condition. Only a dedicated voltage monitoring relay watches the supply continuously and disconnects the load before damage occurs.

This is precisely the engineering need that Novatek Electro's RN-111M and RN-113 single phase voltage monitoring relays are designed to address — in panel-mount DIN-rail formats suited to commercial distribution boards, with adjustable voltage thresholds, configurable time delays, and contactor-switching outputs that can handle real-world commercial loads.

What to Look for in a Single Phase Voltage Relay

Not every voltage relay on the market is suitable for commercial and light-industrial deployment. Before selecting a device, verify the following parameters against your installation requirements:

1. Voltage Trip Thresholds — Fixed or Adjustable?

Fixed-threshold relays are convenient but inflexible. Commercial installations in areas with chronically low voltage (common in rapidly urbanising industrial estates) benefit from adjustable under-voltage thresholds so that the protection window can be tuned without replacing the device. Both the RN-111M and RN-113 offer adjustable voltage windows on the 220–240 V AC supply range.

2. Time Delay — Restart and Trip Delay

A voltage relay without a configurable restart time delay is a liability on compressor loads. Refrigeration compressors require a minimum off-time (typically 3–5 minutes) before restart to allow head pressure to equalise. A relay that reconnects immediately after voltage restoration will short-cycle the compressor. Look for adjustable restart (reconnection) delay and trip delay (to avoid nuisance tripping on transient dips).

3. Neutral Break (Neutral Loss) Detection

In Indian distribution networks, neutral conductor breaks are far more common than in European grids. A neutral break causes single-phase loads to experience wild voltage swings — sometimes as high as 380–400 V momentarily — as the load becomes part of an unintended series circuit across two phases. A relay without neutral break protection will not respond fast enough; the RN-111M and RN-113 both include neutral break detection as a standard protection function.

4. Contact Rating and Load Type

A 16 A relay output is sufficient to switch a contactor coil or directly protect loads up to approximately 3.5 kW on 230 V. A 32 A output gives the flexibility to switch heavier contactors or, in some cases, directly protect larger commercial loads. Match the relay contact rating to your contactor coil current, not to your full load current.

5. DIN Rail Mount and Form Factor

Commercial distribution boards and AMF panels use standard 35 mm DIN rail. Both RN-111M and RN-113 are designed for DIN rail mounting — clean integration without additional adapters or custom cutouts.

Model Comparison: RN-111M vs RN-113

Prices as per Novatek Electro Price List 2026-27, effective 01.04.2026. GST @ 18% applicable extra. Contact authorised distributors for current dealer pricing.

Quick Selection Guide — Application vs Model

Application-Based Selection Guide

If your installation requires switching a contactor coil rated up to 16 A — choose RN-111M

The RN-111M's SPDT output at 16 A is well-matched for switching standard IEC contactor coils (typically 5–15 VA burden) to protect commercial ACs, CCTV UPS inputs and POS terminal supply circuits. At Rs. 2,000 per unit (ex-GST), it offers an economical protection solution for small retail and office fit-outs where multiple single-phase circuits are involved.

If your installation requires a 32 A contact output for heavier contactors or direct load switching — choose RN-113

The RN-113 steps up to a 32 A contact rating — suitable for switching heavier AC contactors protecting condensing units in cold storage rooms, motor starters for small lifts, and CNC machine auxiliary supply circuits. At Rs. 2,875 per unit (ex-GST), the RN-113 is the appropriate choice wherever the switched element carries higher current or the relay doubles as a direct series protection device in the supply circuit.

If neutral break risk is high — both models are suitable

Both RN-111M and RN-113 include neutral break (neutral loss) detection. In distribution networks with ageing infrastructure, overhead HT/LT lines, or in rural and semi-urban commercial zones, neutral conductor failures are a documented cause of catastrophic over-voltage events. Any installation in such an environment should specify a relay with neutral break protection as a mandatory feature — not an optional upgrade.

Common Selection Mistakes to Avoid

• Matching relay contact rating to full load current: The relay output switches a contactor coil — not the full load. Sizing the relay at 16 A when your contactor coil draws less than 1 A is perfectly correct. Do not over-specify to RN-113 purely on load current grounds if 16 A contact capacity is sufficient.
• Ignoring restart time delay requirements for compressor loads: Both RN-111M and RN-113 include configurable time delays. Verify that the restart delay is set correctly for the connected compressor type before commissioning. Many field failures attributed to the 'relay' are actually caused by operators over-riding or bypassing the delay during commissioning.
• Using a voltage relay alone without a contactor: The relay output switches a contactor coil in the load circuit. The relay output is not rated to directly interrupt a running compressor motor. Always wire the relay to a suitably-rated IEC contactor.
• Installing without verifying nominal supply voltage: Both relays operate on 220–240 V AC. In feeder circuits where the incoming supply is stepped down to 110 V or 415 V, a separate transformer or the correct relay model for that voltage must be used.
• Omitting surge protection on relay coil circuits: In environments with frequent switching transients (automotive workshops, CNC shops), a suitably-rated MOV or RC snubber across the contactor coil will extend the relay contact life significantly.

Installation Tips from the Field

• Mount the relay on a 35 mm DIN rail with at least 20 mm clearance on either side for adequate airflow and easy wiring access.
• Use 1.5 mm² copper wire for signal terminals and 2.5 mm² or 4 mm² for the output contact circuit, depending on contactor coil current.
• Always include a bypass switch (maintained contact, key-operated or lockable) in parallel with the relay output if continuous operation during maintenance is a requirement — but ensure this bypass is clearly labelled and only used by authorised personnel.
• Set the under-voltage trip threshold conservatively: if your equipment is rated for operation down to 200 V, set the relay trip at 195–198 V to avoid nuisance tripping while still providing protection before the equipment's own thermal limit is reached.
• For cold storage applications, co-ordinate the relay restart delay with the thermostat controller to prevent simultaneous restart of multiple condensing units on power restoration.
• Label the relay clearly on the panel door schedule: 'VOLTAGE PROTECTION RELAY — RN-111M / RN-113 — DO NOT BYPASS WITHOUT AUTHORISATION.'

Why Novatek Electro?

• ISO 9001:2015 Certified Manufacturer: Quality management systems audited and certified — not just a trading company relabelling imports.
• CE Certified Products: RN-series relays comply with applicable European CE directives, confirming compliance with international EMC and safety standards.
• Made in India: Designed, manufactured and tested at Novatek Electro India Private Limited, Delhi — supporting domestic manufacturing with genuine after-sales accountability.
• 30+ Years of Application Experience: Novatek Electro has over three decades of experience in electrical protection devices across single-phase and three-phase applications — the product range reflects real-world Indian grid conditions, not just laboratory specifications.
• Distributor and Panel-Builder Support: Technical datasheets, connection diagrams and application notes are available for panel builders, system integrators and OEMs. Pre-sales and post-sales technical assistance is available via the contact details below.

Frequently Asked Questions