MCK-301-61 & MCK-301-85 Digital Temperature Controllers for Cold Chain & HVAC

When a Mechanical Thermostat Fails at 3 AM — and Your Cold Chain Cannot Afford It

Picture this: a refrigerated storage facility holding temperature-sensitive biologics. Outside, the ambient temperature is pushing 45°C during a peak Indian summer. Inside the compressor room, the control panel houses a 30-year-old bimetal mechanical thermostat — the same one installed during commissioning, never calibrated since. At 3:47 AM, the compressor short-cycles because the thermostat's setpoint has drifted by nearly 4°C due to vibration fatigue and contact oxidation. The evaporator coils ice up. Airflow collapses. The storage zone breaches its upper limit. By the time the morning shift arrives, the damage is done.

This is not a hypothetical. It is the predictable failure mode of an entire generation of mechanical temperature control devices deployed across cold storage facilities, HVAC chiller plants, textile humidification systems, and food processing lines across India. The engineering root causes are well understood — yet under-addressed in many panel-builder and OEM specifications.

Why Mechanical Thermostats Fail: The Engineering Root Cause

Mechanical thermostats rely on bimetal strips or bellows-and-diaphragm assemblies that deflect with temperature change to open or close contacts. Over time, several failure mechanisms converge:

• Contact oxidation: In humid or chemically aggressive environments — common in textile dyeing and processing areas — contact resistance increases, causing erratic switching or complete failure to trip.
• Setpoint drift: Mechanical calibration is susceptible to vibration (compressors, fans), thermal cycling fatigue, and ageing of the spring elements. A drift of ±3°C to ±5°C is not uncommon after 3–5 years of service.
• No differential control: Mechanical devices cannot implement programmable hysteresis bands. Short-cycling of compressors — with its attendant motor winding stress and refrigerant surge — is a direct consequence.
• No defrost intelligence: Frost accumulation on evaporator coils reduces heat transfer efficiency dramatically. Without scheduled defrost cycles, a refrigeration plant operating in humid Indian summers will see evaporator capacity collapse within days.
• No alarm relay output: When a mechanical thermostat fails, there is no supervisory signal to alert operations or a SCADA/BMS system. The fault is silent until product loss occurs.

The solution is a microcontroller-based digital temperature controller with programmable setpoints, differential bands, timed defrost scheduling, and independent alarm relay outputs. That is precisely what the MCK-301-61 and MCK-301-85 deliver.

Introducing the MCK-301-61 and MCK-301-85: Microcontroller Intelligence for Real Refrigeration Loops

MCK-301-61

MCK-301-85

Both models belong to Novatek Electro's MCK-301-XX family — microcontroller-based intelligent logic controllers designed for HVAC room temperature management and refrigeration control. They accept industry-standard PTC and NTC sensors, operate across a wide supply voltage range of 220V to 415V AC, and provide four configurable operating modes covering electric heater thermostat, air conditioning zone control, alarm, and test conditions. CE certified and compliant with IEC 60947-1, IEC 60947-6-2, CISPR 11, and IEC 61000-4-2, these are not consumer-grade thermostats — they are industrial-grade controllers built for continuous-duty refrigeration and HVAC environments.

Key Technical Features That Address the Refrigeration Control Problem

1. Microcontroller-Based Setpoint Accuracy

Unlike bimetal devices, the MCK-301 series maintains setpoint fidelity through solid-state temperature sensing and digital comparison logic. PTC and NTC thermistors provide rapid thermal response with no moving parts — no drift, no mechanical fatigue, no recalibration cycles in the field.

2. Four Configurable Operating Modes

The controller supports: electric heater thermostat mode (for humidification and heating stages in textile processing), air conditioning zone control mode (for chiller and split-system regulation), alarm mode (independent over-temperature or under-temperature trip), and test mode (for commissioning and annual maintenance checks without disrupting the controlled load). This four-mode architecture means a single SKU can be configured at the panel-builder stage for multiple application types.

3. Compressor Cycling Protection

Programmable differential (hysteresis) bands prevent compressor short-cycling by ensuring the controller does not re-energise the compressor contactor until the measured temperature has moved sufficiently past the setpoint. This directly protects motor windings from thermal stress caused by frequent start-inrush currents.

4. Defrost Scheduling

The MCK-301-XX family handles defrost cycle management — a critical requirement for walk-in cold rooms, blast freezers, and HVAC chiller evaporators operating in Indian humidity conditions. Timed defrost prevents evaporator icing without manual intervention.

5. Alarm Relay Output for Supervisory Integration

Independent alarm relay contacts allow integration with building management systems (BMS), SCADA panels, or simple local annunciators. Over-temperature alarms for vaccine storage and food-grade cold rooms can be wired to GSM diallers or remote monitoring panels — closing the 'silent failure' gap of mechanical thermostats.

6. Wide Voltage Tolerance: 220V to 415V AC

India's industrial power supply regularly fluctuates. The MCK-301 series accommodates both single-phase and three-phase supply environments within the 220V–415V AC band, making it suitable for diverse panel configurations across light industrial and heavy industrial sites without additional voltage conditioning.

7. EMC and Industrial Immunity Compliance

Compliance with IEC 61000-4-2 (electrostatic discharge immunity) and CISPR 11 (industrial, scientific, and medical equipment emissions) ensures the controller operates reliably in electrically noisy environments — compressor rooms, VFD-driven chiller plants, and textile machinery floors where switching transients and RFI are constant concerns.

Technical Specifications at a Glance

Prices effective 01 April 2026. GST @ 18% applicable extra.

Quick Selection Guide

Application Categories Where MCK-301-61 and MCK-301-85 Are Typically Deployed

• Cold chain warehousing and distribution centres: Multi-zone temperature monitoring and compressor contactor control for refrigerated storage of perishable goods.
• Vaccine and pharmaceutical storage: Precise setpoint control with alarm relay output to meet WHO and CDSCO cold chain storage guidelines for 2°C to 8°C storage bands.
• Food processing and blast freezing: Defrost scheduling and over-temperature alarming for hygienic food-grade environments.
• HVAC chiller plants in commercial and industrial buildings: Zone temperature regulation and chiller unit cycling for energy-efficient climate control.
• Textile manufacturing — humidification and HVAC: Maintaining process temperature and humidity bands in spinning, weaving, and dyeing areas where fibre quality is directly dependent on ambient conditions.
• Dairy and beverage processing: Chiller and pasteurisation temperature control in liquid food processing lines.
• Telecom infrastructure cooling: Precision temperature control for equipment room air conditioning and free-cooling systems.
• Agricultural produce cold storage: Potato, fruit, and vegetable cold rooms with defrost management for humidity-rich environments.

Why Novatek Electro?

• ISO 9001:2015 certified manufacturing: Every MCK-301-XX unit is produced under a documented quality management system — traceability, incoming inspection, and final functional test are mandatory, not optional.
• CE certified and IEC compliant: CE marking and compliance with IEC 60947-1, IEC 60947-6-2, CISPR 11, and IEC 61000-4-2 means these controllers meet the same electromagnetic compatibility and safety standards required for European markets — a benchmark that matters for OEM export projects.
• Made in India — Delhi-based manufacturer: Domestic manufacturing ensures faster lead times, spare parts availability, and rupee-denominated pricing without import duty exposure.
• 30+ years of electrical protection device expertise: Novatek Electro's product range spans voltage relays, phase sequence relays, timers, power quality analysers, and temperature controllers — a depth of application knowledge that generic importers cannot match.
• After-sales and technical support: Direct access to application engineering support through authorised distributor channels and the Intelli-Electro online platform — not a grey-market supply chain.

Frequently Asked Questions