Maintenance of self-regulating electric heating cables

Maintaining self-regulating heating cables is crucial to ensure stable, long-term operation, prevent breakdowns, and extend their service life. Unlike constant-power heating cables, self-regulating heating cables are characterized by their self-regulating power output, but their structure and materials (especially the PTC core strip) have specific installation and maintenance requirements.

The following is a systematic maintenance guide for self-regulating heating cables, divided into several sections: Daily Inspection, Periodic Maintenance, Troubleshooting, and Precautions.

I. Daily Inspection and Monitoring

This is the foundation of preventive maintenance, especially during initial system commissioning, extreme weather conditions, or changes in process conditions.

Visual Inspection:

Heating Cable Body: Inspect the outer sheath for mechanical damage (such as cuts, wear, nicks), overheating, melting, deformation, or cracks due to aging. Pay special attention to areas prone to friction, such as valves, flanges, and brackets.

Accessories and Junction Boxes: Check that the power junction box, two-way or three-way junction box, and electrical box are properly sealed, with no water leaks, corrosion, or peeling. Ensure that the sealant or waterproofing compound is not cracked or peeling.

Insulation Layer: This is crucial! Check that the insulation layer is intact and dry. Any damage, water immersion, or lack of insulation will result in significant heat loss, forcing the heating cable to operate at high power continuously, which will eventually lead to overload damage or the inability to maintain the temperature.

Electrical Parameter Check:

System Operating Status: Confirm that the thermostat (if applicable) is functioning correctly and that the indicator lights on the control circuit are illuminated.

Current Measurement: Use a clamp meter at the power supply box to measure the operating current of each circuit and compare it to the initial installation and commissioning current value or the product's rated current. Abnormal increases or decreases in current may indicate a fault (such as aging of the sections, moisture, short circuit, or open circuit).

Performance Check:

Temperature Check: Use a contact or infrared thermometer to measure the surface temperature at several representative points on the pipes or equipment (especially at the ends and coldest points), ensuring it remains within the established maintenance range.

II. Regular Maintenance (Recommended annually before winter or when the system is shut down). Complete Inspection in Case of Power Outage:

Completely disconnect the power and post a "Do Not Reconnect" warning sign.

Open all junction boxes and inspect the internal wiring connections for safety and to check for signs of electrical sparks, corrosion, or moisture. Clean away dust and debris, and reseal the connections.

Check the fit between the heating cable and the conduit. If it is loose, re-secure it with aluminum tape or heat-sensitive tape.

Insulation Layer Inspection:

If the insulation layer is damp, it must be completely replaced with dry insulating material. Damp insulation not only affects insulation performance but can also corrode the conduit and heating cable.

Repair any damaged insulation and outer sheathing (such as aluminum foil or colored steel plate).

Electrical Testing:

Insulation Resistance Test: Measure the insulation resistance between the heating cable core and the metallic shielding layer (or conduit) using a 500 VDC or 1000 VDC megohmmeter. A minimum resistance of 20 MΩ is generally required. A significant drop in resistance (e.g., below 2 MΩ) indicates possible moisture or damage to the insulation.

Loop resistance test: Measure the DC resistance of the entire heating wire loop and compare it to the product's factory specification or historical records to determine if the conductor is damaged. Control system verification:

Inspect and calibrate the thermostat and temperature sensor.

Test the circuit breaker, residual current device (RCD), contactor, etc., to ensure proper operation.

III. Key Precautions and Contraindications

Strictly Prohibited: Overlapping installation is strictly prohibited: The main feature of self-regulating heating cables is their self-regulating temperature, but overlapping them will cause overheating due to poor heat dissipation, which can eventually lead to burns. This is the most common installation error.

Strictly Prohibited: Each type of self-regulating heating cable has a maximum exposure temperature and a holding temperature limit. When used near high-temperature environments (such as steam cleaning), products with the appropriate temperature resistance rating must be selected, or insulation measures must be taken.

Proper Cutting and Sealing: Cut only at the marked points with scissors. The ends and connections of the wiring must be tightly sealed with special fittings; wrapping them with ordinary electrical tape is absolutely prohibited.

Prevention of Mechanical Damage:Tools (such as tin snips and screwdrivers) can easily puncture the heating cable during installation and maintenance. Exercise extreme caution.

Contraindications: Do not use in areas where flammable and explosive gases accumulate and explosion protection requirements are not specified (an explosion-proof type is required); not recommended for main heating of pipes with low thermal conductivity, such as plastic pipes; suitable only for freeze protection.

IV. Maintenance Records: Maintain a complete maintenance log that records the following information:

Installation date, line number, model, and length of the heating cable.

Date of each maintenance session, test data (insulation resistance, operating current), problems detected, and corrective actions taken.

Failure history.

Summary: The key to maintaining the self-regulating electric heating cable lies in ensuring insulation, checking the current, preventing damage, and avoiding overlaps. A dry and intact insulation system is essential for the efficient and long-term operation of the heating cable. Regular electrical inspections and preventative maintenance can effectively avoid the risk of production interruptions in winter. For complex problems, it is recommended to contact your electric heating supplier or professional technicians.