Isolator

What is an isolator

An isolator is a manually operated mechanical switch that creates a visible disconnection between electrical equipment and its power source. Unlike circuit breakers, isolators do not trip automatically on fault conditions; their purpose is safe disconnect for maintenance, inspection or emergency.

For solar PV installations, isolators are required on both DC and AC sides. The DC isolator sits at the inverter DC input or inside the combiner box, rated for the system DC voltage (1000 V or 1500 V) and arc-interrupting capability designed for DC. The AC isolator sits between the inverter AC output and the distribution board or bidirectional meter, allowing the inverter to be isolated from the grid for servicing.

CEA Measures Relating to Safety and Electric Supply Regulations 2023 mandate isolators at defined points in any grid-connected solar installation. DISCOM commissioning verifies presence of both DC and AC isolators.

Why isolators matter

Maintenance safety. Personnel can work on de-energised equipment.

Emergency disconnect. Manual disconnect during fires or other emergencies.

Lockout-tagout (LOTO). Padlock-able isolators enable formal safety procedures.

Regulatory compliance. CEA Measures Relating to Safety require isolators.

Code compliance. CEIG and DISCOM verify isolator presence.

Isolator types

Most modern solar isolators are load-break switch-disconnectors, allowing operation under load.

Technical deep dive

DC isolator specifications

AC isolator specifications

Placement in solar

Lockout-tagout (LOTO)

Real-world applications

PV array isolation at the combiner box, one of the balance of system components sourced alongside the inverter.

Inverter DC input isolation, a step covered in our solar inverter integration EPC setup guide.

Inverter AC output isolation.

Bidirectional meter line side isolation.

Hybrid battery DC isolation, sized alongside the battery in our hybrid solar inverter battery sizing guide.

Emergency disconnect at building entry.

Common isolator problems

Contact welding after operating under fault.

Mechanical wear from frequent operation.

Loose terminations causing heating.

Water ingress in inadequately sealed isolators.

Lockout hardware missing or damaged.

Unbranded isolators failing in 1 to 2 years.

Best practices

Use TUV-certified DC isolators for solar DC applications.

Choose branded products (Schneider, ABB, Phoenix Contact, Siemens, Havells, L&T) for long life.

Specify IP65 or better for outdoor installation.

Include lockout provision.

Document isolator ratings on the single line diagram.

Operate at least twice yearly to verify function.

Thermography during O&M.

Comparison: isolator vs related devices

Indian market context

Major Indian DC isolator brands: Schneider Electric, ABB, Phoenix Contact, Siemens, Havells, L&T, Camsco, Polytron — many of the same brands compared in our guide to inverter suppliers and distributors in India.

ALMM does not list isolators. BIS certification under IS 13947 applies.

DISCOM commissioning verifies isolator presence and rating.

CEIG drawing approval requires isolators marked at correct locations on the SLD, part of the electrical drawing package an EPC submits.

PM Surya Ghar residential installations include both DC and AC isolators.

Standards and certifications

Common mistakes

Using AC isolator on DC circuit.

Inadequate voltage rating for system DC voltage.

Skipping lockout provision.

Unbranded isolator failing early.

Wrong pole count for array configuration.

Operating isolator under fault condition (welding contacts).

Key takeaways

Isolators are manual safety disconnects required on both DC and AC sides of solar PV installations. Indian compliance requires IEC 60947-3 or IS 13947 certified devices, with appropriate voltage and current ratings, IP65 enclosure for outdoor use, and lockout provision for LOTO. Quality branded isolators last 10,000+ operations; unbranded units fail early. CEIG and DISCOM commissioning verify isolator presence at required locations.

Further reading

For how Isolator plays out in real projects, these guides go deeper:

• Solar Inverter Wiring Diagram for Indian Homes 2026: Panels to Meter Board
• Solar Inverter Band Ho Jaye Toh Kya Karein
• Pre-Monsoon Solar System Inspection Checklist India
• Solar Inverter Failure: Safe First Actions

Sources

• IEC 60947-3, Switches, disconnectors, switch-disconnectors and fuse combination units.
• IS 13947, Indian LV switchgear.
• CEA (Technical Standards for Connectivity of the Distributed Generation Resources) Regulations, 2013 (as amended 2019), Central Electricity Authority.
• CEA Measures Relating to Safety and Electric Supply Regulations 2023.
• Manufacturer documentation from Schneider Electric, ABB, Phoenix Contact, Siemens.
• IS 60898, Circuit breakers (for comparison).
• IEC 62548, PV array design.
• IEEE Standard Dictionary of Electrical and Electronics Terms.
• IEC 60529, IP ratings.