The Critical Role of DC Isolators in Solar Safety
When installing a solar PV system, one of the least visible yet most important components is the DC isolator. Acting as a critical safety switch, it disconnects the DC current between the solar panels and the inverter in the event of maintenance or emergencies.
In Australia, the use of DC isolators is not just recommended—it is legally required under AS/NZS 5033 standards for rooftop solar installations. This blog will explore what a DC isolator is, how it works, why it’s essential for solar safety in Australia, and how to choose the right type.
What Is a DC Isolator?
A DC isolator is a manually operated switch that disconnects the direct current (DC) electricity flow between your solar panels and your inverter. It allows technicians to safely service the system without risk of electric shock from the high-voltage DC current.
Key Functions
- Disconnects power at the array level
- Allows safe inverter replacement or fire response
- Meets regulatory compliance (AS/NZS 5033)
How It Works
When activated, the isolator breaks the circuit and stops DC flow. This is particularly crucial because DC current, unlike AC, does not pass through zero voltage, which makes it more difficult to interrupt safely. A good solar isolator is designed to handle arcing and resist heat damage.
AC vs DC Isolators: What’s the Difference?
While both isolators serve safety functions, their applications and construction differ:
| Feature | AC Isolator | DC Isolator |
| Voltage Type | Alternating Current (AC) | Direct Current (DC) |
| Common Use | Disconnect grid from inverter | Disconnect panels from inverter |
| Arc Handling | Easier due to zero-crossing | More complex, needs arc suppression |
| Required By Law (AU) | Only at meter box | Yes, at panel & inverter location |
In Australia, DC isolators are mandatory for rooftop PV systems as per AS/NZS 5033 to ensure solar array safety during maintenance and emergencies.
Why DC Isolators Are Required in Australia
Australia’s sunny climate makes it ideal for solar power, but also increases the risk of fire if systems are not safely isolated. In response to several rooftop fires, the Clean Energy Council (CEC) and Standards Australia made DC isolators compulsory.
Legal Requirements
- AS/NZS 5033 mandates external DC isolators for all rooftop solar installations.
- They must be weatherproof, UV-resistant, and compliant with IEC 60947.3 standards.
Benefits of Compliance
- Faster emergency response
- Simplified shutdown procedures
- Increased safety for electricians & first responders
Risk of Non-compliance
- Insurance invalidation
- Safety hazards
- System shutdowns
Types of DC Isolators & How to Choose
When selecting a DC isolator, consider:
Rated Voltage & Current
Ensure compatibility with your solar array’s output. For example, a 600V system needs isolators rated above this threshold.
Number of Poles
- 2-pole for single MPPT
- 4-pole for dual MPPT or string connections
Weatherproofing (IP Rating)
Outdoor isolators must meet at least IP66, which resists dust, water, and UV damage.
Mounting Style
- Surface-mounted: Typical for rooftop installations
- Din-rail: For internal enclosures
Arc Suppression Design
Look for models with certified arc extinguishing chambers, especially for 1000V+ systems.
Recommended Product from Solar Rains
Explore Solar Rains’ high-performance DC isolator range:
- ZJ Beny BYSS – Compact, IP66-rated, 4-pole switch for rooftop use
- ZJ Beny BYT – Designed for hybrid systems, with external isolator cover and anti-UV housing
These products meet Australian regulations and offer robust protection for both residential and small commercial systems.
Installation Best Practices
Even the best isolator is ineffective without proper installation. Key tips:
- Always mount externally, within 2m of the solar array.
- Use UV-stabilised conduit to protect exposed cable runs.
- Label isolators clearly with “Solar DC Isolator – Do Not Disconnect Under Load.”
- Follow CEC guidelines for wiring, torque, and enclosure ratings.
Improper installation can cause water ingress, arcing, or even fire. Use CEC-accredited installers to reduce risks and ensure warranty compliance.
Common DC Isolator Issues & How to Prevent Them
Water Ingress: Seal all cable entries with approved glands and face isolator away from prevailing rain.
Arcing Due to Overload: Match isolator current rating with array specs. Do not “oversize” strings beyond manufacturer specs.
Heat Damage: Keep isolators shaded and avoid roof locations with direct midday sun if possible.
Incompatible Switches: Do not use AC-rated switches for DC circuits. They cannot safely extinguish arcs.
FAQs
AC isolators disconnect alternating current (used at the meter); DC isolators break high-voltage DC from solar panels, requiring different arc suppression and ratings.
In rooftop installations, near the solar array and accessible from the ground. Both rooftop and inverter-side isolators may be required.
No. Only certified DC isolators meet solar safety and voltage interruption standards.
No. Choose isolators based on array voltage, string count, and installation environment.
At least once a year, or after major weather events. Look for discoloration, signs of melting, or water ingress.
Only if the switch is rated for “under load” disconnection. Otherwise, wait until panel output drops (e.g., late evening).
A protective shield that prevents dust, water, and accidental contact. It extends the product’s lifespan, especially outdoors.
Conclusion & Expert Advice
In Australia, DC isolators are a safety essential, not an afterthought. Whether you’re a homeowner, installer, or commercial operator, ensuring your solar system includes certified, well-installed DC isolators helps protect lives and property.
For trusted products, Solar Rains offers a curated range of DC isolators that meet all Australian standards. From ZJ Beny BYSS to BYT series with isolator covers, you’ll find the right switch to match your system size, inverter type, and environmental exposure.
Need help selecting the right model? Reach out to the Solar Rains technical team for guidance tailored to your installation needs.
