Disconnection Points Vs DC Isolators: A Solar Inspector’s Experience

Let’s shed some light on the ongoing debate between disconnection points and rooftop isolators; two critical aspects that have stirred discussions within the solar industry.

As a Licenced Electrical Inspector, I’m here to delve into the intriguing world of real-world solar installations in the Australian market. This is the first article in a monthly series.

The Emergence Of DC Isolators

DC isolators caused quite a stir upon their introduction early last decade. See the article : The principle benefits of SolarEdge solar techniques. Depending on who you talk to, either firefighters in Victoria played a significant role in advocating for them, or it was a typical “nanny state” decision.

The idea is that in the event of a fire, the solar panel arrays on your roof could be safely switched off by anyone on the roof using the rooftop isolator – so they could be confident they would not be electrocuted as they battled the flames.

DC isolators became mandated nationwide via the Australian Standard for solar installations: AS5033.

As with any new technology, challenges arose, including concerns about workmanship, product quality, and the impact of UV exposure degrading the plastic isolators.

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The Rise And Fall Of Rooftop DC Isolators

Fast forward to late 2021, and an update to the 5033 standard meant – in many cases – rooftop DC isolators were no longer mandatory. See the article : array. An alternative option in the latest standard is the disconnection point.

A disconnection point is a connector that can be pulled apart, opening the DC circuit to the solar panel array, isolating it from the inverter.

This development was generally well-received by installers, as it promised streamlined installations and reduced potential failure points.

However, like any change, it also brought unique challenges, such as additional cabling requirements and restrictions on specific installation locations.

Let’s now explore the pros and cons of each approach:

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Disconnection Points (DPs) Pros & Cons:

Pros:

✅ Simplified installations: Disconnection points offer installers a more straightforward and efficient installation process. On the same subject : array.

✅ Reduced potential failure points: With fewer components, the risk of failures due to faulty parts is minimized.

This is an image of a disconnection point with the correct labelling.

Cons:

❌ Increased cabling requirements: Implementing disconnection points may necessitate additional cabling, which could complicate the installation process.

These new measures aim to minimise the risk of cables falling if a ceiling collapses – which can happen in a house fire.

Specifically:

  • Cables and conduits must be firmly attached so they don’t accidentally come loose. They shouldn’t be placed closer than 50 mm to the bottom of the roof.
  • If cables are between 1 and 1.5 meters from an outside wall, they should be at least 0.6 meters above the ceiling. If they’re lower, they must be tied to the roof.
  • If cables are anywhere else in the ceiling space, they must be 0.6 meters above the ceiling. If there is less than 0.6 meters of space in the ceiling, the cables must be within 1 meter of the outside wall.
  • If people can get into the roof or floor space where the cables are, you need to put up a sign.

Here’s an example from an inspection where a disconnection point has been used, but the cabling is not compliant with the stricter rules:

This is an image of some DC cabling in the roof cavity. It is non-compliant as it has been installed too close to the ceiling and is well away from an outside wall.

❌ Exclusion zones: Certain installation areas, such as cathedral ceilings, may not be suitable for disconnection points, requiring careful planning.

This is an image of a non-compliant disconnection point. The steel cable tie fixing the label in position is done in a way that does not allow the conductor to be disconnected.

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Rooftop Isolators:

Pros:

✅ Maintenance convenience: Rooftop isolators provide an advantage for maintenance, making testing and access more accessible for installers.

✅ Familiarity for some installers: Those already accustomed to rooftop isolators may find them more comfortable to work with initially.

This is an image of a DC isolator that installers are used to and were easily operated. This would not be compliant with the current standard.

Cons:

❌ Stricter requirements: Utilising rooftop isolators demands additional measures, such as liquid drain valves, to prevent water ingress.

❌ Potential complexities: Installing rooftop isolators may involve additional considerations, including larger shrouds and other safety measures.

This is an image of a compliant DC isolator. Note the liquid draining device installed on the very short piece of conduit.

This is an image of a conduit enclosing DC cabling to an inverter with an integrated DC isolator. Again, note the liquid-draining device on the conduit at its lowest point.

Installer Preferences And Real-World Observations

From my observations, most solar installers in the industry have embraced disconnection points. They seem to be the preferred choice, with rooftop isolators being used only when no other options are available. This may be due to situations where the DC cabling must be run through a cathedral ceiling or a shallow cavity that cannot achieve the minimum clearance required.

However, some installers may still be adjusting to the new concept, leading to occasional issues like running cables within exclusion zones or improperly implementing the vertical drop method, like in the image above.

Even if installers opt for rooftop isolators, the stricter requirements now in place call for careful attention. Liquid draining devices and larger/more enclosed shrouds are a must, making the process more intricate.

The liquid draining device may seem a little conservative, especially when installed on a piece of conduit that may only be 300mm long and has a multi-hole gland sealing the end. It seems that the rules are encouraging no conduit to be installed directly into isolators containing DC to reduce the risk of water ingress causing damage to equipment.

The popularity of disconnection points since their introduction cannot be denied. In most installations I see, the installer has demonstrated that they understand the new disconnection point standards. However, some major non-conformances are detected; such as the DC cabling installed inside exclusion zones. Generally, most defects found are minor, like misplaced labelling or the location of DPs.

In conclusion, as a Licenced Electrical Inspector, I support using disconnection points when executed correctly. They offer benefits in terms of inspections and installation efficiency, leading to positive outcomes for consumers. As with any change, continuous education and training are vital for installers to stay current with the latest standards and ensure high-quality, reliable solar installations.

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