Cable Conduits on a Roof with Solar – Necessity or Monstrosity?
By Aniket Bhor on in New Zealand Solar Legislation
As it is, many people don't consider solar panels on a roof as particularly beauty-enhancing. So when the discussion moves to solar panels with visible conduits laid on the roof, the topic becomes somewhat infuriating - even to people in the industry. So why do every now and then we see a house with its roof strangling beneath ugly and evil-looking conduits? Let’s go into some more detail to find out.
The (Supposed) Need for Cable Conduits
Despite the massive advancement of our human race, we are still decades away from truly wireless electrical systems, where power can be transmitted wirelessly. Until then, we’ll need to connect our solar arrays with cables.
Connecting adjacent solar panels together is not so tricky - installers simply connect wires together underneath the panel surface. However, things become complicated when a roof does not have a single, large space for an array, and installers need to split bunches of panels over multiple roof areas.
The simplest way to connect these multiple bunches or arrays of solar panels together is to join them with cables and lay those cables on the roof in a conduit. You can lay as many conduits on a roof as you want without any technical complexity. But beauty is not always simplicity. Here is an example of solar panels connected with ugly-looking conduits:
Ugly solar installation by an unknown solar installer. Picture taken by Mike Ward from Solar365
In the picture above, the conduit is stretched a long distance between solar arrays. We have never see soo much conduit on one roof! Perhaps the roof couldn't be penetrated near one of the arrays... so the installer just sighed and put those cables in a conduit and ran it all over the roof like ugly tentacles.
That said, there may be cases when running a conduit or two may be the best idea.
When to Run Cables in a Conduit?
Concealing DC cables in a roof, however superior over open conduits, often poses its own challenges. Firstly, if your roof doesn’t offer a single large open space and you have to connect too many solar arrays together, concealing cables means drilling too many holes in your roof.
Any roofing specialist will tell you that too many roof penetrations is a bad idea. No matter how good a job is done, the less you disturb a roof, the better for your house. Moreover, there are strict regulations on how to have concealed cables in a roof.
For instance, the standards in Australia and New Zealand make it mandatory to encase the concealed cables in a heavy-duty conduit and label it as “Solar DC” every two metres or where it changes direction. This is meant to avoid the accidental cutting of the cables - which is extremely important considering that another name for high-voltage DC cables is “Deadly”.
The latest solar installation standard, AS5033:2021, has even more specific requirements for cable routing inside ceiling spaces. Here’s an image showing some of the requirements:
Source: GSES
Naturally, routing cables into the ceiling multiple times is not only difficult but also time-consuming. And however ugly conduits might look, there is no court of aesthetics that punishes you for visible conduits, especially when they are short and barely visible. An example of this is when solar panels are laid on a roof on different sides and a small conduit joins both arrays near the hip of the roof.
Expert Opinion on Cable Conduits
On the topic of cable conduits, we decided to speak to an expert. Our founder Kristy Hoare reached out to Greg Hoskins, Principal at Hoskins Energy Systems, to hear his opinion on cable conduits. Greg has 35 years of solar PV and storage expertise, and is a master electrician and the industry's go-to technical expert. He shapes NZ's solar industry standards through roles on the SEANZ board and the AUS NZ EL-042 Standards Committee. Here’s a summary of their conversation.
Kristy: I was wondering if you could give me some clarification on the circumstances where conduit on the roof is allowed.
Greg: As long as it’s watertight and [a proper] solar conduit, there are no rules broken, though it looks bad and I would not complete installs like this or want it on my roof. Generally a penetration into the roof space, one under each array is the more professional and safer way to install wiring between sub-arrays.
The extended external conduit with bends and glued joints may not stay watertight over a long period of time, once water gets in it will create a short in most PV cables as they are not made to be submersed.
There - you have it! Cable conduits on the roof are not only unsightly but also considerably unsafe, especially when we’re talking about systems that need to last 25 or 30 years.
Conclusion
A short summary of our above discussion can be given as this:
- As far as possible, do not run conduits on the roof.
- If the roof requires too many penetrations, use short, barely visible conduits in a minimal number of places.
- Definitely do not use conduits because you are a lazy installer or lack the expertise to penetrate the roof in multiple places for carefully running a concealed conduit (use an expert in this case).