Help! My Vintage Solar Inverter Has Finally Failed

If you are reading this because you have a failed ‘vintage’ inverter, you probably bought your solar power system ten or more years ago. In which case…

Congratulations!

As an early adopter, you spent ten times more money than solar systems cost today, and now the little red inverter light is lit, you’ve unlocked the next level in the solar energy adventure game:

The Failed Solar Inverter

There are pitfalls at every turn in this choose-your-own-adventure, but remember the saving grace is  you (still?) have the premium feed-in tariff that paid off the system and continues to make an outsized impact on your electricity bills.

28061kWh, had they all been exported at 50cents, there’s a little over 14 grand before it gave up.

This post is mainly aimed at those who have a transformer-based inverter. They’re usually quite heavy, bolt honest, and from an electrical point of view, fundamentally safe devices that were common 10+ years ago.

There’s no dead giveaway as to what your inverter has inside, so referring to the manual or searching online will usually find its specification. If, like me, you bought a Latronics inverter and the fan is whirring away with resplendent four LED “display”, then it might be worth getting serviced before Latronics winds down in 2025 because the solar panel array will be wired to suit nothing else.

Latronics PVE. The old grey mare isn’t spectacular to look at, but it’s Australian-made and still supported if you freight it back to Queensland.

Other common transformer machines sold in Australia include the old SMA Sunny Boys, the Fronius IG series, Xantrex, Aerosharp, and the Sharp jh1600. There are a few mentioned in this handy reference.

Sadly these solar inverters are almost unobtainable now, so there are two options with some variations.

Option #1: Repair The Inverter

I’m all for repairs – it saves on invested energy and e-waste. With no Distributed Network Service Provider (DNSP) approval or feed-in tariff complications, it’s simply plug-and-play. The challenge is finding someone willing¹ to look under the bonnet and fix it, and what warranty they might offer on the repair. Or you can have look on Gumtree to find a like-for-like replacement, which I know some service-orientated electricians have done; preemptively buying a cheap spare unit when they’re trawling the demolition adverts.

It’s not unusual for a cheap and cheerful new solar inverter plus associated wiring to cost $1500-$2000 or even more. However, I’ve seen old units repaired for around $300; in this instance retaining the great quality SMA machine without having to disturb asbestos eaves and Super 6 roofing.

With cables all very neatly stitched into the service riser when the house was rewired, this unit would be hard to replace neatly. image credit Solar Depot

Option #2: Replace The Inverter

Replacement can become a can of worms because what was legal 10 years ago remains legal, until you change something.

As solar has progressed, inverter topology has moved to faster, lighter and more responsive transformerless designs. These shiny new machines brought on the need for new standards and an additional layer of wiring to make safe the somewhat leaky nature of power-handling electronics.

There’s nothing quite as constant as change, and changing the solar inverter means changing the wiring it’s connected to, which is almost certainly non-compliant now – not least because old systems didn’t have earth wires.

Earthing

The green and yellow wire forms an equipotential bond, meaning any metal part of the electrical system in your house is grounded. If you have a vintage transformer-based inverter, you don’t need to earth the solar array on the roof, whereas modern transformerless models do need an extra wire, run from the array to your switchboard.

Fun fact: when the industry seagulls were squabbling over the sadly defunct SolarShop, the eventual winner ended up using the customer database to send letters to customers with existing systems. They were trying to scare people, implying a change of standard meant old wiring had to be updated to the latest rules… for a fee of course. 

To put it simply, modern solar inverters “leak” electricity². In operation, as much as 120 volts can be present on the module frames. Think of it like static or an electric fence. While it’s not enough energy for a dangerous electric shock, it will be very uncomfortable.

What does earthing achieve? It bleeds off the available current bringing the frame to zero volts, and that prevents falls. No, really. Imagine you’re cleaning gutters and you get a zap from the roof. The electric shock won’t kill you, but hitting the ground after you recoil might.

The other electrical safety function of array earthing is to make it safe under fault conditions. Solid state devices can fail in a couple of ways. When they blow open circuit like a fuse, there is no internal connection; so that’s considered safe.

HRC fuses might not look outwardly burnt like this, but inverter components can burn open or weld closed.

The more dangerous failure is a short circuit.

Accidentally connecting the mains AC supply to the DC wiring from your solar system is a terrible idea. By installing an earth you have a low resistance path for the fault to follow, which in turn causes the circuit breaker in the switchboard to trip before anyone gets electrocuted.

Other Traps

I have been involved in moving secondhand solar modules from one roof to another. Be warned, it can put you and your electrical contractor on a hiding to nowhere. Panels that appear fine from the front can have burns on the back. Despite working as an assembly, they can show faults when the electrical insulation is tested or the plugs are disturbed.

Cracks in the backing sheet like this may not show an electrical fault; yet.

This solar panel is showing its age with the browning of the cells, but the crack in the back sheet isn’t apparent from the front.

If you replace the inverter and the DC wiring then discover a damaged panel, find insulation that tests poorly or seized hardware on the framing, it’s a slippery slope leading straight to a complete replacement system with all new equipment and the comforting reassurance of a new warranty. However, that might cost you the prized feed-in-tariff, so it’s snakes and ladders.

DNSP Requirements

Your local poles and wires organisation may have differing rules, but some are very specific. And because nobody offers a new 4.6kW solar inverter, I believe there are some Queenslanders who struggled to find solutions until Fronius found a way, albeit with a transformerless unit.

In South Australia, SAPN have a more pragmatic approach at least. If you’re within 500 watts of your original approved inverter capacity, you can install a new solar inverter or panels and keep the 44 cent feed-in-tariff

SAPN new energy services :

 

“All customers are able to replace an existing inverter and/or panels without a change to the Feed-in Tariff (FiT) as long as the following is adhered to:

 

·       Approval for the replacement is obtained prior to installation
·       There is no increase to the generating capacity i.e. no extra panels or an energy storage device are installed
·       The inverter meets all current technical requirements, ie AS4777 and the technical standards outlined in Technical Standard TS129, and is a like for like replacement
·       A previous approval was issued for the SEG(s) installed

 

An example of a like for like inverter replacement means a previously approved 2kVA inverter would be replaced with a 2kVA inverter.  If a 3kVA inverter was to be installed this would be classified as an upgrade as 2kVA inverters that meet current standards are available. We do recognise that some inverter capacities are no longer available, to accommodate this our application form has been built with a 0.5kVA tolerance. So for example if the previously approved inverter was 1.7kVA and it is to be replaced with a 2kVA inverter, this would still be considered a like for like replacement.

 

Where existing panels require replacing and panels of a greater wattage are to be used then, for example, if 18 x 250 watt panels are replaced by 20 x 300 watt panels, this would be an increase in generation capacity and, in accordance with the FiT legislation, the FiT would be removed. If eligibility for the FiT is to be retained 15 x 300 watt panels will need to be installed.

 

Any replacement or upgrade application should be for the equipment that will remain on site once the replacement installation has occurred.”

So my South Australian friend Marc³ could possibly blow up his 2.5kW Sunny Boy again, and replace it with a new 3kW inverter. While his 16 x 185 W solar panel array (2.96 kWp) can be replaced with 8 x 370w, it can’t be expanded.

Two SMA SunnyBoy 1700s are still humming away in 2022.

Speaking Of DNSP Rules

New systems must, of course, comply with current rules regarding connection to the grid, including AS4777.2.2020. New inverters should also be internet connected as required to protect the broader grid.

New solar inverters replacing old ones may be treated differently in your area, so if you can wrangle it, Fronius offers a great solution for small systems that don’t have earth wiring.

The Fronius Galvo is a transformer-based 3kW model that is no longer manufactured, but it’s analogous to the current Primo inverter range and is still offered directly from Fronius as a new inverter with warranty and monitoring solutions available. It’s not compliant with the latest AS4777, but it’s a great solar inverter if your DNSP will allow it.

Fronius deserves an honourable mention here because not only do they offer great service, they’re proactive in reaching out to make sure this article is correct⁴.

If you have an Aerosharp, there’s a very good chance it just needs a fuse replaced inside, but a Fronius is four times the inverter for half the weight. Image credit: Inverter Repairs Adelaide.

Just Bite The Bullet

As mentioned, some early adopters are on Gumtree asking $375 for the 1.1kWp Sunny Boy system that years ago cost $12,000 because they want to make a real dent in their expanding consumption. For the same spend, you can get ten times the system now, and feed-in tariffs become irrelevant when you just add a zero to the system capacity.

For those worried about the embodied energy in solar panels that might be going to landfill, you can rest a little easier knowing there are now around five recycling plants in Australia. And better still, many panels are being bought secondhand and shipped to developing countries for reuse. Even “faulty” panels that won’t pass insulation testing for 500-volt strings are perfectly good for less ambitious battery charging or running solar pumps.

So, Where Should You Spend Your Money?

First, you probably shouldn’t ask me because I’m great at spending other people’s money.

I’m willing to bet some local electricians will check your solar system out, change an inverter, add an earth wire, charge modestly and move on without batting a regulatory or compliance eyelid. Competent electrical workers doing that with small systems don’t pose much risk to you or the network, but the network should still be notified, and the inverter is internet-connected where required.

If your solar inverter is showing a fault light, you might follow the instructions on the shutdown procedure sticker yourself, turn off the isolators, disengage the plugs, and lift the machine off the wall and into your car to be diagnosed and repaired. However, even if you are confident, I would still recommend getting a qualified and experienced solar electrician to have a look. It’s something you promised the DNSP you would do every five years anyway.

It can’t hurt to run and get a quote for a big, new solar system in any case. If you look at the totals on your retail meter (and it hasn’t been swapped since the system was installed), you may be pleasantly surprised at how much you’ve already saved.