Rhonda Bracey: At Random

For most of this year, my renewable energy rebates have been way down. When I compared this year’s billing to previous years’ rebates for the same billing periods, there was a noticeable drop-off. For example, from Nov 2017 to Jan 2018, the system fed some 800 renewable units back into the grid. From Jan to Mar 2018, a period of perfect, mild, sunny, summer weather, it fed only 79 units into the grid, compared to Jan to Mar 2017, when it fed 500 units in, and Jan to Mar 2016 when it fed back 408 units. The same pattern occurred over the billing cycles for the first half of this year — the feed-in units were down substantially, and we hadn’t changed our electricity use.

I called my solar PV people to see if there might be a reason for this big drop. On their advice I checked the overall output from the system, which was a tad down on the average, but not enough to be significant. We decided to wait another billing cycle and see if there was any change. When the latest bill arrived, it was clear that something was up. Instead of the usual 100 or so feed-in units over May to Jun (winter months), it was zero. Nada. Nothing.

I decided to take two measurements at the same time over two consecutive days of similar weather. And it was then I noticed that something wasn’t right with some of the figures displayed on the inverter. In particular, the PIN 1 and PIN 2 figures. When the system was installed, I was told that the PIN figures were the ones to focus on as they told me how much electricity the system was producing at any moment in time. The PIN figures have always been slightly different, but always within 50 or so of each other.

However, when I checked on these two days, the PINs were way out. For example:

Normally, these figures should be about the same. Instead, they differed by more than 1500 units. The same for the next day.

I got back on the phone to the solar PV people and sent them the photos I’d taken of all the displayed information on the inverter, and my concern about the wildly varying PIN numbers. Yep, something was up. They organised for a local solar guy to come out and check the system, particularly the arrays on the roof. And it was there that he found the reason. One of the two isolators (one for each array) was full of condensation, what looked to be salt (we live near the ocean), and some rusty grungy stuff. No wonder it wasn’t working! (click the photo to see it larger, with all the water drips on the top and back, and the salt particles on the dry surfaces)

Yesterday, he came out and replaced both isolators (I figure if one was like this after 5 years, the other might not be good either, even though he said it was fine and still well sealed). The new isolators have better weather protection (a new standard brought in since we had our system installed 5 years ago), so here’s hoping the problem has been solved for good.

When he’d finished, I checked the inverter display and both PINs were back to being within a few units of each other. Problem solved!