Monday Rookie Mistakes: How I Left 5 Combiner Boxes Off for 2 Months

Let me tell you about one of my most humbling moments in solar O&M.

Back in 2021, I was managing an O&M service while also doing monitoring. During routine preventive maintenance, one of my technicians accidentally left 5 combiner boxes disconnected.

Honestly? I get why it happened. Those boxes had the weirdest closing system, no LED indicators, and all the cables were buried. Easy mistake to make.

But here's where it gets worse...

The tech didn't check his work when he finished. I didn't verify it from the control room. We didn't even catch it in our end-of-month performance review.

Two. Full. Months.

It was only when I finally dug into the PR and energy performance index trends that I saw something was off. We pulled up the heat map and there it was—5 combiner boxes just sitting there, disconnected.

Cue the emergency truck dispatch and some very awkward conversations.

Here's what I learned (so you don't have to learn it the hard way):

The real issue wasn't the technician's mistake. It was our process—or lack thereof. No combiner box monitoring. No systematic inverter comparison after maintenance. No immediate performance spot-checks.

We got lucky. The PR impact was minimal. But that wake-up call changed everything about how we approach maintenance verification.

Today, these mistakes don't happen anymore. Not because we became perfect, but because we built systems that catch human error before it costs time and money.

What's your "oops, we missed that" moment? Share below—we're all learning together.

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