Last night when we were headed to bed we heard an unfamiliar noise in the upstairs hallway. It sounded like a clock ticking really fast, like 4 times a second. We checked the clocks in the adjoining rooms before realizing the sound was coming from the attic. At first we thought maybe the attic fan was either vibrating or blocked by something, but when I climbed up there it turned out one of the two Rapid Shutdown Devices (RSDs) was making the sound. Here’s a video I took:
https://www.youtube.com/watch?v=JtqvQ4BL1fs
I texted Derrick about it and he said that was really weird because those devices should always be in their “shutdown” mode when the Inverters aren’t powered up. The inverters’ knobs were left in the “on” position but they should still be powered down because the big solar cutoff switch outside by the electric meter is in the “off” position. He told us to go turn the knobs on the inverters off as well.
When we went into the garage to do that, we noticed one of the RSDs in the garage attic was making the same ticking sound. The inverter displays were blank, suggesting they really were powered down. But when we turned the inverter knobs to the “off” position both ticking sounds stopped!
Derrick is going to come out with the crew today and get to the bottom of the mystery. He said he’s never heard of this happening before. He’s bringing a couple replacement RSD devices just in case they’re faulty. I’ll let you know what happens!
The Hickory Hill Solar Project 