Solar glass roof - tapping sound from j-boxes in attic

[Keoni8888]

I have a solar roof with 4 strings of tiles. The installers placed 4 j boxes in the attic. I noticed that in the early morning as the sun is starting to come up they all start to make a tapping sound that gets slower and fainter as the sun rises. Can anyone explain what is going on to cause this. Not a complaint, just a curiosity. Thanks!

 

[jboy210]

I would think any electrical junction making noise should be investigated. I am not an electrician so I don't know if that is normal. And the only thing I can think of is connections heating.

 

[wjgjr]

Do you have Rapid Shutdown Devices installed near your roof? When we had our install done, the lead warned us to listen for a sound similar to what you are describing. He said there had been a bad batch of equipment and a lot of people heard clicking - I believe they worked otherwise but were being replaced for the sound issue. He thought they had gotten through that batch, and we have had no issue, but it is something else to check on. I believe the Delta RSS devices are supposed to go through a daily self-test, so I don't know if this correlates with the noise.

 

[Keoni8888]

Ah interesting. Thank you. I have had the roof for one year now and this has been a symptom the whole time. They do use Delta equipment and I think the rapid shutdown devices are in the j boxes. I will report to Tesla and ask them to investigate.

 

[woferry]

Yeah, the Delta RSDs click as the sun comes up in the morning, I can't hear the ones in my attic unless I'm in the attic when they do it, but there are two in the garage that I can hear from my dining room table. The RSDs are just relays controlled by a signal coming from the inverter. I'm pretty sure what happens is in the morning once there's enough voltage from the PV to activate the relay it clicks on, but then the loading presented by the inverter now being connected causes them to trip off again, until there's enough voltage coming from the PV that they can stay on. My RSDs do this for maybe a minute or so each morning. I don't think this is a problem, it's just what they do when they're right on the border of their minimum operating voltage. Some of my RSDs were replaced for a different issue, and the new ones click just like the original ones did.

 

[wjgjr]

Yeah, the Delta RSDs click as the sun comes up in the morning, I can't hear the ones in my attic unless I'm in the attic when they do it, but there are two in the garage that I can hear from my dining room table. The RSDs are just relays controlled by a signal coming from the inverter. I'm pretty sure what happens is in the morning once there's enough voltage from the PV to activate the relay it clicks on, but then the loading presented by the inverter now being connected causes them to trip off again, until there's enough voltage coming from the PV that they can stay on. My RSDs do this for maybe a minute or so each morning. I don't think this is a problem, it's just what they do when they're right on the border of their minimum operating voltage. Some of my RSDs were replaced for a different issue, and the new ones click just like the original ones did.

I went to Delta's site to verify, and https://filecenter.deltaww.com/Prod... RSS without bracket Quick Guide_Rev00[5].pdf indicates that they do perform a self test "each day during start-up." I do not know what that entails, but it might be related to the cluster of sounds being heard in the morning.

 

[Keoni8888]

Yeah, the Delta RSDs click as the sun comes up in the morning, I can't hear the ones in my attic unless I'm in the attic when they do it, but there are two in the garage that I can hear from my dining room table. The RSDs are just relays controlled by a signal coming from the inverter. I'm pretty sure what happens is in the morning once there's enough voltage from the PV to activate the relay it clicks on, but then the loading presented by the inverter now being connected causes them to trip off again, until there's enough voltage coming from the PV that they can stay on. My RSDs do this for maybe a minute or so each morning. I don't think this is a problem, it's just what they do when they're right on the border of their minimum operating voltage. Some of my RSDs were replaced for a different issue, and the new ones click just like the original ones did.

Thanks woferry. Good to know I am not unique here. And this makes sense as the sounds happen as the sun is just starting to come up. But on my side, it goes on for about 20-30 minutes. Possibly it is due to roof layout with both north and south facing tiles, and the sun getting to different parts at different times, extending out the time is makes the tapping sound. I'll give them a call today, but knowing this I doubt that it will result in action. As long as they are not defective, I can live with the noise.