What is All This Water Doing in the Inverter? – What Can Happen When Rooftop Conduit Fittings Are Improperly Installed

While it may seem like a minor detail to new solar installers, using the wrong conduit fittings, or installing the right ones incorrectly, can have disastrous consequences. Conduit fittings are used to connect sections of electrical conduit, which protect and direct electrical wiring on installations. When installers use improper fittings or don’t install them properly, the system owner is bound to have some residual issues. 

In this excerpt from Residential Field Operations and Maintenance, HeatSpring instructor Keith Rohman walks students through troubleshooting water intrusion in the inverter and ultimately solving the mystery of what the homeowners called “ an underperforming solar system.” Here’s a short video clip of a portion of his process or check out the transcript below. 

Want to see the whole process? Consider enrolling in Residential Field Operations & Maintenance to follow along Keith as he fixes this challenge and many more residential solar site issues.

This service call came through as an inverter troubleshoot. This is a Delta inverter. The homeowner called and stated that they had higher electric bills and that they thought their inverter was not working. They were 100% correct. There’s not a single light, not anything on the screen – very indicative that the inverter’s completely shut off.

So there’s a major problem here. The homeowner was correct. 

Upon opening the dead front, you can see a horrible case. To date, this is probably one of the worst cases of water intrusion on an inverter at the ground level that I have ever seen. Water literally poured out of this lower DC disconnect portion. We call them the lower cabinets. It was probably filled about halfway. As soon as I took the lower two screws off in the bottom corners – boom – water poured out. 

We’re going to go ahead and look at some more photos on this job and show you how I was able to determine that this is actually coming from the roof. It came down to an issue with conduit and conduit fittings. 

So here’s a little more of a closeup of that lower cabinet. Here on the left, you can see the actual level of corrosion that this water was causing: wires completely disintegrated; terminals completely disintegrated; water and rust over time will wear down almost anything, especially metal components. 

Then when I came over here, this picture on the right is what we call an LB – left bend conduit body. It’s very commonly used to transition a piece of straight conduit into a lower cabinet of an inverter. They can go around corners and walls.

It’s an outdoor rated conduit fitting. There’s nothing wrong there, but you can see at the bottom of that LB where that water was also pooling. It’s very clear, and this is the raceway or the conduit coming directly off the roof. With the rust and the corrosion sitting in the bottom like that, it’s very clear that is where the water was coming from. It was coming off the roof, running down this raceway and pouring into that lower portion of the inverter. 

So that’s obvious right then and there – this is a rooftop raceway installation problem. So all that water that we saw going into that inverter is a result of, in this case, the improper conduit fittings.

Now let’s talk a little bit about conduit.