Ground fault on DC string inverter system.

[Jpcmerritt]

I'm working on a Fronius IG central inverter. The display is stating a error 434 (Ground Fault). The solar panels are in series with no optimizers or micro-inverters. How would I go about safely checking for continuity between ground and the strings while the panels are all still producing roughly 300vdc strung together?:blink:

 

[GoldDigger]

I'm working on a Fronius IG central inverter. The display is stating a error 434 (Ground Fault). The solar panels are in series with no optimizers or micro-inverters. How would I go about safely checking for continuity between ground and the strings while the panels are all still producing roughly 300vdc strung together?:blink:

There is a fair chance that the error results from an inverter fault (false alarm).
First thing to do, if possible, is to isolate the strings from one another and the inverter (both + and - end). Then look for a string that has a stable offset voltage to ground at both ends. That voltage measurement will tell you roughly where along the string the ground fault is located.

 

[jaggedben]

As far as safety, if on a rooftop with any kind of fall hazard, you'd do well to harness in and wear insulating gloves before climbing around touching the array. Shock hazard is more serious than arc flash, at least with a single string.

I always insisted with these systems that my guys place connectors (e.g. MC4) on all home runs outside the junction box so that all strings could be easily isolated and tested without loose wires and tools touching energized terminals. Without knowing more about how many strings and what equipment you have (combiner?), it's a little hard to give more specific advice as to method. But Goldigger is correct that you have to isolate strings from each other. Without doing that it's very difficult to isolate the fault, as voltages measured from one string through the grounded busbar to ground usually make it look like all strings have a fault.

I'm assuming this is an older inverter with 'grounded' conductors tied to a common without fuses. Advice above is according to that.