Sorry for the long post. I don't know how else to communicate this issue. We installed an Energy Recommerce data system on a project last year that we have not been able get working properly. Everything works except the monitoring of the series string amperage outputs from the solar array. There are 3 pv source circuit combiner boxes with 11 series strings of 14 modules and 1 with 10 series strings of 14. Each combiner box feeds one inverter with its own conduit run. The data system shows amperage from each circuit consistent within each combiner box, typically with a range of variance of about 1.5 amps DC between series strings. Each combiner box will show totally divergent amperages. For example, combiner box 1 might read 2 amps, combiner box 3 reads 10 amps, and at the same time our clamp meters are reading the actual amperage at around 5 amps consistently between every box for every circuit. The same combiner boxes will consistently read either too low or too high. The problem may be in the interface between the Hall Effect sensors that the circuit board in the combiner box uses to measure the DC current. The Hall Effect sensors deliver a calibrated voltage based on the strength of the magnetic field around the series string circuit as it goes through the box. The combiner box then calculates the amperage based on the millivolts that the Hall Effect sensor produces. For example 500 millivolts equals 5 amps. The DC output voltage of the Hall Effect sensor varies by about 50 millivolts or more, so rapidly that itÂ’s hard for our meters to follow it. We have spent countless hours on the phone with Energy Recommerce technicians trying everything that anyone could think of to trouble shoot the problem. Their system uses a MODBUS protocol for transferring the data and there seems to be no problem with the data transmission or connectivity. I would love to hear from anyone that sees a pattern to this problem that might help us find a solution.
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