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XW MPPT60 (Dual) / Common PV Negative / Crossed PV leads.

Midnite Solar advertises a solar array combiner that allows the installer to cut the DC bus bar to supply up to 3 breakers to (2) separate charge controllers.
The combiner uses a common PV (-) for both arrays, which will not work with dual MPPT systems because of the internal current sensing resistors within the MPPT. This creates a low resistance path for stray current to flow. This will corrupt the power output readings and cause erratic operation. See attached drawing. Also attached is a drawing that shows current flow when PV leads are crossed, which will also lead to undesireable operation. When measuring for reversed PV leads, it is necessary to remove PV (+) and PV (-) from BOTH controllers and measure for Voc across the disconnected leads.
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