Matt:
This connection is not advised for these reasons: 1. The assumption is that two controllers were installed because one charge controller could not handle the charging duties. Due to small differences in manufacturing tolerances, charge controllers never operate at exactly equal values. The charge controller working harder will get warmer. Thermal runaway is possible with the harder working charge controller working harder and harder until it is passing all of the charging current, exceeding its rating and risking damage, overheating and attendant fire risks. 2. If two of this particular charge controller are installed, one is supposed to act as GFDI enabled device. Cross connecting negatives could defeat this function. As usual, there is no substitute to doing a job correctly. William Miller Solar 17395 Oak Road, Atascadero, CA 93422 805-438-5600 www.millersolar.com CA Lic. 773985 *From:* RE-wrenches [mailto:[email protected]] *On Behalf Of *Matt Sherald *Sent:* Thursday, November 7, 2019 11:46 AM *To:* RE-wrenches *Subject:* [RE-wrenches] Two MPPT Charge Controllers, One PV Circuit Hi All, I recently posted a request for suggestions regarding a 600Vdc xfer switch. In the intervening time, I've been out to visit and review the system in question and found that the original installer had been called back and had added a second XW MPPT 80. The installer did not run separate strings to each of the two MPPTs, but instead they split the PV output circuit with split bolts and now feed the two MPPTs from this splice. A Schneider tech whom I spoke with said that this was a safety issue, but was unable to clearly explain why it posed a danger. Can anyone lend some insight? I can imagine how the MPPT function might be skewed, but the wire size of the feeders are adequate for the combined current of the full PV array and the units are producing power. -Matt I'd like to give the system owner advice with t -- Matt Sherald PIMBY Energy, LLC NABCEP Certified Solar PV Installer® 304-704-5943 www.getpimby.blogspot.com www.getpimby.com
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