From the bloggers at the National Association of RV Parks and Campgrounds:
Starting with its next iteration in 2020, the National Fire Protection Association’s NFPA 70 standard, the national electric code, will require all newly-manufactured RVs to come equipped with a reverse polarity detector. But, in the meantime, issues involving reverse polarity continue to challenge RV park owners and operators.
Because of this potential safety hazard, most RV manufacturers are not waiting until 2020, however, and have already started installing reverse polarity detectors in current new models.
ARVC recommends that campground owners check sites for reverse polarity at the beginning of the season before campers start arriving, so problems can be detected before guests arrive.
The full blog as well as more information about what causes reverse polarity and how it can be corrected, is available at www.arvc.org.