The refer outside receptacle is NOT to plug in a light or warming system. It is there to supply 120 power to the refer. But, you can plug a light into the extra socket. BTW, a LOT of those refer plugs are single outlet ONLY. Yes, RV Absorbsion refers will not work or work correctly below 20 to 25 degrees F ambient. It has to do with the Ammonia and how it vaporizes and condensates at low temps. As others pointed out, below 20 degrees you will have a hard time keeping the Water system from freezing even if you take precautions. Doug