Vesta Smart Technology - VST condensing high-efficiency tankless water heaters are built using premium grade stainless steel heat exchangers. The VRP Model comes with a built-in Grundfos 15-58 recirculation pump and SSTL 1/2-gallon internal buffer tank. The internal buffer tank insures water temperature fluctuation is eliminated. Recirculation mode options are: internal, external or on-demand (Title 24). It operates at 0.91 UEF with turndown ratio of 10:1. The negative pressure gas valve utilizes existing 1/2” gas pipe up to 24’. A gas conversion kit NG to LP is provided with each unit. It uses 2” PVC vent up to 60’ (3” up 150’). It is EnergyStar rated, low NOx compliant and lead free. At installation, the contractor utilizes the self-calibration mode for customization of unit operation parameters.