Grant developed their first oil-fired Outdoor Module in 1986 and although the concept was new to the oil market, it quite quickly became a popular addition to the Grant's boiler range. It is therefore appropriate that Grant has again taken the lead with the introduction of three new Grant Vortex Condensing Outdoor Modules, with outputs between 15 and 46 kW's (50 - 157,000 Btu/hr)