About SL 26-260 G3 and SL 40-399 G3 boilers

Printed Installation and Operating instructions manual for the SL 26-260, 40-399 G3 boilers

The gas-fired modulating boilers are low pressure, fully condensing units that have a variable input range. Approved as "Category IV" vented appliances, the boilers use either direct vent (sealed combustion) or indoor combustion air.