The Series GM™ gas-fired cast iron boiler is the ideal choice for large residences, especially when a cascade application is required. When this boiler is used in single or multiple boiler installations it is designed to be vented into a conventional chimney and can work in higher pressure applications requiring up to a 100 PSIG relief valve. The fully-packaged, atmospheric boiler is available in four sizes with inputs of 214.5 MBH to 299 MBH.