An installer needs to provide heat from a conventional gas-fired boiler to a large buffer tank. The tank is necessary because of a highly zoned distribution system.
John Pughe is a long-time colleague of mine and a true hydronics professional. He recently sent me an “as installed” and “as corrected” schematic for a hydronic heating system with twin 200,000 Btu/hr mod/con boilers, and 15 zones, each powered by its own circulator.