Enhancements have been made to the Copper-Fin® line of commercial gas boilers and water heaters that further improve its serviceability and ease of installation. They are available in models from 495,000 to 2,065,000 Btuh. Compact sizes and the stack frame option allow for installation of two units in the area normally required for one. The control panel, building management system connections, and other field connections are now positioned on terminal boards at the front of the unit to allow for easier access. The operator interface panel continues to provide two-stage electronic temperature control and comprehensive diagnostic status without opening the control panel. To improve accessibility to the lower front chamber, the lower front panel is now removable without also requiring removal of the upper front panels. The combustion air grilles previously located on the front panels have been eliminated and replaced by a combustion air filter box on the back of the appliance. The diagnostic LCD light panel has been moved toward the center of the boiler for easier access, as well. The larger units ranging from 985,000 to 2,065,000 Btuh are now rated for installation on combustible floors. The smaller units may be installed on a combustible floor when equipped with an optional combustible floor kit.