New On-Board Micro-Processor Monitors Inlet Water Flow, Inlet Water Temperature, Outlet Water Temperature, and regulates the burner to maintain the set HOT Water Temperature. The compact design fits in any tank water heater cut-out opening with a new hinged door design easy latch closing. For a conventional installation, the Girard Tankless Water Heater is connected to the RV's cold-water system deriving its water input from a pressurized (45 psi or greater) source such as a shore connection or an RV water pump connected to the RV's freshwater storage tank. Includes optional black door for Atwood/ Suburban 10/12 Gallon Water Heater opening, along with gas, water lines and owner's manual.