Where should the manual shut-off valve for a vented wall furnace be installed?

The manual shut-off valve for a vented wall furnace should be installed ahead of all controls to ensure safety and accessibility. This positioning allows for quick and immediate access to the shut-off valve in case of an emergency or when maintenance is required. By placing it ahead of all other controls, the valve can be easily reached without interference from the furnace's operational controls, minimizing the risk of accidents and ensuring compliance with safety standards.

Installing the valve next to the furnace may seem practical, but it can lead to accessibility issues if the furnace is in use or during routine maintenance. The other options, such as positioning the valve behind the furnace or in a nearby wall, could create challenges in accessibility and visibility, as they may not allow for quick action in case of a gas leak or malfunction. Proper installation of the shut-off valve is crucial for maintaining safety in the operation of gas appliances like a wall furnace.