When outside oil tanks are used, where must a thermally operated shut off valve be installed?

The correct placement of a thermally operated shut-off valve is critical for ensuring safety and compliance in oil heating systems. This valve must be installed where the oil line enters the building and near the appliance because this location provides the most effective means of immediate response in the event of a fire or overheating scenario.

When heating oil is utilized in a building, it presents a risk, particularly if there's a leak or if the heat in the surrounding environment causes the oil to become dangerously pressurized. By positioning the thermally operated shut-off valve at this point, the system can quickly cut off the oil supply if the temperature exceeds a safe threshold, preventing further fuel from reaching the appliance and reducing the risk of fire.

This strategic placement enhances safety measures by ensuring that the oil flow can be quickly controlled in the vicinity of where it is used. The other options do not provide the same level of safety and responsiveness. For instance, having the valve at the bottom of the tank could delay shutdown in emergencies, while positioning it on the exterior wall or at the oil supply pump could be less effective in stopping the flow of oil right at the source where it is needed most.