When is it acceptable to deviate from approved heating device installation instructions?

Deviating from the approved installation instructions of heating devices is particularly sensitive due to safety and performance concerns. The correct answer indicates that any alterations to the installation process should only occur with prior manufacturer approval. This is crucial because manufacturers design their products with specific installation instructions to ensure safety and optimal functionality. If an installer modifies the installation without the manufacturer's consent, it could lead to performance issues, safety hazards, or even void the warranty.

In an environment where regulations and safety standards are paramount—like in oil fuel installation—following the manufacturer's guidelines closely is essential. By obtaining the manufacturer's approval before making any changes, the installer ensures that they are adhering to standards that protect the integrity of the device and the safety of the premises.

The other options suggest actions that could compromise safety or violate guidelines set forth by the manufacturer or regulatory bodies. Examples include making decisions based on cost-saving measures, during emergencies, or simply because of ongoing upgrades, which could introduce risks if the modifications are not validated by the manufacturer. Therefore, the necessity for manufacturer approval serves as a critical safeguard in the installation of heating devices.