What must be true about furnaces and boilers installed in closets and alcoves?

Furnaces and boilers installed in closets and alcoves must be listed for such installation to ensure safety, compliance with local codes, and proper operation. When a heating appliance is listed, it means that it has been tested and certified by a recognized testing laboratory to meet specific safety and performance standards. This listing often includes guidelines for spacing, ventilation, and other clearances required for safe operation in confined spaces.

Ensuring that the equipment is specifically listed for installation in closets or alcoves is crucial because these areas may have unique challenges, such as restricted airflow and potential for heat accumulation. Proper listing helps to mitigate risks related to overheating and ensures that the appliance operates as designed, providing effective heating without compromising safety.

The other choices do not align with the specific requirements set forth in the codes. For instance, oversized units can lead to inefficiency and increased wear, while the necessity of being installed with a vent depends on the type of appliance and local code requirements. The broad statement about being any type does not reflect the need for compliance with regulations regarding specific models and installation environments.