They can be installed in a mechanical closet as long as there is a sufficient supply of air. To ensure sufficient air follow the guide lines below.

- Indoor air: two openings that are sized one square inch for every 1000 BTUs. For example you have a unit that is rated for 200,000 BTUs. You need two opening each sized 200 square inches.

- Outdoor air: two openings that are each 100 square inches

- Maintain 24 inch clearance in front of the unit so as not obstruct the unit's air intake.

For more details refer to the combustion air specifications in the Vent Pipe Installation section of your installation manual, located athttp://support.noritz.com/technical-literature.php