rmcfall
01-16-2011, 05:01 PM
Any issue with putting a return grille directly into the plenum itself? That is, with a HP with strip heat for back up. No gas. Supply air is also introduced to the room with the unit. The air handler/plenum is in a basement room that is next to other rooms in the basement. Four rooms in basement total, all open to one another.
Based on M1602.2, seems fine, unless I am missing something. Seems odd to put a return air grille directly into the plenum, but is there a problem when it is a HP with strip heat for backup, plenty of supply air, and no appliances within 10 feet? In this case a return in the plenum would help with circulation on one side of the basement.
- M1602.2 Prohibited sources. Outdoor and return air for a forced-air heating or cooling system shall not be taken from the following locations:
- - 1. Closer than 10 feet (3048 mm) to an appliance vent outlet, a vent opening from a plumbing drainage system or the discharge outlet of an exhaust fan, unless the outlet is 3 feet (914 mm) above the outside air inlet.
- - 2. Where flammable vapors are present; or where located less than 10 feet (3048 mm) above the surface of any abutting public way or driveway; or where located at grade level by a sidewalk, street, alley or driveway.
- - 3. A room or space, the volume of which is less than 25 percent of the entire volume served by such system. Where connected by a permanent opening having an area sized in accordance with ACCA Manual D, adjoining rooms or spaces shall be considered as a single room or space for the purpose of determining the volume of such rooms or spaces.
- - - Exception:The minimum volume requirement shall not apply where the amount of return air taken from a room or space is less than or equal to the amount of supply air delivered to such room or space.
- - 4. A closet, bathroom, toilet room, kitchen, garage, mechanical room, furnace room or other dwelling unit.
- - 5. A room or space containing a fuel-burning appliance where such room or space serves as the sole source of return air.
- - - Exceptions:
- - - - 1. The fuel-burning appliance is a direct-vent appliance or an appliance not requiring a vent in accordance with Section M1801.1 or Chapter 24.
- - - - 2. The room or space complies with the following requirements:
- - - - - 2.1. The return air shall be taken from a room or space having a volume exceeding 1 cubic foot for each 10 Btu/h (9.6 L/W) of combined input rating of all fuel-burning appliances therein.
- - - - - 2.2. The volume of supply air discharged back into the same space shall be approximately equal to the volume of return air taken from the space.
- - - - - 2.3. Return-air inlets shall not be located within 10 feet (3048 mm) of any appliance firebox or draft hood in the same room or space.
- - - - 3. Rooms or spaces containing solid-fuel burning appliances, provided that return-air inlets are located not less than 10 feet (3048 mm) from the firebox of such appliances.
Based on M1602.2, seems fine, unless I am missing something. Seems odd to put a return air grille directly into the plenum, but is there a problem when it is a HP with strip heat for backup, plenty of supply air, and no appliances within 10 feet? In this case a return in the plenum would help with circulation on one side of the basement.
- M1602.2 Prohibited sources. Outdoor and return air for a forced-air heating or cooling system shall not be taken from the following locations:
- - 1. Closer than 10 feet (3048 mm) to an appliance vent outlet, a vent opening from a plumbing drainage system or the discharge outlet of an exhaust fan, unless the outlet is 3 feet (914 mm) above the outside air inlet.
- - 2. Where flammable vapors are present; or where located less than 10 feet (3048 mm) above the surface of any abutting public way or driveway; or where located at grade level by a sidewalk, street, alley or driveway.
- - 3. A room or space, the volume of which is less than 25 percent of the entire volume served by such system. Where connected by a permanent opening having an area sized in accordance with ACCA Manual D, adjoining rooms or spaces shall be considered as a single room or space for the purpose of determining the volume of such rooms or spaces.
- - - Exception:The minimum volume requirement shall not apply where the amount of return air taken from a room or space is less than or equal to the amount of supply air delivered to such room or space.
- - 4. A closet, bathroom, toilet room, kitchen, garage, mechanical room, furnace room or other dwelling unit.
- - 5. A room or space containing a fuel-burning appliance where such room or space serves as the sole source of return air.
- - - Exceptions:
- - - - 1. The fuel-burning appliance is a direct-vent appliance or an appliance not requiring a vent in accordance with Section M1801.1 or Chapter 24.
- - - - 2. The room or space complies with the following requirements:
- - - - - 2.1. The return air shall be taken from a room or space having a volume exceeding 1 cubic foot for each 10 Btu/h (9.6 L/W) of combined input rating of all fuel-burning appliances therein.
- - - - - 2.2. The volume of supply air discharged back into the same space shall be approximately equal to the volume of return air taken from the space.
- - - - - 2.3. Return-air inlets shall not be located within 10 feet (3048 mm) of any appliance firebox or draft hood in the same room or space.
- - - - 3. Rooms or spaces containing solid-fuel burning appliances, provided that return-air inlets are located not less than 10 feet (3048 mm) from the firebox of such appliances.