The net free area of the opening shall be a minimum of one square inch per 3000 Btu/h of combined input rating of the fuel-burning appliances drawing combustion and dilution air from the room, and not less than the combined cross-sectional flow areas of the appliance flue collars or draft hood outlets.
The cross-sectional area of the duct shall be equal to or greater than the required size of the opening.
The appliances shall have a minimum clearance to the surfaces of the room of one inch at the sides and back of the appliance and 6 inches at the front of the appliance.
A combination of openings to the outside and openings to other rooms may be used in accordance with this paragraph.
One opening shall connect directly to the outdoors, connect to the outdoors through a horizontal duct, or connect to the outdoors through a vertical duct.
The net free area of the opening shall be a minimum of one square inch per 5000 Btu/h of combined input rating of the fuel burning appliances drawing combustion and dilution air from the room.
The cross-sectional area of a duct, if used, shall be equal to or greater than the required size of the opening.
The equipment shall be located in a space with a volume not less than 50 cubic feet per 1000 Btu/h of the combined input rating of all fuel-burning appliances installed in that space.
The space may be made up of more than one room if the rooms are connected through openings without doors or connected through sets of openings described in subd. 4.
When needed to connect rooms, two openings shall be provided, one within one foot of the ceiling of the room and one within one foot of the floor.
The net free area of each opening shall be a minimum of one square inch per 1000 Btu/h of combined input rating of the fuel burning appliances drawing combustion and dilution air from the communicating rooms, but shall be not less than 100 square inches.
The required size of openings for combustion and dilution air shall be based on the net free area of each opening.
The net free area of an opening shall be that specified by the manufacturer of the opening covering or by a source approved by the department.
In the absence of such information, openings covered with metal louvers shall be deemed to have a net free area of 75 percent of the area of the opening, and openings covered with wood louvers shall be deemed to have a net free area of 25 percent of the area of the opening.
Where the combustion air openings are provided with volume, smoke or fire dampers, the dampers shall be electronically interlocked with the firing cycle of the appliances served, so as to prevent operation of any appliance that draws combustion and dilution air from the room when any of the dampers are closed.
Manually operated dampers shall not be installed in combustion air openings.
The equipment and appliance within every room containing fuel-burning appliances shall be installed so as to allow the free circulation of air.
Provisions shall be made to allow for the simultaneous operation of mechanical exhaust systems, fireplaces, clothes dryers or other equipment and appliances operating in the same room or space from which combustion air and dilution air is being drawn. The provisions shall prevent the operation of the appliances, equipment and systems from affecting the supply of combustion and dilution air.
SPS 323.06 Note
Note: Wood typically has a heating value of 8600 BTU per pound.
SPS 323.06 History
Cr. Register, November, 1979, No. 287
, eff. 6-1-80; am. (intro.), (1) (a) and (2) (a), Register, January, 1989, No. 397
, eff. 2-1-89; r. and recr. Register, March, 2001, No. 543
, eff. 4-1-01;
correction in (2) (a) made under s. 13.92 (4) (b) 7.
, Stats., Register March 2009 No. 639
; correction (2) (a) made under s. 13.92 (4) (b) 7.
, Stats., Register December 2011 No. 672
; CR 15-041: cr. (1) (d) to (f) Register December 2015 No. 720, eff. 1-1-16.
SPS 323.062 Mechanical draft systems.
Where a mechanical draft system, such as a fan is used, provision shall be made to prevent the flow of gas to the main burners when the draft system is not performing so as to satisfy the operating requirements of the system for safe performance.
SPS 323.062 History
Cr. Register, March, 2001, No. 543
, eff. 4-1-01.
SPS 323.065 Equipment maintenance information.
Required regular maintenance actions for equipment shall be clearly stated and incorporated on a readily accessible label. The label may be limited to identifying, by title or publication number, the operation and maintenance manual for that particular model and type of equipment. Maintenance instructions shall be furnished for equipment which requires preventive maintenance for efficient operation. Manufacturer's manuals for all installed heating and cooling equipment and service water heating equipment shall be provided.
SPS 323.065 History
Cr., Register, January, 1999, No. 517
, eff. 2-1-99.
All air distribution systems shall be sized using the velocities and static pressure losses listed in Table 323.07.
(2) System sizing.
The distribution system, including the evaporator coil, air filters (installed external to the heating unit), ducts, fittings, grilles and registers, shall be sized so that the total external static pressure shall not exceed the static pressure capacity of the fan at the system rated air flow.
(3) Changes in duct size.
Where duct sizes are changed, the slope angle of the transition duct shall not exceed 45°
SPS 323.07 History
Cr. Register, November, 1979, No. 287
eff. 6-1-80; correction in (1) made under s. 13.92 (4) (b) 7.
, Stats., Register December 2011 No. 672
Ducts designed for the transmission of air shall be used for no other purpose.
(2) Interior ducts.
All interior ducts shall be constructed in accordance with the following:
(a) Supply and return air ducts.
Supply and return air ducts shall comply with this paragraph except that ducts attached to appliances may be constructed of materials specified in the appliance listing.
Kitchen exhaust ducts and ducts for air exceeding 250°
F shall be constructed of sheet metal or lined with sheet metal or constructed of other noncombustible noncorrugated materials.
Ducts connected to furnaces shall be constructed of sheet metal for at least 6 feet from the furnace.
Spaces formed by unlined wood joists, studs or wood I-joists with solid webs may be used as return air ducts. Spaces used as return air ducts shall be cut off from all remaining unused portions of the space by tight-fitting stops of sheet metal or of wood joist material. Bridging shall be removed from the joist space.
(b) Under-floor plenums.
An under-floor space may be used as a plenum in a single dwelling unit in accordance with this section.
The use of the under-floor space shall be limited to buildings not more than 2 stories in height. Except for the floor immediately above the under-floor plenum, supply ducts shall be provided extending from the plenum to registers or other floor levels.
The under-floor spaces shall not be used for storage, shall be cleaned of all loose scrap material and shall be tightly and substantially enclosed.
The enclosing material of the under-floor space, including the side wall insulation and vapor barriers, shall not be more flammable than one-inch (nominal) wood boards (flame spread classification of 200).
Access shall be through an opening in the floor which shall be 18 inches by 24 inches.
The furnace supplying warm air to the under-floor space shall be equipped with an automatic control which will start the air circulating fan when the air in the furnace bonnet reaches a temperature not higher than 150°
F. Such control shall be one that cannot be set higher than 150°
The furnace supplying warm air to the under-floor space shall be equipped with an approved temperature limit control that will limit outlet air temperature to 200°
A noncombustible receptacle shall be placed below each floor opening into the air chamber. The receptacle shall be securely suspended from the floor members and shall be not more than 18 inches below the floor opening. The area of the receptacle shall extend 3 inches beyond the opening on all sides. The perimeter of the receptacle shall have a vertical lip at least one inch high at the open sides if it is at the level of the bottom of the joist, or 3 inches high if the receptacle is suspended.
Floor registers shall be designed for easy removal to permit access for cleaning the receptacles.
Exterior walls and interior stud partitions shall be firestopped at the floor.
Each wall register shall be connected to the air chamber by a register box or boot.
A duct conforming to par. (a)
shall extend from the furnace supply outlet at least 6 inches below combustible framing.
The entire ground surface and enclosing exterior walls of the under-floor space shall be covered with a vapor barrier having a vapor permeability rating of one perm or less and a flame spread rating of 200 or less.
A smoke detector shall be placed in the under-floor space. The alarm and low-battery signal of the smoke detector shall be audible in the occupied areas of the dwelling, when actuated.
SPS 323.08 Note
Note: Subch. VII of ch. SPS 322 was repealed.
Electrical wiring installed in the plenum shall be in conformance with the Wisconsin Administrative Electrical Code Volume 2.
SPS 323.08(3)(a)(a) General.
Except as provided in par. (b)
, ducts, which are located in garages, storage attics and similar spaces susceptible to physical damage, shall be constructed of galvanized steel or corrosion-resistive metal.
Plastic may be used for bath fan or air-to-air heat exchanger exhaust runs located in spaces outside the dwelling.
(4) Underground ducts.
Ducts, plenums and fittings constructed of metal encased in concrete or ceramic, or other approved materials, may be installed in the ground. Encasement of underground supply air ducts shall be moistureproof.
SPS 323.08 Note
See s. SPS 322.42
for insulation requirements for underground ducts.
(5) Duct construction.
Ductwork shall be constructed and installed in accordance with any one of the appropriate following standards:
SMACNA, Residential Comfort System Installation Standards Manual
SMACNA, HVAC Duct Construction Standards-Metal and Flexible.
Sheet metal ducts shall conform to the minimum thicknesses listed in Table 323.08-A.
(7) Duct support.
Rigid metal ductwork shall be supported in accordance with Table 323.08-B.
1 These hangers are the minimum required to support the weight of the duct off of the joist, stud or similar structure. The band, wire or strap cradling the duct shall not cause any deformation of the duct.
2 “Pair" means that there are 2 vertical legs. One continuous strap can form both vertical legs.
SPS 323.08 Note
Note: This table does not prohibit nailing for duct support.
(8) Joints and seams.
All joints and seams shall be securely fastened or locked. Round pipe slip joints shall be lapped at least one inch.
(9) Vibration control.
When used, vibration isolation connectors shall be installed at the joint between the duct and fan or heating equipment. Vibration isolation connectors shall not be used where the air temperature is in excess of 250°