Wis. Admin. Code Department of Safety and Professional Services SPS 371.24

Current through December 30, 2024

Section SPS 371.24 - Air systems

This section shall apply to active solar energy systems and components that use air as a heat transfer fluid.

(1)AIR DISTRIBUTION.

(a)Size. Air distribution components shall be adequately sized to insure a uniform distribution of air.

(b)Dust and dirt prevention.

1. `Flow efficiency and health hazard.' Duct and fan systems shall be protected against accumulation of deposits of dust or dirt that could reduce flow and efficiency or create a potential health hazard when admitted into occupied spaces.

2. `Air filters'. Air filters shall be installed on the outlet side of the thermal storage in solar energy systems. Air filters shall be removable to allow cleaning. Solar energy systems used for space heating shall incorporate the use of a high efficiency air filter installed in the cold air riser duct to the collectors unless the air does not pass over the absorber.

(c)Insulation. The primary solar duct system shall be insulated as specified in s. SPS 371.21(3).

(d)Ductwork.

1. `Interior ducts'. Interior ducts shall comply with chs. SPS 320 to 325 for one- and 2-family dwellings or chs. SPS 361 to 366 for commercial buildings.

2. `Exterior ducts'. Ducts located outside the dwelling or building shall be constructed of galvanized steel or corrosion-resistant metal.

(e)Temperature, pressure and exposure. Ducts, insulation, gaskets, sealants and adhesives shall be capable of withstanding maximum operating temperatures, pressures and environmental exposure.

(f)Bypass. Solar energy systems providing both space heating and domestic water heating shall be equipped with a bypass of the thermal storage during the nonheating season.

(2)SEALING OF AIR SYSTEMS.

(a)Duct system. The primary solar duct system shall be sealed in accordance with the following requirements:

1. All joints in metal ducts shall be made with good fit-up and closure.

2. Joints and seams shall be sealed with adhesives, mastics or compatible combinations of tape binders and adhesives in ducts conveying air to and from storage units and solar collectors and in ducts conveying air from such circuits to points of connections with ducts circulating air to and from the occupied space.

3. Tapes shall be used in accordance with manufacturer's recommendations.

4. Oil-base caulking and glazing compounds may not be used.

5. Stapled closures of duct connections and stapled fitting assemblies shall be sealed.

Note: The purpose of these requirements is to reduce the duct loss to 10% or less. It is not the intent to require testing of the installed system to determine duct leakage, but to assure construction standards which will essentially provide the required degree of airtightness in the primary solar duct system. Construction which will provide equivalent airtightness will be allowed in lieu of the sealing requirements.

(b)Thermal storage. Thermal storage shall be constructed and sealed or otherwise fabricated to limit air leakage. Sealing shall include joints in thermal storage, duct and access openings.

Note: This is not intended to apply to thermal storage which is thermally coupled to heated spaces. Concrete should be considered potentially porous and may require lining and sealing to limit air leakage. Problems associated with shrinking, warping and cracking should be considered for thermal storage constructed of wood.

(c)Collectors and components. Collectors and other components, such as air handling units, heat exchangers and filters, shall be assembled and sealed in accordance with manufacturer's and system designer's instructions. Sealing shall include all joints between components and ducts. Equivalent airtightness shall be provided for site-built collectors.

(3)FREEZE PROTECTION.

(a)Cold airflow prevention. The solar energy system shall be designed and installed to prevent cold airflow across the water heater coil. If mechanical dampers are used to meet this requirement, they shall not allow leakage of more than 5% of the solar energy system design airflow rate at one-inch water column.

(b)Secondary freeze protection. Solar energy systems using electrical or mechanical devices for freeze protection, shall incorporate a secondary freeze protection system in case of mechanical failure. An electrical freeze sensor which activates the pump to circulate fluid through the water heater coil may be used to meet this requirement.

(c)Nonautomatic freeze protection. Any nonautomatic freeze protection shall be noted as such in the operation and maintenance manual.

(4)THERMAL STORAGE.

(a)Air quality. Heat transfer fluid, heat storage media and thermal storage materials, including any interior protective coating, may not impart toxic elements or offensive odors to air distributed to areas of human occupancy.

(b)Insulation. Thermal storage shall be insulated in accordance with s. SPS 371.21(3).

(c)Loads and environmental conditions. Loads shall meet the requirements of s. SPS 371.21(7). Thermal storage located outside or underground shall be waterproof.

(d)Rock storage. When rock is utilized for thermal storage, the rock shall be cleaned and dried before it is placed into the storage area. The thermal storage shall be provided with an inlet and an outlet plenum.

(e)Phase change. If phase change storage materials are used, they shall be placed in sealed containers.

(5)DAMPERS.

(a) Volume control dampers shall be installed in each branch or zone duct. Single leaf dampers which are a part of a manufactured air grille may not be used.

(b) Opposed blade dampers which are a part of a manufactured air grille shall be acceptable if sufficient space is provided behind the grille face for proper operation of the damper. Where space prohibits the use of an opposed blade damper behind the grille face, an opposed blade damper may be installed in the register stack at a location where it is accessible from the grille opening.

(c) Volume control dampers shall be of a type and size that will satisfy the design conditions of the duct system.

(d) Backdraft dampers or motorized dampers shall be installed so as to prevent air passage through the collectors when solar energy is not being collected.

(e) Dampers installed in the primary solar duct system shall have felted blade edges or otherwise be treated to insure tight cutoff of the airstream.

(f) Volume control dampers shall be furnished with a locking control device to hold the damper in its fixed control position unless the damper is motor controlled.

(6)BLOWERS.

(a) Blowers shall be of a type and size that will satisfy the design conditions of the solar energy system.

(b) All blowers shall be rated by the manufacturers in cfm capacity against a specific external static pressure.

Wis. Admin. Code Department of Safety and Professional Services SPS 371.24

Cr. Register, June, 1986, No. 366, eff. 7-1-86; CR 01-139: am. (1) (d) 1. Register June 2002 No. 558, eff. 7-1-02; correction in (1) (c), (d) 1., (4) (b), (c) made under s. 13.92(4) (b) 7, Stats., Register December 2011 No. 672.