Wis. Admin. Code Department of Safety and Professional Services SPS 371.25

Current through December 30, 2024

Section SPS 371.25 - Liquid systems

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

Note: The connection of a solar energy system to the potable water supply system may require the obtaining of a local plumbing permit.

(1)LIQUID DISTRIBUTION.

(a)Design. Components shall be designed for flow rates, temperatures, pressures, mechanical stresses, material properties and heat transfer fluid characteristics to provide proper and efficient performance.

(b)Pipe.

1. `Size.' Pipe sizing shall be in accordance with accepted design practice or recognized methods.

Note: The sizes of pipe to be used for mains and risers may be selected from the ASHRAE Guide and Data Book, published by the American Society of Heating, Refrigerating and Air-Conditioning Engineers; or from the manuals published by The Hydronics Institute, 35 Russo Place, Berkely Heights, New Jersey 07922 or the Mechanical Contractors Association of America, 5410 Grosvenor Lane, Suite 120, Bethesda, Maryland 20814.

2. `Pipe materials.' Piping materials for open loop systems shall comply with s. SPS 384.30. Piping materials for closed loop systems shall be schedule 40 black pipe, type K, L or M copper, or other pipe approved by the department. Unglazed, nonconcentrating collectors, limited to unpressurized systems for swimming pool and spa heating applications, with a maximum operating temperature of 200ºF, may utilize rubber or plastic plates and piping.

3. `Draining and filling.' Where the design requires piping to be drained to protect the solar energy system from freezing or where the heat transfer fluid must be replaced as part of regular maintenance, the piping shall be pitched toward a designated point in the solar energy system to permit drainage. Appropriate valving to drain and fill the solar energy system shall also be supplied.

4. `Hangers and supports'. Pipe hangers and supports shall be in accordance with s. SPS 382.60.

5. `Identification of potable and nonpotable water.' The identification of potable and nonpotable water piping systems shall be in accordance with s. SPS 382.40(3) (b).

6. `Insulation.' Piping shall be insulated in accordance with s. SPS 371.21(3).

(c)Valves.

1. Relief valves shall be designed and installed in accordance with s. SPS 371.22(3).

2. All required shutoff or control valves shall be readily accessible.

3. Valves used to charge or drain closed loop systems shall be the loose-key type, have valve outlets capped or have handles removed when the solar energy system is operational.

4. The cold water branch to each thermal storage tank or water heater shall be provided with a valve located in the same room near the equipment and serving only this equipment in accordance with s. SPS 382.40(4).

(d)Sealants and gaskets. Gaskets, sealants, hoses and other plastic, rubber and synthetic parts may not be adversely affected by contact with heat transfer fluids, high temperatures, high pressures or sunlight to an extent that their ability to function is impaired.

(2)PUMPS. Pumps shall be sized to provide an adequate flow. Pumps shall be properly matched with the heat transfer fluid so that potable water quality is maintained and pump and loop parts are not degraded under normal operating conditions.

Note: It is recommended to use centrifugal-type pumps.

(3)PROVISIONS FOR LIQUID EXPANSION.

(a)Liquid expansion required. Any portion of the solar energy system utilizing a closed loop shall be provided with a means for liquid expansion. The expansion tank, or other approved method, shall have the capacity to withstand the heat transfer fluid expansion from minimum to maximum design temperatures and be compatible with the heat transfer fluid.

(b)Open expansion tanks. Solar energy systems, equipped with an open expansion tank to satisfy heat transfer fluid expansion, shall be provided with an indoor overflow, from the upper portion of the expansion tank, in addition to an open vent. The indoor overflow shall be carried within the building or dwelling to an approved drain.

(c)Closed loop systems.

1. Closed loop systems shall have an airtight tank or other suitable air cushion that shall be:

a. Consistent with the volume and capacity of the closed loop system; and

b. Suitably designed for a hydrostatic test pressure of 2.5 times the design pressure of the closed loop system.

2. Expansion tanks for closed loop systems designed to operate at or above 50 psig shall be constructed in accordance with ch. SPS 341.

(4)THERMAL STORAGE. Thermal storage for domestic or industrial use shall meet the requirements of s. SPS 382.40(5) and the following:

(a) Thermal storage shall be located in heated areas whenever possible.

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

(c) Thermal storage shall be located to provide for servicing.

(d) Thermal storage shall be designed and installed to withstand all anticipated loads and environmental conditions.

(e) Thermal storage shall be designed for maximum operating temperatures and pressures.

(f) Pressurized thermal storage shall be provided with relief valves in accordance with s. SPS 371.22(3).

(g) Only pressurized thermal storage shall be used for potable water.

(h) Concrete thermal storage tanks may not be pressurized.

(i) Thermal storage buried outdoors shall be located at least 3 feet away from the building for every foot excavated below the footing.

(j) Nonpressurized thermal storage shall be provided with a vent to the outside atmosphere. The thermal storage opening for the vent shall be sealed at the penetration of the thermal storage, and the vent shall be provided with a 1/16-inch mesh screen to prevent the entrance of vermin.

(k) Nonpressurized thermal storage shall be provided with an overflow piped to an approved drain.

(5)JOINTS AND CONNECTIONS.

(a) Except as provided in pars. (b) and (c), joints and connections for solar energy systems shall meet the requirements of s. SPS 384.40.

(b) Joints and connections for closed loop systems with nonconcentrating collectors and type K, L or M copper tubing may be soldered with 50/50 solder to within 5 feet of the collectors. Within 5 feet of the collectors, soldering shall be in compliance with par. (a).

(c) Joints and connections within 5 feet of concentrating collectors shall be silver brazed or attached with proper flare, compression or threaded joint.

(6)FREEZE PROTECTION.

(a) All solar energy systems, except draindown and drainback systems, utilized during periods when outdoor temperatures are below 40ºF, shall be provided with freeze protection.

(b) Components containing liquid heat transfer fluids shall be provided a means of protection from freeze damage. Automatic freeze protection shall be provided in a power failure mode.

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

(d) Collectors and piping which must drain for freeze protection shall be installed with a slope of at least 1/8 inch per foot.

(7)POTABLE WATER PROTECTION.

(a)Prohibited connections to fixtures and equipment. Protection against backflow or back siphonage shall be provided for connections to potable water supply systems in accordance with s. SPS 382.41.

(b)Recirculating water. Water used for space heating may not be returned to the potable water system.

(c)Toxic elements. Heat transfer fluids, heat storage media and thermal storage materials, including any interior protective coatings, may not impart toxic elements to potable water.

Wis. Admin. Code Department of Safety and Professional Services SPS 371.25

Cr. Register, June, 1986, No. 366, eff. 7-1-86; corrections in (1) (c) 4., (3) (c) 2., (4) (intro.) and (7) (a) made under s. 13.93(2m) (b) 7, Stats., Register June 2002 No. 558; correction in (1) (b) 2., 4., 5., 6., (c) 1., 4., (3) (c) 2., (4) (intro.) (b), (f), (5) (a), (7) (a) made under s. 13.92(4) (b) 7, Stats., Register December 2011 No. 672.