Section SPS 371.22 - General mechanical requirements(1) INTERCONNECTIONS. When a solar energy system and an auxiliary energy system are interconnected, the design temperature or design pressure of either system may not be exceeded. The interconnection may not compromise or bypass any required safety devices on either system. Auxiliary equipment shall be compatible with the solar energy system output, including but not limited to, temperatures, pressures and heat transfer fluid type.(2)IDENTIFICATION OF MATERIALS. Components and materials used in solar energy systems shall be permanently marked or labeled by the manufacturer as to the component's limitations. All listed components shall have the seal of the listing agency permanently affixed to the component.(3)RELIEF VALVES. (a)Pressure relief.1. All components of the solar energy system having valves capable of isolating heat generating or heat transfer components shall be provided with an approved, adequately sized pressure relief valve. The installation of the relief valve discharge shall be in accordance with s. SPS 382.40(5).2. The pressure relief valve shall be set at a pressure not to exceed the design pressure of the solar energy system or component or 150 psig, whichever is lesser. The relief valve settings may not exceed the recommendations of the valve manufacturer.(b)Vacuum relief. Vacuum relief valves shall be installed as required in s. SPS 382.40(5).(c)Temperature relief.1. Temperature relief valves shall be of adequate relief rating expressed in Btu/hr for the components served.2. Temperature relief valves shall be installed in thermal storage so that the temperature sensing element is immersed within the top 6 inches of a storage tank that contains liquid. The temperature relief valve shall be set to open at 210° F or less.(d)Combination pressure-temperature relief valves. Combination pressure-temperature relief valves shall comply with all the requirements of the separate pressure and temperature relief valves.(e)Entrapped air. Except for drainback systems, the solar energy system shall provide means for removing air at the highest point of the system when liquid heat transfer fluids are used.(4)HEAT EXCHANGERS. (a) Except as provided in par. (b), wherever potable water is interfaced with toxic heat transfer fluids, a double wall heat exchanger, with positive leak detection vented to the atmosphere, shall be provided. The vent shall be located at the lowest part of the heat exchanger or as approved by the department.(b) Where air is the heat transfer fluid, a single wall heat exchanger may be used. Where potable water is the heat transfer fluid, direct connection to the potable water system is allowed or a single wall heat exchanger may be used.(5)HEAT TRANSFER FLUIDS. (a) Solar energy systems using liquid heat transfer fluids shall have a label attached to the thermal storage indicating the heat transfer fluid's name, freezing point and pH, and the system designer's recommendations for checking and maintaining the heat transfer fluid.(b) The heat transfer fluid contained in a non-draindown or non-drainback system shall be able to withstand temperatures of at least -35ºF before freezing.(c) Only heat transfer fluids recommended by the system designer for use in the solar energy system shall be used. Ethylene glycol may not be used for solar energy systems in one- and 2-family dwellings, but may be used in buildings.(d) Flammable liquids may not be used as heat transfer fluids.(e) The heat transfer fluid shall be capable of withstanding design temperatures without rapid thermal degradation.(f) The flash point of the heat transfer fluid shall exceed, by 50ºF, the maximum operating temperature of the solar energy system.(g) Drains and other designated heat transfer fluid discharge or fill points in solar energy systems at which toxic, combustible or high temperature heat transfer fluids may be discharged shall be labeled with a warning describing the identification and hazardous properties of the fluid, instructions concerning the safe handling of the fluid, and emergency first aid procedures.(6)CONTROLS. (a) Controls, dampers and valves shall be marked to identify their function. Any control that serves as an emergency shutdown device shall be so identified by a conspicuous and permanent label.(b) Automatic control of the heat transfer fluid circulation between the collector and thermal storage or load shall be used to limit operations to conditions when useful energy can be collected.(c) Fail-safe controls shall be designed so that in the event of a power failure, or a failure of any component in the solar energy system, the temperature or pressure or both developed in the solar energy system, will not damage the component or the building or present a danger to the occupants.(d) Controls shall be selected and installed so that the solar energy system and auxiliary energy system will operate together and independently.(e) Space heating and control thermostats shall be installed in accordance with the manufacturer's or system designer's instructions. Space heating thermostats shall be located away from drafts, heat sources and exterior walls. Mercury bulb thermostats shall be leveled to assure satisfactory operation. Thermostats mounted outdoors shall be suitable for outdoor environmental exposure.(f) Controls shall be installed to prevent component damage from thermal shock.(g) Controls shall include provisions for manual bypass, adjustment or override of automatic controls as is required to facilitate installation, startup, shutdown and maintenance.(7)CORROSION. (a) All materials used in the solar energy system shall be compatible. All components in contact with the heat transfer fluid used in the solar energy system shall be compatible with the heat transfer fluid.(b) All metal parts, including screws, bolts, and washers, which are not inherently corrosion resistant and are exposed to atmospheric conditions, shall be protected from corrosion by painting, plating, or similar means.(c) Metallic parts which provide protection to either electrical components or internal building structures shall be galvanically compatible and protected from corrosion.Wis. Admin. Code Department of Safety and Professional Services SPS 371.22
Cr. Register, June, 1986, No. 366, eff. 7-1-86; corrections in (3) (a) and (b) made under s. 13.93(2m) (b) 7, Stats., Register June 2002 No. 558; correction in (3) (a) 1., (b) made under s. 13.92(4) (b) 7, Stats., Register December 2011 No. 672.