1、 RECOMMENDATION E Recommendation Against Mixing Hydronic Heating Water with Potable Water Issued April 2016 Hydronic radiant heating is a comfortable and efficient technology for heating a wide range of buildings, from residential applications to large commercial and industrial facilities. In most p
2、rojects, it is possible to meet the heat loss of buildings through a heated floor using relatively low-temperature heated fluid, often under 120F (48C). This gives radiant heating systems the flexibility to work with a wide variety of heating sources, such as low-temperature condensing boilers, geot
3、hermal water-to-water heat pumps, air-to-water heat pumps, thermal solar collection systems, and even wood-fired boilers. In certain cases, domestic water heaters may be used as the source of warm water for radiant heating systems, subject to local code requirements. Typical applications of this typ
4、e of heat source include special dual-purpose water heaters intended for supplying both hydronic heating and hot domestic water and designed so that the heating water and the domestic water do not mix. Also, when allowed by local code regulations, a domestic water heater may be installed as a heat s
5、ource with an approved backflow prevention device, pressure relief valve and pressure reducing valve, piped to produce warm water for supply to hydronic radiant heating or fan coil systems, for instance. This application of a domestic water heater provides a relatively low-cost source of warm-water
6、for smaller radiant heating systems. However, when combined hydronic and potable systems are constructed whereby the potable water travels through or otherwise contacts hydronic heating pipes and components such as fan coils, valves or manifolds, potential health and safety issues may be created. Th
7、ese potential issues include: 1. Certain hydronic heating components are not intended and certified to be used for potable water. These include certain types of pipes, fan coils, mixing valves or distribution manifolds. If these components are installed so that domestic water flows through them, thi
8、s type of installation may violate regulations regarding the approval of components for drinking water safety1, or regulations requiring so-called lead-free2components intended to contact potable water, or both. 2. Stagnant water in heating systems is a potential breeding ground for dangerous bacter
9、ia such as Legionella3. In a system with a shared water heater, the stagnant water from the heating distribution system is likely to be mixed with domestic hot water when the heating system is reactivated. This situation has the potential to expose users of the domestic hot water to Legionellabacter
10、ia through showers and other hot-water uses, potentially leading to serious health risks. Therefore, it is the recommendation of the PPI that designers and installers not specify or build systems where the mixing of hydronic water with potable water may occur. 1Water treatment or distribution produc
11、ts in North America are required to comply with NSF/ANSI Standard 61: Drinking Water System Components Health Effects by most government agencies that regulate drinking water supplies. Developed by a team of scientists, industry experts and key industry stakeholders, NSF/ANSI 61 sets health effects
12、criteria for many water system components. 2 Congress enacted the Reduction of Lead in Drinking Water Act on January 4, 2011, to amend Section 1417 of the Safe Drinking Water Act (SDWA) regarding the use and introduction into commerce of lead pipes, plumbing fittings or fixtures, solder and flux. Th
13、e Act established a prospective effective date of January 4, 2014. 3 Legionnaires disease is a severe, often lethal, form of pneumonia. Its caused by the bacterium Legionella pneumophila found in both potable and non-potable water systems. The disease was named in 1976, when American Legion members
14、who attended a Philadelphia convention, suffered from an unusual pneumonia (lung infection). Reference Publications: 1. http:/legionella.org/ “Legionella.org provides educational resources for anyone who has been affected by Legionnaires disease” 2. http:/www.cdc.gov/legionella/about/ “Legionella (L
15、egionnaires Disease and Pontiac fever)” 3. http:/www.legionella.org/100960699-1.pdf M.L. Pedro-Botet, J.E. Stout, V.L. Yu: “Legionnaires Disease Contracted from Patient Homes: The Coming of the Third Plague?” 4. http:/www.antimicrobe.org/b118-index.asp “Legionella species (Legionnaires disease)” 5.
16、http:/ David Yates, Contractor: “Legionnaires Disease” 6. http:/ Robert P. Mader, Contractor: “Legionella can be kept out of radiant heating systems” 7. http:/legionella.org/media/28614/ashraeguideline12-2000.pdf “Minimizing the Risk of Legionellosis Associated with Building Water Systems” 8. http:/ Lance MacNevin, HPAC Magazine: “Mixing Hydronic Heating Water with Potable Water” page MH26 - MH27
