Code Classroom Continued from page 20
should be listed. If you are interested in serving on the ad-hoc committee, please contact IAPMO.
IAPMO hires new director of standards development IAPMO has hired Abraham I. Murra as director of
standards development. Mr. Murra recently worked at the Canadian Standards Association (CSA) as a project manager, where he managed 16 national and bi-national committees of more than 300 professional volunteers to develop and maintain technical standards for plumbing products. I had a chance to spend some time with Mr. Murra at
an ASME/CSA joint meeting in Phoenix in January. He is a pleasure to work with, and he has a passion for his work. Recently, Murra led committees developing stan- dards on water conservation, water reuse and waste- water. He is a civil engineering graduate of Universidad de los Andes in Bogotá, Columbia, and he also holds a Master of Civil Engineering degree from Cornell University in Ithaca, New York. He will oversee devel- opment and maintenance of IAPMO’s plumbing stan- dards, property and installation standards and IAPMO Guide Criteria.
ASSE scald awareness committee addresses water heater thermostats The American Society of Sanitary Engineering pro-
duced the first white paper on scalding hazards associat- ed with low flow showerheads last year. The committee has now moved on to the next white paper. This paper, which should be nearing completion by the end of the year, will address the inability of the water heater ther- mostat to accurately control hot water temperature, Although water heater manufacturers are recommend-
ing that installers set thermostats at 120 to 125 F, most of them ship the water heaters at lower temperature set- tings. This is because of lawsuits that the water heater manufacturers have had to deal with because of scalds. Scald injuries are very preventable. We have the tech- nology to prevent scalds with proper hot water tempera-
Figure 2 – Water Heater Thermostat Temperature Variations.
with the use of a master thermostatic mixing valve. Hot water systems are generally designed and water heaters are generally sized to store hot water at 140 F or higher. When the thermostat is set at a lower temperature, the water heater has a reduced capacity to deliver hot water. Lower thermostat settings can also cause condensation in a water heater. When maintenance workers lower the water heater thermostats, it is common for users to run out of hot water during peak periods, which leads to complaints. When, to address the complaints, the ther- mostat is re-adjusted to a temperature above 120 F, the heater usually delivers water at very hot temperatures to unsuspecting bathers or users. Water heater thermostats were never intended to pro-
Figure 1 – Water Heater Thermostat Temperature Variations.
Page 22/Plumbing Engineer
vide precise temperature controls. For example, the ther- mostat dial calibration test of ANSI Z21.10.1-1998, which is the applicable standard for gas-fired water heaters, allows the temperature to vary significantly above or below the thermostat setting. I have talked to water heater manufacturers who indicated that the con- trols can vary as much as 15 to 18 degrees F above or below the thermostat set point. I have witnessed temper- atures 35 degrees above the set point at the water heater outlet. This is because the thermostat is inserted into the lower portion of a water heater tank, where the cold
Continued on page 24 June 2011
ture controls. We just do not have the teeth in the codes when it comes to existing installations. Existing systems are not required to be upgraded to meet the current code because of two factors. One is cost: Building owners do not want to be forced to spend the money. The other issue is education: Most people do not understand the dangers associated with hot water scald injuries in sys- tems without compensating type shower valves or mas- ter mixing valves. Plumbing design professionals often recommend that
hot water systems be designed with higher storage tem- peratures to reduce the threat of Legionella bacteria growth in the hot water tank; they recommend reducing the hot water delivery temperature to a safe temperature
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