UFC 3-420-01
25 October 2004
maximum heat loss rates stated in this section are minimum design requirements. The
quality of insulation should be upgraded if the designer can show an improvement in the
system performance or that insulation improvements are cost effective."
H.
Add "SECTION 506 SIZING HOT WATER SYSTEMS.
506.1 Sizing Calculations. Design in accordance with American Society of
Heating, Refrigerating and Air Conditioning Engineers (ASHRAE) Handbook -
accordance with ASHRAE Standard 90.1, Energy Efficient Design of New
Buildings Except Low-Rise Residential Buildings. In addition to criteria provided
in the ASHRAE Handbook, consideration should be given to differences in costs
of building area required to support systems when calculating life cycle costs.
For low-rise residential buildings, design in accordance with The ICC
International Residential Code. Size hot water system and set service water
heater (SWH) storage temperature set point for not less than 140F (60C) to
limit the potential for growth of Legionella pneumophila. Provide a hot water and
cold water blending, tempering valve immediately downstream of the SWH
storage tank to provide anti-scalding protection. Provide a balanced-pressure-
type tempering valve. Set the blending valve to deliver 110F (43C) water to
the fixtures except where higher temperatures are required by specialized
equipment as indicated in ASHRAE Handbook Applications. For Army and
Air Force projects, use the set point temperatures indicated in Table 506.
Table 506. WATER SERVICE TEMPERATURES
Service
Degrees F ( Degrees C)
General use such as showers,
sinks, family housing,
administration facilities, etc.
120 (49)
Commercial type dishwashers
with internal boosters
140 (60)
Commercial type dishwashers
without internal boosters
180 (82)
Commercial type laundries
180 (82)
506.1.1 Sizing distributed or residential SWH systems. Use ASHRAE
Chapter 48, Table 5 to size small SWH systems typical for family housing,
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