Clasificación Sectorial de la Red Solidaria:
4. Indicadores de Gasto en Desarrollo Humano
Water heating energy use is second only to space conditioning in most residential buildings, and is also significant in many commercial and industrial settings. In some climates and applica-tions, water heating is the largest energy use in a building. Moreover, quick availability of ade-quate amounts of hot water is an important factor in user satisfaction. Both water and energy waste can be significant in poorly designed service water-heating systems: from over- or undersiz-ing pipes and equipment, from poor buildundersiz-ing layout, and from poor system design and operatundersiz-ing strategies. Good service water-heating system design and operating practices can often reduce first costs as well as operating costs.
System Elements
A service water-heating system has (1) one or more heat energy sources, (2) heat transfer equipment, (3) a distribution system, and (4) terminal hot-water usage devices.
Heat energy sources may be (1) fuel combustion; (2) electrical conversion; (3) solar energy;
(4) geothermal, air, or other environmental energy; and/or (5) recovered waste heat from sources such as flue gases, ventilation and air-conditioning systems, refrigeration cycles, and process waste discharge.
Heat transfer equipment is direct, indirect, or a combination of the two. For direct equip-ment, heat is derived from combustion of fuel or direct conversion of electrical energy into heat and is applied within the water-heating equipment. For indirect heat transfer equipment, heat energy is developed from remote heat sources (e.g., boilers; solar energy collection; air, geother-mal, or other environmental source; cogeneration; refrigeration; waste heat) and is then trans-ferred to the water in a separate piece of equipment. Storage tanks may be part of or associated with either type of heat transfer equipment.
Distribution systems transport hot water produced by water-heating equipment to terminal hot-water usage devices. Water consumed must be replenished from the building water service main. For locations where constant supply temperatures are desired, circulation piping or a means of heat maintenance must be provided.
Terminal hot-water usage devices are plumbing fixtures and equipment requiring hot water that may have periods of irregular flow, constant flow, and no flow. These patterns and their related water usage vary with different buildings, process applications, and personal preference.
Legionella pneumophila (Legionnaires’ Disease)
Legionnaires’ disease (a form of severe pneumonia) is caused by inhaling the bacteria Legio-nella pneumophila. It has been discovered in the service water systems of various buildings throughout the world.
Service water temperature in the 140°F range is recommended to limit the potential for L. pneumophila growth. This high temperature increases the potential for scalding, so care must be taken such as installing an anti-scald or mixing valve.
More information on this subject can be found in ASHRAE Guideline 12-2000.
2013PocketGuides.book Page 93 Tuesday, October 7, 2014 12:44 PM
© 2013 ASHRAE (www.ashrae.org). For personal use only. Additional reproduction, distribution, or
transmission in either print or digital form is not permitted without ASHRAE's prior written permission.
Copyrighted material licensed to Ali Alshuaibi on 2015-07-26 for licensee's use only. All rights reserved. No further reproduction or distribution is permitted. Distributed for ASHRAE by Thomson Reuters (Scientific) LLC, www.techstreet.com
94
Service Water Heating
Load Diversity
The greatest difficulty in designing water-heating systems comes from uncertainty about design hot-water loads, especially for buildings not yet built. Although it is fairly simple to test maximum flow rates of various hot-water fixtures and appliances, actual flow rates and durations are user-dependent. Moreover, the timing of different hot-water use events varies from day to day, with some overlap, but almost never will all fixtures be used simultaneously. As the number of hot-water-using fixtures and appliances grows, the percent of those fixtures used simultaneously decreases.
Some of the hot-water load information here is based on limited-scale field testing combined with statistical analysis to estimate load demand or diversity factors (percent of total possible load that is ever actually used at one time) versus number of end use points, number of people, etc.
Much of the work to provide these diversity factors dates from the 1930s to the 1960s; it remains, however, the best information currently available (with a few exceptions, as noted). Of greatest concern is the fact that most of the data from those early studies were for fixtures that used water at much higher flow rates than modern energy-efficient fixtures (e.g., low-flow shower heads and sink aerators, energy-efficient washing machines and dishwashers). Using the older load diversity information usually results in a water-heating system that adequately serves the loads, but often results in substantial oversizing. Oversizing can be a deterrent to using modern high-efficiency water-heating equipment, which may have higher first cost per unit of capacity than less efficient equipment.
Table 6.1 Typical Residential Use of Hot Water [2011A, Ch 50, Tbl 4]
Use High Flow,
Hand dish washing 4 4 3
Automatic dishwasher 15 15 3 to 10
Clothes washer 32 21 5 to 15
Shower or bath 20 15 10 to 15
Face and hand washing 4 2 1 to 2
2013PocketGuides.book Page 94 Tuesday, October 7, 2014 12:44 PM
© 2013 ASHRAE (www.ashrae.org). For personal use only. Additional reproduction, distribution, or
transmission in either print or digital form is not permitted without ASHRAE's prior written permission.
Copyrighted material licensed to Ali Alshuaibi on 2015-07-26 for licensee's use only. All rights reserved. No further reproduction or distribution is permitted. Distributed for ASHRAE by Thomson Reuters (Scientific) LLC, www.techstreet.com
95
Service Water Heating
Table 6.2 HUD-FHA Minimum Water Heater Capacities for One- and Two-Family Living Units [2011A, Ch 50, Tbl 5]
Number of Baths 1 to 1.5 2 to 2.5 3 to 3.5
gpm, 100°F rise 2.75 2.75 3.25 3.25e3.75 3.25 3.75 3.75 3.75
Manufacturer-rated draw,
gal in 5 min, 100°F rise 15 15 25 25e 35 25 35 35 35
Note: Applies to tank-type water heaters only.
aStorage capacity, input, and recovery requirements indicated are typical and may vary with manufacturer. Any com-bination of requirements to produce stated 1 h draw is satisfactory.
bBoiler-connected water heater capacities (180°F boiler water, internal or external connection).
cHeater capacities and inputs are minimum allowable. Variations in tank size are permitted when recovery is based on 4 gph/kW at 100°F rise for electrical, AGA recovery ratings for gas, and IBR ratings for steam and hot-water heat-ers.
dBoiler-connected heater capacities (200°F boiler water, internal or external connection).
eAlso for 1 to 1.5 baths and 4 bedrooms for indirect water heaters.
Table 6.3 Overall (OVL) and Peak Average Hot-Water Use [2011A, Ch 50, Tbl 6]
Group
Average Hot-Water Use, gal
Hourly Daily Weekly Monthly
OVL Peak OVL Peak OVL Peak OVL Peak
All families 2.6 4.6 62.4 67.1 436 495 1897 2034
“Typical” families 2.6 5.8 63.1 66.6 442 528 1921 2078
2013PocketGuides.book Page 95 Tuesday, October 7, 2014 12:44 PM
© 2013 ASHRAE (www.ashrae.org). For personal use only. Additional reproduction, distribution, or
transmission in either print or digital form is not permitted without ASHRAE's prior written permission.
Copyrighted material licensed to Ali Alshuaibi on 2015-07-26 for licensee's use only. All rights reserved. No further reproduction or distribution is permitted. Distributed for ASHRAE by Thomson Reuters (Scientific) LLC, www.techstreet.com
96
Service Water Heating
Table 6.4 Hot-Water Demands and Use for Various Types of Buildings*
[2011A, Ch 50, Tbl 7]
Type of Building Maximum Hourly Maximum Daily Average Daily Men’s dormitories 3.8 gal/student 22.0 gal/student 13.1 gal/student Women’s dormitories 5.0 gal/student 26.5 gal/student 12.3 gal/student Motels: Number of unitsa
20 or less 6.0 gal/unit 35.0 gal/unit 20.0 gal/unit
60 5.0 gal/unit 25.0 gal/unit 14.0 gal/unit
100 or more 4.0 gal/unit 15.0 gal/unit 10.0 gal/unit
Nursing homes 4.5 gal/bed 30.0 gal/bed 18.4 gal/bed
Office buildings 0.4 gal/person 2.0 gal/person 1.0 gal/person Food service establishments
20 or less 12.0 gal/apartment 80.0 gal/apartment 42.0 gal/apartment
50 10.0 gal/apartment 73.0 gal/apartment 40.0 gal/apartment
75 8.5 gal/apartment 66.0 gal/apartment 38.0 gal/apartment
100 7.0 gal/apartment 60.0 gal/apartment 37.0 gal/apartment
200 or more 5.0 gal/apartment 50.0 gal/apartment 35.0 gal/apartment Elementary schools 0.6 gal/student 1.5 gal/student 0.6 gal/studentb Junior and senior high schools 1.0 gal/student 3.6 gal/student 1.8 gal/studentb
*Data predate modern low-flow fixtures and appliances.
aInterpolate for intermediate values.bPer day of operation.
2013PocketGuides.book Page 96 Tuesday, October 7, 2014 12:44 PM
© 2013 ASHRAE (www.ashrae.org). For personal use only. Additional reproduction, distribution, or
transmission in either print or digital form is not permitted without ASHRAE's prior written permission.
Copyrighted material licensed to Ali Alshuaibi on 2015-07-26 for licensee's use only. All rights reserved. No further reproduction or distribution is permitted. Distributed for ASHRAE by Thomson Reuters (Scientific) LLC, www.techstreet.com
97
Service Water Heating
Table 6.5Hot-Water Demand per Fixture for Various Types of Buildings [2011A, Ch 50, Tbl 10] (Gallons of water per hour per fixture, calculated at a final temperature of 140°F) Apartment HouseClubGymnasiumHospitalHotelIndustrial PlantOffice BuildingPrivate ResidenceSchoolYMCA 1.Basin, private lavatory2222222222 2.Basin, public lavatory46868126—158 3.Bathtubc2020302020——20—30 4.Dishwashera1550-150—50-15050-20020-100—1520-10020-100 5.Foot basin33123312—3312 6.Kitchen sink1020—20302020102020 7.Laundry, stationary tub2028—2828——20—28 8.Pantry sink510—1010—1051010 9.Shower3015022575752253030225225 10.Service sink2020—20302020152020 11.Hydrotherapeutic shower400 12.Hubbard bath600 13.Leg bath100 14.Arm bath35 15.Sitz bath30 16.Continuous-flow bath165 17.Circular wash sink2020302030 18.Semicircular wash sink1010151015 19.DEMAND FACTOR0.300.300.400.250.250.400.300.300.400.40 20.STORAGE CAPACITY FACTORb1.250.901.000.600.801.002.000.701.001.00 Note: Data sources predate low-flow fixtures and appliances. aDishwasher requirements should be taken from this table or from manufacturers’ data for model to be used, if known. bRatio of storage tank capacity to probable maximum demand/h. Storage capacity may be reduced where unlimited supply of steam is available from central street steam system or large boiler plant. cWhirlpool baths require specific consideration based on capacity. They are not included in the bathtub category.
2013PocketGuides.book Page 97 Tuesday, October 7, 2014 12:44 PM
© 2013 ASHRAE (www.ashrae.org). For personal use only. Additional reproduction, distribution, or
transmission in either print or digital form is not permitted without ASHRAE's prior written permission.
Copyrighted material licensed to Ali Alshuaibi on 2015-07-26 for licensee's use only. All rights reserved. No further reproduction or distribution is permitted. Distributed for ASHRAE by Thomson Reuters (Scientific) LLC, www.techstreet.com
98
Service Water Heating
Table 6.6 Tankless Water Heater Output Heat Rates, Btu/h* [2011A, Ch 50, Tbl 15]
Flow Rate, gpm
Temperature Rise
10°F 25°F 50°F 55°F 75°F 77°F 100°F
0.1 504 1,260 2,520 2,772 3,780 3,881 5,040
0.5 2,520 6,300 12,600 13,860 18,900 19,404 25,200
1.0 5,040 12,600 25,200 27,720 37,800 38,808 50,400
1.5 7,560 18,900 37,800 41,580 56,700 58,212 75,600
2.0 10,080 25,200 50,400 55,440 75,600 776,196 100,800
2.5 12,600 31,500 63,000 69,300 94,500 97,020 126,000
3.0 15,120 37,800 75,600 83,160 113,400 116,424 151,200
3.5 17,640 44,100 88,200 97,020 132,300 135,828 176,400
4.0 20,160 50,400 100,800 110,880 151,200 155,232 201,600
4.5 22,680 56,700 113,400 124,740 170,100 174,636 226,800
5.0 25,200 63,000 126,000 138,600 189,000 194,040 252,000
6.0 30,240 75,600 151,200 166,320 226,800 232,848 302,400
7.0 35,280 88,200 176,400 194,040 264,600 271,656 352,800
8.0 40,320 100,800 201,600 221,760 302,400 310,464 403,200
9.0 45,360 113,400 226,800 249,480 340,200 349,272 453,600
10.0 50,400 126,000 252,000 277,200 378,000 388,080 504,000
*Divide table values by input efficiency to determine required heat input rate.
2013PocketGuides.book Page 98 Tuesday, October 7, 2014 12:44 PM
© 2013 ASHRAE (www.ashrae.org). For personal use only. Additional reproduction, distribution, or
transmission in either print or digital form is not permitted without ASHRAE's prior written permission.
Copyrighted material licensed to Ali Alshuaibi on 2015-07-26 for licensee's use only. All rights reserved. No further reproduction or distribution is permitted. Distributed for ASHRAE by Thomson Reuters (Scientific) LLC, www.techstreet.com
99
Service Water Heating
Table 6.7Hot-Water Demand in Fixture Units (140°F Water) [2011A, Ch 50, Tbl 16] ApartmentsClubGymnasiumHospitalHotels and DormitoriesIndustrial PlantOffice BuildingSchoolYMCA Basin, private lavatory0.750.750.750.750.750.750.750.750.75 Basin, public lavatory—11111111 Bathtub1.51.5—1.51.5—— —— Dishwasher*1.5Five fixture units per 250 seating capacity Therapeutic bath———5 ————— Kitchen sink0.751.5—31.53—0.753 Pantry sink—2.5—2.52.5——2.52.5 Service sink1.52.5—2.52.52.52.5 2.52.5 Shower1.51.51.51.51.53.5—1.51.5 Circular wash fountain—2.52.52.5—4— 2.52.5 Semicircular wash fountain—1.51.51.5—3—1.51.5 Note: Data predate modern low-flow fixtures and appliances.
2013PocketGuides.book Page 99 Tuesday, October 7, 2014 12:44 PM
© 2013 ASHRAE (www.ashrae.org). For personal use only. Additional reproduction, distribution, or
transmission in either print or digital form is not permitted without ASHRAE's prior written permission.
Copyrighted material licensed to Ali Alshuaibi on 2015-07-26 for licensee's use only. All rights reserved. No further reproduction or distribution is permitted. Distributed for ASHRAE by Thomson Reuters (Scientific) LLC, www.techstreet.com
100
Service Water Heating
Figure 6.1 Modified Hunter Curve for Calculating Hot-Water Flow Rate [2011A, Ch 50, Fig 25]
(Data Predate Modern Low-Flow Fixtures and Appliances)
Figure 6.2 Enlarged Section of Modified Hunter Curve [2011A, Ch 50, Fig 26]
(Data Predate Modern Low-Flow Fixtures and Appliances)
2013PocketGuides.book Page 100 Tuesday, October 7, 2014 12:44 PM
© 2013 ASHRAE (www.ashrae.org). For personal use only. Additional reproduction, distribution, or
transmission in either print or digital form is not permitted without ASHRAE's prior written permission.
Copyrighted material licensed to Ali Alshuaibi on 2015-07-26 for licensee's use only. All rights reserved. No further reproduction or distribution is permitted. Distributed for ASHRAE by Thomson Reuters (Scientific) LLC, www.techstreet.com
101
Solar Energy Use