Building Design and Construction Handbook - Merritt - Ventech!

WATER-SUPPLY, SPRINKLER, AND WASTEWATER SYSTEMS 14.29
1 in for mains with up to three 3 ⁄4-in or eight 1 ⁄2-in or fifteen 1 ⁄8-in branches
The adequacy of these sizes, however, depends on the pressure available at the
water source and the probability of simultaneous use of the plumbing fixtures.
14.10 DOMESTIC WATER HEATERS
The method of heat development for water heaters may be direct (heat from combustion
of fuels or electrical energy directly applied to water) or indirect (heat from
a remote heat source utilizing some other medium, such as steam, to heat water).
Direct-heat-type water heaters are classified as follows:
1. Automatic storage heaters, which incorporate burners or heating elements, storage
tank, outer jacket, insulation, and controls as a packaged unit
2. Circulating tank heaters, which consist of what is essentially an instantaneous
heater and an accessory storage tank. Hot water is circulated through the heating
section by means of a circulating pump
3. Instantaneous heaters, which have little water storage capacity and generally
have controls that modulate the heat output based on the demand
4. Hot-water supply boilers, which provide high-temperature hot water in a manner
similar to hot-water heating boilers
Fuel for direct-fired water heaters is generally one of the fossil fuels, such as
natural gas or oil, or electric power.
Indirect-type water heaters are classified as follows:
1. Storage type, which consists of a heat exchanger installed in a storage tank (Fig.
14.7) or in a separate storage tank and stand-alone heat exchanger provided with
a circulating water system.
FIGURE 14.7 Storage heater for domestic hot water.