Hot water heating

Heat exchangers with flowing cold electrolyte in fresh-water heat pump reservoirs must be treated similarly [9]. Here the cold electrolyte circuit need not have expensive insulated bushings installed as shown in Fig. 20-3, and the entire water pump equipment does not have to be grounded but must be covered to prevent contact. Electrical separation as in Fig. 20-3 is only undertaken with hot-water heat exchangers. 

The design resi.stance of hot-water flow through a coil normally never exceeds 4 kPa in accelerated low-pressure hot-water heating installations. 

Heisswasser-behdlter, m. hot-water tank or container, -heizung, /. hot-water heating, -triebter, m. hot-water funnel. 

A hot-water heating system forces water into pipes, or arrangements of pipes called registers that warm from contact with warm water. Air in the room warms from contact with the pipes. Usually, the pipes are on the floor of a room so that warmer, less dense air around the pipes rises somewhat like a helium-filled balloon rises in air. The warmer air cools as it mixes with cooler air near the ceiling and falls as its density increases. This process is called convection and the moving air is referred to as convection current. The process of convection described here is pipe-to-air and usually does a better job of heating evenly than in an air-to-air convection system—the circulation of air by fans as in a forced-air heating system. 

The fifth type of passive system is the natural convective loop, in which the collector is placed below the living space and the hot air that is created rises to provide heat where it is needed. This same principle is nsed in passive solar hot water heating systems known as thermosiphons. The storage tank is placed above the collector. Water is heated in the collector, becomes less dense, and rises (converts) into the storage tank. Colder water in the storage tank is displaced and moves down to the collector where it is heated to continue the cycle. 

By far the most numerous class of boiler within the UK must be the low-pressure hot water heating or hot water domestic supply boiler, and these are found installed in various types of situations (e.g. offices, factories, shops, hotels) and now widely used in connection with private dwelling houses. 

Figure 15.25 Hot water heat load. Theannual heating requirement is 5.2 X 10 kWh...

Figure 15.26 Chilled water heat load. The annual chilled water heat load is 13 x 10 kWh the annual hot water heat load for absorption-type chillers is 17.4 x 10 kWh (a COP of 75 per cent)...

Figure 20.6 Hot-water heated LPG vaporizers. (Courtesy of Esso Petroleum Co. Ltd)...

Warm and hot water heating systems 27/453 Design water flow temperature 27/454 Maximum water velocity 27/454 Minimum water velocity 27/454 System temperature drop 27/455 Use of temperature-limiting valves on emitters 27/455... 

Table 27.8 Design water temperature for warm and hot water heating systems...

Table 27.11 Hot water heating boilers - recommended sizes of relief valves...

The plant should be able to hold the room at the desired temperature when heat is not being dissipated in the room. The plant should also be able to raise the temperature of the room from cold under winter conditions (e.g. after a power failure or an outage). In considering the temperature to be achieved under test the comments given in test 2 of Section 29.9.6 also apply here. If hot water heating is used, full temperature elevation will not be achieved because high return air temperatures will reduce the coil output. For instance, where the design rise was 22°C above an external of —1°C 19°C, 29°C and 14°C are satisfactory with ambient of 5°C, 10°C and 15°C, respectively. 

Boilers may be used for domestic hot water heating, space heating, waste heat, or chemical recovery. They also may be used for mechanical work, electrical power generation, cogeneration, and innumerable industrial process applications using direct (live) steam or indirect steam (e.g., coil heated) processes. Both FT and WT designs are commonly employed for heat-recovery applications. 

NOTE The minimum regulatory BD requirement for steam-raising land boilers (stationary or trailer-mounted) is usually for a once-per-day opening of the bottom valve. Hot water heating boilers and LP steam boilers employed for hydronic system duty are almost never blown down daily, but should be blown down regularly, albeit usually for the minimum period necessary to ensure the continued safe operation of the bottom BD valve. 

Hot water heating boilers almost never require softeners (oxygen corrosion and sludge buildup are the most common problems) because MU generally is minimal. 

WATERSIDE AND STEAMSIDE PROBLEMS HOT WATER HEATING AND LOW-PRESSURE STEAM BOILER SPECIFICS... 

Hot Water Heating and Low-Pressure Steam Boiler Specifics 175... 

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