Document zaq7Gp1O4pdrkD9g6dZKDKmR

Heating Ventilating Air Conditioning Guide 1938 7. State the advantages and disadvantages of tunnels over conduits. The advantages of pipe tunnels over conduits are: 1. Accommodation for miscellaneous services other than steam. 2. Provision of an underground passage between buildings. . 3. Easy installation of additional pipes and easy replacement of existing pipes with larger sizes. 4. Easy inspection and maintenance of pipes. The disadvantages of pipe tunnels over conduits are:. 1. Higher firet cost. 2. Higher maintenance cost in general. 8 Is the steam consumption less in a building that shuts off its steam at night than in one that does not? Why? It has been thoroughly demonstrated that the steam consumption is less in a building where the steam is shut off at night. Although there is, in some cases, an increased con sumption of heat when steam is again turned on in the morning, there is a large net saving which may be explained by the fact that the lower inside temperature maintained during the night obviously resultsin lower heat loss from the building, and less heat need therefore be supplied. 9 Is the condensate from a building supplied with purchased steam always discharged to the sewer? 'No. In some cities where the customers are not spread over too wide a territory, arid where natural water conditions make the treatment of boiler feed water expensive, the steam company provides mains for the return of the condensate to the boilers. 10 What are the common methods for salvaging heat in condensate? .The most common methods are: 1. The use of a water heating economizer for preheating the hot water supply to the building. 2. The use of a cooling radiator. 11 What are the common means used to graduate the heat supply according to variations in outside temperature? a. A weather compensating thermostat regulates the steam supply automatically according to the outdoor temperature;, and gives frequent short intervals of inter mittent steam supply; at the same time it insures delivery of steam to all the radiators. b. Another method which is.very simple is the use of an ordinary vacuum.return line system in which the pressure in the radiators is varied between a high vacuum and a few pounds to produce some control over the heat output^' c. The use of an orifice system graduates heat supply. d. The time-limit control which may be set to provide no service, continuous service, or periodic service, is also used. For periodic service, steam may be supplied during each period in increments of a certain number of minutes for each successive setting of the switch, steam being shut off during the balance of the period. This type of service is provided by several intermittent settings. A night switch will maintain the intermittent day setting, or interrupt the day operation and cut off the supply of steam at night during any desired hours. 782 Chapter 43. WATER SUPPLY PIPING AND WATER HEATING Maximum Possible Flow, Maximum Probable Flow, Average Probable Flow, Factor of Usage, Kind of Pipe Used, Sizing of Risers, Sizing of Mains, Sizing of Systems, Hot Water Supply, Hot Water Heating, Hot Water Storage, Swimming Pool Heat ing Requirements .. . DOMESTIC water supply systems present the engineer with a design problem that requires combining the somewhat empirical rules and; formulae in use with the more or less exact hydraulic principles involved. Unlike heating and ventilating layouts, there are practically no definite data for estimating the quantity of water likely to be consumed or the probable rate of water flow at any particular moment. Metered results in one building often show two or three times the metered amount in another building of the same size and with the same type of tenants. In hotels, one riser will often have an almost constant flow that may never be reached by another at peak load. In office buildings, the women's toilets show a far greater daily consumption than those of the men, yet at no time will they approach the hourly consump tion of the men's toilet during the first hour of the day. This condition has led to a multiplicity of rules of practice which vary as much as the data used. All must of necessity be based on an assumed rate of con sumption and on-an assumed probability of simultaneous use, and while the formulae employed may have been derived on sound technical basis the assumptions are often in error. To arrive at a safe standard, the approximate rate of flow of each fixture to be supplied must be known and the probable number of fixtures in use at any one time must be assumed. Obviously, the maximum number of fixtures assumed to be in use must be taken at the peak of demand and the lines must be made adequate to supply such a peak regardless of the riser or branch on which the demand may occur. Thismeans that all water piping under the usual conditions will be over-sized. In tall buildings it is customary to divide the water supply systems, both hot and cold, into sections of 10 to 20 stories. Such zoning1 or *It is impractical to attempt to size piping so as to produce the proper pressure on fixtures at different levels by employing friction, owing to the fact that this friction will be built up to the amount desired only in times of maximum demand and at all other times the friction will be only a fraction of the maximum friction so that the fixtures by this method are subjected to a varying pressure on the water supply line. A much more practical method is to throttle the flow at the fixture, or to use flow regulators, so that the qspulaasnhtiintygoofrwnaotiseer.delivered will approximate the fixture demands and so that this is accomplished without 783