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302 CHAPTER 13 1953 Guide X HEAT SOURCES WITHIN THE CONDITIONED SPACE" People. The rates at which heat and moisture are given off by human beings under different states of activity are given in Table 25. In many applications these sensible and latent heat gains become a large fraction of the total load. Appreciable variations in heat-emission rates must be recognized according to the age and sex of the individual, state of activity, environmental influences, and duration of occupancy (since for short . occupancy the extra heat and moisture brought in by people may be a significant factor). , While Chapter 6 should be referred to for detailed information, Table 25-Table Rates of Heat Gain fbom Occupants of Conditioned Spaces" Degree of Activity Typical Application Total Heat Adults, Male Btu/Hb Total Heat Adjusted Btu/Hr Sensible Heat Btu/Hb Latent Heat Btu/Hb Seated at Rest............................ Seated, Very Light Work........... ' Moderately Active Office Work: Standing, Light Work; or Walking Slowly............................ Walking; Seated........................... Standing; Walking Slowly.......... Sedentary Work........................... Light Bench Work........................ Moderate Dancing........................ Walking 3 mph; Moderately Heavy Work............ Bowling....................................... Heavy Work................................. Theater-Matinee. . Theater-Evening.... Offices, Hotels, Apartments...:....... Offices, Hotels, Apartments............ Department Store, Retail Store Dime Store............. Drug Store Restaurant............. factory.................... Dance Hall............. Factory.................. Bowling Aliev__ f actory............. 390 390 450 475 550 550 490 800 900 1000 1500 350 400 450 450 500 550 750 850 1000 1450 150 195 155 195 205 200 250 200 250 300 330 530 245 605 300 700 465 985 * Note: Tabulated values are based on 80 F from dry-bulb temperature. For 78 F room dry-bulb, the total heat remains the same, but the sensible heat values should be increased by approximately 10 percent, and the latent heat values decreased accordingly. b Adjusted total heat gain is based on normal percentage of men, women,'and children for the application listed, with the postulate that the gain from an adult female is 85 percent of that for an adult male, and that the gain from a child is 75 percent of that for an adult male. - c Adjusted total heat value for sedentary work, restaurant, includes 60 Btu per hour for food per individual (30 Btu sensible and 30 Btu latent). . d For bowling figure one person per alley actually bowling, and all others as sitting (400 Btu per hour) or standing (550 Btu per hour). 25 in this chapter summarizes practical data representing conditions com monly encountered. Lighting. In general, the instantaneous rate of heat gain from electric lighting31 may be calculated from the following relation: ?.i = /total light J use (wattage . X {factor /special allowX {ance factor X 341- Btu Per hr' (15) The total light wattage is obtained from the ratings of all fixtures installed, both for general illumination and for display use. The use factor is the ratio of the wattage in use, for the conditions under which the load estimate is being made, to the total installed wattage. For commercial appli cations such as stores, the use factor would be unity. The special allowance factor is introduced to care for fluorescent fixtures, and for fixtures which are cither ventilated or installed so that only part of their heat goes to the conditioned space. For fluorescent fixtures, the special allowance factor is recommended to be taken as 1.20 in order to allow for power consumed in the ballast. For ventilated fixtures, recessed fixtures, and the like, manufacturers' or other data" Cooling Load 303 must be sought to establish the fraction of the total wattage which may be expected to enter the-conditioned space. Power. When equipment of any sort is operated within the conditioned space by electric motors, the heat equivalent of this operation must be considered in the cooling load. The general equation for calculating this load is: = fH^wer RatingV x / Load \ x ^ Btu per hr \ Motor Efficiency ) \Factor/ > :(16) It is assumed that both the motor and the driven equipment are within the conditioned space. If the motor is without the space, then do not divide by the motor efficiency in Equation 16. The load factor is merely the fraction of the rated load which is being delivered under the conditions of the cooling-load estimate. \ Motor efficiencies may be approximated as follows: about 50 to 60 percent at f hp rating, increasing to 80 percent at 1 hp, and to 88 percent at 10 hp and above.- Appliances. Care must be taken in a cooling-load estimate to take into account the heat gain from all appliances, electrical, gas, or steam. Table 26 presents recommended data.33 Note, that the maintaining rate in Table 26 is the heat input required to maintain, the appliance at the normal operating temperature even though it is not being used, i.e., no coffee is being made, no toast is being made, no food is being cooked in the fry kettle, etc. The maintaining rate is useful in setting up a lower limit to the heat gain to a room from the appliance when in operation. Experienced judgment must be used in the application of data given in Table 26. Consideration must be given to the heat contributed by appli ances which are in use at the time of peak load. The quantity of heat will depend upon whether products of combustion are vented to a flue, whether they escape into the space to be conditioned, or whether appliances are hooded allowing part of the heat to escape through a stack. There are no generally accepted data available on the effects of venting and shielding heating appliances, but it is believed that when they are properly hooded with a positive fan exhaust system through the hood, 50 percent of the heat will be carried away and 50 percent dissipated in the space to be condi tioned. The same effectiveness of the hood should be figured for both latent and sensible heat. LOAD FROM MOISTURE TRANSFER THROUGH PERMEABLE BUILDING MATERIALS The diffusion of moisture through all common building materials is a natural phenomenon which is always present to a greater or lesser degree. The permeability and permeance values for various building materials are given in Table 2 of Chapter 10, together with an explanation of mois ture transmission through these materials. In the usual comfort air-conditioning application, it is common prac tice to neglect moisture transfer through walls, for the actual rate is quite small and the corresponding latent-heat load is hardly significant. Socalled vapor barriers are frequently employed in modern construction for the purpose of keeping moisture transfer to a minimum, and reducing the deteriorating and insulation-destroying effects of moisture. Industrial jobs, on the other hand, frequently call for a low moisture