Document g2RQL5NL58bV4M5Y9MKaOzeYq

266 CHAPTER 14 1949 Guide after careful consideration of all local conditions. In many cases, these heat sources should not be allowed to affect the size of the installation at all, although they may have a marked effect on the operation and control of the system. In general, it is safe to say that where audiences are in volved, the heating installation must have sufficient capacity to bring the building up to the stipulated inside temperature before the audience arrives. In industrial plants, quite a different condition exists, and heat sources, if they are always available during the period of human occupancy, may be substituted for a portion of the heating installation. In no case should the actual heating installation (exclusive of heat sources) be reduced below that required to maintain at least 40 F in the building. Electric Motors and Machinery Motors and the machinery which they drive, if both are located in the room, convert all of .the electrical energy supplied into heat, which is retained in the room if the product being manufactured is not removed until its temperature is the same as the room temperature. If power is transmitted to the machinery from the outside, then only the heat equivalent of the brake horsepower supplied is used. In some mills this is the chief source of heating and it is frequently sufficient to overheat the building even in zero weather, thus requiring cooling by Table 4. Heat Equivalents of Various Sources* Machinery (Motor in room = Motor Hp/efficiency x 2544 Btu/hr. Machinery (Motor outside room) = Motor Hp x 2544 Btu/hr. Electric Lights = Kilowatts x 3413 Btu/hr. Gas (Producer = 150) (Manufactured = 535) (Natural = 1000) Btu/cu ft. * Additional values are given in Chapter 15, Table 25. ventilation the year 'round. Table 4 shows the heat output equivalent of various sources of heat in a factory. For information concerning the heat supplied by persons, refer to data given in Chapter 12, and also Table 24, Chapter 15. For appliances see Table 25, Chapter 15. INTERMITTENTLY HEATED BUILDINGS . In the case of intermittently heated buildings additional heat is required for raising the temperature of the air, the building materials and the ma terial contents of the building to the specified inside temperature. The rate at which this additional heat must be supplied depends upon the heat capacity of the structure and its material contents and upon the time in which these are to be heated8. - This additional heat may be figured and allowed for as conditions re quire, but inasmuch as the heating system proportioned for taking care of the heat losses will usually have a capacity about 100 per cent greater than that required for average winter weather, and inasmuch as most buildings may either be continuously heated or have more time allowed for heating-up during the few minimum temperature days, no allowance is usually made except in the size of boilers or furnaces. For churches, auditoriums and other intermittently heated buildings, additional capacity should be provided. RESIDENCE HEAT LOSS PROBLEMS Example 5. Calculate the heat loss of the residence shown in Fig. 2 located in the vicinity of Chicago. From Table 1, design outdoor conditions are --10 F and 12 mph Heating Load 267 Notes for Table 5. The inaidMUtside temperature difference is 70- (-10).or 80 F except where otherwise noted. b y0iume of infiltration, cfh - (no. air changes) x (floor or ceiling area) x (ceiling height). c From equation 4a, p. 245. . d The ceiling heat losses are calculated by estimating the attic temperature and then calculating the loss . tL. ceiling wring the proper temperature difference. This unheated attic is not ventilated during months The attic temperature is estimated from Equation 1 to be 30.2 F when the outside tem- WlQ Him is -- 10 F and room temperature is 70 F. The temperature difference is then 70--30.2 or 39.8 deg. f^the insulated residence, attic temperature becomes 4.6 F and temperature difference 70--4.6 = 65.4 deg. Temperature in garage asumed to be 35 F. f Coefficient for wall adjoining garage calculated on basis of metal lath and plaster on both sides of studs, m = 0.39). . t One half of value from Table 4, Chapter 8, for storm windows or weatherstnppmg. b Exposed on two sides, weatherstripped windows offset by fire-place. Use 1$. Window on one side weatherstripped but double-doors are hard to close tightly. Hence conservative value of 1$. i Assuming kitchen vent, door to vestibule usually open, allow full table value of 1J. k One half value in Table 4, Chapter 8, increased to 1} by nearby outside door in vestibule. * Full value in Table 4, Chapter 8, to allow for frequent opening of outside door. m Two sides exposed, large doors but large vol ume. Use value li as given in Table 4, Chapter 8. n Two small unweatherstripped windows in pro tected location, but fireplace, indicate 1 change. Since garage is assumed colder than ground, heat gain results should be subtracted from heat losses elsewhere. - p Heat losses from these rooms into garage are heat gains for garage. u Neglect heat loss to basement, as losses from ' boiler, piping, etc, will probably keep basement near, if not above, 70 F. r Upstairs hall ceiling figured with downstairs. Heat should be provided downstairs for both. scoonooan/* Fig. 2. Floor Plans of Residence