Document 3eXDGgd4yQoBO6Rry56VYYMOE

HEATING VENTILATING AIR CONDITIONING GUIDE 1942 pendent domestic hot water heater, it is necessary to know the total quantity of water to be heated per day, and the maximum amount which will be used in any one hour, as well as the duration of the peak load. In cases where the requirements for hot water are reasonably uniform, as in residences, apartment buildings, hotels, and the like, smaller storage capacity is required than in the case of factories, schools, office buildings, etc., where practically the entire day's usage of hot water occurs during a very short period. Correspondingly, the heating capacity must be pro portionately greater with uniform usage of hot water than with inter mittent usage where there may be several hours between peak demands during which the water in the storage tank can be brought up to tempera ture. As a general rule it is desirable to have a large storage capacity in Table 10. Estimated Hot Water Demand per Person for Various Types of Buildings Type of Building Res., apts., hotels, etc. Office buildings Factory buildings Restaurants $0.50 meals $1.00 meals $1.50 meals Restaurants 3 meals per day Restaurants 1 meal per day Hot Water required at 140 F Max. Hourly Demand in Relation to Day's Use Duration of Peak Load Hours Storage Capacity in Relation to Day's Use Heating Capacity in Relation to Day's Use 40 gal per person per day H 4 X H 2 gal per person per day X 2 X X 5 gal per person per day X 1 % X 1.5 gal per meal 2.5 gal per meal 4.5 gal per meal Ho H Ho 8 ~ X- 2% Ho Ho X order that the heating capacity and consequently the size of the heater, or the load on the heating boiler may be as small as possible. In estimating the hot water which can be drawn from a storage tank it should be borne in mind that only about 75 per cent of the volume of the tank is available, as by the time this quantity has been drawn off the incoming cold water has cooled the remainder down to a point where it can no longer be considered hot water. Where steam from the heating boiler is used to heat domestic hot water, the computed load on the boiler should be increased by 4 sq ft EDR (eauivalent direct radiation) for every gallon of water per hour heated V 100 X 8.33 0 ,,,, ti. through a 100 F rise. The actual requirement is-----240-- = sq U 828 CHAPTER 46. WATER SUPPLY PIPING AND WATER HEATING per gallon of water heated 100 F. The value of 4 allows for transmission losses, etc. There are two ways in common use of estimating the hot water require ments of a building; first, by the number of people and second, by the number of plumbing fixtures installed. Where the number of people to be served is known or can be reasonably estimated, the data in Table 10 may be used. Example 6. From Table 10, a residence housing five people would have a daily requirement of 5 X 40 = 200 gal per day, and a maximum hourly demand of 200 X X = 28.5 gal. The heater should have a storage capacity of 200 X X = 40 gal and a heating capacity of 200 XK = 28-5 gal per hour. The conditions given in Example 6 may be cited as average. It is possible to vary the storage and heating capacity by increasing and Table 11. Hot Water Demand per Fixture for Various Types of Buildings Gallons of water per hour per fixture, calculated at a final temperature of HO F Apart ment House Basins, private lavatory.... 2. Basins, public lavatory...... 4 Bathtubs.............. -........ 20 Dishwashers................... 15 Foot basins,............ -..... 3 Ritr>hpn dint 10 Laundry, stationary tubs.... 20 Pantry sink ................... 5 Showers.,..,...... ...... ...... 75 Slop sink............. .. 20 Hourly beating capacity factor............... .......... 30% Storagecapacity factor...... 125% Club 2 6 20 50-150 3 20 23 10 150 20 30% 80% Gym nasium 2 -8 30 -- 12 225 40% 100% Hos Hotel pital. 22 68 20 20 50-150 50-200 33 20 20 23 28 10 10 75 75 20 SO 25% 25% 60% 80% Indus trial Plant 2 12 30 20-100 12 20 225 20 40% 100% Office Build ing 2 6 15 30% 200% Public Bath Private Resi School `dence YM. CA. 2 222 12 15 8 45 20 30 15 20-100 20-100 3 3 12 ,, 10 10 20 20 28 5 10 10 225 75 225 225 15 15 20 20 50% 120% 30% 40% 40% 70% 100% 100% decreasing one over the other. Such a condition is illustrated in Ex ample 7. Example 7. Assume an apartment house housing 200 people. From the data in Table 10: Daily requirements = 200 X 40 = 8000 gal. Maximum hours demand = 8000 X X = 1140 gal. Duration of peak load = 4 hours. Water required for 4-hour peak = 4 X 1140 = 4560. If a 1000 gal storage tank is used, hot water available from the tank = 1000 X 0.75 = 750. Water to be heated in 4 hours = 4560 -- 750 = 3710 gal. Heating capacity per ,hour = --37-1--0 = 930 ga.l. If instead of a 1000 gal tank, a 2500 gal tank had been installed, the required heating capacity per hour would be------------ --^---------------- - = 671 gal. In cases where the number of fixtures only are known, the data in Table 11 have been found satisfactory. 829