The Golden State: Where & How to Live, Secure, Visit, Enjoy and Thrive in California
Hot Water Suply
Care should be taken not to have the tube a less than 3 inches distant from the steam coil, because, if placed nearer, the intense heat of the water at this point would cause the steam valve to shut off before all the water in the tank became heated. For the same reason it should not be placed too near the top of the tank. The cold- water inlet to the tank should be on the opposite end from the thermostat a. There should be arrangements for draining continuously any condensate which might collect at the inlet side of the valve g when the latter is closed, as otherwise there may be objectionable noises whenever the valve g opens after having been closed for some time. The storage tank must have a pressure relief valve, thermometer, etc., not shown in the illustration.
Details Of Hot-Water Systems
41. Fuel Required for Heating
Water.—Computations of the fuel required for heating water are relatively simple if the 'ollowing approximate values are assumed. They are sufficiently accurate for the purpose.
(a) 1 gallon of water weighs 8.3 pounds.
(b) 1 B.t.u. will heat 1 pound of water 1 degree.
(c) The obtainable heat in a small manually-fired coal-burning water heater probably will not exceed 50 per cent of that shown by laboratory analysis of the fuel. This is due to a small combustion chamber and infrequent attention. As a result, the heat available per pound of coal may be assumed as not to exceed 7,000 B.t.u.
(d) Gas can be burned at much higher efficiency in a small boiler than can solid fuel. A reasonable percentage of efficiency would be 70. Therefore, if the gas has a heat value of 700 B.t.u. per cubic foot, there would be available 490 B.t.u. per cubic foot.
(e) Fuel oil can be burned in a small boiler at about 65 per cent efficiency. If No. 4 oil is used, the usual grade for small boilers, having a heat value of 140,000 B.t.u. per gallon, 91,000 B.t.u. per gallon of oil will be available.
(/) The unit of electrical energy, the kilowatt, is equivalent to 3,415 B.t.u. The transfer of heat from electricity to water is practically 100 per cent efficient, but there will be radiation losses from the storage tank, so that an efficiency of 90 per cent probably is fair, say 3,000 B.t.u. per kilowatt.
(g) The latent heat of steam at atmospheric pressure is about 1,150 B.t.u. per pound, but allowing for inevitable losses it is fair to consider 1,000 B.t.u. available for water heating per pound of steam.
