Handbook for heating and ventilating engineers . unds, then the pressure is .42 pounds per square inch foreach foot in height. Stated in other words, one pound dif-ferential pressure will sustain feet of water. With apressure difference of 3 pounds, this gives 3 -r- .42 = from the water level in the boiler to the point X, nottaking into account the friction of the piping and checkwhich would vary from 10 to 30 per cent. Assuming this 136 HEATING AND VENTILATION friction to be 20 per cent, we have ^ .80 = 9 feet of headto produce motion of the water. The length of the riser pipe
Handbook for heating and ventilating engineers . unds, then the pressure is .42 pounds per square inch foreach foot in height. Stated in other words, one pound dif-ferential pressure will sustain feet of water. With apressure difference of 3 pounds, this gives 3 -r- .42 = from the water level in the boiler to the point X, nottaking into account the friction of the piping and checkwhich would vary from 10 to 30 per cent. Assuming this 136 HEATING AND VENTILATION friction to be 20 per cent, we have ^ .80 = 9 feet of headto produce motion of the water. The length of the riser pipe B and its diameter, dependupon the differential pressure between the condenser andthe receiver, and upon the rapidity of condensation In thehorizontal. With a differential pressure of 2 pounds this would sus-pend 2 X = feet of solid water. The specific gravity,however, of the mixture in this pipe Is much less than thatof solid water. For the sake of argument let this specificgravity be 20 per cent, of that of solid water, then we would. Fig. a possible lift, not including friction, of 5 X = 24feet. This is 24 — 9 = 15 feet below the water level in theboiler. The diameter of the riser may vary for differentplants, but for any given plant the range of diameters Isvery limited. These, as has been stated, are usually foundby experiment. A drain cock should be placed in the receiver at thelowest point. When cold water has collected In the re-ceiver It Is necessary to drain this water to the sewer beforethe loop will work. An air valve should be placed at the topof the goose-neck to draw off the air. If the horizontal pipeIs filled with air, there will be no condensation and the loopwill refuse to work. Nover connect a steam loop to a boiler HOT WATER AND STEAM HEATING 137 in connection with a pump or any other boiler feeder. Todetermine whether a loop is working or not, place the handon the horizontal pipe. If this is cold it is not working. The last method me
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