RANGE BOILERS
The hot-water supply to the household is of so much importance, that the installation of the range boiler should be made with great care, and an understanding of the principle on which it works should be fully appreciated by all who have to do with its management. The ability of the boiler to supply the demands put upon it depends in a great measure on its size and the arrangement of its parts, but proper management is necessary to assure a supply of hot water when required.
Range boilers are used for storing hot water heated by the water-back of the kitchen range or other water heater, during a period when water is not drawn. It serves as a reserve supply where the heater is not of sufficient size to heat water as fast as is demanded.
As commonly used, range boilers are galvanized-steel tanks made expressly for household use. They are standard in form and may be bought of any dealer in plumbing or household supplies. In capacity they range from 20 to 200 gallons and are made for either high-or low-pressure service. They are said to be tested at the factory to a pressure of 200 pounds to the square inch and are rated to stand a working pressure of 150 pounds. Range boilers are galvanized after they are made and coated both inside and out. The coating of zinc received in the galvanizing process helps to make their seams tight and at the same time renders the surface free from rust.
There is no definite means of determining the size of tank to be used in any given case, because of the varying demands of a household but a common practice is to allow 5 gallons in capacity to each person the house is able to accommodate.
The Water-back.
—The most common method of heating water for the range boiler is by use of the water-back or water-front of the kitchen range. The water-back is a hollow cast-iron piece that is made to take the place of the back fire-box lining of the range. In some ranges the heater occupies the front of the fire-box instead of the back, in which case the heater becomes the water-front.
The arrangement of pipes connecting the source of water supply with the boiler is such that cold water is constantly supplied to the tank as the hot water is drawn. If no water is drawn from the tank, it will continue to circulate through the tank and heater, the water becoming constantly hotter.
The connecting pipes are usually of iron but sometimes pipes of copper or brass are used. The joints should be reamed to remove the burr that is formed in cutting. The angles should be 45-degree bends or better still 90-degree bends in connecting the heater with the tank so as to cut down the amount of friction as much as possible.
Fig. 113.—A common method of connecting the range boiler to the water-back.
In Fig. 113 is shown a standard range boiler connected to the range. The water is brought into the top of the tank through the pipe a-a, and passing through it enters the water-back by means of the pipe b. After passing through the water-back the water again enters the tank through the pipes c and d, as indicated by the arrow. The flow pipe (carrying the out-going water) from the water-back may be connected with the tank at e, as shown dotted or in some cases the connections are made at both places. The velocity of circulation depends on the vertical height of the column of hot water and the greater height will, therefore, improve the circulation and thus increase the efficiency of the heater. The circulation of the water through the tank and heater is produced by its change in weight as the water is heated. As the hot water comes from the water-back it rises in the pipe because it is lighter in weight than the cooler water of the tank. In the case of the pipe shown dotted in Fig. 113 the longer vertical rise will give a greater upward velocity of the hot water and consequently a better circulation through the entire circuit.
The construction of the water-back is shown in the small drawing. The connections are made at b and c as before. A division plate in the water-back causes the water flowing in at b to follow the length of the heater at the bottom and return at the top as indicated by the arrow, when it is discharged at C.
The hottest water is always at the top of the tank and the temperature grades uniformly from the hottest at the top to the coolest at the bottom. The reason for extending the pipe a so far down into the tank is that the cold water may not mingle with the hot water and reduce its temperature on entering the tank. Near the top of the pipe a is a small hole f that is intended to prevent the water from being siphoned from the tank in case a vacuum is formed in the cold-water pipe. In this arrangement the water enters and leaves at the top of the tank. In case the supply is shut off at any time the tank is left almost full of water, because the siphoning effect cannot extend below the small hole f.
Excessive Pressure.
—Accidents due to the explosion of hot-water backs are not at all rare and it should be borne in mind that there is danger of excessive pressure being formed should the pipes b and c become stopped. Under normal conditions the pressure generated by the heated water is relieved by the water in the tank being forced back into the supply pipe. The pressure in the tank, therefore, cannot become greater than that of the source of supply, but if b and c should become stopped with the water-back full of water a dangerous pressure might result. The greatest danger from this cause is that of freezing. It frequently happens that houses are closed during cold weather and the water-back is left undrained. The water freezes and when a fire is started in the range, the ice in the water-back is the first to melt. In a short time steam will be generated that will soon produce a sufficient pressure to burst the water-back. This has happened many times with disastrous results. Such dangers may be avoided by the exercise of a reasonable amount of care in the management of the range. To drain the water-back, the water is first shut off at the point where the supply pipe enters the house. The water in the range boiler is then drawn off by means of the cock h.
Fig. 114.—Blow-off for removing sediment.
Blow-off Cock.
—When a considerable amount of sediment is carried in the water the range boiler acts as a settling tank and the deposit accumulated at the bottom will in time amount to a source of trouble. The accumulation is shown in Fig. 114. The part W, which connects with B, is sometimes provided with a blow-off cock that will admit of a discharge of the sediment. More commonly the piping is arranged as shown in Fig. 113, when sediment is removed by occasionally drawing water from the cock h.
Fig. 115.—Method of connecting the range boiler when placed on the floor below the heater.
Location of Range Boiler.
—It is sometimes desired to place the range boiler on a different floor, either above or below the range. While such arrangements are entirely possible the circulation of the water is not so good as that described above. The weight of the two columns of water in the connecting pipes are so nearly balanced that good circulation is not always possible. In Fig. 115 the connections are shown, where the tank is located in the basement. In connecting the water-back to the tank under such conditions the piping is relatively the same as is shown in the dotted connections of Fig. 113, but the connections are longer. The circulating pipe comes from the bottom of the tank and leads to the bottom of the water-back. The flow pipe from the top of the water-back is extended up to a distance equal or greater than the distance from the water-back to the bottom of the tank. The hot water is taken from the top of the flow pipe at any place above the tank.
Double Heater Connections.
—Two heaters are sometimes connected to one range boiler, each circuit being independent of the other. Under such conditions one or both heaters may be used. When the tank is connected as shown in Fig. 116 the pipe a, from the bottom of the tank, branches and leads to b and b´, at the bottom of each of the heaters. The flow pipes from the top of the heaters enter the tank at separate places, the lower heater sending its water into the side of the tank at c, and the upper heater flowing into the pipe d, at the top of the tank. It would be perfectly possible to reverse the connections for the flow pipes in the arrangement of Fig. 116 and attain the same results. In such combinations the heaters are sometimes piped tandem, the water flowing through each of the heaters in turn. This, however, is not the best method to employ, for if only one of the heaters is used the second acts to cool the water.
Fig. 116.—Double connections for the range boiler where a heater is placed in the basement for occasional use.
Horizontal Range Boilers.
—It occasionally happens that in a small kitchen there is no convenient floor space for the range boiler and it becomes necessary to suspend it from the ceiling. It is perfectly possible to station the ordinary range boiler in such a position and have it work fairly well but from the location of the cold-water inlet, only that part of the range boiler above the cold water pipe is actually used for storage. The water in the lower half constantly mixes with the entering cold water before it is heated by passing through the water-back. When hot water is drawn from the top of the range boiler, cold water enters by the cold-water pipe and reduces the temperature of most of the lower half. Fig. 117 illustrates such an arrangement. In this case the pipes connected with the water-back are those that correspond to the circulating pipes a and e in Fig. 113.
Suppose the range boiler is full of water, and that it is being heated. The lower pipe at the left-hand end is conducting the water to the water-back and it is being returned to the range boiler by the upper pipe at the same end. When the hot water is drawn from the top of the range boiler by the hot-water pipe, the entering cold water mixes with hot water in most of the lower half of the range boiler before it has been heated by passing through the water-back and so reduces the temperature of most of the lower half of the tank.
Fig. 117.—Method of connecting the vertical range-boiler in a horizontal position.
Fig. 118.—Horizontal range-boiler suspended from the ceiling.
A much better tank for the purpose is that indicated in Fig. 118. This is a tank made particularly for such a location. The cold water enters at the bottom of the tank and also leaves the bottom on its way to the water-back. Circulation takes place through the water-back as before but when hot water is drawn from the top of the tank, the entering cold water at the bottom mixes with only that at the lower part of the tank and so cools but a small amount of the hot water in storage. Hot-water tanks of this kind are tapped for pipe connections in two places on both the top and bottom sides and also at the ends as shown in the drawing.
Tank Heaters.
—When the demand for hot water is sufficient to warrant a separate hot-water heater the apparatus similar to Fig. 119 is used. With such a heater, the conditions of overheated water—to be described later—may be almost entirely avoided. In this case the connections are arranged similarly to those of the range boiler but a separate furnace takes the place of the water-back. The heater is simply a small furnace made expressly for heating water. Connected with the discharge pipe p is a draft-regulating valve which controls the drafts of the heater. The draft-regulator is set to so control the furnace that water at the desired temperature will always be in the tank. The mechanism of this regulator is the same as the draft-regulator described under hot-water heating plants.
Overheated Water.
—Under ordinary conditions the water contained in the range boiler is below the atmospheric boiling point (212°F.) but at times when a hot fire is kept up in the range for a considerable period, the temperature will rise to a degree much above that amount. The temperature to which the water will rise will depend on the pressure of the water supply. As an example—suppose the gage pressure of the water supply is 25 pounds. The temperature corresponding to that pressure is 258°F. The temperature of the water in the tank will rise to that amount but not further because any additional temperature will produce a higher pressure, but a higher pressure would be greater than the pressure of the water supply and hence will back the water into the supply pipe. This condition of things, then, acts as a safety valve to the tank to prevent excessive pressures.
Fig. 119.—Independent hot-water heater with temperature regulator.
When the water at a high temperature is drawn from the tap a considerable part of it will instantly vaporize, because of the reduced pressure. If water at a pressure of 25 pounds is drawn from the faucet, the temperature, 258°F., is sufficient to send all of the water instantly into steam. This high temperature will scald at the slightest touch. The water drawn from the faucet will continue to vaporize as it comes into the air until the water in the tank is cooled by the incoming cold water. The only means of relieving the overheated condition is to open the faucet a slight amount and allow a portion of the heated water to be drawn off.
It is evident from what has been said of the range boiler that it operates under a variety of conditions. It is first a storage tank in which is accumulated the water, heated from a greater or less period of use of the range. Should the range fire be maintained through the day or night the supply of hot water will be excessive and superheating is the result. If the heater is to be used during short periods of time, the piping should be arranged to produce the best circulation; on the contrary, should the heater be used continuously—as in the case of a furnace coil—a slow circulation through the tank is most to be desired and the piping should be arranged for that purpose.
In the use of furnace heaters, superheating is likely to occur during cold weather when a hot fire must be used over a long period of time. In order to conserve the heat accumulated under such conditions a hot-water radiator is frequently connected with the range boiler through which to dispose of the excess heat. This radiator may be placed in any desired position and so connected by a valve as to discontinue its use at any time.
Fig. 120.—The range boiler connections when a furnace coil is used for hot-water heating.
Furnace Hot-water Heaters.
—It is sometimes more convenient to use the furnace as a means of heating water than the kitchen range. Such an arrangement is shown in Fig. 120, where a loop of pipe in the fire-box of the furnace takes the place of the water-back. The arrangement of the pipes in the range boiler are as before, the water entering the tank through the pipe A, circulates through the pipes B and C, receiving its heat while passing through the loop in the furnace, in exactly the same way as in the water-back. It would be quite possible to also connect the kitchen range with the tank as shown by the dotted lines indicating the water-back. Such an arrangement would virtually be that shown in Fig. 116, where the two heaters on different floors are connected with the boiler.
Instantaneous Heaters.
—In isolated bathrooms where no constant supply of hot water is available, instantaneous hot-water heaters are much used. In many houses where a range fire is used intermittently, particularly during the summer months, a like method is used for the hot-water supply. These heaters are made in many forms to suit any condition. Some are very simple, being made of a gas heater, the heat from which is held against a long coil of pipe or a large amount of heating surface in other form, through which the water circulates on its way to the tap. Others are quite elaborate, being made entirely automatic in their action. The Ruud heater, for example, is so constructed that when the hot-water faucet is opened the reduced water pressure starts a gas heater in contact with a series of pipe coils through which the water circulates. As soon as the water faucet is closed the water pressure automatically closes the gas valve, cutting off the supply of gas. A little gas jet used for igniting the burner is left constantly burning, ready to light the gas whenever hot water is required.
Fig. 121 illustrates a simple form of instantaneous heater that is relatively inexpensive and has met with a great deal of favor. A sheet-iron casing encloses a sinuous, multiple coil of pipes through which the water passes. The heat furnished by a Bunsen burner of a large number of small jets is evenly distributed over the bottom of the heater. The heating coils are arranged to interrupt the heat passing through the casing and absorb as much as possible. To do good work such a heater must be connected by a pipe to a chimney flue which furnishes a good draught.
Instantaneous water heaters should not be used in bathrooms unless the products of combustion from the heater are carried away by a chimney. The combustion of the required amount of gas produces a large volume of carbonic acid gas which if allowed to remain in the room is not only deleterious but may be a positive danger to life. Cases of asphyxiation from this cause are not at all rare.
Fig. 121.—Gas heater for hot-water supply.
Fig. 122.—Hot-water supply with gas heater, connected to the range boiler.
Fig. 122 shows the heater connected with a range boiler. In this case the heater may be considered as taking the place of the water-back. It may, however, be used as an auxiliary heater. In the picture of the kitchen shown in Fig. 80, an instantaneous heater is shown attached to the range boiler. It is located in this case between the kitchen range and the boiler.
CHAPTER VII
WATER SUPPLY
The use of water enters into each detail of the affairs of everyday life and forms a part of every article of food; its quality has much to do with the health of the family, and its convenience of distribution lends greatly to the contentment of its members. The family water supply should be as carefully guarded as means will permit, and judicious care should be exercised to prevent the possibility of its pollution. Where the source of the water is known, it should be the subject of unremitting attention.
Water comes originally from rain or snow and as it falls, it is pure. Water, however, in falling through the air absorbs the contained vapors and washes the air free from suspended organic matter in the form of dust, so that when it reaches the earth rain water contains some impurities.
As the water is absorbed by the earth, it comes into contact with the mineral matter and organic materials of animal and vegetable origin contained in the soil; and as water is a most wonderful solvent, it soon contains mineral salts and possibly the leachings from the organic substances through which it passes. The impurities usually found in well water are in the form of mineral salts that have been taken up from the earth, but other contaminating materials may come from the surface and be carried into the well by accidental drainage.
Water that is colorless and odorless is usually considered good for drinking and in the absence of more accurate means of determination may be used as a test of excellence; but it often happens that water possessing these qualities is so heavily freighted with mineral salts as to be the direct cause of impaired health. Again, water that appears pure may be polluted with disease-producing bacteria to such an extent as to endanger the lives of all who use it. The fact that a source of drinking water bears a local reputation for purity, because of long usage, cannot be taken as a test of its actual purity until it has been subjected to chemical and bacterial examination.
It must not be inferred that all water is likely to be unsuitable for drinking; there is, however, a possibility of the water being polluted from natural sources and from accidental causes, that are sometimes preventable; and the only means of determining the purity of water is by chemical and bacterial examining.