AGING TEST.

Another valuable test to make on circulating water heaters is to connect them to a tank or tanks, from which the water is withdrawn with sufficient rapidity to prevent overheating in the same manner as in domestic use.

Then run them several hours each day-all alike—and make monthly determinations of their efficiency.

It will be found that some heaters stop up much sooner than others, and in some localities where considerable precipitate is formed, it may be impossible to use certain heaters even though their efficiency is very high when new.

INSTANTANEOUS WATER HEATERS.

The Direct Instantaneous Water Heaters, or those in which the products of combustion come in direct contact with the water, must necessarily be operated without back pressure.

This class has the great advantage of a very low thermal capacity, of condensing much of the water vapor formed by combustion, where water somewhat below the boiling point is being withdrawn, making it possible to obtain much higher efficiency than by the indirect method and for the same capacity, less size and cost than for the indirect heaters.

While again there are several disadvantages; the heater must be placed near the point where the water is to be used, it being necessary to regulate the supply at the heater, this is sometimes prohibitive, and if very hot water, that is, water near the boiling point, is required, there is an excessive loss in the flue, for as it is impossible for all the water to reach exactly the same temperature, when passing through the heater, the temperature of some will exceed the boiling point and, as it is not confined, will be lost up the flue as steam.

The Indirect Instantaneous Water Heater may have the advantage of being automatic, of being placed in any convenient location, regardless of where the water is to be used, and it may be adjusted so that water which is almost boiling, and in fact even steam may be obtained. Being under higher pressure, a high temperature can be maintained without formation of steam. Under an absolute pressure of 14.7

pounds, the formation of steam takes place at a temperature of 212 degrees; if this pressure is increased the boiling point is raised, which makes it evident that where an indirect heater is used under say 60 pounds gauge pressure, or 74.7 pounds absolute pressure, the boiling point is 307 degrees, so that the

METHOD of TESTING

INSTANTANEOUS HEATER.

temperature of the water in the heater may be raised above the atmospheric boiling point without the formation of steam on the interior of the heater.

It is apparent that each heater has its advantages, and both classes give excellent results where properly applied.

Where very hot water is required, or where it is inconvenient. to have the heater at the place where the hot water is used, or where hot water is wanted at several places, the indirect heater is superior.

But, if water somewhat below the boiling point is to be used, such as for the bath, or washing, etc., much higher efficiency may be expected from the direct heater, with less space occupied and less cost of installation.

Both have the very serious disadvantage of an excessive gas demand, which may necessitate the installation of an abnormally large service and meter for the consumer whose monthly bills are below normal.

METHOD OF TESTING INSTANTANEOUS WATER HEATERS.

This method is similar in principle to the method of testing circulating heaters, the connections being made as shown in Fig. 7.

As some of these heaters are designed for large gas consumption, a service, meter and regulator of ample capacity must be used.

A twenty light meter tested for accuracy may be arranged as shown in the figure, with a large dial calibrated to tenths of a foot, and with the hand attached to the spindle of the ten foot hand on the original meter dial.

A rubber band placed loosely over the spindle and one corner of the large dial, as shown, will take up the back lash of the train of gears in the meter, making it possible to estimate readings to hundredths of a foot.

The water supply is the same as for the circulating

heaters.

A thermometer is placed in the water supply pipe near the heater, and a special cock, such as that shown for circulating heaters, is used to control the rate of flow, unless a good valve is supplied by the maker attached to the heater.

Another thermometer is placed in the outlet pipe, trapped as shown in the figure, and the water caught as before and weighed.

Those heaters having automatic controlling devices should have them cut out or removed during the tests.

A flue is supplied, the top of which is six feet above the burner.

The first test is to determine the efficiency of the heater at maximum consumption of gas, and with the flow of water adjusted so that a fifty degree rise that a fifty degree rise in temperature is

obtained.

A similar test is then made for each multiple of five feet gas consumption down to twenty feet, with a fifty degree rise in the temperature of the water in each case.

Then with the same rates of gas consumption as before, a similar set of tests is made, except that the water is drawn off at a temperature of 120 degrees in each case.

By plotting curves of the results obtained from each test, it will be readily apparent, when the requirements of a particular case are known, which heater should be supplied.

DISCUSSION OF GAS RANGES.

The very large number of gas ranges which are at present in use is sufficient indication that they have generally met with public approval, and there is no doubt that, compared with other methods of cooking, the gas range has no rival. Nevertheless, every gas manager knows that gas is not the most economical fuel, and this is the only reason for the gas range not being adopted by every individual situated where gas can be obtained. This being the case, it would seem entirely to the gas companies' interests to make a gas range as economical as possible. There is no doubt that where any gas apparatus is used for a variety of purposes, it is difficult to obtain high efficiency for each purpose, and this is probably the reason for the low efficiency of a gas range. For instance, though we have three different sizes of burners on the top of a range, under no condition does their efficiency run much above 50%. If it were possible to permanently place standard vessels on the top of a gas range, much higher efficiency might be expected, for then the burners would be arranged to do specific work. While the top burners are arranged as