262 The N.Z. Journal of Science and Technology. [Jan. 
It would, of course, be possible to reduce the figures for electricity by 
improving the insulation of the oven. The same reduction is not so 
easily possible in the case of gas, as a draught of air must be 
kept through the stove to consume the gas. Heat is lost by the out¬ 
flowing gases, the higher the temperature the greater being the loss from 
this cause. 
IV. Comparison of Fuels for heating Water for Baths, etc. 
Tests were made on a bathroom califont of the ordinary type shown 
in fig. 2. The efficiency for ordinary rates of flow was found to be 82 
per cent. This is a high efficiency, but there appears no reason why 
califonts should not be constructed with 90 per cent, efficiency, as the 
only serious loss of heat that is unavoidable is that carried away by the 
consumed gas and air, which can be 
reduced to the temperature of the 
water by suitable design, with cor¬ 
responding increase of efficiency. 
With the califont tested the tempera¬ 
ture of the hot water was 160° F. 
Heating water by electricity for 
immediate use could obviously be 
done at an efficiency of nearly 100 per. 
cent, by immersion heaters, provided 
that sufficient current were available 
for the purpose. A heater consuming 
10 kilowatts would be required, how¬ 
ever, for the purpose— i.e., 45 amperes 
at 220 volts — which is capable of 
heating about 1 gallon of water per 
minute from 60° to 115° F. If 
cisterns were available with very good 
heat-circulation a high efficiency could 
be obtained with the use of much 
smaller power. Such a system could 
undoubtedly be used to utilize the 
“ off peak ” load, in the case of a 
maximum-demand rate of charging, 
for example. 
We thus obtain the following fig 
systems :— 
Fig. 2.—Cas-califont of the ordinary 
type. 
for the efficiency of hot-water 
—.— 
Efficiency. 
B.Th.U. for ]d. 
Per Cent. 
Coal-range 
13 
4,200 
Gas-califont 
82 
3,700 
Electricity 
90 
2,050 
