62 



BULLETIN 



U. S. DEPARTMENT OF AGRICULTURE. 



erating machines, even though the creamery is already equipped 

 with a steam engine. This will depend, however, on the arrange- 

 ment and efficiency of the steam plant and on the cost of electric 

 power and must be determined in each individual case by those on 

 the premises. The cost of power per ton of refrigeration as averaged 

 from steam-driven plants in operation will compare with electric 

 drive at about 3 cents per kilowatt-hour. 



There are other advantages in employing electric drive over steam, 

 the value of which can not be estimated in dollars and cents, viz, 

 cleanliness, less space required, and that the power required can be 

 determined accurately at any time. 



Fig. 29. — Maximum and average summer temperatures in different States. 



Cleanliness in milk plants, creameries, and dairies is of special 

 advantage, and with electrical drive practically all the dirt arising 

 from smoke, coal dust, and ashes is eliminated. 



It is possible to install electric motors in out-of-the-way places 

 where engines could not be located. This feature makes it practical 

 to locate the refrigerating machine close to the cooling rooms, thereby 

 eliminating long leads of refrigerating piping located outside the 

 rooms to be cooled. 



The fact that the power required to operate the compressor can 

 be determined accurately at any time is of great importance. This 

 feature, however, may not seem of very great value at first thought, 

 but it has been proved in many instances to produce higher economy. 

 That the cost of production can be determined accurately is due to 

 the fact that the cost of power is given in each monthly bill or, for 

 that matter, can be calculated each day from the meter readings. 

 With exact figures at his command the operator is able to detect 



