MECHANICAL REFRIGERATION 301 
melting into water at the same temperature. Its actual 
ice making capacity is usually about 50% less. 
Size of Compressor. In a moderately well insulated 
creamery handling from twenty to twenty-five thousand 
pounds of milk daily, a four-ton compressor will be large 
enough. With a compressor of this size the machinery 
will not have to be run more than five or six hours a day. 
If the machinery is run longer than this a smaller com- 
pressor will do the work. 
Power Required to Operate. The power required per 
ton of refrigeration is less the larger the machine. With 
a four-ton compressor the power required is from two to 
two and one-half horse power per ton of refrigerating 
capacity in twenty-four hours. 
Refrigerating Pipes. The refrigerating pipes vary 
from one to two inches in diameter. With moderately 
good insulation it is estimated that by the direct expansion 
system one running foot of two-inch piping will keep a 
room of forty cubic feet content at a temperature of 32° 
F. With brine nearly twice this amount of piping would 
be necessary. 
For cooling the brine in the brine tank, about 140 feet 
of 1%4-inch pipes are required per ton of refrigerating 
capacity. 
Expense of Operating. When a refrigerating plant 
has once been installed and charged with the necessary 
ammonia, the principal expense connected with it will be 
the power required to operate the compressor. This 
power in a creamery is supplied by the creamery engine. 
The ammonia, being used over and over again, will add 
but a trifle to the running expenses. Nor can the water 
used for cooling the ammonia vapors add much to the 
cost of operating. It is true, however, that the refrigera- 
