36 BULLETIN 1375, U. S. DEPARTMENT OF AGRICULTURE 
Electric service is usually delivered to large terminal elevators at 
high voltage, such as 550, 1,100, or 2,200 volts, and is then cut down 
by means of a transformer in the power plant to the subvoltage re- 
quired. Instances of this are cuts to 440 volts, as used by some ele- 
vators to run the belts, and 110 or 220 for lighting or other low-power 
service. A number of instances have been noted where the voltage 
received is considerably under that expected, in which case the differ- 
ence is automatically carried forward when a subdivision of the 
original voltage is made at several points. Tests on electric circuits 
before entering the heaters of moisture testers have given figures 
varying from 95 to 115 volts on 110-volt circuits. 
There always is an additional drop in pressure or in voltage as 
the heaters are put into operation, provided nothing is done to keep 
the voltage bolstered up to the point specified on the heating appa- 
ratus. If one will think of a large tank of water of definite volume 
with a series of spigots turned on, one after the other, it will soon 
become apparent that the rate or speed at which any spigot, or series 
of spigots for that matter, will flow is decidedly influenced by the 
number of other spigots running at the same time. This is more 
and more noticeable as the tank empties. If the tank receives a 
renewed supply of water as fast as it runs out at the base, the rate 
of flow will be constant. Electric pressure is influenced in the same 
way. All other interfering factors eliminated, if the voltage remains 
constant, the rate of flow of electric energy or the watts will also 
remain constant. 
The second important factor regarding drops in voltage is found 
in the wiring conditions from the power station or from the trans- 
forming box to the machine. Wiring circuits installed in buildings 
are usually designed to carry current for a certain number of electric 
lamps, usually not more than ten 100-watt lamps. In such case this 
number, or the equivalent current, should not be exceeded. To use 
an ordinary lighting circuit for a four or six compartment moisture 
tester is not only entirely unsatisfactory as far as moisture testing 
is concerned, but is a very dangerous fire risk. The danger comes 
from excessive, heat developed in the line by forcing too large a cur- 
rent of electricity over a small wire. This feature is taken care of 
by the national underwriters, who specify certain maximum allow- 
able current strength for all wires used in interior wiring. 
Table 11 shows the allowable current for both "rubber" and 
" other than rubber " insulated wires. The values for wires of various 
sizes are given in the first two horizontal columns of the table. These 
values should never be exceeded. The current and voltage at which 
an electrically heated moisture machine is designed to work is usually 
given on a plate attached to the machine as it comes from the factory. 
The vertical column in Table 11, headed "Amperes required by 
machine," gives the amperes required by one of the common types of 
electrically heated testers, of two, four," and six compartments. 
The application of the table as to length of circuit can best be 
shown by an example. Assume a 6-compartment moisture testing 
machine operated on 220 volts, located so that it will require a 
circuit 40 feet long. In Table 11, under the subheading " For 220 
volt circuits," read along the horizontal line starting with six com- 
