WHAT SIZE PLANT TO INSTALL
The farmer's wife his partner--Little and big plants--Limiting
factors--Fluctuations in water supply--The average plant--The
actual plant--Amount of current required for various
operations--Standard voltage--A specimen allowance for electric
light--Heating and cooking by electricity--Electric power: the
electric motor.
The farmer's wife becomes his partner when he has concluded the
preliminary measurements and surveys for building his water-power
electric plant. Now the question is, how big a plant is necessary, or
how small a plant can he get along with. Electricity may be used for a
multitude of purposes on the farm, in its sphere of furnishing
portable light, heat and power; but when this multitude of uses has
been enumerated, it will be found that the wife shares in the benefits
no less than the farmer himself. The greatest dividend of all,
whether dividends are counted in dollars or happiness, is that
electricity takes the drudgery out of housework. Here, the work of the
farmer himself ends when he has brought electricity to the house, just
as his share in housework ends when he has brought in the kerosene,
and filled the woodbox. Of the light and heat, she will use the lion's
share; and for the power, she will discover heretofore undreamed-of
uses. So she must be a full partner when it comes to deciding how much
electricity they need.
How much electricity, in terms of light, heat, and power, will the
farmer and his wife have use for? How big a plant should be installed
to meet the needs of keeping house and running the farm?
The answer hangs mainly on how much water-power there is available,
through all the seasons of the year, with which to generate
electricity. Beyond that, it is merely a question of the farmer's
pocketbook. How much money does he care to spend? Electricity is a
cumulative "poison." The more one uses it, the more he wants to use
it. After a plant has been in operation a year, the family have
discovered uses for electricity which they did not think of in the
beginning. For this reason, it is well to put in a plant larger than
the needs of the moment seem to require. An electrical horsepower or
two one way or another will not greatly change the first cost, and you
will always find use for any excess.
Once for all, to settle the question of water-power, the water wheel
should be twice the normal capacity of the dynamo it drives, in terms
of power. This allows for overload, which is bound to occur
occasionally; and it also insures smooth running, easy governing, and
the highest efficiency. Since the electric current, once the plant is
installed, will cost practically nothing, the farmer can afford to
ignore the power going to waste, and consider only how to get the best
service.
_The Two Extremes_
The amount of water to be had to be turned into electricity, will vary
with location, and with the season. It may be only enough, the
greater part of the year, for a "toy" plant--a very practical toy, by
the way--one that will keep half a dozen lights burning in the house
and barn at one time; under some conditions water may be so scarce
that it must be stored for three or four days to get enough power to
charge a storage battery for these six or eight lights. A one-quarter,
or a one-half kilowatt electrical generator, with a one horsepower (or
smaller) wheel, will light a farmstead very satisfactorily--much
better than kerosene lamps.
On the other hand, the driving power of your wheel may be sufficient
to furnish 50 or 100 lights for the house, barn, and out-buildings,
and barn-yard and drives; to provide ample current for irons,
toasters, vacuum cleaners, electric fans, etc.; to do all the cooking
and baking and keep the kitchen boiler hot; and to heat the house in
the coldest weather with a dry clean heat that does not vitiate the
air, with no ashes, smoke or dust or woodchopping--nothing but an
electric switch to turn on and off; and to provide power for motors
ranging from tiny ones to run the sewing machine, to one of 15
horsepower to do the threshing. A plant capable of developing from 30
to 50 kilowatts of electricity, and requiring from 50 to 100
horsepower at the water wheel, would do all this, depending on the
size of the farmstead. One hundred horsepower is a very small water
project, in a commercial way; and there are thousands of farms
possessing streams of this capacity.
_Fluctuations in Water Supply_
It would be only during the winter months that such a plant would be
driven to its full capacity; and since water is normally plentiful
during these months, the problem of power would be greatly simplified.
The heaviest draft on such a plant in summer would be during
harvesting; otherwise it would be confined to light, small power for
routine work, and cooking. Thus, a plant capable of meeting all the
ordinary requirements of the four dry months of summer, when water is
apt to be scarce, doubles or quadruples its capacity during the
winter months, to meet the necessities of heat for the house.
A dynamo requires only as much power to drive it, at any given time,
as is being used in terms of electricity. There is some small loss
through friction, of course, but aside from this the power required of
the prime mover (the water wheel) is always in proportion to the
amount of current flowing. When water is scarce, and the demands for
current for heating are low, it is good practice to close a portion of
the buckets of the turbine wheel with wooden blocks provided for this
purpose. It is necessary to keep the speed of the dynamo uniform under
all water conditions; and where there is a great fluctuation between
high and low water periods, it is frequently necessary to have a
separate set of pulleys for full gate and for half-gate. The head must
remain the same, under all conditions. Changing the gate is in effect
choking or opening the nozzle supplying the wheel, to cut down or
increase its consumption of water.
_The Average Plant_
It will be the exceptional plant, however, among the hundreds of
thousands to be had on our farms, which will banish not only the oil
lamp and kitchen stove, but all coal or wood burning stoves as
well--which will heat the house in below-zero weather, and provide
power for the heavier operations of the farm. Also, on the other hand,
it will be the exceptional plant whose capacity is limited to
furnishing a half-dozen lights and no more.
A happy medium between these two conditions is the plant large enough
to supply between five and ten electrical horsepower, in all seasons.
Such a plant will meet the needs of the average farm, outside of
winter heating and large power operations, and will provide an excess
on which to draw in emergencies, or to pass round to one's neighbors.
It is such a plant that we refer to when we say that (not counting
labor) its cost, under ordinary conditions should not greatly exceed
the price of one sound young horse for farm work.
Since the plant we described briefly in the first chapter, meets the
requirements of this "average plant" let us inquire a little more
fully into its installation, maintenance, and cost.
_An Actual Plant_
In this instance, the water-power was already installed, running to
waste, in fact. The wheel consists of the so-called thirty-six inch
vertical turbine, using 185 square inches of water, under a 14-foot
head. Water is supplied to this wheel by a wooden penstock 33 inches
square, inside measurements, and sloping at an angle of 30° from the
flume to the wheel.
[Illustration: Details of voltmeter or ammeter]
This wheel, under a 14-foot head, takes 2,312 cubic feet of water a
minute; and it develops 46.98 actual horsepower (as may be figured by
using the formulas of Chapter III). The water supply is provided by a
small mountain river. The dam is 10 feet high, and the race, which
feeds the flume from the mill pond is 75 yards long. The race has two
spillways, one near the dam, and the second at the flume itself, to
maintain an even head of water at all times.
_Half-Gate_
Since the water supply varies with the seasons, it has been found
practical to run the wheel at half-gate--that is, with the gate only
half-open. A set of bevel gears work the main shaft, which runs at
approximately 200 revolutions per minute; and the dynamo is worked up
to its required speed of 1,500 revolutions per minute through a
countershaft.
The dynamo is a modern four-pole machine, compound-wound, with a rated
output of 46 amperes, at 125 volts--in other words a dynamo of 5.75
kilowatts capacity, or 7.7 electrical horsepower. At full load this
dynamo would require a driving power of 10 horsepower, counting it as
75 per cent efficient; and, to conform to our rule of two water
horsepower to one electrical horsepower, the wheel should be capable
of developing 20 horsepower. As a matter of fact, in this particular
instance, shutting down the wheel to half-gate more than halves the
rated power of the wheel, and little more than 15 horsepower is
available. This allowance has proved ample, under all conditions met
with, in this plant.
The dynamo is mounted on a firm floor foundation; and it is belted
from the countershaft by an endless belt running diagonally. A
horizontal belt drive is the best. Vertical drive should be avoided
wherever possible.
_The Switchboard_
The switchboard originally consisted of a wooden frame on which were
screwed ordinary asbestos shingles, and the instruments were mounted
on these. Later, a sheet of electric insulating fibre was substituted,
for look's sake. The main requisite is something substantial--and
fireproof. The switchboard instruments consist of a voltmeter, with a
range of from 0 to 150 volts; an ammeter, with a range, 0 to 75
amperes; a field regulating rheostat (which came with the dynamo); a
main switch, with cartridge fuses protecting the machine against a
draft of current over 60 amperes; and two line switches for the two
owners, one fuse at 20 amperes, and the other at 40 amperes. Electric
fuses are either cartridges or plugs, enclosing lead wire of a size
corresponding to their rating. All the current of the line they
protect passes through this lead wire. If the current drawn exceeds
the capacity of the lead wire, it melts from the heat, and thus opens
the circuit, and cuts off the current.
[Illustration: A switchboard and its connections: _G._ Dynamo; _A._
Shunt field coils; _B._ Series coils; _DD._ Fuses; _FF._ Main switch;
_F._ Field switch; _C._ Ammeter; _V._ Voltmeter; _E._ Lamp; _R._
Rheostat. Dotted lines show connections on back of board]
_Items of Cost_
This water wheel would cost $250 new. There is a duplicate in the
neighborhood bought at second-hand, for $125. The dynamo cost $90,
and was picked up second-hand in New York City. New it would cost
$150. The voltmeter cost $7, and the ammeter $10; and the switches and
fuses could be had for $5. A wheel one-half the size, using one-half
the amount of water at full gate, would do the work required, and the
cost would be correspondingly less.
_Capacity_
This plant supplies two farms with electric light. One farm (that of
the owner of the wheel) has 30 lamps, of 16 candlepower each, and two
barn-yard lamps of 92 candlepower each. His wife has an electric iron
and an electric water heater. Needless to say, all these lamps, and
the iron and water heater are not in use at one time.
[Illustration: Carbon Lamps Gem Type (1/4 scale)]
The partner who owns the electric part of the plant has 30 lamps in
his house and barn, many of them being 25 watt tungsten, which give
more light for less power, but cost more to buy. They are not all in
use at one time, though (since the current costs nothing) the
inclination is to turn them on at night and let them burn. In his
kitchen he has an electric range, and a water heater for the 40 gallon
boiler. In addition to this he has all sorts of appliances,--irons,
toasters, grills, a vacuum cleaner, a vibrator, etc. Naturally all
these appliances are not in use at one time, else the draft on the
plant would be such as to "blow" the fuses. For instance, all the
baking is done in daylight; and when the oven is used after dark, they
are careful to turn off all lights not needed. An ideal plant, of
course, would be a plant big enough to take care of the sum of lamps
and handy devices used at one time.
To make this plant ideal, (for, being an actual affair, it has
developed some short-comings, with the extension of the use of
electricity) it would require a dynamo whose capacity can be figured,
from the following:
Watts
15 carbon lamps, 16 candlepower, @60 watts each 900
10 tungsten lamps, 20 candlepower, @25 watts each 250
2 tungsten lamps, 92 candlepower, @100 watts each 200
Water heater, continuous service 800
Toaster, occasional service 600
Iron, occasional service 400
Oven-baking, roasting, etc 2,000
2 stove plates @1,000 watts each 2,000
1 stove plate 400
Vacuum cleaner, occasional service 200
Vibrator, occasional service 100
Small water heater, quart capacity 400
Small motor, 1/4 horsepower, occasional 250
Motor, 1/2 hp, pumping water, etc 500
Electric fan, occasional service 100
-------
Total current, one house 9,100
30 carbon lamps, 16 candlepower, @60 1,800
2 lamps, 100 watt tungsten 200
Electric iron 400
Small water or milk heater 600
-------
Total current, 2nd house 3,000
1st house 9,100
-------
12,100
Thus, in this plant, if every electrical device were turned on at
once, the demand on the dynamo would be for 12.1 kilowatts, or an
overload of over 100 per cent. The main-switch fuse, being for 60
amperes, would "blow" or melt, and cut off all current for the
moment. To repair the damage would be merely the work of a second--and
at a cost of a few cents--simply insert a new fuse, of which there
must be a supply on hand at all times. Or, if either owner exceeded
his capacity, the line fuses (one for 20 amperes, and the other for 40
amperes) would instantly cut off all current from the greedy one.
[Illustration: 25 and 40 watt Mazda tungsten lamps (1/4 scale)]
_Lessons From This Plant_
The story of this plant illustrates two things which the farmer and
his wife must take into account when they are figuring how much
electricity they require. First, it illustrates how one uses more and
more current, as he finds it so serviceable and labor-saving, and at
the same time free. The electric range and the water boiler, in the
above instance, were later acquisitions not counted on in figuring the
original installation. Second, it illustrates, that while the normal
load of this generator is _5.75_ kilowatts, one does not have to limit
the electrical conveniences in the home to this amount. True, he
cannot use more electricity than his plant will produce _at any one
time_,--but it is only by a stretch of the imagination that one may
conceive the necessity of using them all at once. Ironing, baking, and
the use of small power are usually limited to daylight hours when no
lights are burning.
As a matter of fact, this plant has proved satisfactory in every way;
and only on one or two occasions have fuses been "blown", and then it
was due to carelessness. A modern dynamo is rated liberally. It will
stand an overload of as much as 100 per cent for a short time--half an
hour or so. The danger from overloading is from heating. When the
machine grows too hot for the hand, it is beginning to char its
insulation, to continue which, of course would ruin it. The best plant
is that which works under one-half or three-quarters load, under
normal demands.
_Standard Voltage_
We are assuming the farmer's plant to be, in 99 cases out of 100, the
standard 110-volt, direct current type. Such a plant allows for at
least a 10 per cent regulation, in voltage, up or down the scale;
supplies for this voltage are to be had without delay in even the more
remote parts of the country, and (being sold in greater volume) they
are cheaper than those for other voltages.
There are two general exceptions to this rule as to 110-volt plants:
(1) If the plant is located at a distance greater than a quarter of a
mile from the house, it will be found cheaper (in cost of transmission
line, as will be shown later) to adopt the 220-volt plant; (2), If the
water supply is so meagre that it must be stored for many hours at a
time, and then used for charging storage batteries, it will be found
most economical to use a 30-volt plant. A storage battery is made up
of cells of approximately 2 volts each; and, since more than 55 such
cells would be required for a 110-volt installation, its cost would
be prohibitive, with many farmers.
So we will assume that this plant is a 110-volt plant, to be run
without storage battery. It will be well to make a chart, dividing the
farm requirements into three heads--light, heat, and power.
_Light_
[Illustration: 60 and 100 watt Mazda tungsten lamp. These lamps may be
had in sizes from 10 to 500 watts (1/4 scale)]
[Illustration: The lamp of the future. A 1000 watt Mazda nitrogen
lamp, giving 2000 candlepower (1/4 scale)]
Light is obtained by means of incandescent lamps. There are two styles
in common use, the carbon and the tungsten lamp. It requires 3.5 to 4
watts of electricity to produce one candlepower in a carbon lamp. It
requires from 1 to 1.25 watt to produce one candlepower in the
tungsten lamp. The new nitrogen lamp, not yet in general use, requires
only 1/2 watt to the candlepower. Since tungsten lamps give three
times the light of the carbon lamp, they are the most economical to
use in the city or town where one is paying for commercial current.
But, in the country where water-power furnishes current for nothing,
it will be found most economical to use the carbon lamp, since its
cost at retail is 16 cents, as compared with 30 cents for a
corresponding size in tungsten. A 60 watt carbon lamp, of 16
candlepower; or a 25 watt tungsten lamp, of 20 candlepower, are the
sizes to use. In hanging lamps, as over the dining room table, a 100
watt tungsten lamp, costing 70 cents, and giving 92 candlepower light
is very desirable; and for lighting the barn-yard, these 100 watt
tungsten lamps should be used. For reading lamps, the tungsten style,
of 40 or 60 watt capacity, will be found best. Otherwise, in all
locations use the cheaper carbon lamp. Both styles have a rated life
of 1,000 hours, after which they begin to fall off in efficiency. Here
again, the farmer need not worry over lack of highest efficiency, as a
lamp giving only 80 per cent of its rated candlepower is still
serviceable when he is not paying for the current. With care not to
use them at voltages beyond their ratings, lamps will last for years.
_A Specimen Light Allowance_
Below is a typical table of lights for a large farm house, the barns
and barn-yard. It is given merely as a guide, to be varied for each
individual case:
Watts
Kitchen, 2 lights @60 watts 120
Dining room, 1 light, tungsten 100
Living room, table lamp with 3 tungstens @40 120
Living room, 2 wall fixtures, 4 lamps @60 watts 240
Parlor, same as living room 360
Pantry, 1 hanging lamp 60
Cellar, one portable lamp 60
Woodshed, 1 hanging lamp 60
2 bedrooms, 2 lights each @ 60 240
2 bed rooms, 1 light each @60 120
Bathroom, 1 "turn-down" light, @60 60
Hall, downstairs, 2 lights @60 120
Hall, upstairs, 1 light 60
Attic, 1 light 60
Porch, 1 light 60
Barn and barn-yard:
Barn-yard entrance, 1 tungsten 100
Watering trough, 1 " 100
Front gate, 1 " 100
Horse barn, 4 lights @60 240
Cow barn, 4 lights @60 240
Pig house, 1 light 60
Hay barn, 2 lights, @60 120
-------
Total for farmstead 2,800
This provides for 44 lights, an extremely liberal allowance. How many
of these lights will be burning at any one time? Probably not one-half
of them; yet the ideal plant is that which permits all fixtures to be
in service at one time on the rare occasions when necessary. Thus, for
lighting only, 2,800 watts maximum service would require a 4 kilowatt
generator, and 10 water horsepower, on the liberal rating of two to
one. A 3 kilowatt generator would take care of these lights, with a 30
per cent overload (which is not excessive) for maximum service. The
above liberal allowance of lights may be cut in two, or four--or even
eight--and still throw a kerosene lamp in shadow. It all depends on
the number of lights one wants burning at one time; and the power of
the water wheel.
If the 36 carbon lights in the above table were replaced by 25 watt
tungsten lights, the saving in power would be 35 watts each, or 1,260
watts, nearly two electrical horsepower; while the added first cost
would be 14 cents a light, or $5.04. A generator of 2 kilowatt
capacity would take care of all these lights then, with 460 watts to
spare.
_Heating_
Electric heating and cooking is in its infancy, due to the prohibitive
cost of commercial current in our cities. Here the farmer has the
advantage again, with his cheap current.
For heating the house, it is calculated that 2 watts is required for
each cubic foot of air space in a room, during ordinary winter
weather. Thus, a room 10 × 12, and 8 feet high, would contain 960
cubic feet, and would require 1,820 watts energy to heat it in cold
weather. Five such rooms would require 9.1 kilowatts; and 10 such
rooms, or their equivalent, would require 18.2 kilowatts.
Electric heating devices are divided into two classes: (1) those which
can be used on lamp circuits, _and do not draw more than 660 watts
each_; and (2) those which draw more than 660, therefore _require
special wiring_. The capacity of these devices is approximately as
follows:
Lamp circuit devices: Watts
Electric iron 400 to 660
Toaster 350 to 660
Vacuum cleaner 200 to 400
Grill 400 to 660
Small water heater 400 to 660
Hot plates 400 to 660
Lamp circuit devices:
Coffee percolator 400 to 660
Chafing dish 400 to 660
Electric fan 100 to 250
Special circuit devices:
Hot water boiler heater 800 to 1,200
Small ovens 660 to 1,200
Range ovens 1,200 to 3,000
Range, hot plates 400 to 1,300
Radiators (small) 750 to 1,500
Radiators (large) 1,500 to 6,000
The only device in the above list which is connected continuously, is
the hot water boiler, and this can be credited with at least one
electrical horsepower 24 hours a day. It is a small contrivance, not
much bigger than a quart can, attached to the back of the kitchen
boiler, and it keeps the water hot throughout the house at all hours.
Its cost will vary with the make, ranging from $8 to $15; and since it
is one of the real blessings of the farm kitchen and bathroom, it
should be included in all installations where power permits. Electric
radiators will be used 24 hours a day in winter, and not at all in
summer. They are portable, and can be moved from room to room, and
only such rooms as are in actual use need be heated. The other devices
are for intermittent service, many of them (like the iron) for only a
few hours each week.
The grill, chafing dish, coffee percolator, etc., which are used on
the dining room table while the family is at meals, each draw an
equivalent of from 6 to 10 carbon lights. By keeping this in view and
turning off spare lights, one can have the use of them, with even a
small plant. Thus, a one kilowatt plant permits the use of any one of
these lamp circuit devices at a time, with a few lights in addition.
_Power_
Electric power is to be had through motors. A direct current dynamo
and a direct current motor are identical in construction. That is, a
motor becomes a generator if belted to power; and a generator becomes
a motor, if connected to electric mains. This is best illustrated by
citing the instance of a trans-continental railroad which crosses the
Bitter Root Mountains by means of electric power. Running 200 miles up
a 2 per cent grade, it is drawn by its motors. Coasting 200 miles
down the 2 per cent grade on the other side of the mountains, its
motors become generators. They act as brakes, and at the same time
they pump the power of the coasting weight of this train back into the
wires to help a train coming up the other side of the mountains.
[Illustration: Connections of shunt motor and starting rheostat]
Just as there are three types of direct current generators, so there
are three types of direct current motors: _series_, _shunt_, and
_compound_, with features already explained in the case of generators.
Motors are rated by horsepower, and generators are rated by kilowatts.
Thus a one kilowatt generator has a capacity of 1,000 watts; as a
motor, it would be rated as 1000/746 horsepower, or 1.34 horsepower.
Their efficiency varies with their size, ranging from 40 to 60 per
cent in very small motors, and up to 95 per cent in very large ones.
The following table may be taken as a guide in calculating the power
required by motors, on 110-volt circuits:
1/4 Horsepower 2-1/2 amperes, or 275 watts
1/2 hp 4-1/2 amperes, or 500 watts
1 hp 9 amperes, or 990 watts
2 hp 17 amperes, or 1.97 kilowatts
3 hp 26 amperes, or 2.86 kilowatts
5 hp 40 amperes, or 4.40 kilowatts
7-1/2 hp 60 amperes, or 6.60 kilowatts
10 hp 76 amperes, or 8.36 kilowatts
15 hp 112 amperes, or 12.32 kilowatts
An electric motor, in operation, actually generates electricity, which
it pushes back into the line as a counter-electromotive-force. The
strength of this counter force, in volts, depends on the motor's
speed, the same as if it were running as a dynamo. For this reason,
when a motor is started, and before it comes up to speed, there would
be a rush of current from the line, with nothing to hold it back, and
the motor would be burned out unless some means were provided to
protect it for the moment. This is done by means of a starting
rheostat, similar to the regulating rheostat on the dynamo
switchboard. This resistance box is connected in "series" with the
armature, in the case of shunt and compound motors; and with the
entire motor circuit in the case of a series machine.
A _series_ motor has a powerful starting torque, and adjusts its speed
to the load. It is used almost altogether in street cars. It can be
used in stump pulling, or derrick work, such as using a hay fork. It
must always be operated under load, otherwise, it would increase in
speed until it tore itself to pieces through mechanical strain. The
ingenious farmer who puts together an electric plow, with the mains
following behind on a reel, will use a series motor.
A _shunt_ motor should be used in all situations where a fairly
uniform speed under load is required, such as separating, in milking
machines, running a lathe, an ensilage cutter, vacuum cleaners,
grinders, etc.
The _compound_ motor has the characteristics of the series and shunt
motors, giving an increased starting torque, and a more nearly
constant speed under varying loads than the shunt motor, since the
latter drops off slightly in speed with increasing load.
_Flexible Power_
An electric motor is an extremely satisfactory form of power because
it is so flexible. Thus, one may use a five horsepower motor for a one
horsepower task, and the motor will use only one electrical horsepower
in current--just enough to overcome the task imposed on it. For this
reason, a large-sized motor may be used for any operation, from one
requiring small power, up to its full capacity. It will take an
overload, the same as a dynamo. In other words it is "eager" for any
task imposed on it; therefore it must be protected by fuses, or it
will consume itself, if too big an overload is imposed on it.
A one horsepower shunt or compound motor is very serviceable for
routine farm operations, such as operating the separator, the churn,
the milking machine, grinder, pump, and other small power jobs. Motors
of 1/4 horsepower are handy in the kitchen, for grinding knives,
polishing silver, etc., and can be used also for vacuum cleaners, and
running the sewing machine. For the larger operations, motors will
vary from three horsepower for cutting ensilage, to fifteen horsepower
for threshing. They can be mounted on trucks and conveyed from one
point to another, being fed current from the mains by means of
suitable wires wound on reels.
Remember, in estimating the size of your plant for light, heat, and
power, that it does not have to be big enough to use all the devices
at one time. Also remember, that two water horsepower to one
electrical horsepower is a very liberal allowance; and that a
generator working under one-half or two-thirds capacity at normal
loads will require less attention than a machine constantly being
worked above its capacity. Therefore, let your generator be of liberal
size, because the difference in cost between a 5 and 10 kilowatt
machine is not in proportion to their capacity. In fact (especially
among second-hand machines), the difference in cost is very small. The
mere fact that the generator is of 110 electrical horsepower capacity
does not require a turbine of 20 horsepower. The chances are that
(unless you wish to heat your house and do large power jobs) you will
not use more than 3 to 5 electrical horsepower normally; therefore an
allowance of 10 water horsepower, in this case, would be ample. A
plant used simply for lighting the house and barn, for irons, and
toasters, and one horsepower motors, need not exceed 2 or 2-1/2
kilowatts for the generator, and 5 or 6 horsepower for the turbine
wheel. Normally it would not use one-half this capacity.