I just installed a whole house fan, all except the power.  I
have the necessary testers, tools and ability.  But what I am
unsure of is whether or not the motor (belt driven) needs it's
own ciruit or could I tap into an existing circuit with several
wall outlets and light fixtures with a total of approximately
500 watts of light along with maybe 2 clock radios.  Sometimes
the outlets will be used by a vacuum, hair dryer, shampooer or
something of that nature.

I have changed every outlet and turned most of the wall switches
into dimmers, so I know the wiring fairly well.  I read the
section on dedicated circuits and I am not positive whether this
1/3 hp, split capacitor, 120 volt motor would require it's own
circuit.

Any help or guidance you could give me would be greatly
appreciated.

That 1/3 horse power motor should pull about 7.2 amps on 120
volts. The NEC allows you to install that wholehouse fan on
either a 15 or 20 general lighting branch circuit. However I
would advise that you install that wholehouse fan on a dedictated
20 amp 120 volt circuit. Reasoning for that statement is what we
call a bounce of electricity. You mentioned a splt capaciter
style motor. This split capaciter design is telling us that the
fan blade is heavy enough to cause a prolonged high amp load type
start phase of this motor. What I am saying is that motor is
going to have to work harder than you think when that motor is
energized and while it is trying to get that fan blade turning
from 0 RPM to either 1750 RPM for mechanical speed or 3450 RPM
for fan speed. Some wholehouse fans use mechanical speed and some
us fan speed. When a motor initially startsup the branch circuit
carrying that load experiences what we call an in-rush that is
several times higher in amps than the run phase using that motors
normal full load current. That 7.2 amp full load current may jump
to 35 amps or more for the length of time for that motor to force
that fan blade to reach full speed. This in rush will cause that
bouce of electricity. Most likely the affect on a 15 or 20 amp
branch circuit would be a dimming of lights etc. due to that
motor hogging all the electricity while it is trying to get that
fan blade up to speed. If you can I would install this wholehouse
fan on a single 20 amp 120 volt circuit.

Before you do anything check the name plate on that motor and
confirm that I am close on the 7.2 amp FLC [full load current].
Also confirm on that name plate on that motor that your motor is
a 120 volt motor. Some of these wholehouse fan motors are dual
voltage rated. If so then confirm on the name plate a wiring
schematic showing the internal connections where you connect your
power source whether that motor is wired for high voltage 220
volts or low voltage 120 volts.

An extra thought for you. Commonly the wholehouse fans are
installed with a thermostat in the attic controlling the
activation of that wholehouse fan this way the fan reacts when
the attic gets so hot thus keeping your cooling costs down.
Either way I would include a switch in the home to be able to
turn the fan on and off overriding that fan's automatic controls
when desired. Like when you need to yell at the neighbors for not
mowing your grass too? Things like that when you don't want
interrupted by the sound of the fan running.

You might also want to check to see if your are required an
electrical permit to install this new wiring serving that
wholehouse fan to protect your house insurance's validity in case
of a house damage claim. You don't want to negate your house
insurance becuase they found wiring that had no permits. Just be
safe and good luck.

Let us know how you came out.

Wg

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