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Optimizing The Turfgrass Canopy Environment
With Fans
by Patrick M. O'Brien
Reprinted from the USGA Green Section Record
1996 July/August Vol 34(4): 9-12
Although most people in the turf industry have seen electric or
gas-powered fans used on the golf course, the rationale for their
use often is misunderstood. As an agronomist for the USGA Green
Section, I am frequently asked questions about the use of fans.
To help those involved with this issue a discussion of the benefits
and liabilities of the use of fans is presented.
Years of experience have shown that golf superintendents have the
most trouble growing bentgrass or Poa annua greens during the summer
at a site surrounded by trees or other barriers that allow almost
no air movement. A USGA-type green provides a very effective base
for growing putting green turf, but it cannot compensate for the
lack of air circulation. In this environment, disease and higher
rootzone moisture associated with these areas cause turfgrass plants
to decline. Fans help improve air flow across greens, and the survival
of bentgrass has been shown by Taylor to improve at sites with the
increased air movement provided by fans.1 The positive effects of
fans drying out the soil and increasing evapotranspiration are the
two major benefits influencing the bentgrass. Fans offer little
cooling benefit to the turfgrass, which is contrary to most popular
opinion.
Fans should be specifically used to help improve turf quality at
problem green sites. By far the most popular use of fans is at boxed
or pocketed sites surrounded by trees or other features that restrict
air movement. In the past, these sites have been more prone to summer
decline caused by disease, excess moisture, and surface algae. Green
sites with wet rootzones also benefit from a fan program. Even small
problem areas at open sites can benefit from the use of fans directed
to the specific problem area.
Most superintendents place two stationary fans at the 10 and 2 o'clock
positions at the rear of the green, approximately 15 to 30 feet
from the edge of the green. Fan height above the green surface normally
is 10 feet or less with these stationary fans. Most fan companies
sell poles that are usually seven feet tall, since OSHA requires
finger guards on any fans positioned at lower heights. Finger guards
can restrict air flow distance by up to 12%. Hand guards, which
restrict air flow less than finger guards, are required for fans
on poles taller than 7 feet. Trees are sometimes used instead of
a poles, if available.
The key is to position the fan as close to a green and as low to
the ground as possible to generate maximum air flow across the green
surface. The main goal is to achieve a 3- to 4-mph wind speed over
the turfgrass canopy. If fans are too far away or elevated too high,
wind speed power will be lost by deflection off the grass itself,
or by natural friction loss. A Turbometer, which costs about $120,
is an effective instrument to help determine fan placement at each
site. The Turbometer should be set on the green surface during measurements,
and with the fans running, check various areas around the green
for the 3- to 4-mph wind speed.
Another popular method to help determine fan location is the use
of engineering flags. On a calm morning, place engineering flags
over the green surface at 3- to 5foot intervals with the flag height
at approximately 3 inches above the ground. Clipping the metal pole
on the engineering flags to a 3-inch length will speed this step.
Turn the fans on and adjust the fan position until most of the flags
are waving. Other superintendents check fan position by igniting
smoke bombs at several sites on a green to detect air movement.
Golf superintendents need to pay attention to fan schedules, since
each site may have different requirements. Fans usually run 24 hours
per day at green sites that hold soil moisture and at pocketed areas.
Running fans from early to mid morning to the early evening is advised
at the small problem sites on certain greens. Other sites may require
fan usage only during the early morning to mid morning when dew
and surface moisture are greatest. In the Southeastern Region, surface
moisture also can come out of the rootzone during the daylight hours,
even at times of very high humidity. Fan use seldom will be required
at open-air sites on sunny days with low humidity.
Nearly all fan types commonly seen have done a good job when positioned
and run properly. Caged, oscillating, or turbo fans are the most
common types observed. Oscillating fans are by far the most popular
at golf courses. In the past, fan oscillating motors have caused
problems, but today oscillating motors have improved power, similar
to the other fan motors. Fan diameters can range from 22 to 48 inches.
Because most fans are stationary to poles elevated above the greens,
fan diameter size has been increasing with the demand for additional
air movement from these products. Many fans now can throw a column
of air more than 200 feet. With the improved power of many fans,
some air movement can occur even at areas where the fan is not directed.
Stationary fans do have the potential to dry the turf, since wind
speeds can be much higher than 3 to 4 mph next to the fan. Extra
irrigation may be needed for the turf in some situations when these
fans are used.
Portable or floating fans are also popular, and most courses have
at least two available. Most portable fans are the 48-inch cage
types. A combination of both permanent and portable fans is a plus
at some problem greens. Portable fans are used to treat special
areas that require extra air circulation, such as a wet soil condition.
Many superintendents move these floating fans to problem sites late
in the evening and allow them to run all night. The fans can be
positioned right next to the green during the night to provide an
extra "blast" of air without affecting golfers. The portable fans
can be repositioned and moved further away from the green the next
morning, especially taking into consideration the hole location
for that day. The additional air movement and mixing from this fan,
especially when combined with the prevailing wind and the permanent
fans, promotes faster drying. Portable fans can also be used at
the maintenance building to help cool the mechanic's working area
on hot days.
Setting up the electrical system for the fans on an existing golf
course is very difficult, so a certified electrician should do all
electrical work. Unfortunately, the electrical wire at the irrigation
control boxes is too small for the high current requirements of
electric fan motors, so alternative power supplies are needed. Usually,
water coolers, irrigation pump houses, lift pumps, bathrooms, maintenance
buildings, and clubhouses are sources of electrical power. Often,
sites with fans are not close to any of these sources, and new meter
service then is the only option. Gas generators are a last resort,
with the inconvenience of refilling the generator with gas, transportation
requirements, and the extra noise. New golf courses should initially
install larger wire coming into the irrigation control boxes so
that if electricity is required later for fans, the larger wire
can handle the additional amperage for a fan motor.
Most fans used today have single-phase motors, although three-phase
motors are preferred because of their higher power efficiency. Smaller
wire can be used for three-phase motors, resulting in a lower initial
installation cost. Many water coolers, irrigation and lift stations,
and clubhouses have three-phase power for fans near these sites.
Sometimes step-down transformers are needed, especially for the
oscillating motor, which is always single-phase power, and luckily
these transformers usually cost just $30.
All new electrical equipment and service must meet the local codes.
Tables are available to calculate the wire size needed based on
the distance from the power sources to the fan and the resistance
loss in the wire. Direct burial cable wire (usually #4 or #6 cable)
normally is pulled into the ground with a vibratory plow on a ditch-witch
trencher with minimal disturbance to the surface, although occasionally
small trenches are made to insert the wire. Wire depths vary according
to the local codes, but most installations require an 18- to 24-inch
depth. Wire is sometimes placed in a plastic conduit (depending
on the local codes) under cart paths and service roads and across
bridges for additional protection. Avoid the use of junction boxes
whenever possible, as they could become sources of problems later.
At the green installation site, the wires, switches, timers, and
plugs usually are placed in a sealed irrigation valve box with drainage.
Avoid wiring the fan directly, as removing the fan later with this
type of connection system is more difficult. Installing an extra
plug to power a portable fan that may be needed later is always
a plus, but a larger size wire will be needed initially to handle
this extra power requirement. Timers also can be installed in the
valve box to vary the operation of the fans. At The Honors Club,
course superintendent David Stone has even connected his fans to
the irrigation radio controllers. A switch to turn the fan off and
on is another plus. It is always a good idea to install a ground
fault interrupter at the plug to act as circuit breaker to enhance
the safety of maintenance workers and golfers. Circuit breakers
at the meter also help to avoid electrocution concerns. Afterwards,
have an inspector check all electrical work to insure that all local
codes are met.
Fans are used most during the months of May through September in
the southern portion of the United States. Obviously, operation
time will vary depending on the location of the golf course and
the weather each summer. Most utility companies offer seasonal or
full-time service for these meters. Flexible programs depending
on the projected power consumption and usage are offered by many
power companies, and consultants can detail your options. Most superintendents
report typical electrical power costs for running two fans at a
green site average between $75 and $100 per month.
Fans have required very little preventive maintenance so far on
golf courses. Rust spots and scratches will occur over time just
from being outside. A few fan distributors even offer annual maintenance
services to wax and paint fans, but so far very few customers have
taken advantage of this service. Most superintendents bring the
fans inside the maintenance building or into a pole barn for the
winter months. In any case, the structure must be tall enough so
the fans can be stored in an erect position so moisture cannot enter
the fan motor. Pole fans are easily disconnected by unscrewing the
poles from their stands. The outside electrical components are protected
by capping the plastic storage box. Some superintendents prefer
to leave the fans at their permanent sites, especially if not enough
storage space is available at the maintenance area. Heavy-duty fan
covers that will not tear or blow away are now available from most
distributors.
The auditory effects of fans are also a consideration. Most courses
have home sites near some of their greens today, and some residents
may be close enough to hear the fan motor noise. Educating your
neighbors about the importance of the fans is essential for the
superintendent. Letters sent to these homeowners each spring discussing
the agronomic value and fan operational hours may help reduce complaints.
Fans do have an impact on the Rules of Golf, depending on whether
they are permanently or temporarily installed. Any time fans are
installed in a permanent base, the golfer can assume the fan won't
be moved. Permanently positioned fans are considered immovable obstructions
according to the Rules of Golf. If the fan interferes with the lie
of the golf ball or the swing or stance of the golfer, relief is
provided under Rule 24-2. Sometimes the fan may be found between
the golf ball and the hole location. Under this Rule, line-of-sight
relief is not provided for with permanently installed fans, and
the ball must be played as it lies. Fans that have been set up on
a temporary basis are treated as temporary immovable obstructions.
Intervention on the golfer's line of play would warrant relief.
If a golf ball deflects off a fan, it is a rub of the green and
the golfer plays the ball where it lies. If a fan deflects a golf
ball out-of-bounds, the golf ball is still considered out-of-bounds.
Fans have made a major impact on many golf courses by helping the
turf survive where it previously had died each summer. Many golfers
also enjoy the additional comfort of a cool breeze while putting.
However, sometimes fans are a nuisance to golfers because of the
extra noise and their impact on the Rules of Golf. These negative
factors must be weighed against the gain of improved health and
playability of putting green turf.
1 Gene Rupen Taylor II. 1995. The Effects of Mechanically Induced
Air Movement on the Temperature, Water Potential and Soil Moisture
Percentage of Creeping Bentgrass (I L.) Golf Greens. MS Thesis,
North Carolina University.
PATRICK O'BRIEN is director of the USGA Green Section's Southeastern
Region.
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