Midwest HVAC News
Dairy Farm's Challenge
with Milking Units' Winter Freeze-Ups Gets Thawed with Air
Wisconsin's subfreezing winters take a toll on milking parlor's
equipment, but air curtains above cow entryways retain heat inside.
Holy cow! Milking parlors on dairy farms are yet another application
for air curtains, the energy-saving devices that keep outdoor and
indoor environments separate at open doorways.
After decades of energy-saving applications for industrial openings
and more recently for commercial building entrances such as
hospitals, hotels and schools, air curtains now have been proven
successful at preventing milking parlor equipment freeze-ups on
Milk productivity setbacks were frequent challenges from November
through March during subfreezing days for Griesen's Family Dairy
located 60 miles northwest of Madison, Wis., in Prairie du Sac, Wis.
The medium-sized 680-cow farm suffered product losses, production
delays from automatic milking equipment freeze-ups nearest the
parlor entrances, and potential injury issues from slippery floors
and poor indoor air comfort for employees.
Materials handling equipment dealer Bernie's Equipment Co., Holmen,
Wis., recommended air curtains by Berner International, New Castle,
Pa., to retain heat in the milking parlor.
On ambient temperature days above 32°F, the floor's radiant system
supplied by a 400,000-Btu, stainless steel, 95.1-percent efficient
Munchkin boiler manufactured by Heat Transfer Products, Scottsboro,
Ala., combined with each cow's inherent 4,000-BTU/hr heat output,
adequately maintains the milking parlor's target temperature range
of 38°F to 40°F. The heating system was adequate despite the fact
co-owner Hans Griesen prefers the two 16 x 8-foot entryways to
remain open through three daily shifts for optimum productivity and
animal movement in and out of the 24-stall herringbone-style milking
parlor manufactured by DeLaval/Germania, Vernon Hills, Ill. On
subfreezing days however, the heating system couldn't maintain set
point temperatures near the entryway.
Griesen first tried portable salamander forced-air heaters. The
entrances were warmer, however the $100/day cost for fuel, kerosene
emission odors and potential fire hazard, sent Griesen looking
An employee dedicated to opening and closing the two doorways all
day was considered cost prohibitive, even at minimum wage rates,
according to Griesen.
Griesen also considered both strip curtains and air curtain
technology so the entry doors could stay open. Strip curtains were
too obstructive to the animals. His first review of an air curtain
at a nearby farm wasn't a positive experience, either. The farm used
an inexpensive foreign air curtain brand with short lengths bolted
in tandem to span the wide doorway. The air curtain was noisy, its
modular construction vibrated and it didn't provide the proper
volume, velocity or uniformity of air stream to prevent outdoor air
infiltration, according to Griesen.
Finally, Clyde Conger, Bernie's general sales manager, and Berner
manufacturer's representative, Tim Spreda, vice president-sales, MII
Equipment, Milwaukee, Wis., worked with factory sales engineers to
specify two USA-made,16-foot-long, one-piece air curtains from the
Berner's VSA model product line. The air curtains are mounted above
the milking parlor's open doorways and retain up to 80-percent of
the facility's energy even during wind loads of up to five-mph. Each
air curtain features a corrosion-resistant powder-coated finish,
five high-efficiency 1/2-hp motors and a welded aluminized steel
frame that retains a strong structural integrity they span across
such a wide opening. Consequently, there are no gaps in the
7,631-cfm, 1,635-fpm air stream it provides across the 16-foot-wide
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"Hans had already
educated and sold himself on the air curtain concept before we
got involved; therefore he knew exactly what he wanted and had
designed the application in his head," said Conger.
"Some of our co-workers were skeptical as to whether air
curtains would solve the problem, but they're believers now
since we haven't had any more frozen equipment issues," said
Griesen, who hired a carpenter to reinforce the doorway headers
that receive the air curtain support brackets. "One employee
took infrared color temperature readings and there was a big
difference in temperature inside the doorway with the air
curtains on and off."
Air curtains consist of fan motors, blowers, nozzles and
directional vanes and a control package. When properly
engineered for the proper horsepower, nozzle discharge and
airstream angle, an air curtain essentially "seals" a doorway
from outdoor elements, flying insects and dust. The airstream
must strategically "break" at the threshold of the doorway for
ultimate performance. While air curtains are typically activated
by a plunger switch after a door opens, the milking parlor air
curtains are activated by a thermostat located near the
entrance. Gas-fired hot water or steam, and electric heating
coil options were considered, however Griesen felt the milking
parlor's heat radiant heat system was sufficient if cold air
infiltration could be curtailed.
Although Griesen's main concern was subfreezing air
infiltration, the air curtains are also saving the facility
energy, because the radiant floor system's boiler cycles on less
to maintain the set point temperature.
The air curtains supplement the overall cutting-edge energy
efficiency design and construction conception when the Griesen
family relocated from the Netherlands to build the 40-acre farm
from the ground-up in 2005. Other technologies are:
metal halide fixtures with lamps by Sylvania.
drive on the milking vacuum pump
compressors by Copeland--div. of Emerson Climate Technologies,
Sidney, Ohio, for milk refrigeration.
exchangers by DeLaval/Germania for compressor heat recovery
plate cooler by
All the efficiency
equipment combined saves the farm an estimated $35,000 annually in
energy savings, according to Griesen.
While the milk producers association, the Dairy Council of
California continually uses its "Got Milk?" campaign to advertise
milk's benefits to consumers, Griesen's air curtain success should
prompt dairy farmers to ask themselves, "Got Air Curtains?"
SIDEBAR: Specify Air Curtains for Velocity, Volume and
Velocity, volume and uniformity work together to create the ideal
air curtain performance, therefore relying on only one or two of
three could skew performance results.
Velocity: To properly design an air curtain installation, the
airstream must hit the floor with enough velocity to create a split.
The split, which creates stability, strength and direction for the
air entrained on each side of the airstream, should occur right at
the doorway’s threshold. An installation with a weak airstream, one
that barely splits for example, is only viable for applications
involving temperature differential without wind, such as internal
doorways. They’re capable of stopping infiltration or cross
contamination of environments due to airflow caused by the
temperature differential, but they become ineffective once wind is
introduced. Few external doorways are not affected by wind loads.
on the other hand, is the building block that allows a properly
designed and pressurized discharge plenum to generate a high
velocity laminar jet stream. The taller the opening, the more volume
that is required to generate a thicker, higher velocity airstream to
resist wind loads of four to five mph. Obviously an air curtain for
a fast food restaurant’s drive-through window doesn’t need as strong
a volume as a 16-foot high door in a shipping area. Once an air
curtain activates and creates a split, it creates a “skin” over the
building’s volume of indoor air and uses this internal pressure to
resist wind. The split then rolls the entrained conditioned and
unconditioned air back to their respective areas.
Another important factor to consider in air curtain performance and
selection is uniformity, which only impacts the airstream
effectiveness when it drops below 75-percent. An air curtain that
focuses too much energy on generating a high uniformity loses
velocity, therefore reducing its effective wind resistance.
About Berner: Berner International Corporation is North
America's original air curtain manufacturer since 1956 and remains a
leader in the air door/air curtain equipment manufacturing industry.
Berner is a member of the U.S. Green Building Council (USGBC), The
Green Building Alliance (GBA), the Air Movement & Control
Association (AMCA), the American Society of Heating, Refrigerating &
Air Conditioning Engineers (ASHRAE) and also a certified Women’s
Business Enterprise National Council member (WBENC). For more
information on Berner and its products, please call (724)-658-3551
x403 or visit