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```Air inlet systems


For optimal control of both bird performance and energy
usage a modern poultry house should ideally have three
inlet systems
With each inlet system specifically designed to obtain
very specific objectives:
Minimum Ventilation Inlet Systems
Michael Czarick
The University of Georgia
Hot weather inlet system

Designed to produce maximum bird cooling



Rapid air exchange
Produce high air velocities over the birds
Tunnel fans with side wall inlets

Tunnel ventilation
It is important to realize what makes tunnel ventilation so
effective in producing bird cooling is not really the fan
power…but rather the inlet system.
Moderate weather/temperature control
inlet system
If you were to operate all your tunnel fans through your
side wall inlets, birds would not receive nearly the same
amount of cooling.
500 ft/min
250 ft/min

1,000 ft/min
Designed to control house temperature during moderate
weather with older birds.


150 ft/min to 50 ft/min

Broilers/turkeys
Breeders
Pullets
= 4 to 5 cfm per ft2 of floor space
= 3 to 4 cfm per ft2 of floor space
= 2 to 3 cfm per ft2 of floor space
1
Moderate weather/temperature control
inlet system

For our moderate weather ventilation system we need
approximately 1 ft2 of inlet area for every 750 cfm of
exhaust fan capacity used for temperature control

Example (40’ X 500’ broiler house):
Fan capacity
= 40’ X 500’ X 4 cfm/ft2
= 80,000 ft3/min
Roughly four 48” fans
Inlet area
= 80,000 / 750
= 106 ft2





Last but not least…

We need a minimum ventilation inlet system specifically
designed to bring in just enough fresh air to maintain air
quality during cold weather:


If we were to install a typical 44 ¾” X 5 ¾”
air inlet….

Inlet area = (44.75” X 5.75”)/144”
= 1.8 ft2

Number of inlets = 106 ft2 / 1.8 ft2 = 60

Minimum ventilation inlet system

Traditionally we have used our moderate weather inlet
system for both temperature control and minimum
ventilation but…
Maximize heating of incoming cold air before moving down to
floor level
Distribute small amounts of cold fresh air evenly throughout a
house without causing drafts
they may not be ideal for use during
minimum ventilation
Our traditional inlet systems are typically
designed for maximum air flow


4 to 6 cfm per square foot of floor space
Which is significantly more than we would like to use
during cold weather.
2
The problem is that with traditional side
wall inlets
The fact is..

That with young birds will generally use 1 cfm per square
foot of timer fan capacity or less.

40’ X 500’ house would generally require 20,000 cfm of timer
fan capacity on younger birds or less.
900
800
700
600
500
400
300
200
100
0



= 0.6 X 20,000
= 12 square feet
Moderately tight house (0.8 square feet per 1,000 ft2)


Leakage area
But this is for a perfectly tight house…
Even a very tight house has a significant amount of
leakage
How much do 60 inlets need to open for
minimum ventilation?
Very tight house (0.6 square feet per 1,000 ft2)
Leakage area
= cfm / 750
= 20,000/750
= 27 square feet
0.12
0.11
0.1
0.09
Static pressure
0.08
0.07
0.06
0.05
0.04
0.03
0.02
0.01
750 cfm/ft2


Inlet area required

Leakage area

When we want to bring in a little air from an inlet system
designed to bring in a lot of air we end up with very small
inlet openings.
Inlet opening

0
Cfm per square foot
How much would our 60 inlets need to open
to bring in 20,000 cfm


= 0.8 X 20,000
= 16 square feet

Inlet area required



For a very tight house we need to provide


= cfm / 750
= 20,000/750
= 27 square feet
27 – 12 ft2 (leakage) = 15 ft2 of sidewall inlet opening
For a moderately tight house we need to provide

27 – 16 ft2 (leakage) = 11 ft2 of side wall inlet opening
3
How much do 60 inlets need to open for
minimum ventilation?

Most inlets tend to direct incoming air up…not out
along the ceiling when opened a small amount
Very tight house

Inlet opening



85.0°F
= 15 ft2 / (60 X 44”/12)
= 15 ft2 / 220
= 0.068’
= 0.8”
80
70

Very moderately tight house

Inlet opening



= 11 ft2 / (60 X 44”/12)
= 11 ft2 / 220
= 0.05’
= 0.6”
60
50.0°F
Plus very small openings don’t tend to throw
the cold air very far
To get the air to throw properly it often
takes a fairly large inlet opening (i.e., 2”)
90.0°F
90
100.0°F
100
90
90
90
90
90
80
80
80
80
80
70
80
70
80
70
60
70
60
70
60
70
60
50
60
40.0°F
45.0°F
50.0°F
55.0°F
60.0°F
65.0°F
So….

In order to maximize environmental control during cold
weather producers typically convert their temperature
control inlet system to a minimum ventilation inlet
system by latching closed ½ or more of the side wall
inlets
50.0°F
Minimum ventilation inlet system

It works, but requires a fair amount of management time:


Latching inlets closed during the night possibly unlatching inlets
during the day
Which typically means it will not get done like it should
4
Furthermore, if we are not careful environmental
conditions can become highly variable

What we ideally need is a stand alone
minimum ventilation inlet system
With a few inlets, widely spaced, opened a lot.
90.0°F
90
80
70
60
55.0°F
Specifically designed for use for very cold
weather for use with just a few exhaust fans.


For a 40’ X 500’ house





Air cannons?
1 – 2 cfm per square foot (broiler, breeder, pullet).
Maximum of 40,000 cfm
Minimum of 20,000 cfm or less
Maximize heating of incoming cold air before moving to
floor level
Distribute cold fresh air evenly throughout a house
without causing drafts
While at the same time keeping fuel usage to a minimum
Recessed minimum ventilation inlets
Solair wall
5
A better example of a minimum ventilation
inlet is an attic inlet
Attic inlet systems

Attic inlets are typically located near the
center of the house


That is where your hottest air tends to accumulate
Maximizes the distance between the cold incoming air
and the birds
Everything about an attic inlet system makes it well suited
for use as a minimum ventilation inlet
Attic inlets are typically located above a
house’s heating system

Insures a quick interaction between the coldest and
hottest air in a house
99.0°F
99.4
97.4
95
94.2
90
92.1
89.6
86.1
85
83.6°F
Attic inlets above directing air above a
houses heating system
Attic inlets with a hot water heating system
6
Attic inlets tend to maximize the throw of
cold incoming air
Attic inlet above heating system


Maximizes the throw/conditioning of the
incoming air
Top of the inlet is the ceiling…
Air comes in straight along the ceiling...
Attic inlets pull their air from the attic
100.0°F
100

Which is less affected by strong winds and…
90
80
70
60
55.0°F
Daytime attic temperatures
1-Feb
30-Jan
28-Jan
26-Jan
24-Jan
22-Jan
20-Jan
18-Jan
16-Jan
90
85
80
75
70
65
60
55
50
45
40
35
30
25
20
14-Jan
Temperature (F)
(typically 5–30oF higher than outside)
12-Jan
is often warmer than outside air.
Date
attic
outside
7
Drawing in warmer air can lead to reduced
fuel usage
90
85
80
75
70
65
60
55
50
45
40
35
30
25
20

5 to 15% lower fuel usage
House tightness
Management
Time of year



85.0°F
85
78.2°F
75
80
70
75
65
30-Jan
29-Jan
28-Jan
27-Jan
26-Jan
70
25-Jan
Temperature (F)
Nighttime temperatures are the same as
outside
60
65
55
60.0°F
Date
attic
outside
But more importantly slightly higher
daytime house temperatures…
53.1°F
resulting in higher daytime ventilation
rates…
300
250
82
Cubic feet per hour
50
Conventional Inlets
Attic inlets
Side wall inlets
Attic inlets
Attic inlets
2-Feb
1-Feb
2-Feb
1-Feb
80
75
70
65
60
55
50
45
40
35
31-Jan
4-Jan
6-Jan
8-Jan
10-Jan
12-Jan
14-Jan
16-Jan
18-Jan
20-Jan
22-Jan
24-Jan
26-Jan
28-Jan
30-Jan
1-Feb
3-Feb
5-Feb
7-Feb
9-Feb
11-Feb
13-Feb
15-Feb
17-Feb
19-Feb
Relative humidity
Total cubic feet of air moved /
10,000
13,000
12,000
11,000
10,000
9,000
8,000
7,000
6,000
5,000
4,000
3,000
2,000
1,000
0
Attic inlets
Higher ventilation rates lead to lower Rh
both day and night…
27-Jan
which leads to higher overall daily
ventilation rates of around 20%...
Date
31-Jan
28-Jan
2-Feb
1-Feb
1-Feb
31-Jan
31-Jan
Date
Conventional Inlets
0
26-Jan
Set temperature
30-Jan
30-Jan
29-Jan
29-Jan
28-Jan
28-Jan
70
30-Jan
72
100
30-Jan
74
150
29-Jan
76
200
28-Jan
78
29-Jan
80
25-Jan
Temperature (F)
84
Conventional inlets
8
and a lower daily Rh over the course of the
flock…
and drier litter – lower ammonia
80
75
Relative humidity
70
65
60
55
50
45
3-Jan
5-Jan
7-Jan
9-Jan
11-Jan
13-Jan
15-Jan
17-Jan
19-Jan
21-Jan
23-Jan
25-Jan
27-Jan
29-Jan
31-Jan
2-Feb
4-Feb
6-Feb
8-Feb
10-Feb
12-Feb
14-Feb
16-Feb
40
Attic inlet house
Side wall inlet house
There are a variety of attic inlets on the
market
Single direction
Single direction attic inlets above tube
heaters
Two way / Bidirectional
95.0°F
90
71.5
57.9
43.4
80
70
60
55.0°F
9
Bi-directional attic inlets above tube heaters
44.5
Bi–directional inlets
95.0°F
58.2
73.7
90
80
70
60.0°F
Four way door inlets
and four way drop bottom inlets
There are a couple of different methods of
opening/closing attic inlets as well
Counterweighted or spring

Machine actuated
10
Counterweighted or spring

Door opening static pressure is typically between 0.05”
and 0.07”
The opening static pressure can be modified
by adding weight to the counterweight

5/8” nut will increase the opening static pressure to 0.07”
11
Attic inlets
Attic inlets

All these attic inlet systems have proven to work well as
minimum ventilation inlets and have been used broiler,
layer, turkey, and swine houses for decades.

.
Installation tips

How well they will work depends, like many other things,
on proper installation and of course management
House tightness is very important

The effectiveness of an attic inlet system is heavily
influenced by house tightness


Minimum house tightness standard = 0.13” using 1 cfm/ft2
of floor space of exhaust fan capacity

Minimum ventilation fan capacity

1 – 2 cfm per square foot (broiler, breeder, pullet)

Attic inlet systems are typically designed for 1.5 cfm per
square foot of floor space

40’ X 500’ house
Attic inlet capacity



0.8 ft2 of leakage per 1,000 square feet
Many manufacturers of attic inlet publish a
rated capacity of their inlets
Number required?

The tighter the house the more air that will enter through the
attic inlets
= house size X 1.5 cfm/ft2
= 40’ X 500’ X 1.5 cfm/ft2
= 30,000 cfm
12
Double L – TJ4200
Aerotech ceiling inlets
How many four way attic inlets should be
installed
Be careful about how the capacity of the
attic inlet was determined

The rated capacity of the Double L TJ4200 and Eagan four
way inlets is approximately 1,800 cfm per inlet






A minimum attic inlet capacity should be determined
when opened at 2” to 3” …not 6” to 12”
Number required:
40’ X 400’ =12
40’ X 500’ =15
50’ X 500’ =18
60’ X 500’ =22
Minimum ventilation inlet open too much
The greater the capacity per inlet…the fewer
installed…the greater the distance between attic
inlets

Highly variable environmental conditions

When an inlet capacity is over estimated they will tend to
open more than they should.
13
Attic inlets opening too much during
minimum ventilation
Attic inlets opening too much during
minimum ventilation
95.0°F
90
80
70
60.0°F
What is the capacity of a 24” two directional
attic inlet




Though they can open 5 or 6 inches their capacity should
be determined around 3 to 4 inches.
Inlet capacity = (length X opening size)/144 X 750 cfm/ft2
= (48” X 4)/144 X 750
= 1,000 cfm
Do not put in more than specified!


Attic inlets are for MINIMUM ventilation, not
temperature control
When an excessive number of attic inlets are installed:



House with 56 attic inlets
When minimum ventilation fans come on
they don’t even open
They will not operate as effectively when used with minimum
ventilation fans
May have to latch half of them closed during very cold weather.
House may become drafty
Do not put in more than specified!


They are for MINIMUM ventilation, not temperature
control
When an excessive number of attic inlets are installed:




They will not operate as effectively when used with minimum
ventilation fans
May have to latch half of them closed during very cold weather.
House may become drafty
House will tend to have problems with overheating during
mild/hot weather.
14
Install attic inlets throughout the house

Not just on the brooding end



Attic inlet placement

Will result in poor temperature/air quality uniformity
What would happen if you just put conventional inlets on the
brooding end of a house
40’ wide


Alternating just either side of the peak of the house
Hottest air from the peak of the attic
Most of the benefits associated with attic inlets occur
after the birds are turned out.

40’
The primary benefit of attic inlets is not fuel savings, but rather
increased ventilation rates
Attic inlets in a 40’ wide house
Attic inlet placement

40’ wide



Alternating just either side of the peak of the house
Hottest air from the peak of the attic
Maximizes distance from the side wall
40’
Attic inlets tend to do a very good job of
throwing air along the ceiling

Sometimes too good of a job…
Air from attic inlet rolling down side wall
95.0°F
95.0°F
90
90
80
80
70
70
60.0°F
60.0°F
15
Four way attic inlet too close to the side wall
Two way attic inlets can be problematic in
narrower houses
40’ wide house
10 four way inlets
10 two way inlets
Four way inlets break up fresh air into four
smaller jets
40’ wide house
Four smaller air jets
95.0°F
95
250
250 250
250
90
85
80
500
500
75
70.0°F
Two larger air jets can lead to significant
side wall cooling
Two larger air jets
95.0°F
95
95.0°F
95
90
90
85
85
80
80
75
75
70.0°F
70.0°F
16
Two larger air jets can lead to significant
side wall cooling
Two larger air jets can lead to significant
side wall cooling
95.0°F
95.0°F
90
90
80
80
70
70
65.0°F
Four air jets are less likely to cause side
wall cooling
65.0°F
Generally speaking you typically need more
two-way attic inlets that four way
95.0°F
90
80
70
65.0°F
The four way attic inlets can also be rotated
45 degrees to increase distance to side wall
Attic inlet placement

50’ wide



Alternating approximately 2’ – 3’ from the peak of the house
Allows room for center feed/water lines.
Facilitates the installation of a center row of circulation fans.
17
Attic inlet placement

Four way attic inlet placement
(40’ vs. 60’ wide housing)
+60’ wide



Alternating approximately 6’ to 8’ from the peak of the house
Improved distribution of fresh air
Prevents center of the house from becoming too drafty with
four way inlets
40’ wide
15 inlets
Inlets spacing = 32’
60’ wide
22 inlets
Single row of four way inlets in 60’ wide
house
Inlets spacing = 22’
Four way attic inlet placement in 60’ wide
house
2’ – 4’ between rows
10’ – 12’ between rows
Two way inlet can be advantageous in wider
houses with large number of attic inlets
+20 – four way inlets
Two way attic inlets in 66’ wide house
98.0°F
90
+20 – two way inlets
80
70
65.0°F
18
Bidirectional attic inlets with two rows of
tube heaters
Single direction attic inlets with two rows of
tube heaters
Two rows of single direction attic inlets can
also be effective in wider house
Counterweighted or Machine actuated?

Both have similar advantages when it comes to reduced
fuel usage, improved air quality, drier litter, etc when
properly installed and operated

Machine actuated
Machine actuated

Higher initial cost.


Inlets, machine, cabling, wiring
Ideally should have a controller specifically designed to
handle to both inlet systems.



Easy to close the attic inlets when not in use.
Directly controlled by the houses environmental
controller.
A inlet machine will insure that the attic inlets close when
not in use.
19
Attic moisture damage?

When you put a hole in your dropped ceiling for ANY
type of attic inlet there is the potential for warm, moist
air traveling from the house into the cold attic space and
condensing.


Deterioration of ceiling insulation
Possible weakening of trusses
Insufficient weight holding doors closed
To minimize leakage into the attic
space…



To minimize leakage into the attic
space…




Pre-opening attic inlets

A significant amount of warm, moist air can enter the
before the exhaust fans start to turn on
When installing attic inlets make sure there is a tight seal
between the attic inlet and the ceiling (common problem)
Attic inlets should close snuggly when not use.
Counterweighted attic inlets sufficient counter
weight/spring tension that when installed at an angle still
remains closed.
When installing attic inlets make sure there is a tight seal
between the attic inlet and the ceiling (common problem)
Attic inlets should close snuggly when not use.
Counterweighted attic inlets sufficient counter
weight/spring tension that when installed at an angle still
remains closed.
Attic inlet machine should NOT pre-open the attic inlets
before the exhaust fans come on.
To minimize leakage into the attic
space…





When installing attic inlets make sure there is a tight seal
between the attic inlet and the ceiling (common problem)
Attic inlets should close snuggly when not use.
Counterweighted attic inlets sufficient counter
weight/spring tension that when installed at an angle still
remains closed.
Attic inlet machine should NOT pre-open the attic inlets
before the exhaust fans come on.
Attic inlet cabling should be checked from time to time to
make sure the inlets are closed when they are supposed
to.
20
To minimize leakage into the attic
space…
Machine actuated attic inlets open during
tunnel ventilation

Counterweighted inlets

Counter-weighted inlets should be cleaned on a regular
basis
Counterweighted inlets
No, wear an tear on an inlet machine
On a five minute timer an inlet machine can move up to
576 times day.

Can utilize very short timer cycles
81
80
79
Temperature
78
77
76
75
2:10 AM
2:05 AM
2:00 AM
1:55 AM
1:50 AM
1:45 AM
1:40 AM
1:35 AM
1:30 AM
1:25 AM
1:20 AM
1:15 AM
74
Time
Counterweighted inlets
Basic attic inlet operation
What about a 3 or 2 ½ minute cycle?
81
80
79
77
76
75
2:10 AM
2:05 AM
2:00 AM
1:55 AM
1:50 AM
1:45 AM
1:40 AM
1:35 AM
1:30 AM
1:25 AM
1:20 AM
74
1:15 AM
Temperature
78
Time
21
Between flocks use attic inlets to help
remove moisture from the litter



Attic inlets between flocks
Keep end wall doors closed, curtains up,
Use two to three 36” fans for minimum ventilation
Operate off a timer with attic temperature override of
approximately 70oF

Attic inlets can typically increase daytime house
temperature approximately 10oF above outside air
temperature.


Side wall inlets
85oF outside = 95oF inside
The tighter the house the greater the heating produced.
With attic inlets
(spring)
(spring)
63.1
85.0°F
85
85.0°F
85
92.7
80
80
75
62.0
75
62.7
69.1
76.4
70
65
65
60.0°F
Side wall inlets
70
60.0°F
With attic inlets
(summer)
(summer)
100.0°F
100
100.0°F
100
95
95
90
90
85
85
80.0°F
80.0°F
22
With attic inlets
Attic inlets between flocks




(summer)
Attic inlets can typically increase daytime house
temperature approximately 10oF above outside air
temperature.
100.0°F
100
85oF outside = 95oF inside
The tighter the house the greater the heating produced
95
Improved litter drying

90
Lower ammonia levels
85
80.0°F
Once chicks are placed…
Attic inlets used prior to chick placement

110
105
100
95

90
Temperature/Rh
Close some or all the attic inlets on nonbrooding end
during cold weather.
85

80
75
70

65
60
55
50
Set side wall inlet machine to maintain a static pressure of
0.11” to 0.13”

45
6:00 AM
6:00 PM
12:00 AM
6:00 AM
12:00 PM
6:00 PM
12:00 AM
6:00 AM
12:00 PM
6:00 PM
12:00 AM
6:00 AM
12:00 PM
6:00 PM
12:00 AM
6:00 AM
12:00 PM
6:00 PM
12:00 AM
6:00 AM
12:00 PM
12:00 AM
40

T im e
tre a tm e n t
co ntro l
tre a tm e n t rh
Do not try to operate attic inlets at a high negative
pressure.

Attic inlets work very well at relatively low static pressures

Higher static pressure settings tends to reduce the
effectiveness of attic inlets

This will keep the side wall inlets closed during timer fan
operation!
The side wall inlets will begin to open as the second stage
“temperature control fans” come on
con tro l rh
With any attic inlet system…

At night there is no warm air in the attic.
Do not open until birds are spread evenly throughout the
house.
Leakage area

Moderately tight house (0.8 square feet per 1,000 ft2)


Leakage area
= 0.8 X 20,000
= 16 square feet
0.05” – 0.07”
23
900
800
700
600
500
400
300
200
100
0




= 0.6 X 20,000
= 16 ft2
Leakage amount = 16 X 550 cfm/ft2
= 8,800 cfm

Attic inlets

= 0.6 X 20,000
= 16 ft2
Leakage amount = 16 X 820 cfm/ft2
= 13,120 cfm

Leakage area

Less warm air enters the center of the house, more
“cold” air enters the ends of the house
This results in greater temperature differentials between
the centers of ends of the house

Use attic inlets with the side wall inlets



Do not switch directly from attic inlets to side wall inlets.
It is best if you use the attic inlets with the side wall
inlets.
Going directly from attic inlets to side wall inlets can
result in a sudden change in house temperature


Fans turn on the center to cool off the house
Heating systems turn on the ends to warm up the house
= 6,880 cfm
Attic is 5 to 30oF above outside air temperature
Most importantly fewer fans will operate over the course
of the day
Total air moved every 15 minutes
Total air moved
Attic inlets
= 11,200 cfm
Operating attic inlets at high static pressure


Leakage area
0.12
0.11
0.1
0.09
Static pressure
0.08
0.07
0.06
0.05
0.04
0.03
0.02
0.01

Moderately tight house (0.6 square feet per 1,000 ft2)

Moderately tight house (0.6 square feet per 1,000 ft2)

Close up the attic inlets to get a higher
pressure (0.12”)

Leakage

0
Cfm per square foot
How much would our 60 inlets need to open
to bring in 20,000 cfm
1,400,000
1,300,000
1,200,000
1,100,000
1,000,000
900,000
800,000
700,000
600,000
500,000
400,000
300,000
200,000
100,000
0
29-Jan
Date
Machine attic inlets
28-Jan
27-Jan
26-Jan
25-Jan
24-Jan
23-Jan
Counter weighted
Side wall inlets
24
Total air moved every 15 minutes
Avoiding bird “overheating”
900,000

Total air moved
800,000
700,000
Attic inlets will not lead to “overheating” if an attic inlet
system is sized, installed and operated...
600,000
500,000
400,000
300,000
200,000
100,000
0
28-Jan
27-Jan
Side wall inlets
Time
inside
outside
attic
outside
Side wall inlets open and overwhelm the
attic inlets
What about leaving attic inlets open when
tunnel-ventilating?
110
108
106
104
102
100
98
96
94
92
90
88
86
84
82
80
78
76
74
72
70
9:50 AM 10:50 AM 11:50 AM 12:50 PM 1:50 PM 2:50 PM 3:50 PM 4:50 PM 5:50 PM

inside
outside
12:00 AM
11:00 PM
9:00 PM
10:00 PM
8:00 PM
7:00 PM
6:00 PM
5:00 PM
4:00 PM
3:00 PM
2:00 PM
1:00 PM
12:00 PM
11:00 AM
9:00 AM
10:00 AM
8:00 AM
125
120
115
110
105
100
95
90
85
80
75
70
65
60
55
50
45
40
6:00 AM
12:00 AM
9:00 PM
Temperature (F)
inside rh
11:00 PM
Time
attic
10:00 PM
8:00 PM
7:00 PM
6:00 PM
5:00 PM
4:00 PM
3:00 PM
2:00 PM
1:00 PM
12:00 PM
11:00 AM
9:00 AM
10:00 AM
8:00 AM
7:00 AM
inside
Temperature (F)
Attic inlets in use the day chicks were place
125
120
115
110
105
100
95
90
85
80
75
70
65
60
55
50
45
40
6:00 AM
Temperature (F)
Attic inlets between flocks
7:00 AM
26-Jan
Date
Machine attic inlets
Counter weighted

It is not as much as a problem as many people think if the
attic inlets are not oversized!
Volume coming through tunnel openings is large in
comparison to attic inlets.
attic
25

Attic inlets left open in tunnel mode
105
100
95
90
85
80
75
70
65
60
12:00 AM
6:00 AM
12:00 PM
6:00 PM
12:00 AM
6:00 AM
12:00 PM
6:00 PM
12:00 AM
6:00 AM
12:00 PM
6:00 PM
12:00 AM
6:00 AM
12:00 PM
6:00 PM
12:00 AM
6:00 AM
12:00 PM
6:00 PM
12:00 AM

During the latter stages air brought in by the attic inlets is
small in proportion to the air entering through the tunnel
inlet
Hot air tends to stay near the ceiling.
Temperature (F)
What about leaving attic inlets open when
tunnel-ventilating?
Center
(attic temperature=120oF)
95
93
91
89
87
85
83
81
79
77
75
14:30
1.5 F
14:40
front
inside
14:50
rear
15:00
95
93
91
89
87
85
83
81
79
77
75
14:30
But if they are not, it is not the end of the world.
Outside
2.5 F
14:40
front
outside
Yes, attic inlets should be closed

Temperature (F)
13 attic inlets open
(40’ X 500’ Tunnel fan cap. = 200,000 cfm)
Temperature (F)
No attic inlets
Fan end
inside
14:50
rear
15:00
outside
When should I close attic inlets?

When you are no longer going into minimum ventilation
mode at night.



Summer
Winter
Fall-Spring
=10 days of age
=never
=no min. vent. at night
26
When should I close attic inlets?





Spring actuated inlet with closing cable
When you are no longer going into minimum ventilation
mode at night.
Summer
Winter
Fall-Spring
=10 days of age
=never
=no min. vent. at night
With counter-weighted inlets that are connected to a
machine for closing purposes

Stage prior to going into tunnel ventilation, possibly sooner.
Eagan four way attic inlet
(drop bottom)

Or adjusting and external counter weight
poultryventilation.com
27
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