Minimum Ventilation Bernard Green Ventilation Technical Service Manager - Asia
Minimum Ventilation At or below set point temperature minimum ventilation Regardless of outside temperature, a certain amount of fresh air must be brought into the house Maintain air quality Maintain floor/house temperature Bird comfort is achieved through maintaining good temperature control NO air movement at bird level Fans operate on a cycle timer Transition and Tunnel Ventilation Set Point Temperature Minimum Ventilation
Bird Requirements Warm floor during brooding Heating Good air quality (oxygen) No temperature fluctuations No drafts No environmental stresses
Your House The Starting Point The quality of the house can make or break any ventilation system Ventilation is all about CONTROL of air The better you can seal, the more you can CONTROL SEAL THE HOUSE Gives better control over what is happening inside Reduces the effect of outside conditions A good house is: Well sealed, air tight Well insulated
Test Fan (m³/hr) Minimum House Pressure Based on Fan Capacity and House Size (UGA) 51000 47600 44200 41000 37500 34000 30600 1115 1500 1850 2230 2600 3000 3350 3720 House Floor Area (m²)
Poor Sealing Always seal from outside
Seriously!!
Cold Air Leakage at Catching Door
Sealed vs. Unsealed Side Wall
Tunnel Door Leakage
Chick Spread Uninsulated, Poor Seal
Signs of Air Leakage
House Leakage Wasted Heat Cold floors, wet litter, heater activated
Curtain Leakage on a Windy Day
Heating Make sure there is MORE than enough heating capacity More capacity lower total consumption Ensure good, even distribution of the heat Ensure tubes are correctly designed Preheat the house for at least 2-3 days Litter must be warm before chicks arrive(30ºc min)
Bringing in Cold Air Valuable Heat Wasted Negative Pressure Ventilation Chicks chilled, wet litter
Why Is Negative Pressure Important? Air enters evenly through every inlets If your house leaks, it also comes through all the leaks! By spreading inlets evenly can get even fresh air distribution By restricting inlet size, can regulate incoming air speed Control over how far the air goes into the house
Why Is Negative Pressure Important? Air should go to the middle of the roof Higher incoming speed allows better mixing Pressure determines the incoming air speed High pressure high air speed Low pressure low are speed The wider the house higher the pressure Pressure enables us to move the air to where we want it to be (CONTROL)
Air Movement Based on Pressure Just right Bit higher Higher Low Pressure
Negative Pressure vs House Width The following is a rough guide for the negative pressure at different house widths House Width 10m 12m 14m 15m 18m Operating Pressure 10Pa 13Pa 15Pa 20Pa 25Pa Note: The above is only a guide. Actual operating pressure may vary depending on the type of inlet and shape and angle of the ceiling/roof, etc.
Minimum Ventilation Air speed at bird level < 0,25m/s
Inlet Air Flow
Seeing Air Movement Pressure low Pressure better, but still low Pressure right Length of cassette tape ±150mm We want to see if air is along ceiling If tape is too long, can be misleading
Selecting Side Wall Inlets The side wall inlet is probably the most critical piece of ventilation equipment The success of minimum ventilation revolves around this piece of equipment
Managing Minimum Ventilation Inlets How do we get the air to the middle of the house? Is negative pressure the only requirement? NO! There are 3 requirements to get the best air flow 1. Minimum inlet opening 3-4cm 2. Static pressure 3. Air direction
Managing Minimum Ventilation Inlets For a given pressure, air flow will vary depending on the size of the inlet opening Air flow is better along a smooth ceiling Air Flow = (Opening >3cm) + (Pressure) + (Direction)
Managing Minimum Ventilation Inlets Important!! KNOW that the air is reaching the peak of the roof KNOW how to set/calibrate your inlet winch on the controller TESTS: Smoke bomb Cassette tape/plastic strips Stand in front of the inlet at various distances Climb up a stepladder in front of an inlet Air flow should be against the ceiling
Managing Minimum Ventilation Inlets Setting Air Inlets Inlets should open 3-4cm (min) during minimum ventilation Having fewer inlets opening correct amount is better than too many opening only a little Inlets must open equally Inlets in use must be evenly distributed Try not to use inlets directly opposite each other for minimum ventilation Must operate on static pressure There is no need to close inlets near the fans
Minimum Ventilation Air Inlets Air Direction Plate Hooks To Stage Inlet Opening Inclined Door Set Into Frame
Manual System To Lock Inlets Closed
Importance of Air Direction Plates
OBSERVE No dust! Air hits beam and deflects down Beam obstructs air flow Dust on ceiling from air entering the house Air direction plate set wrong
Setting The Air Direction Plate Problem! Laser pointer
Seeing Air Movement
Roof Air Deflector Install in front of the minimum ventilation inlets
Controlled Air Flow
Older Type Inlet
Minimum Ventilation Rate Theoretical/calculated rates are only a guide! The right minimum rate is critical for bird performance and to minimise heat consumption Under ventilation bird performance is compromised Over ventilation excessive heat consumption, dry house, possible drafts on birds Evaluate your minimum ventilation setting every day Minimum ventilation fans should operate on a cycle timer
Example of Minimum Ventilation Rate
Example Calculation Assume: Bird weight = 800g ; 25 000 birds Ventilation factor = 0,609m³/hr/bird Calculation: Ventilation = 25 000 x 0,609m³/hr/bird = 15 225m³/hr Cycle Timer Setting: 5 minute cycle ; 2 x fan @ 17 000m³/hr (example) Time ON = (15 225 x 5) (2 x 17 000) = 2,24 minutes Time ON = 2 minutes 14 seconds Time OFF = 2 minutes 46 seconds Note: This is an example on how to perform the calculation, and does not necessarily suggest that the Ventilation Factor used above is the only way to calculate minimum ventilation
Cycle Time (ON + OFF) What cycle time should I use? 5 minutes, 10 minutes? Cycle time is just another management tool Whatever is going to: Keep the chicks comfortable Maintain an acceptable air quality Cycle time can change through the cycle Make sure minimum ON time is enough for air to reach the peak of the roof
100% RH 0 C ; 100%RH 20 C ; 25%RH 10% RH
Evaluating Minimum Ventilation Best done by visiting the house Done preferably first thing each morning Evaluate in the first 30-60 seconds: Bird comfort, spread, activity Stuffiness Humidity level Ammonia Condensation/sweating (walls, drinker pipes, steel) AIR QUALITY What you feel in first 30-60 seconds is what the chicken lived with all night Purging the house in the morning is unacceptable (Purging running many fans to clear the air)
KEEP IT SIMPLE!! Ventilation Controller The controller is a management tool. If you don t know how to use it, then it will control you. There is NO NEED what so ever for the control system to be overly complicated
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