Heating Systems

Heating of a broiler house is important, as chicks are not able to maintain a constant body temperature until approximately 14 days of age. Until then, it is crucial that floor temperature be maintained between 90 95°F with little variation. The easiest way to heat a broiler house is using a forced-air furnace. This type of heat source uses an open flame to heat air being pulled through the unit. Although they are very successful in providing heat for older birds, these heaters are problematic during brooding. Furnaces are basically top-down heating systems. The hot air coming from a furnace does not move along the floor and keep the chicks warm, but rises quickly to the ceiling of the house. Therefore, in order to get the hot air down to chick level, you have to fill up the ceiling of the house with hot air until you have added enough heat to make it down to floor level.

Because of the need for warm floor temperatures, radiant heat is an efficient way of accomplishing this. The most common types of radiant heat sources are pancake and radiant brooders. One of the advantages of radiant heat is that roughly 50% of the heat energy is directed to the floor, making it possible to maintain a floor temperature well above air temperature. When brooders are used, the floor temperature is warmest directly under the brooder, with temperatures decreasing as the distance from the brooder increases. Research studies have demonstrated that floor temperatures between 80 110°F are beneficial in getting optimum broiler performance. The advantage to this is that birds have some ability to control the amount of heat they receive. The closer they move to a brooder, the more radiant heat they receive. As they move away from the brooder, they receive less heat.

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Fig. 1 Tunnel inlet end of a commercial broiler house. Evaporative cooling system, air inlets, and 36 inch exhaust fans can been seen. (View this art in color at www.dekker.com.)

adjustable inlets in the ceiling that are designed to direct the air along the ceiling (Fig. 2). As air moves along the ceiling, it heats up. As the air is heated, the moisture-holding ability increases, which helps remove moisture from the house as air is pulled out by the exhaust fans. Fans are controlled with a combination of interval timers and thermostats. Interval timers allow growers to adjust air quality by fan run time. This allows the grower to run one or two fans at various intervals during brooding, while increasing both the number of fans and run times as the birds get older. The width of the inlet opening is automatically adjusted by a machine to maintain a desired static pressure level. The typical static pressure is between .05 and .10 inches of water column to promote proper air mixing.

HOT WEATHER VENTILATION

COLD WEATHER VENTILATION

During colder weather, the amount of air entering the broiler house has to be tightly controlled. The grower has to bring in enough fresh air to minimize excess moisture buildup, minimize dust, limit the buildup of harmful gases, and provide oxygen for respiration. Overventilation must be avoided because this can cause drafts that can chill the birds and results in excessive fuel usage.

Negative Pressure/Inlet Ventilation

Exhaust fans actively remove the air present in a broiler house and create a negative pressure. The negative pressure within the house causes air to enter through

The purpose of hot weather ventilation is to ensure air exchange every minute, prevent excessive heat buildup, and provide a wind speed of at least 400 ft/min. Air movement is one of the most effective methods of cooling birds during hot weather. As air moves over a bird's body, heat is removed from the bird, making it feel cooler (i.e., windchill). Birds will not only think the house is cooler when exposed to air movement during hot weather, but will continue to eat and grow as if the air temperature is 10 degrees lower than it actually is. To get the desired cooling effect, wind speed needs to be between 400 600 ft/min, depending on factors such as bird age, house temperature, and bird density.

In curtain-sided houses, curtains are 4 5 ft in height which are fully opened during hot weather to facilitate

Fig. 2 Commercial broiler house prior to chick placement. Water lines, feed lines, radiant brooders, circulation fans, exhaust fans, and air inlets can be observed. (View this art in color at www.dekker.com.)

Fig. 3 Tunnel fan end of commercial house, where 48 inch cone fans are used to move air down and out of the house. This particular house is curtain sided and has a pocket at the top of the curtain opening to allow for a tight seal during brooding and tunnel ventilation. (View this art in color at www.dekker.com.)

maximum air exchange. One 36-inch fan for every 750 to 1500 ft2 is typically used to blow air over the birds to increase convective cooling. To get total floor coverage, it takes a large number of fans and it creates safety hazards and increases operating costs and maintenance.

In tunnel-ventilated houses, exhaust fans are located in one end of the building and two large openings are installed in the opposite end (Fig. 3). Air is drawn through these openings and then down the house in a wall-like fashion. This provides uniform air movement across the birds, creating the windchill effect discussed earlier. The air entering the house can be cooled by drawing it through evaporative cooling pads, or by the use of misting nozzles located throughout the house.

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