Chapter 8 - Heating Methods and Equipment

Two types of heaters are common in poultry facilities: forced hot-air space heaters and radiant brooders. Space heaters heat the air in the building. Radiant brooders, such as pancake and infrared brooders provide some heat to the air but are used primarily to heat the birds and floor. Both types of heaters can use natural or propane gas and are rated by their BTU per hour (BTUh) heat output. Houses may employ one or both types of heaters.

The decision on whether to use space or radiant heaters or a combination of the two is not clear-cut. Broilers are successfully raised using all three systems. When the emphasis is chick comfort up to about two weeks of age, floor-level temperatures are very important and radiant brooders are generally used. Older broilers are more tolerant of cool temperatures and have learned to move around to find a comfortable temperature. For these situations, space heaters may be more economical. Many producers have found that the increased initial cost and great complexities when using both types of heating equipment are offset by long-term energy savings and bird comfort.

Space heaters

The temperature in a house with a well-designed forced-air space heating system is relatively uniform from floor to ceiling and around the house. Agricultural forced-air heaters range from 15,000 BTUh to over 300,000 BTUh, with poultry houses commonly rated between 80,000 to 250,000 BTUh. The industry standard is to provide around four heaters in a 500-foot long broiler house, rather than one or two large heaters. This improves heat distribution in the house.

Large heaters are only marginally more expensive than units with half the BTUh capacity, so it is common to over-design for houses that will contain brooding chicks. Some heaters can operate down to 60% of their rated capacity without sacrificing combustion efficiency. Units are often installed near one sidewall. Heated air is distributed with the heater fan and through mixing with the incoming ventilation air jet. Maintaining warm temperatures near the floor during early brooding is a common problem with space heaters.

Most space heaters use interior air and are unvented, which means they exhaust carbon dioxide, moisture, and incomplete combustion products directly into the building. Approximately 1.7 lbs of water vapor is producer per lb propane gas combusted. Thus, to prevent moisture accumulation caused by unvented heaters, it is recommended that minimum ventilation rate be increased by 2.5 CFM per 1,000 BTUh heater capacity.

Radiant brooders

Radiant brooders use radiation to direct heat energy at the floor and at broilers near the heater. The amount of radiant heat felt on a surface is dependent on the temperature of the radiating element and the distance between the radiating element and the surface. In order to be heated, an object must be able to ‘see’ the hot radiant element in the brooder. When we experience radiant heating from a campfire, for example, only the parts of the body facing the fire are warmed. Broilers are warmed by the thermal radiation from the brooder and warm floor.

The comfortable temperature zone of a radiant brooder is doughnut-shaped, as is reflected in the pattern in which chicks distribute themselves under the brooder. For example, with a conventional pancake brooder, floor temperatures directly under the unit may be as high as 150°F, while seven feet away the temperature is down to 75°F. Brooder location recommendations are often based on how many chicks they can comfortably warm without causing chicks to pile up under the brooder unit. Use space heaters in addition to the radiant heaters if air temperatures cannot be maintained or if inadequate radiant heat zones exist. Perimeter insulation becomes more important in radiant-heated houses, since it will reduce heat loss through the warmed floor.

Temperatures in radiant heated houses are not uniform from floor to ceiling as space-heated houses and may feel cool to the operator. A desirably warm temperature can be maintained at broiler-level while the surrounding air is often 5-10°F cooler. Temperature sensors for brooders should be placed about 6 inches off the floor for proper zone control. Provide radiant protection for the sensor, or it too will be heated by the radiant energy and not reflect a true air temperature in the floor zone.

Radiant or infrared brooders come with two major types of radiant elements: a small ceramic disk or large stainless steel cone. Traditionally, radiant ‘pancake’ brooders have been spaced uniformly, hanging near the feed lines and within 18-30 inches of the floor along the brooding section of a house. Low hanging, small brooders have problems providing an adequately-sized, comfortable zone.

Modern radiant brooders have automatic ignition and more uniform radiant heating than older models. Good radiant brooders have large radiant zones because they have large radiant elements, are fuel efficient, and can be hung five feet from the floor. They typically provide a 30-40 foot diameter heated zone.

Various industrial radiant heaters consisting of gas combusting within a long pipe are less common in poultry housing. Electrical lamps are seldom used in large-scale poultry facilities due to the high cost of electric energy compared to other fuels.

Location of heaters and thermostats

Heaters are placed uniformly throughout the large poultry facilities. Common practice is to place proportionally more heaters in the brood end of a partial-brood house. For example, if six heaters are required, four may be placed in the brood half. A forced-air heater is equipped with a small fan so that heated air is distributed into the room. For example, one manufacturer’s 250,000 BTUh heater unit has a ten-inch diameter fan with a 1,300 CFM capacity that can throw air approximately 50 feet.

To avoid hot spots, it is important that hot air be mixed with room air. Mixing in most poultry facilities is accomplished by appropriate placement of fresh air inlets. If inlet air mixing is not adequate, stratification occurs, with warmest air near the ceiling rather than at broiler level. Many houses utilize recirculation fans (see Figure 8.1), which are hung from the ceiling to blow air in a racetrack pattern around the house in a horizontal direction or slightly canted upward toward the ceiling. A less common destratification technique uses paddle (ceiling) fans (Figure 8.2). Either type of circulation fan is designed to activate when heaters are on. Interior mixing fans must not create cold drafts at bird level during brooding. Paddle fans should have forward and reverse speeds so that they can direct airflow upwards in winter to minimize windchill on small birds.

Figure 8.1 - Circulating fan

Figure 8.2 - Paddle fan

It is important that the temperature sensor from the heater controller(i.e., thermostat) measure a temperature that is indicative of conditions the birds are experiencing. Place the sensor near the center of the house cross-section that the heater supplies and as close to broiler level as practical. Do not place sensors directly in the path of hot air, in cold drafts, in the path of inlet jet, or near sidewalls. Improper sensor placement will cause inefficient heater operation.

Air tempering

There are various methods for tempering cold outside air before bringing it into a poultry house in an attempt to limit cold drafts and reduce annual heating fuel costs. The two most prevalent methods to temper air are various configurations of heat exchangers and geothermal earth tube systems. While, in principle, these systems have potential for significant energy savings, practical implementation in poultry facilities has been less successful. Major obstacles have been dust accumulation on heat exchangers, high installation costs, high airflow through earth tubes, and the complexity of controls associated with earth tube systems.