Chapter 11 - Introduction

As poultry production systems become increasingly automated, monitoring systems are being integrated with control systems to provide growers with real-time and historical information on how various systems such as environment control, feeding, egg handling, and water are performing. The use of buildings that are 400 or more feet in length and which may be from hundreds of feet to miles away from the farm office presents a number of technical problems to the farm manager who wants to carefully monitor and control the conditions in poultry houses.

The evolution of electromechanical and electronic equipment used in poultry facilities has been continuously progressing. The reason is simply economics. Monitoring and control systems greatly reduce labor costs. They can provide improved environmental conditions and air quality, improved broiler performance, and opportunities for improved management. For example, it is sometimes desirable to provide a feeding in the middle of the night. Lights and feeders can be scheduled by the control system to introduce this special event. Some ventilation control systems provide hourly house temperature targets. This allows for the house to be cooled at night to maintain daily house temperature targets during hot weather. Automatic control systems, if properly used, make flock management more consistent, since humans tend to forget.

An electronic device is an environmental controller with one or more temperature sensors and one or more relays that are used to activate equipment. An example of an electromechanical device is a conventional thermostat, which is a temperature-activated relay used to turn on or off equipment such as heaters or fans as air temperature varies. Either of these example devices can be used to operate a fan. The type of control system used will also affect the troubleshooting options and approaches when problems arise.

Table 11.1 lists the operation and use of electromechanical and electronic components which are typically found in poultry production facilities. The common feature of these items is their ability to turn a piece of equipment (fan, heater, feed auger) on or off according to some set point or schedule based on temperature, time, feed level, etc.

Table 11.1 - Operation and use of electronic and electromechanical devices

The most common control device used to activate or deactivate electrical equipment is a relay. A relay is a remotely actuated switch, and it is usually switched on/off by switching power to the relay coil. The coil, when activated, sets up an electromagnetic field that pulls the switch closed. A relay’s switch points are usually called ‘contacts’ or ‘poles,’ and it is quite common to provide more than one set of contacts. For example, to switch 240 VAC circuits, a 2-contact relay (commonly called a double-pole relay) is necessary.

A thermostat can be thought of as a relay whose contacts are switched automatically in response to air temperature. A mechanical timer is a relay which is switched according to a pre-set timing sequence. The term ‘electronic controller’ can be used to describe anything from a self-contained solid-state thermostat which contains no moving parts and a remote temperature sensor to an intelligent computer-based controller which controls and monitors many parameters with control and monitoring strategies which can be changed at will be the operator

Most controllers are not built to directly switch large electrical loads such as fan or feed auger motors. Instead, they typically have a control relay which is activated by the controller. The control relay is connected to coil of a so-called power relay which switches the larger load of the actual equipment on or off. At least one per ventilation stage is needed. Several companies manufacture relay boxes consisting of several power relays pre-wired with auto/on/off switches. The on position provides a manual override of the controller, the off position is used to disconnect, and the auto position is used during normal operation.

For environment control systems utilizing centralized controllers, attention should be paid to how the controller interacts with the building’s air inlet system. In many older facilities there is no air inlet control except perhaps one or more hand cranks to adjust inlet (or curtain) width. New facilities typically use air inlet controllers that work to maintain a constant static pressure difference between inside and outside. This type of system is easy to use with virtually any environmental control system because the air inlet controller automatically adjusts inlets as the number of fans operating changes.

Some environmental controllers have a feature to adjust air inlets or curtains based on inside temperature. This may be beneficial for buildings using curtains as part of a ventilation strategy. Another method is to connect an independent curtain controller to one stage of an environmental controller, so that the inlets are only controlled during certain ventilation stages.

More recently, tunnel ventilation has become popular as a means to alleviate heat stress in very hot weather. By placing all fans at one end of the building and admitting fresh air at the other end, relatively high air velocity provides additional cooling for broilers. For totally enclosed buildings, tunnel ventilation presents a difficulty for the operator to decide when to shut air inlets and open tunnel curtains at the end opposite the fans. Some environment control systems are available to automate this feature.