A Range of Devices for Precise Control and Simplified Installation
In the HVAC industry, an application-specific controller is a device that comes preprogrammed with a sequence of operations for the equipment it’s intended to control. This could be anything from a boiler or air handler to a rooftop unit or terminal unit.
These controllers come with “canned” sequences to eliminate the need for on-site programming, saving the installing contractor time on installation and commissioning. Once installed, the controller will control the piece of equipment automatically, with little adjustment required in the field.
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| Price’s Single-Duct Terminal Unit with the CO2/RH Thermostat |
For example, an application-specific controller for a single-duct terminal unit comes preprogrammed to control the position of the internal damper as well as any associated reheat coils or valves. The controller modulates the internal damper to its minimum and maximum heating and cooling positions or airflow values based on the internal logic of the controller.
When the set point of the connected thermostat is set below the room temperature, colder air is delivered from the single-duct unit into the space. The controller then targets its cooling minimum or maximum flow set points based on how far away the room temperature and room set point are from each other. The internal proportional/integral (PI) calculates this delta and delivers the correct amount of colder air by modulating the damper to prevent overcooling of the space.
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| When added to the Disio Display Thermostat (left), the Disio Airflow Kit (right) enables the control of flow-sensing VAV diffusers, pressure-independent terminal units and airflow-monitoring applications | |
When the set point of the connected thermostat is set above the room temperature, the controller targets its minimum heating or maximum flow set points to deliver warmer air into the space. If additional heat is required, an associated electric coil or hot water coil can be provided with the single-duct terminal unit.
The controller then sends a signal proportional to the room set point from the connected thermostat to operate the heater to meet the room set point. Once the set point is met, the electric heater will turn off or the hot water valve will close. This is accomplished with either a binary or analog signal; a binary signal results in an on/off-type signal, whereas an analog signal results in a modulating-type signal.
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| The Price Rooftop Unit Controller is designed to operate virtually any constant-volume or variable-volume rooftop unit |
Price offers a wide range of application-specific controllers for rooftop units, single-duct units, fan-powered terminal units, dual-duct units, and fan and blower coil units. These controllers are developed with preset sequences to accomplish control strategies for the project in question.
For more information about how to choose the best application-specific controller for your project, email us at controls@priceindustries.com or visit our website at www.priceindustries.com/controls.
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Brad Cole is Sales Manager for the Controls team at Price. He is based out of the Price Electronics facility in Winnipeg, MB. |
