Cascaded control apparatus for controlling unit ventilators
AssigneeLandis & Gyr Powers, Inc.
InventorsDarryl G. Hurmi, Paul R. Bontrager, Amy L. Ikenn
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Abstract
A controller having two cascaded PID control loops in the control of unit ventilators of the type which have a heating coil, a fan, and a damper for admitting outside air into a room in which the unit ventilator is located. The controller utilizes the sensed room temperature and a room temperature set point to generate a set point for the temperature of the air being discharged from the unit ventilator, and utilizes the discharge temperature set point and the sensed discharge temperature to control the damper position and the operation of the heating coils of the unit ventilator.
Claims91
Apparatus for controlling the operation of a heating and ventilating unit for controlling the temperature of an indoor area, the unit being of the type which contains at least a main heating means, a damper, and a fan for moving air from the unit to the enclosed area, each heating means being capable of being modulated to control the amount of heat produced as a function of the pressure level within a pneumatic control line, said apparatus comprising:
- processing means including memory means for storing instructions and data relating to the operation of said apparatus, said processing means being adapted to receive electrical signals that are indicative of temperature, said processing means generating electrical control signals for controlling at least one valve means operatively connected to the pneumatic control line;
- valve means being adapted to be operatively connected to a pneumatic supply line and to an exhaust and having said pneumatic control line, said valve means controlling the pressure in said pneumatic control line in response to said electrical valve control signals being applied to said valve means, said controlled pressure being within the range defined by the pressures that exist in said supply line and in said exhaust;
- means for generating an indoor area temperature set point, generating a signal indicative thereof and applying the same to said processing means;
- means for sensing the indoor area temperature, generating a signal indicative thereof and applying the same to said processing means;
- means for sensing the temperature of air discharging from the unit, generating a signal indicative thereof and applying the same to said processing means;
- said processing means operating during successive cycles to determine the difference between said area set point temperature and said measured area temperature and provide a discharge temperature set point as a function of such difference, said processing means determining the difference between said discharge temperature set point and the measured discharge temperature and generating a control signal as a function of said difference determination, which control signal is applied to said valve means for controlling the pressure in said control line.
Apparatus for controlling the operation of a heating and ventilating unit for controlling the temperature of an indoor area, the unit being of the type which contains at least a main heating means, a damper, and a fan for moving air from the unit to the enclosed area, each heating means being capable of being modulated to control the amount of heat produced, said apparatus comprising:
- processing means including memory means for storing instructions and data relating to the operation of said apparatus, said processing means being adapted to periodically process received electrical signals that are indicative of temperature, said processing means periodically generating electrical control signals for controlling at least one valve means;
- valve means associated with the heating means and being adapted to modulate the heating means in response to said electrical valve control signals being applied to said valve means;
- means for generating a signal indicative of an indoor area temperature set point and communicating the same to said processing means;
- means for sensing the indoor area temperature, generating a signal indicative thereof and communicating the same to said processing means;
- means for sensing the temperature of air discharging from the unit, generating a signal indicative thereof and communicating the same to said processing means;
- said processing means operating during successive periods to determine the difference between said area temperature set point and said measured area temperature and generate a discharge temperature set point as a function of such difference, said processing means determining the difference between said discharge temperature set point and the measured discharge temperature and generating a control signal as a function of the determined difference, which control signal is applied to said valve means for controlling the same;
- said processing means determining said discharge temperature set point by utilizing a multiple of difference determinations during successive cycles and applying the same to a first control loop which uses successive difference determinations to provide said discharge temperature set point as a function of a particular difference determination and any change in successive difference determinations.
Apparatus for controlling the operation of a heating and ventilating unit for controlling the temperature of an indoor area, the unit being of the type which contains at least a main heating means, a damper, and a fan for moving air from the unit to the enclosed area, each heating means being capable of being modulated to control the amount of heat produced, said apparatus comprising:
- processing means including memory means for storing instructions and data relating to the operation of said apparatus, said processing means being adapted to periodically process received electrical signals that are indicative of temperature, said processing means periodically generating electrical control signals for controlling at least one valve means;
- valve means associated with the heating means and being adapted to modulate the heating means in response to said electrical valve control signals being applied to said valve means;
- means for generating a signal indicative of an indoor area temperature set point and communicating the same to said processing means;
- means for sensing the indoor area temperature, generating a signal indicative thereof and communicating the same to said processing means;
- means for sensing the temperature of air discharging from the unit, generating a signal indicative thereof and communicating the same to said processing means;
- said processing means operating during successive periods to determine the difference between said area temperature set point and said measured area temperature and generate a discharge temperature set point as a function of such difference, said processing means determining the difference between said discharge temperature set point and the measured discharge temperature and generating a control signal as a function of the determined difference, which control signal is applied to said valve means for controlling the same;
- the heating and ventilating unit including an auxiliary heating means spaced from said main heating unit and having an associated valve means for controlling the same, said processing means generating an auxiliary control signal for controlling the associated valve means by determining during said successive cycles the difference between said room temperature set point and the measured discharge temperature and applying the same to a third control loop which uses successive difference determinations to provide said auxiliary control signal as a function of a particular difference determination and any change in successive difference determinations.
A method of controlling the operation of a heating and ventilating unit for controlling the temperature of an indoor area, the unit being of the type which contains at least a main heating means, a damper, and a fan for moving air from the unit to the enclosed area, each heating means being capable of being modulated to control the amount of heat produced, said method comprising:
- defining an indoor area temperature set point;
- sensing the indoor area temperature;
- sensing the temperature of air discharging from the unit;
- periodically determining the difference between said area temperature set point and said sensed area temperature and determining a discharge temperature set point as a function of such difference;
- determining the difference between said discharge temperature set point and the measured discharge temperature and generating a control signal that varies as a function of the determined difference, said discharge temperature set point being determined by utilizing a multiple of difference determinations during successive cycles and using successive difference determinations to provide said discharge temperature set point as a function of a particular difference determination and any change in successive difference determinations;
- and,
- modulating the heating means as a function of the control signal being applied thereto.
Dependencies are inferred from the claim text.