Model based economizer control of an air handling unit
AssigneeJohnson Controls Technology Company
InventorJohn E. Seem
Life of this patent
Estimating the term…
Abstract
A strategy for controlling an air side economizer of an HVAC system uses a model of the airflow through the system to estimate the load in two modes when minimum and maximum amounts of outdoor air are being introduced into the building. Transitions between minimum outdoor air and maximum outdoor air usage occur based on those estimated loads, which in a preferred embodiment are cooling loads. The second embodiment of this economizer control strategy uses the model and a one-dimensional optimization routine to determine the fraction of outdoor air that minimizes the load on the HVAC system.
Claims20
A method for operating a system which regulates an amount of outdoor air that is introduced into a building and operates a mechanical temperature control device that varies temperature in the building, said method comprising:
- calculating a first load on the mechanical temperature control device assuming that outdoor air flows into the building at a first flow rate;
- calculating a second load on the mechanical temperature control device assuming that outdoor air flows into the building at a second flow rate;
- performing a comparison of the first load and the second load;
- and
- varying the flow of outdoor air into the building in response to the comparison.
A method for operating a system which regulates a position of a damper through which outdoor air is introduced into the building and operates a mechanical temperature control device that varies temperature in the building, said method comprising:
- calculating a first load on the mechanical temperature control device assuming that the damper is in a first position;
- calculating a second load on the mechanical temperature control device assuming that the damper is in a second position;
- and
- adjusting the position of the damper in response to the first load and the second load.
A method for operating a finite state machine controller which operates a flow control device which regulates an amount of outdoor air that is introduced into the building and operates a mechanical temperature control device that varies temperature in the building, said method comprising:
- operating in a first state in which the flow control device is operated to introduce outdoor air into the building at a first flow rate;
- operating in a second state in which the flow control device is operated to introduce outdoor air into the building at a second flow rate;
- calculating a first load that would be exerted on the mechanical temperature control device in the first state;
- calculating a second load that would be exerted on the mechanical temperature control device in the second state;
- and
- making transitions between the first state and the second state in response to the first load and the second load.
Dependencies are inferred from the claim text.