# US 6,296,193 B1 · Controller for operating a dual duct variable air volume terminal unit of an environmental control system

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- Number: US 6,296,193 B1
- Document ID: US6296193B1
- Status: Granted
- Kind: B1
- Application number: 09/409,960
- Filed: 1999-09-30
- Granted: 2001-10-02
- Earliest claimed: 1999-09-30
- Assignees: Johnson Controls Technology Company
- Inventors: Jonathan D. West; John E Seem
- Web page: https://patentgrep.com/patent/US6296193B1

## CPC

- G05D 23/1931: {to control the temperature of one space}
- F24F 3/044: Systems in which all treatment is given in the central station, i.e. all-air systems
- F24F 11/30: for purposes related to the operation of the system, e.g. for safety or monitoring
- F24F 11/62: characterised by the type of control or by internal processing, e.g. using fuzzy logic, adaptive control or estimation of values
- F24F 11/64: using pre-stored data
- F24F 11/76: by means responsive to temperature, e.g. bimetal springs
- F24F 11/84: using valves
- G05D 23/1393: {characterised by the use of electric means}
- F24F 2110/10: Temperature
- F24F 2140/00: Control inputs relating to system states
- G05D: SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
- F24F: AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING (removing dirt or fumes from areas where they are produced B08B15/00; vertical ducts for carrying away waste gases from buildings E04F17/02; tops for chimneys or ventilating shafts, terminals for flues F23L17/02)

## Abstract

The flow air from a hot air duct and a cold air duct into a zone of a building is controlled in based upon performing a thermal energy balance calculation for the zone. That calculation produces a heat transfer setpoint from which a hot air flow setpoint and a cold air flow setpoint are derived. The hot and cold air flow setpoints respectively control the flow of air through the hot and cold air ducts.

## Claims

### Claim 1

A method for controlling flow of fluid from a hot fluid conduit and a cold fluid conduit that environmentally controls a zone of a building, said method comprising:
performing a thermal energy balance calculation for the zone thereby producing a heat transfer setpoint Qsp, which indicates a desired heat transfer rate;
in response to the heat transfer setpoint, deriving a hot fluid flow setpoint and a cold fluid flow setpoint which respectively indicate desired flow rates of the hot fluid from the hot fluid conduit and of the cold fluid from the cold fluid conduit;
controlling flow of hot fluid from the hot fluid conduit in response to the hot fluid flow setpoint; and
controlling flow of cold fluid from the cold fluid conduit in response to the cold fluid flow setpoint.

### Claim 2 (depends on 1)

The method as recited in claim 1 wherein the step of performing a thermal energy balance for the zone comprises:
sensing a temperature within the zone to produce a sensed temperature value TZONE;
comparing the sensed temperature value to a temperature setpoint TSP, thereby producing a temperature error signal TE; and
deriving a heat transfer setpoint QSP in response to the temperature error signal.

### Claim 3 (depends on 1)

The method as recited in claim 1 wherein the hot fluid flow setpoint and the cold fluid flow setpoint are derived further in response to a first temperature of fluid in the hot fluid conduit and to a second temperature of fluid in the cold fluid conduit.

### Claim 4 (depends on 3)

The method as recited in claim 3 wherein the first temperature and the second temperature are estimated in response to a first flow rate of fluid through the hot fluid conduit, a second flow rate of fluid through the cold fluid conduit, and a third temperature of a mixture of fluids from the hot fluid conduit and the cold fluid conduit.

### Claim 5 (depends on 4)

The method as recited in claim 4 wherein the first temperature and the second temperature are estimated using covariance resetting, exponential forgetting, and conditional updating.

### Claim 6 (depends on 1)

The method as recited in claim 1 wherein controlling flow of hot fluid from the hot fluid conduit comprises:
sensing a flow of fluid through the hot fluid conduit to produce a hot fluid flow value;
comparing the hot fluid flow value to the hot fluid flow setpoint thereby producing a hot fluid flow error value; and
altering the flow of fluid through the hot fluid conduit in response to the hot fluid flow error value.

### Claim 7 (depends on 1)

The method as recited in claim 1 wherein controlling flow of cold fluid from the cold fluid conduit comprises:
sensing a flow of fluid through the cold fluid conduit to produce a cold fluid flow value;
comparing the cold fluid flow value to the cold fluid flow setpoint thereby producing a cold fluid flow error value; and
altering the flow of fluid through the cold fluid conduit in response to the cold fluid flow error value.

### Claim 8

A method for controlling flow air from a terminal unit which receives air from a hot air duct and a cold air duct and which has an outlet from which air is supplied to a zone of a building, said method comprising:
sensing a temperature within the zone to produce a sensed temperature value TZONE;
comparing the sensed temperature value to a temperature setpoint Tsp thereby producing a temperature error signal TE;
deriving a heat transfer setpoint QSP in response to the temperature error signal;
determining a first temperature of air received from the hot air duct and a second temperature of air received from the cold air duct;
deriving a hot air flow setpoint and a cold air flow setpoint in response to the heat transfer setpoint, the first temperature, and the second temperature;
controlling flow of air from the hot air duct in response to the hot air flow setpoint; and
controlling flow of air from the cold air duct in response to the cold air flow setpoint.

### Claim 9 (depends on 8)

The method as recited in claim 8 wherein the first temperature and the second temperature are estimated in response to a first flow rate of air from the hot air duct, a second flow rate of air from the cold air duct, and a third temperature of air flowing through the outlet.

### Claim 10 (depends on 9)

The method as recited in claim 9 wherein the first temperature and the second temperature are estimated using covariance resetting, exponential forgetting, and conditional updating.

### Claim 11 (depends on 8)

The method as recited in claim 8 wherein controlling flow of air from the hot air duct comprises:
sensing a flow of air from the hot air duct to produce a hot air flow value;
comparing the hot air flow value to the hot air flow setpoint and producing a hot air flow error value; and
altering the flow of air from the hot air duct in response to the hot air flow error value.

### Claim 12 (depends on 8)

The method as recited in claim 8 wherein controlling flow of air from the cold air duct comprises:
sensing a flow of air from the cold air duct to produce a cold air flow value;
comparing the cold air flow value to the cold air flow setpoint and producing a cold air flow error value; and
altering the flow of air from the cold air duct in response to the cold air flow error value.