FAN COIL THERMOSTAT WITH FAN RAMPING

• US 20090032235A1
• Filed: 08/03/2007
• Published: 02/05/2009
• Est. Priority Date: 08/03/2007
• Status: Active Grant

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Sullivan, Daniel J., Geadelmann, Levi H., Wacker, Paul
• Granted Patent: US 9,074,784 B2
• Time in Patent Office: Days
• US Class Current: 165/247
• CPC Class Codes: F24F 1/0007 Indoor units, e.g. fan coil units self-contained units F24F1/02
• CPC Class Codes: F24F 1/0018 characterised by fans with secondary air induced by injector action of the primary air F24F1/01
• CPC Class Codes: F24F 11/30 for purposes related to the operation of the system, e.g. for safety or monitoring
• CPC Class Codes: F24F 11/46 Improving electric energy efficiency or saving
• CPC Class Codes: F24F 11/52 Indication arrangements, e.g. displays
• CPC Class Codes: F24F 11/523 for displaying temperature data
• CPC Class Codes: F24F 11/62 characterised by the type of control or by internal processing, e.g. using fuzzy logic, adaptive control or estimation of values
• CPC Class Codes: F24F 11/63 Electronic processing
• CPC Class Codes: F24F 11/65 for selecting an operating mode
• CPC Class Codes: F24F 11/76 by means responsive to temperature, e.g. bimetal springs
• CPC Class Codes: F24F 11/77 by controlling the speed of ventilators
• CPC Class Codes: F24F 11/83 by controlling the supply of heat-exchange fluids to heat-exchangers
• CPC Class Codes: F24F 11/84 using valves
• CPC Class Codes: F24F 2110/10 Temperature
• CPC Class Codes: F24F 2140/60 Energy consumption
• CPC Class Codes: G05B 19/048 Monitoring; Safety
• CPC Class Codes: G05B 2219/2614 HVAC, heating, ventillation, climate control
• CPC Class Codes: Y02B 30/70 Efficient control or regulation technologies, e.g. for control of refrigerant flow, motor or heating

Abstract

Fan coil thermostats can provide energy savings by, for example, operating a fan coil system more efficiently. Fan coil systems employing such a fan coil thermostat may be more energy efficient. A fan coil system may include a fan coil that is configured for fluid communication with a source of heated fluid and/or a source of cooled fluid, a valve that controls fluid flow through the fan coil and a fan that blows air across the fan coil. The fan coil thermostat may include a controller that implements a control algorithm that calculates an error percentage value relating to a temperature difference between the current temperature and the temperature set point. The error percentage value may include a proportional term related to the temperature difference and an integral term related to the temperature difference. The controller may regulate the fan speed in accordance with the calculated error percentage.

Claims

1. A fan coil thermostat adapted for use with a fan coil system comprising a fan, the fan coil thermostat comprising:

a user interface adapted to permit a user to enter a temperature set point;

a temperature sensor adapted to measure a current temperature; and

a controller that is adapted to implement a control algorithm that calculates an error value relating to a temperature difference between the current temperature and the temperature set point, the error value comprising a proportional term related to the temperature difference and an integral term related to the temperature difference;

wherein the controller regulates the fan speed in accordance with the calculated error value.

2. The fan coil thermostat of claim 1, wherein the fan has a low fan speed, a medium fan speed and a high fan speed.

3. The fan coil thermostat of claim 2, wherein the controller operates the fan at the low fan speed if the error value is below a first threshold.

4. The fan coil thermostat of claim 3, wherein the controller operates the fan at the medium fan speed if the error value is above the first threshold but below a second threshold.

5. The fan coil thermostat of claim 4 wherein the controller implements a degree of hysteresis when switching between the low fan speed and the medium fan speed.

6. The fan coil thermostat of claim 4, wherein the controller operates the fan at the high fan speed if the error value is above the second threshold.

7. The fan coil thermostat of claim 6, wherein the first threshold is set equal to about 40 percent and the second threshold is set equal to about 80 percent.

8. The fan coil thermostat of claim 1, wherein the user interface comprises one or more buttons.

9. The fan coil thermostat of claim 8, wherein the one or more buttons are selected from a temperature up button, a temperature down button, and one or more fan speed buttons.

10. The fan coil thermostat of claim 8, wherein the user interface further comprises an alphanumeric display.

11. A fan coil system, comprising:

a fan coil configured for fluid communication with a source of heated fluid and/or a source of cooled fluid;

a valve that controls fluid flow through the fan coil;

a fan that blows air across the fan coil, the fan having a plurality of fan speeds; and

a fan coil thermostat, the fan coil thermostat including a user interface and a controller implementing a control algorithm that calculates an error percentage value relating to a temperature difference between a current temperature and a temperature set point, the error percentage value comprising a proportional term related to the temperature difference and an integral term related to the temperature difference;

wherein the controller runs the fan at a fan speed selected from the plurality of fan speeds in accordance with the calculated error percentage.

12. The fan coil system of claim 11, wherein the plurality of fan speeds comprises a low fan speed, a medium fan speed and a high fan speed.

13. The fan coil system of claim 12, wherein the controller operates the fan at the low fan speed if the error percentage is below a first threshold, the medium fan speed if the error percentage is above the first threshold but below a second threshold, or the high fan speed if the error percentage is above the second threshold.

14. The fan coil system of claim 11, wherein the controller runs the fan at a speed selected from the plurality of fan speeds in accordance with the calculated error percentage when the valve is open so that fluid flows through the fan coil but does not run the fan when the valve is closed.

15. A method of operating a fan coil system comprising a fan coil accommodating fluid flow therethrough and a fan adapted to blow air across the fan coil, the fan coil system having a temperature set point, the fan having a plurality of fan speeds, the method comprising the steps of:

obtaining a current temperature value;

comparing the current temperature value with the temperature set point to determine a temperature difference;

calculating an error percentage value that includes a contribution made by integrating the temperature difference;

selecting a fan speed based on the error percentage value; and

operating the fan at the selected fan speed.

16. The method of claim 15, wherein calculating an error percentage value further comprises including a contribution that is proportional to the temperature difference.

17. The method of claim 15, wherein selecting a fan speed based on the error percentage value comprises selecting a low fan speed if the error percentage value is below a first threshold.

18. The method of claim 17, wherein selecting a fan speed based on the error percentage value comprises selecting a medium fan speed if the error percentage is above the first threshold but below a second threshold.

19. The method of claim 18, wherein selecting a fan speed based on the error percentage value comprises selecting a high fan speed if the error percentage is above the second threshold.

20. The method of claim 15, further comprising controlling fluid flow through the fan coil in accordance with the temperature set point.

21. The method of claim 20, wherein the controller runs the fan at a speed selected from the plurality of fan speeds in accordance with the error percentage when fluid flows through the fan coil but does not run the fan when fluid does not flow through the fan coil.