Fan coil thermostat with fan ramping

• US 9,074,784 B2
• Filed: 08/03/2007
• Issued: 07/07/2015
• 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, Zhang, Camel, Gao, Jeff
• Primary Examiner(s): Bradford, Jonathan
• Application Number:
  US11/833,703
• Publication Number:
  US 20090032235A1
• Time in Patent Office: 2,895 Days
• Field of Search: 165/247, 165/300, 236/49.3
• US Class Current: 1/1
• 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 having a low fan speed, a medium fan speed and a high fan speed, the fan coil thermostat comprising:

a housing for housing;

a temperature sensor configured to measure a current temperature;

a user interface comprising;

a display;

an up button and a down button that permit a user to enter a temperature set point;

a fan button, that when pressed, steps through the low fan speed, the medium fan speed and the high fan speed for manual selection of a fan speed when in a manual fan speed mode;

a controller configured to implement a control algorithm that calculates a temperature difference T_ERR between the current temperature measured by the temperature sensor and the temperature set point, and further calculates a control error C_ERR, wherein the control error C_ERR comprises a proportional term

Kp*(T_ERR)

and an integral term

2. The fan coil thermostat of claim 1, wherein the control error C_ERR is scaled by the gain Kp to fall along a throttle range, wherein the throttle range is configured to represent a temperature difference at which the controller would instruct the fan to operate at a maximum speed.

3. A fan coil system, comprising:

a fan coil configured for fluid communication with a source of heated fluid 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 discrete fan speeds;

a fan coil thermostat, the fan coil thermostat comprising;

a user interface comprising;

a display;

an up button and a down button that permit a user to enter a temperature set point;

a fan button, that when pressed, steps through the plurality of discrete fan speeds for manual selection of a fan speed when in a manual fan speed mode; and

a controller implementing a control algorithm that calculates a temperature difference between a current temperature and a temperature set point and calculates an error value comprising a proportional term related to the temperature difference and a gain constant Kp, and an integral term related to the temperature difference, a time constant Ti and the gain constant Kp;

wherein the controller, in an automatic fan speed mode, runs the fan at a fan speed selected from the plurality of discrete fan speeds in accordance with the calculated error value, and the controller algorithm implements hysteresis based upon the error value when switching between the plurality of discrete fan speeds.

4. The fan coil system of claim 3, wherein the plurality of fan speeds comprises a low fan speed, a medium fan speed and a high fan speed.

5. The fan coil system of claim 4, wherein the controller operates the fan at the low fan speed if the error value is below a first threshold, the medium fan speed if the error value is above the first threshold but below a second threshold, or the high fan speed if the error value is above the second threshold, subject to the hysteresis of the control algorithm.

6. The fan coil system of claim 3, wherein the controller runs the fan at a speed selected from the plurality of discrete fan speeds in accordance with the calculated error value when the valve is open so that fluid flows through the fan coil, but does not run the fan when the valve is closed.

7. 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 T_ERR;

calculating a control error C_ERR comprising a proportional term related to the temperature difference T_ERR and a gain constant Kp, and an integral term related to the temperature difference T_ERR, a time constant Ti and the gain constant Kp;

in a manual fan speed mode, accepting an input via a single fan speed button to step through the plurality of fan speeds for manual selection of a manually selected fan speed, and operating the fan at the manually selected fan speed;

in an automatic fan speed mode, selecting a fan speed based at least in part on where the control error C_ERR falls relative to a first threshold and a second threshold, and operating the fan at the selected fan speed while providing a degree of hysteresis based on the control error C_ERR when switching between fan speeds.

8. The method of claim 7, wherein a low fan speed is selected when the control error C_ERR is below the first threshold.

9. The method of claim 8, wherein a medium fan speed is selected when the control error C_ERR is above the first threshold but below the second threshold.

10. The method of claim 9, wherein a high fan speed is selected when the control error C_ERR is above the second threshold.

11. The method of claim 7, further comprising controlling fluid flow through the fan coil in accordance with the temperature set point.

12. The method of claim 11, wherein the controller runs the fan at a speed selected from the plurality of fan speeds based at least in part on the control error C_ERR when fluid flows through the fan coil, but does not run the fan when fluid does not flow through the fan coil.