VARIABLE SPEED BLOWER CONTROL FOR HVAC SYSTEMS
FIG1 is a graph of cooling capacity versus temperature for heating, ventilation, and air conditioning (HVAC) systems
FIG1 is a graph 100 of cooling capacity versus temperature for heating, ventilation, and air conditioning (HVAC) systems. Axis 102 indicates temperature, for example in degrees Celsius or Fahrenheit, and axis 104 indicates cooling capacity, for example in tons, British Thermal Units per hour (BTU/h), or Watts (W). The cooling capacity of an HVAC system changes with respect to outdoor ambient temperature. At lower outdoor ambient temperatures, the load on a conditioned space is low, and the ability of the HVAC system to reject heat is higher as a result of the lower outdoor air temperature. As the outdoor ambient temperature increases, the load on the space increases and the effectiveness of the cooling equipment decreases. Load line 106 is an example a load over a range of outdoor ambient temperatures. The load is the amount of heat energy that would need to be removed from a space to maintain a desired temperature. The HVAC system 200 comprises one or more condensing units 203. In one embodiment, the condensing unit 203 comprises a compressor 204, a condenser 206, and a fan 208. The compressor 204 is coupled to the working-fluid conduit subsystem 202 that compresses the working fluid. The condensing unit 203 may be configured with a single-stage or multi-stage compressor 204. A single-stage compressor 204 is configured to operate at a constant speed to increase the pressure of the working fluid to keep the working fluid moving along the working-fluid conduit subsystem 202. A multi-stage compressor 204 comprises multiple compressors configured to operate at a constant speed to increase the pressure of the working fluid to keep the working fluid moving along the working-fluid conduit subsystem 202. In this configuration, one or more compressors can be turned on or off to adjust the cooling capacity of the HVAC system 200. An example of how a multi-stage compressor 204 operates to adjust the cooling capacity of an HVAC system was previously described in in FIG1. In some embodiments, a compressor 204 may be configured to operate at multiple speeds or as a variable speed compressor. For example, the compressor 204 may be configured to operate at multiple predetermined speeds.
graph
310
variable speed control instructions
306
interface
412
second fan speed
304
memory
400
graph
414
second temperature threshold value
302
processor
234
controller
402
versus temperature. Axis
308
variable speed control engine
406
Line
409
third fan speed
404
axis
312
temperature threshold values
410
first temperature threshold value
408
first fan speed
['1. A temperature control system, comprising: a sensor configured to measure air temperature; a variable speed blower; and a controller in signal communication with the sensor and the variable speed blower, wherein the controller is configured to: receive an air temperature measurement from the sensor; determine a temperature value based on the received air temperature measurement; compare the determined temperature value to a first threshold value and a second threshold value; and operate the variable speed blower based on the comparison of the determined temperature value to the first threshold value and the second threshold value, wherein operating the variable speed blower comprises setting the variable speed blower to: a first fan speed when the temperature value is below the first threshold value; a second fan speed when the temperature value is above the second threshold value, wherein the second fan speed is greater than the first fan speed; and a third fan speed that linearly correlates with temperature when the temperature value is between the first threshold and the second threshold, wherein: the third fan speed is a speed between the first fan speed and the second fan speed; and setting the variable speed blower to the third fan speed comprises determining the third fan speed based on the determined temperature value.']