Energy conservative control of terminal reheat heating, ventilating, and air conditioning (HVAC) systems

• US 4,253,153 A
• Filed: 06/28/1979
• Issued: 02/24/1981
• Est. Priority Date: 06/28/1979
• Status: Expired due to Term

• Current Assignee: United Technologies Corporation (Raytheon Technologies Corporation d/b/a RTX)
• Original Assignee: United Technologies Corporation (Raytheon Technologies Corporation d/b/a RTX)
• Inventors: Games, John E., Healey, David M., Bitterli, William W.
• Primary Examiner(s): Smith, Jerry
• Application Number:
  US06/052,701
• Time in Patent Office: 607 Days
• Field of Search: 364/118, 364/505, 318/609, 318/610, 165/12, 165/13, 165/16, 165/22, 165/26, 165/30, 236/1 B, 236/1 C, 236/DIG. 8
• US Class Current: 700/277
• 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 11/64 using pre-stored data
• CPC Class Codes: F24F 11/81 by controlling the air supply to heat-exchangers or bypass channels
• CPC Class Codes: F24F 11/84 using valves
• CPC Class Codes: F24F 2110/10 Temperature
• CPC Class Codes: F24F 2110/12 of the outside air
• CPC Class Codes: F24F 2110/20 Humidity
• CPC Class Codes: F24F 2110/22 of the outside air
• CPC Class Codes: F24F 2110/32 of the outside air
• CPC Class Codes: F24F 3/153 with subsequent heating, i.e. with the air, given the required humidity in the central station, passing a heating element to achieve the required temperature
• CPC Class Codes: G05D 23/1917 using digital means
• CPC Class Codes: G05D 23/20 with sensing elements having variation of electric or magnetic properties with change of temperature G05D23/13 takes precedence

Abstract

A terminal reheat HVAC system which regulates the temperature in a plurality of temperature controlled spaces by modulating the temperature of cool discharge air presented to each of the spaces from an air handler source, each space receiving the cool discharge air through an associated space distribution unit which includes heating apparatus supplied from a common heat source for reheating the cool air to provide temperature regulation within the space in response to a space temperature error signal from an associated space temperature control, is controlled by electronic processing means in combination with dedicated sensing and control apparatus which provide actuation of the air handler and common heat source only in response to actual sensed space temperatures outside of a temperature band established by heat and cool temperature reference signals stored in the electronic processing means, the electronic processing means further providing modulation of the cool discharge air temperature from the air handler, following actuation in response to an actual sensed space temperature higher than the cool temperature reference, in dependence on the temperature difference between the actual space temperature and the cool reference.

Claims

1. Apparatus for controlling a terminal reheat HVAC system which regulates the temperature in a plurality of temperature controlled spaces by reheating, as necessary with heating apparatus associated with each space, cool discharge air provided to each space from a common cooling source, each space heating apparatus being energized from a common energy source and each actuated, individually, in response to command signals from a related heating apparatus control within the associated space, the control apparatus comprising:

plurality of space temperature sensor means, one for each temperature controlled space, each providing an actual space temperature signal for the associated space;

cooling source temperature sensor means for providing an actual cool discharge air temperature signal;

source control means, including a common cooling source control means and a common energy source control means, each adapted for selectable control of the associated source for providing, when selected, exclusive actuation of the associated source in response to cooling source and energy source actuating gate signals presented thereto;

said cooling source control means being further responsive to said actual cool discharge air temperature signal and to a cool air reference discharge temperature signal presented thereto, for providing control of the cool discharge air temperature in response to the presence of said cooling source actuating gate signal in dependence on the difference temperature between said actual cool air discharge temperature signal and said cool air reference discharge temperature signal; and

electronic processing means, connected to said cooling source and to said heating source control means and responsive to said actual space temperature signals, said processing means having a memory for storing signals including a proportional gain signal, an integral gain signal, a heat set point temperature signal and a cool set point temperature signal, said heat and cool set point temperature signal defining the low tempeature limit and the high temperature limit respectively of a temperature drift band, said processing means comparing said actual space temperature signals to said temperature drift band limits for providing said energy source actuating signal in response to an actual space temperature signal below said heat set point temperature signal and for providing said cooling source actuating signal in response to an actual space temperature signal above said cool set point temperature signal, said processing means further providing in the presence of said cooling source actuating gate signal said cool air reference discharge signal at a value proportional to the time integral of the difference magnitude between said cool set point temperature signal and the highest value actual space temperature signal multiplied by said integral gain sigal, in summation with the product of said difference magnitude multiplied by said proportional gain signal.

2. The apparatus of claim 1, wherein said electronic processing means further comprises:

means for successively sampling periodically and registering in said memory, successively sampled values of said actual space temperature signals, said processing means providing in each sampling period said time integral of the product of said integral gain signal and said difference magnitude in each sampling period, integrated over the time interval of the related sampling period, said processing means accumulating a summation thereof in said memory, said processing means providing said cool discharge air reference temperature signal in each sampling period at a magnitude in dependence on the product of said difference magnitude related to said sampling period multiplied by said proportional gain signal in summation with said time integrals accumulated in said sampling.

3. The apparatus of claim 1, further comprising:

means responsive to operator control for providing to said memory of said processing means, parameter signals representative of said heat set point temperature signal, said cool set point temperature signal, said proportional gain signal, and said integral gain signal in response to selective operation thereof.