Method and apparatus for controlling ventilation rates and indoor air quality in an HVAC system

• US 5,292,280 A
• Filed: 10/15/1992
• Issued: 03/08/1994
• Est. Priority Date: 02/14/1992
• Status: Expired due to Fees

• Current Assignee: Johnson Controls Technology Company (Johnson Controls International plc)
• Original Assignee: Johnson Service Company
• Inventors: Drees, Kirk H., Tellier, Mark W., Janu, George J.
• Primary Examiner(s): Joyce, Harold
• Application Number:
  US07/963,319
• Time in Patent Office: 509 Days
• Field of Search: 454/228, 454/229, 454/239, 454/370, 73/1 G, 73/31.01, 73/31.02, 73/23.2, 73/861.04
• US Class Current: 454/229
• CPC Class Codes: F24F 11/0001 for ventilation F24F11/30 takes precedence
• 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 11/74 for controlling air flow rate or air velocity
• CPC Class Codes: F24F 2110/50 Air quality properties
• CPC Class Codes: F24F 2110/52 of the outside air
• CPC Class Codes: F24F 2110/70 Carbon dioxide
• CPC Class Codes: F24F 7/08 with separate ducts for supplied and exhausted air with provisions for reversal of the input and output systems
• CPC Class Codes: Y02B 30/70 Efficient control or regulation technologies, e.g. for control of refrigerant flow, motor or heating

Abstract

An apparatus and method indirectly determines the amount of outside air introduced into the ventilation system of a structure to control the indoor air quality in the structure. Test gas concentrations, preferably carbon dioxide concentrations, are measured for return air, outside air and mixed (supply) air. The flow rate of mixed air is measured. The volume of outside air introduced into the system is determined through use of the test gas concentration measurements without directly measuring the volume or flow rate of outside air. Preferably, a single sensor is utilized to measure each of the trace gas concentrations in the return air, outside air and supply air, and the various measurements sequentially multiplexed to a controller. Moreover, for calibrating the apparatus, a return air sensor is calibrated to the outside air and a mixed air sensor is calibrated to the outside air or the return air to eliminate inaccuracy due to sensor drift.

Claims

1. An apparatus for determining the flow rate of supply fluid being utilized to circulate a mixed fluid of said supply fluid and a return fluid within a volume, said apparatus comprising:

sensor means for sensing a component of said supply fluid, a component of said return fluid, and a component of said mixed fluid; and

for providing a first output indicative of said supply fluid component, a second output indicative of said return fluid component, and for providing a third output indicative of said mixed fluid component;

a circulation device configured to introduce said mixed fluid into said volume; and

means for determining the flow rate of said supply fluid being utilized from the ratio of the difference between said second output and said third output to the difference between said second output and said first output.

2. An apparatus for determining the flow rate of outside air introduced into an HVAC system for circulating in a structure supply air, the apparatus comprising:

a supply air duct coupled to said structure to introduce the supply air comprising said outside air and a portion of return air into said structure;

a return air duct coupled to said structure to remove said return air from said structure;

at least one outside air sensor operatively coupled to said supply air duct and said return air duct for measuring a component of the outside air and producing an outside air signal indicative of said component, for measuring a component of said return air and producing a return air signal indicative of said component, and for measuring said component of supply air and producing a supply air signal indicative of said component;

means for effecting circulation of said supply air in said structure;

means coupled to said supply means for determining a ventilation air flow rate; and

control means for determining said flow rate of outside air from the product of said ventilation air flow rate and the ratio of the difference between said return air sensor means output and said supply air sensor means output to the difference between said return air sensor means output and said outside air sensor means output.

3. An apparatus as defined in claim 2 wherein said component comprises carbon dioxide.

4. A method for determining the flow rate of outside air introduced into a structure wherein supply air comprising outside air and return air is circulated in the structure, the method comprising the steps of:

removing return air from said structure;

recirculating at least a portion of said return air;

measuring a concentration of a component in said return air and producing a return air component concentration;

measuring a concentration of said component in said outside air and producing an outside air component concentration;

measuring a concentration of said component in said supply air and producing a supply air component concentration;

determining said flow rate of outside air from the ratio of the difference between said return air component concentration and said supply air component concentration to the difference between said return air component concentration and said outside air component concentration.

5. A method as defined in claim 4 including the further steps of measuring the rate of flow of said supply air into said system and producing a supply air flow rate and determining said flow rate of said outside air from the product of said supply air flow rate and said ratio.

6. A method as defined in claim 4 wherein said component is carbon dioxide.

7. A method for use in an apparatus for controlling the amount of outside air introduced into a system for circulating ventilation air in a structure, said apparatus comprising intake control means, recirculation control means, outside air sensor means, return air sensor means and supply air sensor means, said method for calibrating said supply air sensor means and said return air sensor means and comprising the steps of:

opening said intake control means;

closing said recirculation control means;

calibrating said supply air sensor means to said outside air sensor means;

closing said intake control means;

opening said recirculation control means; and

calibrating said return air sensor means to said supply air sensor means.