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Monitoring hot water usage in a gas water heater

  • US 9,213,998 B2
  • Filed: 01/26/2012
  • Issued: 12/15/2015
  • Est. Priority Date: 01/26/2012
  • Status: Active Grant
First Claim
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1. A method for determining the volume of hot water dispensed from a hydrocarbon-fueled hot water heater heated by a burner over a given timeframe, comprising the steps of:

  • measuring water heater inlet water temperature data during a given timeframe at a first predetermined sampling rate;

    measuring water heater outlet water temperature data during the given timeframe at the first predetermined sampling rate;

    measuring burner parameter data during the given timeframe at a predetermined sampling rate;

    determining the volume of fuel consumed by the burner during the given timeframe from the burner parameter data;

    processing the inlet water temperature data and the outlet water temperature data to calculate the average inlet water temperature and the average outlet water temperature for the given timeframe; and

    calculating the volume of hot water dispensed during the given timeframe based on the volume of fuel consumed by the burner during the given timeframe and the difference between the average inlet water temperature and the average outlet water temperature;

    wherein measuring burner parameter data comprises measuring temperature data during the given timeframe, and determining the volume of fuel consumed by the burner during the given timeframe comprises;

    obtaining a temperature versus time profile for the given timeframe using the measured temperature data;

    determining first and second derivatives of the temperature versus time profile;

    identifying one or more peaks in the second derivative of the temperature versus time profile;

    identifying one or more valleys in the first derivative of the temperature versus time profile following corresponding ones of the identified one or more peaks in the second derivative of the temperature versus time profile;

    identifying, for each of the identified one or more valleys in the first derivative of the temperature versus time profile, a first valley in the second derivative of the temperature versus time profile that precedes the corresponding valley in the first derivative of the temperature versus time profile;

    wherein the one or more peaks in the second derivative of the temperature versus time profile are used as turn on times of the burner and the one or more first valleys in the second derivative of the temperature versus time are used as turn off times of the burner.

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