Systems and methods for controlling a heat transfer system

A flame sensing unit comprising:

• a flame sense probe;
• a flame sensing device comprising:
• a power regulating device electrically coupled to the flame sense probe and configured to:
• generate a regulated voltage from an input voltage received from a power source;
• and
• output the regulated voltage to the flame sense probe as a dynamic signal having a substantially square or sinusoidal wave form at a frequency higher than 60 Hz and up to approximately 500 Hz;
• a flame current detector electrically coupled to the power regulating device and the flame sense probe, the flame current detector being configured to:
• detect a flame current from the flame sense probe;
• and
• generate an output voltage corresponding to the flame current;
• and
• a first level detector electrically coupled to the flame current detector and configured to generate a flame strength output signal based on the output voltage;
• a second level detector electrically coupled to the flame current detector and configured to generate a flame presence output signal based on a comparison of the output voltage to a pre-determined presence threshold;
• and
• a processor electrically coupled to the first level detector and the second level detector and configured to:
• concurrently receive the flame strength output signal and the flame presence output signal;
• and
• generate an output indicative of a strength and either a presence or an absence of a flame located proximate the flame sense probe,
• wherein the second level detector has a different sensitivity characteristic than the first level detector so that the flame presence output signal is different from the flame strength output signal.

A method of sensing a flame comprising:

• generating, by a power regulating device, a regulated voltage from an input voltage received from a power source, wherein the power regulating device is configured to output the regulated voltage as a dynamic signal having a substantially square or sinusoidal wave form at a frequency higher than 60 Hz and up to approximately 500 Hz;
• providing the regulated voltage to a flame current detector;
• providing the regulated voltage to a flame sense probe such that a flame current along a flame can be measured, the flame being proximate the flame sense probe;
• detecting, by the flame current detector, a flame current from the flame sense probe;
• generating, by the flame current detector, an output voltage corresponding to the flame current;
• generating, by a first level detector, a flame strength output signal based on the output voltage, wherein the flame strength output signal is indicative of a strength of the flame;
• generating, by a second level detector, a flame presence output signal based on comparison of the output voltage to a pre-determined presence threshold, wherein the flame presence output signal is indicative of a presence or an absence of the flame at the flame sense probe;
• receiving, by a processor, the flame strength output signal and the flame presence output signal, wherein the flame strength output signal and the flame presence output signal are concurrently received by the processor;
• and
• generating, by the processor, an output indicative of a strength and either a presence or an absence of a flame located proximate the flame sense probe,
• wherein the second level detector has a different sensitivity characteristic than the first level detector so that the flame presence output signal is different from the flame strength output signal.