The base heat formula calculates the starting percentage of input heat available for useful work, before accounting for losses due to excess air and combustion air preheat. It is determined by subtracting the exhaust temperature loss from a model-specific base value (95%). This step isolates the effect of exhaust gas temperature on available heat, prior to applying air corrections.

\begin{equation}\label{eq:energy-input-exhaust-gas-base-heat-cpp} BH = 95 - 0.025 \cdot T_{exh}\end{equation}

Symbols

\(BH\)	Base heat percentage \([\unit{ \percent}]\)
\(95\)	Base available heat at zero exhaust temperature \([\unit{ \percent}]\)
\(0.025\)	Exhaust temperature loss coefficient \([\unit{ \percent\per\degreeFahrenheit}]\)
\(T_{exh}\)	Exhaust gas temperature \([\unit{ \degreeFahrenheit}]\)