Fluid heating system with combustion trim learning

A method for controlling a fluid heating system, comprising:

• receiving, at a first control loop, a sensor value indicative of a characteristic of the fluid heating system during a first operation;
• determining, at the first control loop, a first trim value based on the sensor value;
• determining, at a second control loop, a second trim value based on the first trim value and an operational parameter of the fluid heating system;
• and
• controlling a second operation of the fluid heating system based on the second trim value;
• wherein the first control loop comprises:
• adding the first trim value to a first buffer,
• determining whether the sensor value is within a defined deviation of an average value of the first buffer,
• in response to determining that the sensor value is within the defined deviation of the average value of the first buffer, determine an error between the sensor value and a reference sensor value, and
• adding the error to a second buffer.

A fluid heating system comprising:

• a controller configured to receive a sensor value from a sensor, the sensor value indicative of a characteristic of the fluid heating system during a first operation;
• wherein the controller is configured to:
• determine, at a first control loop, a first trim value based on the sensor value;
• determine, at a second control loop, a second trim value based on (i) a deviation of the first trim value from a reference trim value and (ii) an operational parameter of the fluid heating system;
• and
• control a second operation of the fluid heating system based on the second trim value.