Operation of an HVAC System

An assembly comprising:

• an inlet port;
• an outlet port;
• a fluid path extending between the inlet port and the outlet port;
• a thermal energy exchanger situated in the fluid path;
• a flow sensor in the fluid path to measure a flow rate along the fluid path;
• a pair of temperature sensors including a first sensor to measure a first temperature at or near the inlet port and a second sensor to measure a second temperature at or near the outlet port;
• a valve member situated in the fluid path, the valve member selectively movable between a closed position which blocks the fluid path and an open position;
• an actuator secured relative to the assembly to move the valve member between the closed position and the open position;
• a controller secured relative to the assembly with a memory storing a lower threshold and an upper threshold, the controller configured to:
• read a first time series of signals from the pair of temperature sensors;
• determine a time series of temperature drops based on the first time series of signals;
• read a second time series of signals from the flow sensor;
• determine a time series of flow rates based on the second time series of signals;
• determine a third time series of rates of thermal energy exchange by the thermal energy exchanger as a function of the time series of temperature drops and the time series of flow rates;
• determine an averaged series of rates by determining a plurality of moving averages of the time series of rates of thermal energy exchange;
• determine a first bounded series of rates by replacing rates of the averaged series less than the lower threshold with rates that equal the lower threshold;
• determine a second bounded series of rates by replacing rates of the first bounded series greater than the upper threshold with rates that equal the upper threshold;
• determine a maximum rate of thermal energy exchange by applying a maximum filter to the second bounded series, the maximum filter returning the greatest rate of the second bounded series;
• read a set point signal indicative of a rate of exchange of thermal energy by the thermal energy exchanger;
• use the maximum rate to limit the set point signal;
• produce a limitation signal from the limited set point signal;
• and
• transmit the limitation signal to the actuator, the limitation signal causing the actuator to limit the position of the valve member.