HVAC Energy-Saving Controller for Residual Heat and Cooling Recovery
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Solution Overview
Problem
Conventional HVAC systems waste energy after the heating or cooling unit shuts off, as the fan stops blowing before residual energy can be harnessed, and thermostats often malfunction, causing continuous fan operation due to unknown signal states, leading to inefficiency and potential system failure.
Innovation Solution
A plug-and-play energy saving controller (ESC) is inserted between the thermostat and air handler, monitoring previous cycle durations to extend fan run time and manage thermostat signal states, ensuring the fan, compressor, or heater are properly turned off, even in malfunctioning scenarios, thereby harnessing residual energy and improving system efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the fan stops blowing immediately after the heating or cooling unit shuts off, then energy consumption is reduced, but residual energy in the heat exchanger is wasted
Solution Approach 1:
The controller extends the fan run time beyond the thermostat's shutdown signal to preemptively capture residual energy from the heat exchanger before it dissipates, delivering additional conditioned air to the space and reducing overall energy waste
Solution Approach 2:
The controller monitors previous cycle durations and heat exchanger temperature to dynamically adjust fan extension timing, using feedback from cycle history to optimize when to extend fan operation for maximum energy recovery
2Reliability
If the thermostat is shut off, then system operation stops, but the fan output command signal goes into a floating or unknown state causing continuous fan operation
Solution Approach 1:
The controller acts as an intermediary device inserted between the thermostat and air handler, mediating the signal transmission and converting unknown thermostat states into definitive on/off commands, thereby isolating the system from thermostat malfunctions
Solution Approach 2:
The controller converts the harmful floating state signal from a malfunctioning thermostat into a beneficial opportunity to extend fan run time and harvest residual energy, transforming a system error into an energy-saving feature
3Loss of energy
If the cooling unit runs continuously for 20-30 minutes, then cooling capacity is maintained, but the wet cooling coil cannot deliver additional cooling energy
Solution Approach 1:
The controller implements periodic shutdowns of the cooling unit after continuous operation for 20-30 minutes, allowing the wet cooling coil to evaporate and dry out, then restarting the unit to capture additional cooling energy during subsequent cycles
Solution Approach 2:
The controller temporarily discards cooling operation to allow the cooling coil to dry, then recovers additional cooling energy by extending fan run time after shutdown to harness evaporative cooling from the wet coil before it dries completely
4Reliability
If the heating unit runs continuously for 20-30 minutes, then heating capacity is maintained, but the furnace temperature reaches maximum and requires shutdown to extend life
Solution Approach 1:
The controller implements periodic shutdowns of the heating unit after continuous operation for 20-30 minutes, allowing the furnace to cool and extend its operational life, then restarting to maintain heating capacity through cyclical operation
Solution Approach 2:
The controller preemptively shuts down the heating unit before excessive temperature damage occurs, extending furnace life by preventing thermal stress accumulation during prolonged operation
Data Source
AI summary
A method for controlling an air handler including a fan and a heater or a compressor, the method including installing an energy saving controller (“ESC”) between a thermostat and the air handler, monitoring by the ESC of ON and OFF durations of the heater if the air handler is in a heating mode, or the compressor if the air handler is in cooling mode, in a first cycle and of ON duration of a second cycle, and determining the fan's first run time extension amount based on the ON and OFF durations of the first cycle and the ON duration of the second cycle.