Energy-conserving thermostat and method

A fuel-conserving thermostat for controlling operation of a heating system that consumes fuel during a fuel-on interval and heats a defined space, thereby increasing a space temperature of said space;

• said space being thermally conductive to an ambient, whereby a heat flux occurs from said space to said ambient;
• said heating system comprising:
• heating means for providing heat during said fuel-on interval;
• delivery means for delivering said heat to said space during a delivery interval, whereby a heat flux occurs from said heating means to said space during said delivery interval;
• a heat exchanger;
• signal-receiving means, coupling said thermostat and said heating means, for:
• initiating one of said fuel-on intervals, which begins when said signal-receiving means receives a fuel-"1" signal from said thermostat;
• terminating said fuel-on interval and initiating a fuel-off interval in which said furnace does not consume fuel, said fuel-off interval beginning said signal-receiving means receives a fuel-"0" when signal-receiving means receives a fuel-"0" signal from said thermostat;
• initiating one of said delivery intervals, which begins when said signal-receiving means receives a delivery-"1" signal from said thermostat;
• and
• terminating said delivery interval and initiating a nondelivery interval in which said furnace does not deliver heat to said space, said nondelivery interval beginning when said signal-receiving means receives a delivery-"0" signal from said thermostat;
• said thermostat including:
• a clock providing clock signals;
• a temperature sensor having means for providing a space-temperature signal representative of said space temperature;
• means for providing a set-point-temperature signal representative of a set-point temperature;
• and
• means for providing said fuel-"0," fuel-"1," delivery-"0," and delivery-"1" signals;
• and said thermostat further comprising:
• means for providing a maximum-on signal representative of a maximum fuel-on interval, said maximum-on signal being provided by signal-generating means for providing a signal representative of how long said heat exchanger can operate during a fuel-on interval in a linear mode before its mode of operation becomes nonlinear, said signal-generating means comprising a probe means for measuring changes over time of a temperature representative of the temperature of the heat exchanger of the specific heating system installed at the location of the defined space;
• first burn-control means for causing a fuel-on interval having a duration of no longer than said maximum fuel-on interval;
• delivery-control means for causing heat to be delivered to said space during a delivery interval comprising said fuel-on interval and continuing after it ends until said heat exchanger falls to a temperature level such that said heat exchanger can operate in a linear mode during a next-following fuel-on interval;
• and
• second burn-control means for causing a nondelivery interval to follow said delivery interval for a duration at least as long as said heat exchanger takes to fall to said temperature level.

An apparatus for providing a signal representative of a maximum fuel-on interval for a furnace, said interval being how long a heat exchanger for said furnace can operate during a fuel-on interval in a linear mode before its mode of operation becomes nonlinear, said apparatus comprising:

• a temperature probe for providing probe signals representative of temperature of said heat exchanger;
• means for:
• receiving said probe signals;
• registering said probe signals at time intervals;
• and
• providing signals representative of temperature increments occuring over said time intervals;
• means for registering and storing a reference temperature increment signal representative of a reference start-up temperature increment over a start-up time interval occurring near the beginning of a delivery interval;
• and
• means for:
• comparing signals representative of temperature increments over successive said time intervals following said start-up time interval, said successive intervals occurring during a continuous fuel-on and delivery interval;
• determining a stop-time point when one of said temperature increments has a normalized value equal to or less than a normalized value of said reference start-up temperature increment multiplied by a predetermined constant c, where 0<c<1;
• and
• providing a probe-means output signal which is representative of the total time elapsing between the beginning of said delivery interval and said stop-time point.

An apparatus for providing a signal representative of a secondary-delivery interval, said interval being how long it takes after a fuel-off interval of a furnace begins before a heat exchanger of said furnace falls to a temperature level such that said heat exchanger can operate in a linear mode during a fuel-on interval following said fuel-off interval, said apparatus comprising:

• a temperature probe for providing probe signals representative of temperature of said heat exchanger;
• means for receiving and storing a reference probe signal which is a probe signal registered at a start-up time occurring when said fuel-off interval begins;
• means for receiving further probe signals which are probe signals registered at successive times following said start-up time, during a continuous delivery interval occurring thereafter;
• means for providing a first difference signal representative of a difference between said reference probe signal and a current one of said further probe signals;
• means for providing a second difference signal representative of a difference between said reference probe signal, on the one hand, and either said set-point-temperature signal or said space-temperature signal, on the other hand;
• means for providing a ratio signal representative of a ratio between said first and second difference signals;
• means for determining a stop-time point when said ratio signal becomes equal to or more than a predetermined constant c, where 0<c<1;
• and
• means for providing a probe-means output signal which is representative of the total time elapsing between the end of said fuel-on interval and said stop-time point.

A method for conserving energy utilization in a heating system for heating a defined space and thereby increasing a space temperature of said space;

• said space being thermally conductive to an ambient, whereby a heat flux occurs from said space to said ambient;
• said heating system
• consuming fuel, during a fuel-on interval, to provide heat;
• delivering said heat, during a delivery interval, to said space;
• having a heat exchanger;
• having signal-receiving means coupled to a thermostat, for:
• initiating one of said fuel-on intervals, which begins when said means receives a fuel-"1" signal from said thermostat;
• terminating said fuel-on interval and initiating a fuel-off interval in which said heating system does not consume fuel, said fuel-off interval beginning when said signal-receiving means receives a fuel-"0" signal from said thermostat;
• initiating one of said delivery intervals, which begins when said signal-receiving means receives a delivery-"1" signal;
• and
• terminating said delivery interval and initiating a nondelivery interval, during which said heating system does not deliver heat to said space, said nondelivery interval beginning when said signal-receiving means receives a delivery-"0" signal
• said method comprising:
• (1) providing said thermostat with a signal maximum-on representative of a maximum fuel-on interval, where said maximum fuel-on interval is how long said heat exchanger can operate during a fuel-on interval in a linear mode before its mode of operation becomes nonlinear;
• (2) sending from said thermostat to said signal-receiving means fuel-"1" signals of duration no longer than said maximum fuel-on interval;
• (3) when one of said fuel-"1" signals reaches a duration of said maximum fuel-on interval, sending a fuel-"0" signal from said thermostat to said signal-receiving means;
• and
• (4) sending from said thermostat to said signal-receiving means delivery-"1" signals while said thermostat sends said fuel-"1" signals.

A method for conserving energy utilization in a heating system for heating a defined space and thereby increasing a space temperature of said space;

• said space being thermally conductive to an ambient, whereby a heat flux occurs from said space to said ambient;
• said heating system
• consuming fuel, during a fuel-on interval, to provide heat;
• delivering said heat, during a delivery interval, to said space;
• having a heat exchanger;
• and
• having signal-receiving means coupled to a thermostat, for:
• initiating one of said fuel-on intervals, which begins when said means receives a fuel-"1" signal from said thermostat;
• terminating said fuel-on interval and initiating a fuel-off interval in which said heating system does not consume fuel, said fuel off-interval beginning when said signal-receiving means receives a fuel-"0" signal from said thermostat;
• initiating one of said delivery internals, which begins when said signal-receiving means receives a delivery-"1" signal;
• and
• terminating said delivery interval and initiating a mondelivery interval, during which said heating system does not deliver heat to said space, said nondelivery interval beginning when said signal-receiving means receives a delivery-"0" signal
• said method comprising:
• (1) measuring a maximum fuel-on interval, said interval being how long said heat exchanger can operate during a fuel-on interval in a linear mode before its mode of operation becomes nonlinear;
• (2) providing a maximum-on signal representative of the duration of said maximum fuel-on interval;
• (3) providing said maximum-on signal to said thermostat;
• (4) measuring a secondary-delivery interval, said interval being how long said heat exchanger takes to cool from its temperature at the end of a maximum fuel-on interval to a temperature level such that said heat exchanger can operate in a linear mode during a next-following fuel-on interval;
• (5) providing a secondary-delivery signal representative of the duration of said secondary-delivery interval;
• (6) providing said secondary-delivery signal to said thermostat;
• (7) sending from said thermostat to said signal-receiving means a fuel-"1" signal of duration no longer than said maximum fuel-on interval;
• (8) when one of said fuel-"1" signals reaches a duration of said maximum fuel-on interval, sending a fuel-"0" signal from said thermostat to said signal-receiving means;
• (9) sending from said thermostat to said signal-receiving means a delivery-"1" signal while said thermostat sends one of said fuel-"1" signals and continuing said delivery-"1" signal thereafter until said secondary-delivery interval ends;
• (10) preventing any fuel-"1" signal from being sent from said thermostat to said signal-receiving means before said secondary-delivery interval ends, thereby providing a fuel-off interval that continues at least until said secondary-delivery interval ends;
• and
• (11) sending from said thermostat to said signal-receiving means a delivery-"0" signal when said secondary-delivery interval ends, thereby terminating a delivery interval and initiating a nondelivery interval.