Abstract: A boiler control utilizing a pressure sensor is provided that operates the system in the low fire mode if the load is light, and can be satisfied in that mode. If the low fire operation is inadequate to hold the load and the pressure drops, the boiler is then operated in a modulating mode which includes a high fire limit. This is accomplished by sensing the variation of a pressure responsive means and by providing a burner control system that monitors that pressure responsive means.

Abstract: A boiler control utilizing a pressure sensor is provided that operates the system in the low fire mode if the load is light and can be satisfied in that mode. If the low fire operation is inadequate to hold the load, and the pressure drops, the boiler is then operated in a modulating mode which includes a high fire limit.

Abstract: By measuring the power supplied to a compressor motor and by measuring four temperatures within a mechanical vapor-compression system, it is possible to develop a device for measuring and/or displaying the specific coefficient of performance of the mechanical vapor-compression system. The use of the temperatures and power supplied to the compressor motor can be used with information on motor losses and a typical temperature-enthalpy and a typical pressure-entropy diagram to allow substantially instantaneous computation of the actual specific coefficient of performance of a mechanical vapor-compression system as it operates. The measuring device can usually be installed totally external to a building in which the mechanical vapor-compression system is being used as a cooling system, or as a heat pump for heating and cooling.

Abstract: A creosote buildup detector utilizes a change in temperature between two sensors. The temperature between the two sensors changes as the creosote builds up. This change in temperature is established by providing an electric heater to heat one of the sensor supports. A temperature comparator senses the change in relative temperatures between the two sensors and annunciates when a sufficient creosote buildup has occurred to indicate that cleaning the chimney is necessary.

Abstract: A humidity responsive circuit is adapted to be connected to a thermostat to provide a humidity comfort offset to the thermostat. The humidity comfort offset circuit can be added to a retrofit item or could be added during the manufacture of an electronic thermostat which has a bridge in its input for measuring the temperature. The humidity comfort offset circuit have an output range with at least one humidity value being equal to the balance value of the bridge.

Abstract: An electromagnetic actuator utilizing a fluid pressure obtained from an electromagnetic pump, wherein according to the present invention, there is provided a responsive member displaceable in response to the pressure of a fluid forced into a second chamber from a first chamber. The responsive member displaceable as described can operate a valve member or the like coupled thereto in an on-off control or a proportional control with a large stroke in a reliable manner.

Abstract: A flame rod inserted in a flame created by the secondary air supplied to a burner is used to generate a flame signal voltage. This flame signal voltage fluctuates with the amount of secondary air available and with the fuel supplied. These fluctuations are relied upon by an integrated control system that utilizes a microprocessor or microcomputer to safely control an induced draft-type of furnace.

Abstract: The high fire and low fire switches normally operated by a damper in a fuel burner installation are verified by a switch test function. In the event that the switches are malfunctioning, the fuel burner sequence is extended to compensate, or the sequence is terminated and annunciated. The extension of the sequence is accomplished by a time sequencer alteration means that is part of a flame safeguard sequencer.

Abstract: A purge time hold circuit is provided in a flame safeguard sequencer to in turn provide a safe start check of a burner control system. If a flame is indicated during a prepurge period, the purge time hold means will reset to a zero status and the timer will hold until the signal clears itself. If the flame signal does not clear itself within a preset time, a safety shut down will be commanded.

Abstract: A flame safeguard sequencer incorporates an interlock checking means that verifies the proper status of the start or preignition interlocks in the burner system and the run interlocks of the burner system. In the event that an interlock opens during a period of time when it should not be open, the system can limit the operation of the sequence to a short time period (typically 30 seconds) to allow the interlock to reestablish a normal running state. If the correct state is reestablished, the system continues normal operation. If the correct state is not reestablished, the system is shut down on safety and a coded fault-hold indicator advises a serviceman of where to find the problem.

Abstract: A two-stage thermostat means for an add-on heat pump installation provides separated control of a furnace and a heat pump. The two-stage thermostat means utilizes a single pole, single throw switch means, and a single pole, double throw switch means to properly stage and control a heat pump and a fossil fueled furnace so that they do not overlap. The control of the temperature of the heated area is independent of any need to connect a circuit between the thermostat in the heated area and any type of thermostat at the heat pump itself.

Abstract: A hydronic type of heating system is operated by a burner control system that relies on measuring the boiler water temperature and comparing the temperature change with a rate of rise set into a burner control means to determine whether the boiler is being properly operated. This system allows for heating the boiler water to a sufficient temperature before circulating the water through the heat exchange means to thereby prevent condensation on the outside of the boiler heat exchanger to eliminate rusting.

Abstract: A voltage isolated gate drive circuit for insulated gate semiconductors utilizes a small, inexpensive pulse transformer to provide a rectangular drive wave form. The small pulse transformer can be operated with an input square wave form at relatively low frequencies, such as 60 hertz, and can be operated from a common power supply with the high voltage supplied to the output field effect transistor.

Abstract: A hot wire type of gas ignition system uses a negative temperature coefficient resistor-ignitor element that is deenergized after ignition has occurred. The ignition and safety monitoring of the circuit is accomplished by a second flame detector means, and the flame responsive circuit that has been disclosed in a flame rectification circuit.

Abstract: A humidity element circuit calibration arrangement utilizing a humidity responsive capacitive element is provided for. A single signal generator arrangement provides two opposite phases of the same voltage to energize the circuit thereby allowing for simple calibration by the adjustment of a single resistance element.

Abstract: A hydraulic actuator and valve are used for the control of fuel to a burner. The actuator is energized to open the valve through a manual start switch and a manual reset switch to prevent the manual start switch from being held in either accidentally or intentionally to overcome a safety monitoring control, such as a flame safeguard programmer.

Abstract: A safety circuit which connects a condition responsive circuit to a cyclic signal detecting circuit. In order to provide the cyclic signal detecting circuit with a continuous cyclic input, the condition responsive circuit and a cyclic redundancy checker is provided. The cyclic redundancy checker identifies a specific series of logic bits from the condition responsive circuit and responds favorably only to that series of logic bits. If any other series of logic bits occurs, the cyclic redundancy checker of the system ceases to function, thereby causing the cyclic signal detecting circuit to cease to function and it in turn opens a series contact to deenergize a critical load in a control system.

Abstract: Two condition sensors of two entirely different types are selected and monitored by a single condition sensor interface means. The interface means provides for selection of the sensor to be activated, or can be operated in a mode to repetitively sample both sensors. The sensors rely on a hybrid type device utilizing an integrated circuit, discrete components, and a mounting substrate. The sensors may be mounted on the substrate for temperature stability.

Abstract: A means for physically opening and closing electrical contacts to check their integrity for safety systems is provided. Contact means are cycled by the movement of two relatively moveable parts and the actual physical operation of the contacts is checked. The system is latched in its operable position by reversing the energization of an electromagnet which was used to unlatch or start the checking sequence.

Abstract: A molded plastic housing mounts a coil adjacent to a conductor to act as a current responsive pickup means. The mounting arrangement for the pickup coil uses no magnetic circuit and is adapted to self-center the structure on conductors of varying sizes without the need to sever and reconnect the current carrying conductor. The pickup means provide a substantially linear output voltage from the pickup coil versus the current being carried in the monitored conductor.