A method for regulating a discharge fan and a coil of a heating, ventilation, and air conditioning (HVAC) system includes maintaining a discharge fan capacity at a low fan capacity setting and varying a coil discharge air temperature between a low discharge air temperature limit and a high discharge air temperature limit. The method also includes, when the coil discharge air temperature reaches the low discharge air temperature limit, varying a fan speed of the variable speed discharge fan between a low fan speed setting and a high fan speed setting so as to maintain a space temperature at a space temperature setpoint set for a space, while maintaining the coil discharge air temperature at the low discharge air temperature limit.

Method for controlling an HVAC ventilation fan in heating or cooling mode and varying the fan-off time delay as a function of heat source or cool source operational time. Method for increasing heater ventilation fan speed from the low speed used for heating to the high speed used for cooling. Method for maintaining the heat pump reversing valve signal at the same position throughout the cool or heat source operational and extended variable fan-off time delay. Method for closing economizer dampers at the end of the cool or heat source operational time while continuing to operate the ventilation fan for an extended variable fan-off time delay.

In an HVAC system Polarity Splitting is used to provide for one or more backchannels from the furnace to the thermostat. Polarity Splitting is also used to allow a four-wire house cable to provide for three thermostat functions as well as furnace power to the thermostat while also providing for one or more backchannels. A serial datalink can be used to provide for a number of thermostat functions and a number of backchannels as well as to provide furnace power to the thermostat while using only three wires between the furnace and the thermostat. A Wi-Fi enabled furnace adapter can allow the use of a Wi-Fi thermostat while supplying only furnace power (two wires) to the thermostat. A Wi-Fi enabled furnace can use only a remote temperature sensor instead of a remote thermostat.

A wall fan includes a control circuit both controlling the wall fan and a temperature control unit comprising a heater, a cooler, or a Heating, Ventilating, and Air Conditioning (HVAC) system. The control system receives a desired temperature and compares the desired temperature to an outdoor temperature. When the outdoor temperature indicates that drawing outside air into indoor space will drive the indoor air temperature towards the desired temperature, the control system activates the wall fan, and de-energizes the heater, cooler, or HVAC system. When the outdoor temperature indicates that drawing outside air into indoor space will not drive the indoor air temperature towards the desired temperature, the control system de-energizes the wall fan, and energizes the heater, cooler, or HVAC system.

An Electronically-Controlled Register vent (ECRV) that can be easily installed by a homeowner or general handyman is disclosed. The ECRV can be used to convert a non-zoned HVAC system into a zoned system. The ECRV can also be used in connection with a conventional zoned HVAC system to provide additional control and additional zones not provided by the conventional zoned HVAC system. In one embodiment, the ECRV is configured have a size and form-factor that conforms to a standard manually-controlled register vent. In one embodiment, a zone thermostat is configured to provide thermostat information to the ECRV. In one embodiment, the zone thermostat communicates with a central monitoring system that coordinates operation of the heating and cooling zones.

In some examples, a damper device includes a frame member defining an opening and at least one bimetallic damper member connected to the frame member. The at least one bimetallic damper member includes bimetallic material and is configured to substantially straighten to form a substantial obstruction of airflow through the opening when at a first temperature and bend when at a second temperature to reduce the obstruction of airflow through the opening by the at least one bimetallic damper member, the second temperature being higher than the first temperature.

An information handling system includes a central processing unit, a temperature sensor to provide temperature information, a humidity sensor to provide humidity information, and an embedded controller. The embedded controller determines a current dew point temperature based on the temperature information and the humidity information. The embedded controller activates a condensation mitigation procedure if a difference between a current temperature and the current dew point temperature is less than a threshold value stored at a register at the embedded controller. The mitigation procedure is a software program executed by the information handling system.

A system and method including the ability of a building automation system controller to automatically determine which VAV boxes are physically associated with which air sources in a building or facility with multiple air sources by coordinating the individual or simultaneous manipulation of the fan speed of the air sources or the VAV damper positions, while obtaining data from networked sensors that measure VAV box airflow or duct pressure or the environmental conditions of a space being supplied with air from one or more VAV boxes.

A thermostat and related methods is provided for controlling an HVAC system having one or two separate transformers for supplying power to the HVAC system. The thermostat includes isolation circuitry housed within the thermostat to safely connect to the HVAC control wires and power wire(s) whether the HVAC system has one or two separate transformers without the use of removable jumpers or manual rewiring. The thermostat can include a processor that sends DC signals for turning on and turning off each of the HVAC functions, and an isolator adapted to electrically isolate the processor from the control wires and power wire(s). The isolator can include a transformer, such as a low cost Ethernet transformer. The circuitry can include one or more field effect transistors adapted and arranged so as to open or close an electrical connections between the control and power wires, thereby turning on or off the associated HVAC function. According to some embodiments, the Rc and Rh terminals are permanently connected using a fuse.

An air-conditioning apparatus includes an outside-air processing device including a total heat exchanger exchanging heat between outdoor air and return air, and blowing out the outdoor air from a supply-air outlet port into a room as supply air, an indoor unit including an indoor heat exchanger exchanging heat between the return air and refrigerant, and blowing out the return air from an indoor outlet port as indoor outlet air, a joining unit connecting the supply-air outlet port and the indoor outlet port to join the supply air and the indoor outlet air, an opening-closing unit arranged in the joining unit and opening and closing the joining unit, a supply-air temperature detecting unit detecting a supply-air temperature of the supply air, an indoor outlet temperature detecting unit detecting an indoor outlet temperature of the indoor outlet air, and a control unit controlling an operation of the opening-closing unit based on the supply-air temperature and the indoor outlet temperature.