The present invention pertains to equipment for providing temperature conditioning of a space and, more particularly to such equipment that includes both heating and cooling modes of operation.
The heating, ventilation and air conditioning (HVAC) equipment used to regulate, or condition, the temperature of a room or other space typically includes a separate heating source such as a furnace and a cooling source such as an air conditioner. Separate controls for each type of equipment are usually provided to control turning the respective equipment on or off and setting each equipment""s operating parameters. A consolidated control interface may be provided (e.g., a wall thermostat unit) but usually requires manual switching between the two types of equipment as well as separately setting the operating parameters for each equipment type.
Other HVAC equipment is used in some environments which include both a heating mode and a cooling mode in a single piece of equipment. In such a piece of equipment, either the heating elements or the cooling elements are selected for operation depending on whether the conditioned space is hotter or colder than desired. The control interface for this type of HVAC equipment is just as confusing and cumbersome as that for the separate HVAC equipment described above. In particular, a room occupant typically is required to manually switch the operating modes between heating and cooling as desired. Furthermore, for each of the different operating modes, the occupant must also set thermostat controls to set the operating parameters of the equipment.
Such an interface to control HVAC equipment is very cumbersome, especially during periods of moderate indoor or outdoor temperature variation in which the HVAC equipment would need to be switched between modes and adjusted often to consistently regulate the conditioned space. For example, such periods of temperature variations could include: seasonal transitional periods where cooling is desired in the day and heating in the evenings; the passing of a cold front during relatively warm periods; and where operation of devices (e.g., ovens, stoves, etc.) drive the room temperature out of a comfortable zone.
There is an unmet need, therefore, for a simple control interface to implement heat/cool mode switching and temperature regulation in HVAC equipment that can regulate room temperature by selecting one of a heating mode or cooling mode of operation.
The present invention meets these, and other, needs by combining hardware and software to provide HVAC equipment with a mode switching algorithm, a heating algorithm, and a cooling algorithm that requires a room occupant to merely enter a setpoint temperature to control equipment that conditions a physical space. In particular, one aspect of the present invention relates to a method for controlling equipment having a heating mode of operation and a cooling mode of operation to condition a physical space. According to this aspect, a setpoint temperature is obtained for the space, the temperature for the space is sensed and the length of time since the mode of the equipment last changed is maintained. The equipment is switched to a cooling mode if the sensed temperature remains above a first threshold temperature for at least a first period of time and the mode of the equipment has not changed within a second period of time. Alternatively, the equipment is switched to a heating mode if the sensed temperature remains below a second threshold temperature for at least a first period of time and the equipment has not changed modes of operation within a second period of time.
Another aspect of the present invention relates to a device for controlling equipment having a heating mode of operation and a cooling mode of operation to condition a physical space. According to this aspect of the invention, the device includes a microcontroller, inputs for receiving a setpoint temperature and the sensed temperature of the space, and a timer that is indicative of the length of time since the equipment last changed operating modes. The device also includes a comparator that compares the sensed temperature with a first threshold value if the equipment is the heating mode or compares the sensed temperature with a second threshold value if the equipment is in the cooling mode. Device outputs provide respective signals to the equipment to switch modes of operation depending on certain criteria. If the sensed temperature has remained above the first threshold value for at least a first time period and the timer indicates that an appropriate length of time has transpired since the last mode switch-over, then the equipment is signaled to switch from the heating mode to the cooling mode. If the sensed temperature has remained below the second threshold value for at least the first time period and the timer indicates that an appropriate length of time has transpired since the last mode switch-over, then the equipment is signaled to switch from the cooling mode to the heating mode.
A still further aspect of the present invention relates to a method for maintaining a room""s temperature about a setpoint utilizing equipment having a cooling mode and a heating mode of operation. According to this aspect of the invention, the room temperature is sensed and a value is maintained indicative of when the equipment last changed operating modes. If the equipment is in the heating mode, then the equipment is switched to the cooling mode if (a) the room temperature remains above a first value for a sufficient length of time and (b) there has been an appropriately long period of time since the equipment last changed operating modes. If the equipment is in the cooling mode, then the equipment is switched to the heating mode if (a) the room temperature remains below a second value for a sufficient length of time and (b) there has been an appropriately long period of time since the equipment last changed operating modes.
Still other objects and advantages of the present invention will become readily apparent from the following detailed description, simply by way of illustration of the best mode contemplated of carrying out the invention. As will be realized, the invention is capable of other and different embodiments and its several details are capable of modifications in various obvious respects, all without departing from the invention. Accordingly, the drawings and description are to be regarded as illustrative in nature, and not as restrictive.