Data processing: generic control systems or specific application – Specific application – apparatus or process – Mechanical control system
Reexamination Certificate
1998-12-02
2002-05-07
Grant, William (Department: 2121)
Data processing: generic control systems or specific application
Specific application, apparatus or process
Mechanical control system
C700S204000, C700S300000, C379S102050
Reexamination Certificate
active
06385510
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field Of The Invention
This invention relates to the field of heating, ventilation and air conditioning (HVAC) monitoring devices and, more particularly, to an apparatus and method for continuously monitoring the performance of a residential or light commercial HVAC systems by comparing the performance of the monitored system to the performance of an ideal industry standard system of identical size and capacity. If the performance of the system being monitored deviates from the performance of the ideal system by more than a pre-set amount, then an operator may be alerted by various means including an alarm signal sent via a modem or other signal transmission means.
2. Description of the Related Art
Actual field surveys have shown that most HVAC systems tested are operating below the manufacturer's specifications. A small deviation from those specifications can mean a large increase in energy consumption. For example, a 10% undercharge in a system can mean the loss of almost two Seasonal Energy Efficiency Ratio (SEER) rating points, and a 23% undercharge can mean a 52% loss of efficiency.
To keep their units operating at peak efficiency, homeowners are urged by their system manufacturers and their contractors to schedule regular system maintenance. A standard maintenance call includes changing all filters, checking coolant levels and recharging, if necessary, cleaning coils and heat transfer surfaces, and making sure all air flow is unobstructed and free from dirt, foliage, etc.
There are a number of problems with regularly scheduled maintenance alone. If the coolant levels are correct, the filters are clean, and there are not other problems, the maintenance call may not have been necessary. This results in unnecessary expense and inconvenience for the homeowner. If system maintenance has just been performed, a leak may develop, or a component may malfunction shortly after the maintenance call. Unless the problem is severe enough to cause a complete system breakdown, the problem may not be noticeable to the homeowner for up to a year or until the next scheduled tune-up. This could result in ever increasing utility bills for the homeowner, and it could result in permanent damage to the HVAC system, severely shortening its life expectancy.
Performance monitors designed to address this problem use sensors to measure the difference between the HVAC system's return (intake) air stream temperature and the supply (exhaust) air stream temperature. This temperature difference, called “Delta T” (D/T or &Dgr;T), is the best indicator of system performance. For one type of performance monitor the contractor installs the sensors in the appropriate ducts and connects the monitor to the thermostat so that it can determine whether the HVAC system is set to heat, cool, or idle. The contractor then enters the high and low heat &Dgr;T limits into the monitor and then the high and low cool &Dgr;T limits. When the HVAC system exceeds any of these &Dgr;T limits an alarm is sounded. These alarms can take the form of a flashing light or sounding buzzer to alert the homeowner, or a phone connection with dialer apparatus can send a recorded voice message to the contractor.
The problem with this type of monitor is that it is dependent on input from the installer to determine the proper &Dgr;T range. The correct &Dgr;T range is determined by many factors and the installer would need to have a great deal of experience to gauge the system's potential performance correctly. This is especially true if the system is of a “mix & match” variety with components from different manufacturers. Other problems occur if the components are all from the same manufacturer but of different ages, or if a new system has been installed and joined to an older, undersized or oversized duct network.
Another type of performance monitor was developed to overcome some of these obstacles. This type of monitor directly measures the &Dgr;T on a newly tuned or installed HVAC system that has been running for several minutes or long enough to have reached operating temperatures. This measurement is then considered the indicator of 100% performance efficiency of the HVAC system. As the performance degrades from the preset level to an unacceptable amount, e.g. 60% of ideal, then the monitor would sound an alarm.
The problem with this type of monitor is that if the HVAC system was initially installed incorrectly, the subsequent monitoring and measurements become meaningless. An additional inherent problem with the previous designs, and the main problem with existing performance monitors, is that they do not take into account the dynamic nature of the &Dgr;T values. The &Dgr;T is a number that is constantly changing over time. It is dependent not only on the temperature of the incoming air, but it is even more dependent on the relative humidity of the incoming air. If, for example, an HVAC unit, having a given CFM/Tonnage rating for cooling, has a return air temperature of 75° F. and return air relative humidity of 25%, the operating &Dgr;T should be 24° F.; however, for the same sized unit and same temperature conditions, but a return air relative humidity of 80%, the operating &Dgr;T drops to only 11° F.
An additional inconvenience for the contractor or installer responding to an alert signal is not knowing what the problem could be until the HVAC unit in question or the actual performance monitor installed at the customer's house can be examined. This can lead to delays, inconvenience, and loss if the correct parts or supplies do not arrive at the job site.
Existing performance monitors, once tripped, must all be reset manually. Even if the contractor knows the problem is temporary and will clear up on its own, someone must physically reset the monitor every time an alarm is sent. Again, this causes inconvenience for the home owner and a loss for the contractor.
Current HVAC performance monitor designs require highly skilled and experience technicians to set up the monitors. Current monitors ignore the effects of humidity of &Dgr;T. Currently monitors can't compare the performance of the HVAC system they are monitoring to the system's nominal performance as published by the manufacturer. Current monitors do not relay specific information to the contractor's office to aid in diagnosing problems. Current monitors must be reset manually.
U.S. Pat. No. 4,611,470, issued Sep. 16, 1998 to Henrik S. Enstrom for “Method primarily for performance control at heat pumps or refrigerating installations and arrangement for carrying out the method,” describes a method of primarily testing and performance controlling heat pumps, refrigerating installations or corresponding systems, in which the system performance is measured and compared to electrical energy input. This methodology has the disadvantage that it requires the electric input to be measured directly to determine if the system is running efficiently.
U.S. Pat. No. 4,432,232, issued on Feb. 21, 1984 to Vanston R. Brantley, et al. for “Device and method for measuring the coefficient of performance of a heat pump,” describes a system for quick and accurate measurement of the coefficient of performance of an installed electrically powered heat pump including auxiliary resistance heaters.
Temperature sensitive resistors are placed in the return and supply air ducts to measure the temperature increase of the air across the refrigerant and resistive heating elements of the system. The voltages across the resistors are proportional to the respective duct temperatures. These voltages are applied to the inputs of a differential amplifier and a voltage-to-frequency converter is connected to the output of the amplifier to convert the voltage signal to a proportional frequency signal. An input power frequency signal is produced by a digital watt meter arranged to measure the power to the unit. A digital logic circuit ratios the temperature difference signal and the electric power input signal to produce a coefficient of performance of the s
Hoog Klaus D.
Knobloch, Jr. Nims P.
Fuierer Marianne
Grant William
Hartman Jr. Ronald D
Hultquist Steven J.
LandOfFree
HVAC remote monitoring system does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with HVAC remote monitoring system, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and HVAC remote monitoring system will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2856376