Abstract:
A differential temperature display system for balancing hydronic systems includes a first sensor for sensing a supply temperature and for outputting a first signal indicating the supply temperature. A second sensor is adapted for sensing a return temperature and for outputting a second signal indicating the return temperature. At least one integrated circuit is adapted for calculating a differential between the supply and return temperature. A single electronic display is adapted for displaying one of the supply temperature and the differential. A method of using the system is also disclosed.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates generally to temperature displays, and more particularly to differential temperature display systems for balancing hydronic systems. 
     Fluid flow in complex hydronic (heating or cooling) systems, like those typically used in large buildings or groups of buildings, needs to be balanced. The goal in balancing the hydronic system water flow is to have a desired temperature change across each heating or cooling unit (fan coil, radiator, heater, hydronic chiller, etc.), consistent with the lowest total pumping resistance. It is practically impossible to predict a balanced flow prior to actual operation in hydronic systems using parallel flow to units. 
     Hydronic systems use “balance valves,” which are valves installed at each of the heating and cooling units that can be partially closed to increase the resistance to flow through that unit. To balance a system, a technician will measure the temperature differential across each unit and adjust the balance valve, i.e., restrict fluid flow, until a desired temperature drop is achieved. 
     One problem is that the technician using a standard differential thermometer only monitors temperature differential, and he does not monitor supply fluid temperature to ensure that fluid flowing through the unit (supply fluid) is at full temperature. For example, there could be a low temperature drop across the unit because there was too little supply fluid flowing to the unit. Also, the temperature display on standard hand-held meters cannot be read from a substantial distance, which makes it more difficult for the technician to read the temperature while balancing the hydronic system. Thus, a simple, easy-to-use and easy-to-read differential thermometer that also prominently displays supply temperature is needed. 
     SUMMARY OF THE INVENTION 
     Briefly, one aspect of this invention is directed to a differential temperature display system for balancing hydronic systems. The display system comprises a first sensor for sensing a supply temperature and for outputting a first signal indicating the supply temperature. A second sensor is adapted for sensing a return temperature and for outputting a second signal indicating the return temperature. At least one integrated circuit is adapted for calculating a differential between the supply and return temperature. A single electronic display is adapted for displaying one of the supply temperature and the differential. The at least one integrated circuit is configured to automatically toggle the display between displaying the supply temperature and the differential. Also, the toggling occurs at a predetermined interval. 
     In another aspect, the display has a height of at least about 0.25 inches so as to be visible from a distance of at least about 3 feet. In this aspect, the display need not necessarily toggle automatically. 
     In still another aspect, a method of balancing a hydronic system uses the temperature display system and comprises placing the first sensor in contact with the supply line and placing the second sensor in contact with the return line. The method further includes adjusting a balance valve based on the displayed supply temperature and displayed differential. 
     Other features of the present invention will be in part apparent and in part pointed out hereinafter. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a front view of a differential temperature display system, 
         FIG. 2A  is a schematic of sensor circuits, 
         FIG. 2B  is a schematic of a digital volt meter and display driver, and 
         FIG. 2C  is a schematic of an alternate display circuit. 
     
    
    
     Corresponding reference characters indicate corresponding parts throughout the several views of the drawings. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to the drawings and in particular to  FIG. 1 , a differential temperature display system of an embodiment of the present invention comprises a display unit designated in its entirety by the reference numeral  31 . The unit  31  includes a single electronic display  33 . The display toggles between displaying a supply temperature and a differential between supply and return temperatures, as indicated by the indicator M 4  adjacent the label “SUPPLY” and the indicator M 3  adjacent the label “DIFFERENTIAL”. The display unit  1  of this embodiment is not designed for displaying data other than the supply temperature and the differential. 
     As shown in  FIGS. 2A-2C , the circuit has three main sections or circuits.  FIG. 2A  shows the sensor section. The temperatures are sensed by two temperature sensor chips that output the temperature linearly at 10 millivolts per degree. A supply sensor chip  35  outputs a signal “sig+” at a predetermined value (e.g., 10 millivolts per degree) indicating the supply temperature. The signal is received to the DVM/display section ( FIG. 2B ). A return sensor chip  36  outputs a signal “sig−” indicating the return temperature. The chips  35 ,  36  are connected to a terminal strip M 5  as shown in  FIG. 2A . 
       FIG. 2B  shows the digital volt meter/driver chip (DVM) (broadly, integrated circuit) and the display  33 . In one embodiment, the DVM is a JK-U4001 chip available from Jack Kennedy Metal Products &amp; Buildings, Inc., Taylorville, Ill. (hereinafter, JK numbers refer to products available from Jack Kennedy Metal Products). The display  33  includes two JK-M0003 LED numeric display elements. The display is at least 0.25 inches high so that the display is visible from a distance of at least 3 feet, and more suitably at least 0.75 inches so as to be visible from 15 feet. 
     Signals input to the DVM are displayed as though they were a voltage. Because the sensors  35 ,  36  output a voltage that is proportional to the temperature in degrees F., the display can be configured and arranged to display degrees F. with a conventional voltage divider (e.g., R 8  and R 10 ). The supply sensor output enters the DVM via pin  10 , and the return sensor output enters via pin  11 . 
       FIG. 2C  shows the third section, the toggling or alternating display. The display includes an integrated circuit or chip  40 , such as a model JK-U0003 chip, with output VOUT at pin  3 . The chip alternately sinks and sources to change pin  3  from a low to a high state at the desired display change rate. When pin  3  of chip  40  is at its low state, the supply indicator M 4  lights (the indicator is connected to the +5 V). Also, the return sensor is not functioning at the low state because pin  5  (VOUT) on terminal strip M 5  is also low (it is effectively ground on pins  4  and  5 ). Note that pin  5  of the strip M 5  is also connected to pin  3  of the chip  40 . At this time, the DVM is only receiving a signal from the supply sensor  35 , and thus the supply temperature is displayed. But when the pin  3  and chip  40  change to the high state, the supply indicator M 4  will turn off (because it now has the same potential, +5V, on both sides), the differential indicator M 3  will light and the return sensor receives power and starts working. 
     Referring to  FIGS. 2B and 2C , the signal from the return sensor  36  is connected to pin  11  of the DVM through another voltage divider (R 9  and R 11 ), similar to that of the supply sensor  35 . When the DVM receives the two signals, it algebraically sums them, and the differential is shown by the display  33 . 
     Other components are mostly conventional “setup” requirements for the chips, but with three exceptions. First, R 12  is a zero set point used to set the DVM to zero volts, which ensures the display  33  will show 0.0 when in the differential mode and when both sensors  35 ,  36  are at the same temperature. Secondly, R 4 , C 10 , and C 11  are an RC oscillator for the clock in the DVM. And third, R 5  and C 13  are the time constant components on the chip that determine the change rate between the supply temperature and the differential temperature. Varying the respective resistance and/or capacitance of the time constant components will vary the change rate. Note that the configuration can be modified to make the rate programmable by the user. The change rate is chosen to be long enough so that the technician has time to read the number, but so that he/she does not have to wait for an extended period to see the other number. The change rate is suitably between 1 and 8 seconds. The configuration can also be chosen so that the differential is displayed for a longer time period than the supply temperature, or vice versa. 
     The power supply is not shown, but is suitably 5 volts, and may be derived from the primary of either 115 or 230 volts AC. Thus, the display unit  1  can be wired directly to a heater&#39;s fan motor, water valve, etc., if desired. 
     As an example, the following chart shows the part numbers for the various components in  FIGS. 2A-2C : 
     
       
         
               
               
               
             
           
               
                   
                   
               
               
                   
                 Part 
                   
               
               
                   
                 Designation 
                 Part Number 
               
               
                   
                   
               
             
             
               
                   
                 C7 
                 JK-C0412 
               
               
                   
                 C8 
                 JK-C0513 
               
               
                   
                 C9 
                 JK-C0501 
               
               
                   
                 C10 
                 JK-C0517 
               
               
                   
                 C11 
                 JK-C0521 
               
               
                   
                 C12 
                 JK-C0501 
               
               
                   
                 C13 
                 JK-C0525 
               
               
                   
                 M3 
                 JK-M0002 
               
               
                   
                 M4 
                 JK-M0002 
               
               
                   
                 M5 
                 JK-M3003 
               
               
                   
                 R1 
                 JK-R0121 
               
               
                   
                 R2 
                 JK-R0105 
               
               
                   
                 R3 
                 JK-R0145 
               
               
                   
                 R4 
                 JK-R0113 
               
               
                   
                 R5 
                 JK-R0162 
               
               
                   
                 R6 
                 JK-R0060 
               
               
                   
                 R7 
                 JK-R0060 
               
               
                   
                 R8 
                 JK-R2314 
               
               
                   
                 R9 
                 JK-R2314 
               
               
                   
                 R10 
                 JK-R2122 
               
               
                   
                 R11 
                 JK-R2122 
               
               
                   
                 R12 
                 JK-M7001 
               
               
                   
                 R13 
                 JK-R0169 
               
               
                   
                   
               
             
          
         
       
     
     As should be apparent, the above configuration is merely one example of the invention, and other embodiments are contemplated within the scope of the invention. For example, other types of sensors, displays and chips may be used within the scope of the invention. 
     In one alternative embodiment, the display unit  1  displays the highest temperature encountered over a given time period by one or both of the supply and return sensors  35 ,  36 . The highest temperature can be displayed on the single display  33  shown in  FIG. 1 , or on separate displays. A “high temp.” feature would be helpful where the system is permanently installed, especially at a steam trap, where a technician can periodically check the high temperatures reached. For example if the return temperature reaches a high that is very near the supply temperature, then this would indicate a steam trap malfunction. This embodiment can include a reset button to reset the system after the high temperatures are checked/registered by the technician. 
     Example Methods 
     Hydronic systems use balance valves to increase the resistance to flow through particular units. In practice, nearly all the balance valves are partially closed. Typically, only the units at the most extreme flow resistance points would be wide open. 
     Generally, a technician will provide power to the display unit  1 , attach the sensors  35 ,  36  to the respective supply and return lines of a given unit (e.g., a heater), and read the supply and differential temperatures. If the differential is low (e.g., 2 degrees), the technician next sees the supply temperature (within a matter of seconds) and can thereby ensure that there is flow through the supply line before he tries to balance the flow. The technician can then adjust the appropriate valve while simultaneously viewing the supply temperature and differential. 
     In more detail, the difficulty encountered in balancing a hydronic system is two-fold. First, the balance valves that are at the lowest resistance points must be closed to force the water to the extremes of the system. Balancing can only be properly done if the water temperature drop across the heating unit is known. As an example, a typical hot water system is designed for a 20 degree drop across each heating unit. Heating units nearer to the pump or with less restrictive piping may have, for example, only a 2 degree drop when their balance valve is wide open. By watching the differential thermometer display unit  1 , a technician can close the valve until water flow is restricted such that a 20 degree drop is achieved in the water flowing through that unit. Next the technician goes to the heating unit that had the next lowest temperature drop and partially closes its balance valve. Note that in each case the act of closing the valve has the effect of both increasing pumping resistance and creating more flow everywhere else in the system, including in the units already balanced. Hence all of the heating units except the last will have to be repeatedly readjusted to maintain the desired drop. 
     The skillful technician will monitor the “last unit”, i.e., the heating unit that shows the highest drop with its balance valve wide open. When that unit gets sufficient water to get its drop down to the desired 20 degrees, the system is balanced. Closing valves thereafter will only increase pump pressure and thereby make the system less efficient. Note the “last unit” may not be the unit furthest from the pump, but may rather be quite close to it physically if that unit&#39;s piping or the unit itself has particularly high resistance. Therefore the term “last unit” in this case refers to the heating unit where the combined piping resistance and the unit resistance is the highest, and does not necessarily mean the unit that is the furthest physical distance from the pump. 
     Another use of the invention involves areas of excess heating capacity in the system. If a given area does not have enough heat, for example, one could open that area&#39;s heating unit valves slightly to create a 10 degree drop, rather than a 20 degree drop. This reduced drop causes a doubling of the output of that heater, and with careful examination of the other heating units outside the given area, one can decide what, if anything, needs to be done regarding the overall system balance. For example, it might be possible to simply rebalance the system by closing, at least partially, a valve in another area where there is excess heating capacity. 
     But there is another problem. When the technician first started closing the valve on the heating unit that had the least drop, he could have been making a mistake. Note that the unit physically nearest the pump may not have been the one that was really in the least resistance path. In fact, it could have been showing a low temperature drop because it was getting little or no water. A simple differential thermometer without a supply temperature indication would have led the technician astray. The display unit  1  of this invention will avoid this problem because the technician immediately and automatically sees the supply temperature. 
     Before a balance valve is adjusted, the technician must know that full temperature water is entering the heating unit. This is accomplished by using a display unit  1  of the invention. If higher water temperatures are found in another location, the low temperature heating unit should be located at that location, not where the supply temperature is low. Hence the alternating temperature display of both the fluid temperature and the temperature drop across a given heating unit is advantageous. 
     The embodiments described here are typical for use with a heating system using water. Embodiments can also be used for steam traps, cooling systems, and for heating/cooling systems that use steam, water-alcohol or water-glycol mixtures, fluorocarbon refrigerants, CO 2 , ammonia, or other media. The temperature sensors can sense the heat carrying medium within the system, or the heated (or cooled) environment itself, e.g., the outside air heated or cooled using the system. Also, embodiments of the invention are useful for all types of hydronic systems, but especially those that use parallel flow to units. Moreover, a display unit of the invention can be permanently installed at one heating unit or at all heating units in a system, and can be configured to interface with a computer, e.g., to send data to a remote location for off-site monitoring. 
     When introducing elements of the present invention or the preferred embodiment(s) thereof, the articles “a”, “an”, “the” and “said” are intended to mean that there are one or more of the elements. The terms “comprising”, “including” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. 
     As various changes could be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.