EP0813671A4 - Thermostat et procede de gestion des charges maximales - Google Patents

Thermostat et procede de gestion des charges maximales

Info

Publication number
EP0813671A4
EP0813671A4 EP95913497A EP95913497A EP0813671A4 EP 0813671 A4 EP0813671 A4 EP 0813671A4 EP 95913497 A EP95913497 A EP 95913497A EP 95913497 A EP95913497 A EP 95913497A EP 0813671 A4 EP0813671 A4 EP 0813671A4
Authority
EP
European Patent Office
Prior art keywords
fuel
time
thermostat
load
predetermined
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP95913497A
Other languages
German (de)
English (en)
Other versions
EP0813671A1 (fr
Inventor
Donald E Jefferson
Arnold David Berkeley
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Individual
Original Assignee
Individual
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Individual filed Critical Individual
Publication of EP0813671A1 publication Critical patent/EP0813671A1/fr
Publication of EP0813671A4 publication Critical patent/EP0813671A4/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
    • F24F11/00—Control or safety arrangements
    • F24F11/30—Control or safety arrangements for purposes related to the operation of the system, e.g. for safety or monitoring
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
    • F24F11/00—Control or safety arrangements
    • F24F11/62—Control or safety arrangements characterised by the type of control or by internal processing, e.g. using fuzzy logic, adaptive control or estimation of values
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
    • F24F11/00—Control or safety arrangements
    • F24F11/70—Control systems characterised by their outputs; Constructional details thereof
    • F24F11/72—Control systems characterised by their outputs; Constructional details thereof for controlling the supply of treated air, e.g. its pressure
    • F24F11/74—Control systems characterised by their outputs; Constructional details thereof for controlling the supply of treated air, e.g. its pressure for controlling air flow rate or air velocity
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
    • F24F11/00—Control or safety arrangements
    • F24F11/50—Control or safety arrangements characterised by user interfaces or communication
    • F24F11/61—Control or safety arrangements characterised by user interfaces or communication using timers
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
    • F24F11/00—Control or safety arrangements
    • F24F11/62—Control or safety arrangements characterised by the type of control or by internal processing, e.g. using fuzzy logic, adaptive control or estimation of values
    • F24F11/63—Electronic processing
    • F24F11/65—Electronic processing for selecting an operating mode
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
    • F24F2110/00—Control inputs relating to air properties
    • F24F2110/10—Temperature

Definitions

  • This invention concerns a thermostat system for controlling building heating, ventilation, and air conditioning (HVAC) systems, and non-HVAC fuel-consuming systems, in a manner that lessens the need for utility peak- load capacity and consumption of fuel by electric utilities and by customers of gas utilities.
  • HVAC building heating, ventilation, and air conditioning
  • the invention also concerns a method for operating HVAC systems under the control of such a thermostat to lessen utility peak-load consumption of fuel.
  • fuel means electrical power and gas, oil, coal, and other fossil fuels.
  • the ASHRAE publications teach methods for predicting the fuel consumption of the HVAC system in a given house, under given external temperatures and given HVAC system thermostat set points. Data also exist for given localities that predict worst case external temperatures, for example, lowest anticipated temperature during a year, or lowest anticipated temperature over a 30-year period. Similarly, data exist for hottest temperature likely to occur in 30 years, etc. Such weather data, when used in conjunction with the ASHRAE formulas for fuel consumption, permit a statistical prediction to be made for the maximum anticipated contribution to peak load fuel consumption by a given house's HVAC system, for a 1-year, 30-year, etc. worst case situation.
  • Peak load is important to gas and electric utilities, because it significantly affects their capital expenditures and demand charges. Peak load is also important to electric utilities in connection with anti-pollution requirements on sulphur dioxide emissions and possible future limits on carbon dioxide emission.
  • Both pipelines and gas distributor utilities must meet a peak hourly demand for gas to be sent to their customers. They purchase gas on the basis of a maximum daily quantity, and also contract to use more than that daily quantity, divided by 24 hours, up to a stated hourly maximum. They pay annual or seasonal demand charges based on these quantities. Therefore, they also want to limit their peak-load consumption or sendout.
  • Each electrical utility uses its own procedure to chart peak usage and to plan its reaction to excessive loads, such as by shutting off some customers, reducing voltage ("brown- out") , and in some instances change of phase angle.
  • both gas and electric utilities employ computer simulations of forecast peak loads and the given utility's available capacity to meet these loads. These models identify the timing and extent of anticipated shortages of capacity.
  • the information developed enables the utility company to determine the kind, size, and timing of capacity additions.
  • Each utility makes its own determination how to react to possible excessive loads. Such determinations are strongly affected by the backup, emergency, or gas storage arrangements at the disposal of the given utility.
  • Some utilities presently control peak load by contracting with some customers to give them a lower rate or a discount in return for the utility's itself having the option to turn off the customers' loads when necessary to limit peak load.
  • This is accomplished by installing radio-controlled (or telephone- controlled) relays at customer sites, and by turning off power at peak load times by sending an appropriate radio (or telephone) signal to such sites.
  • An installer inserts the relay into each HVAC or other unit to be controlled; ordinarily, installation by homeowners on a do-it-yourself basis is infeasible.
  • This method is costly in terms of equipment costs and labor costs for installation. Also, this method permits only a "go/no-go" operation, in which all of the customer units at sites responsive to the controlling radio signal are either completely unregulated by the utility or else are shut off completely, causing a step-function effect on load.
  • a utility For purposes of activating radio-operated systems for cutting off preselected loads during peak-load operation, a utility will compare its current and impending load with its capacity.
  • An electric utility may also impose such a cut-off to avoid using peaking units that burn the most expensive fuels.
  • Gas utilities cannot reduce distribution line pressures, however, so that they must simply curtail interruptible industrial and commercial customers. If such measures are insufficient, the utility may curtail selected regions to avoid a system-wide problem.
  • the invention permits the utility to reduce its total load as well as its peak load. Utilities now seek both these goals. Even though the utility must have enough capacity to meet higher design peaks, it and its customers benefit greatly from.reducing load during all other peaks, especially normal- year peaks.
  • This invention reduces non-design peak loads and thus permits the utility to substitute cheaper peaking plant equipment (e.g., gas turbines) for much more expensive base- load plant equipment (e.g., coal or nuclear plants).
  • a further object of the invention is to decrease fuel consumption by a group of HVAC systems of buildings without causing step-function changes in fuel consumption, and without requiring all HVAC systems affected by the peak-load control to be off at all times during the regulated interval, as occurs with the go/no-go method previously described.
  • a utility may experience a higher load than it would have experienced as a peak load without such cut-offs.
  • Another object of the invention is to enable a utility to choose between a uniform peak-load reduction for all customer sites or a site-specific peak-load reduction that will avoid customer discomfort.
  • the invention can be used in either manner by using the same equipment.
  • Another object of the invention is to enable utility customers to be alerted when their non-HVAC fuel consumption, which may be deferred or reduced if use of the equipment at that particular time is not critical, occurs during a peak- load period; deferral or reduction of such usages can reduce these customers' annual demand charges, which are based on a single peak maximum usage. Non-HVAC usage may also be cut off automatically.
  • the invention provides a control unit that is inserted in the low-voltage signal lines of each individual building's thermostat, which can be accomplished by a simple retrofit operation that does not require access to 115v or 230v power lines or the services of a trained installer or licensed electrician; the control unit can also be incorporated into any jiewly manufactured thermostat.
  • the unit prevents the building's thermostat from turning the HVAC system on, thereby consuming fuel, for more than a predetermined maximum time during each peak-load interval.
  • each building's HVAC system operates independently in accordance with the settings of the control unit of that building.
  • the utility realizes a peak-load saving averaged over all of the buildings equipped with the control unit of the invention.
  • the invention permits a utility to specify at least a primary peak-load limit and also one or more secondary peak- load limits.
  • the primary heating or cooling load limit is based on normal yearly peak load, i.e., worst weather conditions anticipated over a year.
  • a secondary heating or cooling load limit can be based on design-year worst weather conditions, such as the hottest and coldest weather conditions anticipated over 30 years.
  • Primary and secondary limits can also be based on anticipated non-weather determined peak loads, also.
  • the control unit of the invention must generate a signal to indicate that the HVAC system is being curtailed from consuming fuel, because of having reached the utility-defined peak-load limit.
  • This signal can be made available to control any other energy-consuming unit at the site, if that is desired, even though the other unit is not directly controlled by the HVAC system's thermostat. This can be done by conventional, well known techniques using wireless or wire signals from the thermostat. If the utility wishes, it can provide a separate limit control unit that cuts off other energy consuming units when, or at an earlier or later time than, the HVAC unit is cut off.
  • Fig. 1 is a block diagram of the control system of the invention.
  • Fig. 2 is a discrete-logic schematic of portions of the control system of the invention.
  • Fig. 3 is an alternative representation of portions of the control system of the invention, implemented with a programmed microprocessor or microcontroller, rather than discrete logic.
  • Figs. 4, 6 are flowcharts of programmed microcontroller implementations.
  • Fig. 5 is a curve showing percentage of on-time as a function of the ratio of delivery parameter to leakage parameter.
  • a heated space of a home or other building may be modeled in terms of heat flux parameters.
  • the following parameters may be considered:
  • P- jj is the space peak-load design leakage parameter, representing the heat flux between a heated or cooled space in a building and the external environment surrounding the building, dimensioned in °F/sec or a comparable measure. It indicates the rate at which the space in the building leaks heat to the external environment in heating mode, or absorbs heat from the external environment in cooling mode, in a unit time under conditions based on the selected design peak load parameters of the well-known conventional ASHRAE method (explained in the ASHRAE references cited in the second paragraph of this specification) , to produce the maximum peak load on the utility supplying energy (fuel) to the given building.
  • the furnace of an HVAC system might be designed to have sufficient heating capacity, for the particular building in which the furnace is located, to maintain a space temperature of 60°F under the worst (coldest) weather conditions likely to occur in 30 years at that site. (If the thermostat set point is considered to be 68°F instead of 60 ⁇ F, the value of PJJ J calculated by the ASHRAE methodology would be higher and therefore the required furnace capacity to maintain space temperature at that set point would be higher.)
  • P L is a leakage parameter representing the heat flux between the heated or cooled space and its external environment, dimensioned in °F/sec or a comparable measure.
  • This variable parameter indicates the rate at which the space in the building leaks heat to the external environment in heating mode, or absorbs heat from the external environment in cooling mode, in a unit time.
  • the variability of this parameter depends (ignoring occupant and appliance activity in the space) on (a) the difference between the temperature inside the space and the temperature of the external environment, and (b) differences in solar radiation flux (ordinarily significant only in cooling mode) .
  • P L can be directly measured using either manual or automatic means. A method and apparatus for doing so is described in the above-referenced co-pending patent application (allowed as U.S. Patent 5,244,146).
  • a manual means of measuring P L in heating mode is to observe room temperature at the time that the fan (blower) turns off, and start a stopwatch running. A second observation of room temperature is made after a time interval elapses.
  • P L is the ratio between temperature decrease and elapsed time.
  • the value of P L can be determined by using the ASHRAE methodology (described in references cited at beginning of specification) , based on any selected day of the year and location that the utility desires. Ordinarily, this would be the most extreme temperature(s) expected in a normal year (this particular value for this parameter is at times designated below as R LD ' for either the hottest or coldest conditions, it being under ⁇ stood that the value of the parameter is different for hottest and coldest conditions, respectively) .
  • P d is a delivery parameter representing the heat flux between the HVAC system and the heated space or cooled space, dimensioned in °F/sec or a comparable measure. It indicates the rate at which the system can deliver heating or cooling in a unit time, during which leakage heat flux occurs at rate P L . (P d is thus a net heat flux parameter, such that P d - P DC -
  • P d can be directly measured using either manual or automatic means. A method and apparatus for doing so is described in the above-referenced co-pending patent application (allowed as U.S. Patent 5,244,146).
  • a manual means of measuring P d in heating mode is to observe room temperature at the time that the fan (blower) turns on, and start a stopwatch running. A second observation of room temperature is made after a time interval elapses.
  • P d is the ratio between temperature increase and elapsed time.
  • P DC is a delivery parameter representing the heat flux (delivery capacity) from between the HVAC system and the heated (or cooled) space, dimensioned in °F/sec or a comparable measure. It indicates the maximum rate at which the HVAC system can deliver heat (or cooling) to the given space in the building, in a unit time, as a result of HVAC system constraints-such as input BTU/hr, bonnet capacity, type of fuel, blower capacity, duct and grill configuration. Rearranging the equation given above allows P DC to be determined; P DC - P d + P L .
  • ⁇ at ar t refers to the temperature (e.g., in °F) of the heated or cooled space at the start of an on portion of a cycle, for example, at the time when an HVAC system's furnace begins to deliver heat to the space.
  • T ⁇ nd refers to the temperature of the space at the end of such a portion of a cycle, for example, when an HVAC system stops delivering heat to the space. (Under these conditions, T ⁇ tart is a minimum temperature and T end is a maximum temperature for the heated space.)
  • the absolute value of their difference, l ⁇ ⁇ t ar t ⁇ ⁇ ⁇ n d l' n a state of equilibrium is the thermostat deadband, D.
  • corresponding terms with primes may be defined that represent the sums of each of the foregoing terms during any given interval, such as a 30 min peak-load measuring interval.
  • t' total t' on + • t' off , where t' total is the entire interval, e.g., 30 min; t' on is the sum of all on-times during the interval; and t' off is the sum of all off-times during the interval.
  • P L it would be possible for P L to increase with an increasing environmental load (e.g., increasing external environment temperature, in air-conditioning mode) .
  • an increasing environmental load e.g., increasing external environment temperature, in air-conditioning mode
  • P d would decrease and t on would increase so that the percent on- time would approach 100%.
  • P L there would be no adverse effect on the peak load.
  • the conventional ASHRAE method previously referenced provides a design methodology for anticipated worst-case weather conditions (for example, coldest or hottest weather likely to occur in 30 years) .
  • the temperature- sensitive load at a given site under peak design conditions e.g. , worst case in 30 years
  • One method by which a utility can implement the foregoing type of peak-load reduction is to run regulated HVAC systems full on for an interval equal to t' on , and then turn them off for an interval equal to t' off .
  • This is essentially how a radio-control system designated by various names, such as the "Reddi Kilowatt" system, operates, e.g., all systems permitted to be on for the same 13 minutes and then required to be off for the same next 17 minutes.
  • the Reddi Kilowatt method allows, but does not require, all HVAC systems in a given group to be on for the first interval, e.g., 13 minutes.
  • a particular HVAC system in the group may go on and off several times during the foregoing 13-minute interval.
  • the Reddi Kilowatt method requires all systems in the group to be off at all times during the second interval, e.g., the next 17 minutes. Therefore, the hypothetical HVAC system with a short on-off cycle would be off for a total of more than 17 minutes during the 30-minute peak-load measuring interval of this example.
  • the inventors consider it preferable, however, to operate with a set of t on and t off intervals, respectively, that are not necessarily simultaneous with, or as long as, the cumulative on and off times, t' on and t' o££ , and that are distributed across the peak-load measuring interval.
  • the utility can accomplish the above-described reduction by appropriately determining the value of the ratio of P d /P L that results in the desired on-time ratio.
  • the value of t' on can then be determined, for a given peak load measuring interval, for example, 30 minutes, as follows:
  • Fig. 5 provides a graphical representation of the percent on-time as a function of the ratio of delivery and leakage parameters. This ratio depends strongly on environmental factors.
  • P L is larger than P d
  • percent on-time must be between 50% and 100% to control the temperature. Both on-time and off-time must be adjusted to maintain the desired percent on-time during a predetermined peak-load measuring interval. If the utility, by using the above equations and system parameters, determines that making the initially desired peak- load reduction will result in too large a deadband, it can adjust that peak-load reduction (decrease its absolute value) to maintain any desired deadband; by the same token, it can adjust a peak-load reduction (increase its absolute value) where additional deadband can be tolerated.
  • the ratio of the desired on-time ratio to the initial on-time ratio which is also the ratio of the desired KWH (or BTU or other appropriate unit) consumption to the initial KWH (or BTU, etc.) consumption, is R, where 0 ⁇ R ⁇ 1. (In the preceding example, R was 4.5/6.67.)
  • subscripts 1 refer to the old (i.e., unregulated) on and off times
  • subscripts 2 refer to the modified (i.e., regulated) on and off times
  • primes indicate cumulative on and off time totals over a peak-load measuring interval (e.g., 30 minutes).
  • t* total - t' total t' onl + t' offl , such as when a fixed 30-minute load-measuring interval is maintained, then t' on2 is simply equal to R-t' on ⁇ .
  • the utility decides to use the invention to implement a uniform peak-load reduction for all sites, it will not need to use the above equations, system parameters, and techniques.
  • the utility would then just specify cumulative on-time, etc. parameters. For example, the utility might specify a cumulative maximum of 13 minutes on and a cumulative minimum of 17 minutes off for all sites (or a given group of sites) during a 30-minute period, if that is the utility-desired maximum load for the sites.
  • the deadband D under these conditions will be 13 P d or 17 P L . If the HVAC is in heating mode and 17 P L > 13 P d , the temperature of the heated space will drift downwards. If the HVAC is in cooling (air conditioning) mode and 17 P L > 13 P d , the temperature of the cooled space will drift upwards. In any case, a deadband D may be determined.
  • the value of D might be 5°F or more; in that event, customers would probably sense discomfort, even if the temperature did not drift away from set point. Accordingly, customers would probably not consider regulation with this deadband as acceptable, and the on-time ratio would probably need to be increased.
  • t' on would be determined in the first instance with one of the equations discussed above. Then, a determination would be made of the value of D that use of that value of t' on caused. If D exceeded a predetermined value D', such as 3°F, t' on would be increased until D no longer exceeded D'.
  • the value of D might be 2 ⁇ F or less; in that event, customers could absorb a slightly larger deadband without sensing discomfort. Therefore, if the temperature did not drift from set point, a greater load reduction could be imposed at the site without creating discomfort. Under this approach, the on-time ratio would be decreased until discomfort was created, doing so by using the same methodology described in the preceding paragraph.
  • the comfort/discomfort boundary may be defined in terms of an acceptable deadband D' .
  • D' an acceptable deadband
  • the inventors consider 3°F a maximum. While the inventors consider this an appropriately comfort/discomfort level-based value, a utility may choose to adopt some other predetermined maximum value for D'. That would be a matter of design choice, but the methodology described herein for implementing that design choice would be the same, regardless of the particular value of D' selected.
  • a utility may choose to make a survey based on a representative sample of buildings and establish values of R on the basis of the results of the survey.
  • a utility can limit its peak load to a predetermined amount by controlling the relationship between users' on-time and off-time in a predetermined manner.
  • a method and apparatus are now described which accomplish this purpose more inexpensively than does the expedient of control of peak load by using radio-controlled relays to turn HVACs off.
  • the present invention does not require interruption of 115v or 230v AC power lines or at the relay controiling each HVAC unit and the services of a trained installer or licensed electrician.
  • the present invention can be carried out with a simple retrofit kit, since only low-voltage (e.g., 24v) thermostat lines are affected.
  • the invention can also be carried out by integrating the control unit of the invention into a new thermostat, during manufacture. The operation of the invention would be as described herein, irrespective of whether the invention is implemented physically as a separate module or subassembly, on the one hand, or as an integral part of the thermostat, on the other hand.
  • System 10 comprises a thermostat 12 (which can be a conventional bimetallic ther ⁇ mostat) , a limit control unit 14, AND gates 16 and 18, and HVAC relays 20 and 22.
  • thermostat 12 which can be a conventional bimetallic ther ⁇ mostat
  • limit control unit 14 AND gates 16 and 18, and HVAC relays 20 and 22.
  • Relay 20 controls the furnace/AC unit
  • relay 22 controls the blower, of furnace/AC unit and blower 24.
  • These relays conventionally actuate the HVAC system's furnace or air conditioner (as applicable), and the HVAC system's blower, during a fuel-on state.
  • the conventional electrical connections between relays 20 and 22, and furnace/AC and blower unit 24, are not shown in Fig. 1.
  • Unit 24 may also be a heat pump, which for purposes of this specification should be considered equivalent to an air conditioner.
  • FIG. 2 shows discrete logic for implementing limit control unit 14 of the invention with conventional, off-the- shelf TTL chips.
  • a conventional off-the-shelf oscillator chip 200 provides a 10 Hz signal to a clock input of a conventional, off-the-shelf decade counter 202, thereby generating a timing pulse at output CO of counter 202 each second.
  • the timing pulse clocks a first decade counter/decoder chip 204 (and also feeds a NAND gate 218, discussed below) .
  • Decade counter/decoder chip 204 produces a pulse at its RCO output every 10 sec.
  • the latter pulse clocks a second decade counter/decoder chip 206, whose QB and QC outputs are fed to a NAND gate 222, thereby providing a signal at 1 min intervals.
  • This 1 min pulse resets the first and second counter/decoders 204 and 206, and clocks a third decade counter/decoder chip 208.
  • the 1 min pulse primes an AND gate 220, discussed below.
  • Counter/decoder 208 provides a pulse every 10 min at its output RCO, clocking a fourth decade counter/decoder chip 210, whose QA and QB outputs are fed to NAND gate 218, providing a pulse every 30 min (the peak-load measuring interval) .
  • 1 sec timing pulses from decade counter 202 feed NAND gate 218.
  • the output of NAND gate 218 resets third and fourth decade counter/decoder chips 208 and 210, a second decade counter 212, and a fifth decade counter/decoder chip 214; it also feeds a R-S flip-flop 226.
  • the peak-load monitoring intervals keep repeating, so that every 30 min the Q output of flip-flop 226 is a 1.
  • Output CO of counter 212 clocks counter 214, so that it advances every 10 min.
  • Outputs MO, Ml, M2 ... M9 of counter 212 are connected to posts MO, Ml, M2 ... M9 of a terminal set 216; they represent 0, 1, 2 ... 9 min intervals.
  • Outputs M10, M20, M40, and M80 of counter 214 are connected to posts M10, M20, M40, and M80 of terminal set 216; they represent 10, 20, 40, and 80 min intervals.
  • Jumpers Jl and J2 are used to connect selected posts of terminal set 216, which can be selected for a predetermined limit on-time from 1 min to approximately 100 min, to the inputs of a NAND gate 224. When the predetermined limit on-time is reached, NAND gate 224 is enabled.
  • NAND gate 224 will operate to set flip-flop 226. That in turn un-primes AND gates 16 and 18 of Fig. 1, via the Q output of flip-flop 226, opening the HVAC system relays, thereby prohibiting any continued operation of the furnace or blower until the next time flip-flop 226 is reset, which occurs at the end of the peak-load measuring interval.
  • CPU 26 compares the time elapsed since the beginning of the peak-load measuring interval with the value of the peak- load measuring interval (t' total , typically 30 minutes) stored in memory unit 30. When time elapsed equals t' total , the elapsed time and t' on clocks are reset to zero. Then CPU 26 once again sends to AND gates 16 and 18 a l signal, which remains in effect until t' on again exceeds the predetermined limit, t » on .
  • AND gate 18 is controlled identically to AND gate 16 if the HVAC system has no secondary-delivery interval.
  • Fig. 4 a flowchart is shown that sets forth the operation of a programmed microcontroller functioning as described in the preceding paragraphs.
  • the hard-wired and programmed-microprocessor implementations described above utilized jumper settings (Jl, J2) or stored reference signals, respectively, to impose a limited on-time. These settings/signals are intended to be provided by the utility, which would supply the thermostat system to customers in order to control their peak-load usage of fuel. The utility would determine the values of these settings/signals in accordance with its own criteria, together with the formulas described above. Such criteria could be based on general system-capacity considerations with, or without, reference to site-specific thermal parameters, as a matter of utility choice. Thus, a utility might simply decide to limit all HVACs to an on-time that is a selected fraction of the measuring interval.
  • the utility could select settings/signals allowing a predetermined maximum load at a site, and work from that to the on-time ratio and settings/signals.
  • the extent to which a utility decides to limit a given customer's fuel usage is a matter of utility discretion, and as such is not part of this invention. Once the utility has exercised that discretion, the utility's choice can be implemented by using the apparatus and techniques described in this specification.
  • the foregoing system can be used as a retrofit unit with preexisting conventional thermostats.
  • Fig. 1 it can readily be seen that if the fuel and delivery wires of thermostat 12 are interrupted (cut) at lines AA and BB, the control system of the invention can be inserted into a preexisting conventional thermostat system without need for substantial modification. These wires ordinarily carry a 24v AC signal, so that interrupting them (for example, at the terminals of the existing thermostat) for retrofit purposes does not pose a significant safety hazard and is within the capability of a competent handyman or homeowner.
  • the invention can also be incorporated into a new thermostat installation, either as a separate module or integrated with the thermostat. In the latter case, of course, it is not necessary to cut any building wires or disconnect an existing thermostat to provide interruption of the lines from the thermostat to the HVAC relays.
  • the regulation of the on-time ratio may cause the HVAC system to devi ⁇ _e from set point.
  • the temperature at the thermostat may rise above set point during peak load period, and in winter (i.e., heating season) the temperature may fall below set point. It may therefore be desirable to include one or both of two additional refinements.
  • a "no regulation/on-off" switch may be inserted to disable the effect of limit control unit 14, if the user finds the discomfort excessive.
  • a switch can advantageously be inserted in the LIMIT output line coming from limit control unit 14.
  • customers' use of such a switch would be inconsistent with the utility's allowing a discount to the customers for using a thermostat embodying the invention. It is believed that a utility would exclude buildings so equipped from its calculated load reduction.
  • One approach might be to record use of the "no regulation/on-off" switch, or cause a signal to be sent, so that the utility could deprive the customer of the benefit of the discount which the utility allowed for installation of the limit system.
  • the inventors consider it preferable, however, for the utility to supply the customer with a thermostat that does not accommodate the disabling switch. If the customer later has a change of mind, the customer would call the utility to install a different thermostat, and change the applicable fuel rate at the same time.
  • a safety disablement means may be included, to prevent freezing of pipes or adverse comfort and health effects due to excessive lowering of temperature in winter or excessive raising of temperature in summer.
  • a similar high- temperature safety disabler can be used, if that is considered desirable, for an air conditioner.
  • This on-time ratio could be, for example, that resulting from use of the ASHRAE design methodology for worst-case day conditions in a normal year, instead of for a peak-design year (e.g., worst day anticipated over 30 years). That leads to the following equation for on-time ratio:
  • P D -*' is P jjj determined for the worst anticipated day in a normal year, rather than the worst anticipated day over some longer measuring period such as 30 years.
  • the system limits peak-load consumption of fuel to the maximum extent consistent with worst-case design conditions, as determined by applying the ASHRAE methodology to the site- specific thermal parameters of the building at the site.
  • the expedient for triggering the alternative limit for the limit control is advantageously a pair of bimetallic thermostats (auxiliary to the main thermostat 12 of Fig. 1) , one set for the excessive-heat limit (for example, 95°F during cooling season) and the other set for the excessive-cold limit (for example, 40°F during heating season) .
  • two-input AND gates 16 and 18 are each replaced by three-input AND gates.
  • a conventional pull-up resistor connected to a positive voltage is used to feed one side of each bimetallic auxiliary thermostat, and that side is connected to the new third input port of the three-input AND gate, so that a 1 signal is provided to the AND gate's input port when the auxiliary bimetallic thermostat is open circuit.
  • auxiliary bimetallic thermostat is connected to a pull-down resistor connected to a negative voltage, so that a 0 signal is provided to the AND gate's input port when the bimetallic auxiliary thermostat is closed circuit.
  • a 1 is provided when room temperature T is such that 40°F ⁇ T ⁇ 95°F; but a 0 is provided when room temperature T is such that 40°F > T or T > 95 ⁇ F.
  • An inverse circuit then simultaneously actuates a substitute limit control complemented as a duplicate of the limit control unit and the AND gates of Fig. l, storing the alternative limit signals, allowing a predetermined, greater than normal on-time to be placed into effect. This is the secondary limit.
  • the same expedient can be further extended to provide one or more addi ⁇ tional substitute limits.
  • the inventors consider this expedient for alternative limits on on-time to be important because utilities have a great desire and need to control the set-point temperature in buildings that their gas or electricity serve. Users may tend to increase their set point in heating mode (and decrease their set point in cooling mode) , when their on time is limited, for example, by peak load requirements; that could defeat the utilities' peak load reduction programs if the utilities were unable to counteract such conduct.
  • the present invention allows a utility, in effect, to perform a room temperature check with the bimetallic thermostats just described. If this temperature check shows that utility predetermined upper or lower limits are exceeded, the program or circuitry allows an increase in on time to a utility-predetermined secondary limit. In effect that allows an adjustment of room temperature in the direction of increased user comfort. But if the temperature check shows that utility-predetermined upper or lower limits are not exceeded, the program or circuitry does not allow an increase in on time to the utility-predetermined secondary limit, and thus does not allow an adjustment of room temperature in the direction of increased user comfort, which would interfere with the utility's peak load reduction program.
  • the control unit of the invention generates a signal to curtail HVAC fuel consumption, when the peak-load limit that the utility has predetermined as an on-time ratio is reached.
  • This signal may be used to operate other relays besides the HVAC system relays, or to operate other control devices.
  • it is possible to curtail fuel consumption by other machines or devices for example, a hot-water heater, oven, or clothes dryer
  • This can be done, also, without using the signal to curtail use of fuel by the HVAC system.
  • This expedient is conveniently implemented by conventional, well known techniques using wired or wireless communication to actuate relays (or other controllers) controlling power delivery to the other machines or devices.
  • the LIMIT output of limit control unit 14 may advantageously be connected to drive a relay or other control device for controlling delivery of power to the other machines or devices whose power (or fuel) use is to be curtailed when peak loads are being experienced.
  • a hotel might wish to curtail its use of clothes dryers and ironing equipment in its laundry or use of ovens in its bakery during a period of weather-induced or other peak-load fuel consumption, in order to avoid being assessed with heavy annual demand charges that are based on, or increased by, single peak maximum usage.
  • the hotel's HVAC fuel usage was curtailed, the hotel could implement a reduction of non-critical fuel usage in its laundry and/or bakery operations by means of the expedients described in the preceding paragraph.
  • the fuel-supplying utility would therefore not levy demand charges on the hotel because of the possibly excessive contributions to peak load that this expedient would allow the hotel to avoid.
  • HVAC system has been described in terms of an HVAC system using a hot-air furnace and blower.
  • the invention applies equally, however, to a heating system comprising a hot-water boiler and (optionally) a circulation pump.
  • HVAC system should be understood to comprehend such hot-water systems as well as the hot-air systems expressly described above.
  • the present invention can be practiced with an on-off or setback thermostat of the conventional bimetallic or electronic type, among others, provided that the operation of the two systems is not inconsistent. However, it is believed that the invention will not work properly with a thermostat of the increment-decrement type described in Carney et al. U.S. Patent 4,725,001.
  • a refinement of the present invention employs the peak- load fuel-consumption limitation device to control delivery of fuel to a hot water heater, oven, dryer, or other fuel- consuming device, so that they are denied fuel when the invention calls for denial of fuel to the HVAC system.
  • the inventors contemplate use of this refinement, if at all, in conjunction with peak-load regulation of an HVAC system. However, it would be possible, also, to regulate the other fuel-consuming device(s) without simultaneously regulating an HVAC system, although the inventors do not at this time consider that a preferred mode of operation in home applications. The invention should therefore be understood to comprehend that variation. Terminology
  • hard-wired electronic device refers to a PLA, gate array, TTL chip, combinatorial-logic semiconductor device, or other wired (rather than programmed) electronic device.
  • [signal] originating at the site" of an HVAC system refers to a signal originally generated at the HVAC system's site, as contrasted with a signal generated at a remote site and transmitted to the HVAC system's site by radio or other telecommunication means.
  • utility refers to an electric or gas utility, whether privately owned or owned by a government, including any person, government, business organization, or other entity supplying fossil fuel or electric power to residential, commercial, or industrial customers.
  • the term also includes any entity entitled to install equipment limiting peak-load consumption of fuel and/or peak-load demand.
  • autonomous control device refers to a control device such as that described hereinabove in this specification, which operates on the basis of signals generated on site. Such a device is to be contrasted with a device such as a remotely controlled power relay, by which a utility can curtail power consumption of an HVAC system by sending a radio or telephone signal to the device.
  • inhibiting transmittal of said fuel-on signals for time intervals of sufficient length to limit said fuel-on states of said HVAC system's said cycles to said predetermined level refers to a procedure by which the amount of on-time during a given interval ("on-time ratio," as described above) is limited, by inhibition of transmittal of fuel-on signals, to an amount that limits the HVAC system's fuel consumption to a level predetermined by the fuel-supplying utility to be consistent with the utility's peak-load reduction goals.
  • maximum utility-desired sum of fuel-consuming intervals means the maximum amount of time, cumulatively, that a utility desires to allow a fuel-consuming unit to consume fuel during an interval during which the utility measures fuel consumption (i.e., a load-measuring interval).
  • the foregoing maximum amount of time is the sum of on-time intervals during the interval during which the utility measures fuel consumption, i.e., the cumulative on-time (t' on ) during such load-measuring interval (t' total ) . It should be understood, however, as explained earlier in the specification, that there are not necessarily a plurality of intervals within a load-measuring interval.
  • a load-measuring interval can be surrounded by a single larger interval, such as a very long off-time interval beginning before and ending after the particular load-measuring interval begins and ends.
  • predetermined maximum fuel-consumption load refers to a fuel-consumption load at a given site, that a fuel-supplying utility predetermines is the maximum fuel consumption rate at the given site that is consistent with the utility's peak-load reduction goals.

Abstract

Procédé et appareil de commande (14) destinés à limiter la contribution aux charges maximales de systèmes (24) de chauffage, ventilation et climatisation (CVC) et d'autres systèmes. L'appareil de commande (14) réduit le pourcentage de temps de marche et par conséquent la consommation de combustible et d'énergie, ainsi que la demande de capacité de la part du service publique dans une mesure prédéterminée pendant les périodes de charges maximales, par neutralisation des signaux de consommation de combustible allant du thermostat (12) de chaque système CVC à la chaudière, à la pompe à combustible ou au conditionneur d'air du système CVC (24), ou d'un autre système, de manière que le temps de marche total pendant un intervalle de mesure de charge soit réduit à une quantité prédéterminée. En dehors des périodes de charges maximales, l'appareil de commande (14) est inactif et le thermostat (12) gère le système CVC (24). L'invention peut être utilisée pour rattraper un thermostat déjà installé incorporé dans une nouvelle installation de thermostat, ou incorporé dans un thermostat lors de sa production.
EP95913497A 1995-03-07 1995-03-07 Thermostat et procede de gestion des charges maximales Withdrawn EP0813671A4 (fr)

Applications Claiming Priority (1)

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PCT/US1995/002397 WO1996027769A1 (fr) 1995-03-07 1995-03-07 Thermostat et procede de gestion des charges maximales

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EP0813671A1 EP0813671A1 (fr) 1997-12-29
EP0813671A4 true EP0813671A4 (fr) 2000-04-12

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US7432477B2 (en) 2005-04-19 2008-10-07 Robert Teti Set-back control for both HVAC and water heater via a single programmable thermostat

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0015330A1 (fr) * 1979-02-26 1980-09-17 Ormsby, William Joseph, Jr. Appareil et procédé pour commander la demande en puissance électrique
US4465965A (en) * 1981-10-26 1984-08-14 Alan Chernotsky Power limiting apparatus
US4971136A (en) * 1989-11-28 1990-11-20 Electric Power Research Institute Dual fuel heat pump controller

Family Cites Families (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3925680A (en) * 1975-04-04 1975-12-09 William A Dixon Method and system for regulating peak residential power demand
US4141407A (en) * 1975-07-21 1979-02-27 Briscoe Harry H Power demand limiting circuit
US4347575A (en) * 1979-07-02 1982-08-31 Sangamo Weston, Inc. System for controlling power distribution to customer loads
US4345162A (en) * 1980-06-30 1982-08-17 Honeywell Inc. Method and apparatus for power load shedding
US4695738A (en) * 1985-09-30 1987-09-22 Daniel Wilmot Energy management system
US4725001A (en) 1986-10-17 1988-02-16 Arnold D. Berkeley Electronic thermostat employing adaptive cycling
US4819180A (en) * 1987-02-13 1989-04-04 Dencor Energy Cost Controls, Inc. Variable-limit demand controller for metering electrical energy
US5244146A (en) 1992-05-08 1993-09-14 Homebrain, Inc. Energy-conserving thermostat and method

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0015330A1 (fr) * 1979-02-26 1980-09-17 Ormsby, William Joseph, Jr. Appareil et procédé pour commander la demande en puissance électrique
US4465965A (en) * 1981-10-26 1984-08-14 Alan Chernotsky Power limiting apparatus
US4971136A (en) * 1989-11-28 1990-11-20 Electric Power Research Institute Dual fuel heat pump controller

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See also references of WO9627769A1 *

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AU2091295A (en) 1996-09-23
WO1996027769A1 (fr) 1996-09-12
EP0813671A1 (fr) 1997-12-29

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