EP0419214A2 - Système et procédé de régulation de la vitesse d'un ventilateur - Google Patents

Système et procédé de régulation de la vitesse d'un ventilateur Download PDF

Info

Publication number
EP0419214A2
EP0419214A2 EP90310205A EP90310205A EP0419214A2 EP 0419214 A2 EP0419214 A2 EP 0419214A2 EP 90310205 A EP90310205 A EP 90310205A EP 90310205 A EP90310205 A EP 90310205A EP 0419214 A2 EP0419214 A2 EP 0419214A2
Authority
EP
European Patent Office
Prior art keywords
temperature
fan speed
air
air temperature
cooling
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.)
Ceased
Application number
EP90310205A
Other languages
German (de)
English (en)
Other versions
EP0419214A3 (en
Inventor
Dean Scott Calton
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.)
ICC Technologies LLC
Original Assignee
ICC Technologies LLC
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 ICC Technologies LLC filed Critical ICC Technologies LLC
Publication of EP0419214A2 publication Critical patent/EP0419214A2/fr
Publication of EP0419214A3 publication Critical patent/EP0419214A3/en
Ceased legal-status Critical Current

Links

Images

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
    • F24F11/70—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

Definitions

  • the present invention relates to systems and methods for improving the energy efficiency of a building environmental control system by modulating fan speed in response to determined actual thermal loads.
  • the heating, cooling and dehumidification systems which are commonly employed in large commercial single zone applications (i.e. supermarkets) regulate ambient temperature and humidity by toggling their heating and cooling units on and off.
  • the ventilation fans in these systems run at full speed at all time, even when the heating and cooling units are off.
  • These continuously running fans are sized and designed to handle peak conditions, namely, the conditions presented by the hottest and coldest days of the year. These peak conditions, however, occur only about 2% of the year. Since during the rest of the year these fans operate at full speed, these fans spend the vast majority of their time operating in a region of excess capacity and at a speed in excess of what is required to achieve the desired ambient conditions. This situation results in a substantial waste of energy because the energy consumed by these fan motors accounts for almost 30% of the energy consumed by the heating, cooling and dehumidification systems in which these fans are employed.
  • the present invention is directed to the conservation of this wasted energy. Instead of operating the air circulation fan at full speed all the time, the present invention varies the speed of this fan so as to move only the amount of air required to achieve the desired ambient conditions.
  • the speed of the fan is adjusted through a feedback control system which monitors and maintains a constant temperature differential across the heating and cooling units in the air circulation system.
  • This feedback control system tracks the actual load on the system and then varies the fan speed and hence the volume and velocity of air moving through the heating and cooling units so as to maintain this constant temperature differential. In this way the desired comfort level is achieved through the use of significantly lower average fan speeds. This results in a vast energy savings because, as previously mentioned, the fan will only be required to run at full speed approximately 2% of the year.
  • the present invention was employed at the test site in connection with the same fan used previously, however, the speed of the fan was varied and controlled in accordance with the present invention.
  • the fan on average ran well below capacity because the fan was designed to move 24,000 CFM of air and on average it only moved 7,241 CFM.
  • the fan speed in revolutions per minute is linearly related to the CFM of air being moved, it is readily clear that the present invention resulted in significantly lower average fan speeds. This reduction in fan speed resulted in an energy savings of 100,504 KWH over the course of the year (or 82% percent of the energy previously used for driving the fan) while maintaining the same comfort level previously achieved.
  • the energy savings achieved by the present invention is enhanced by the fact that the energy required to drive a fan decreases exponentially as the fan speed decreases linearly. This phenomena is explained in Fan Engineering, An Engineer's Handbook, 7th ed. at pp. 232-233, and is illustrated by the chart and graph depicted below.
  • the relationship between power consumed and CFM also allows the present invention to out perform systems other than those employed in connection with large single zone applications like supermarkets.
  • the fans in these systems run continuously.
  • the fans in residential systems commonly run only when the heating or cooling units in these systems are on or for a limited period after these heating and cooling units are turned off.
  • the fans in these residential systems are always operated at full speed when they are on. This results in wasted energy because during much if the year these fans could achieve the desired ambient conditions by moving less air and turning more slowly.
  • the present invention results in considerable savings in a residential application by operating the fan only at the speed which is required to achieve the desired conditions, thereby eliminating the excess fan speeds currently in use and taking advantage of the relationship between CFM and KW explained above.
  • the basic fan speed controller of the present invention can be employed in connection with other basic control means or methods so as to achieve a number of other additional features and advantages.
  • the basic controller of the present invention employs a feedback control system which varies fan speed and CFM so as to maintain constant temperature differentials across the heating or cooling elements in the system. Once this basic capability for controlling fan speed is employed additional features are readily achievable.
  • One of these features is air pulsing control which the present invention employs in connection with its heating operation.
  • This feature is designed to identify and correct a situation where warm heated air collects near the ceiling of the room, leaving the lower portion of the room undesirably cold. This situation is depicted in a diagram from p.30.4 of the Ashrae Handbook , reproduced below.
  • This air pulsing feature operates by testing the air temperature at a control point located a few feet above the floor in the room. If this control point temperature is too low, the fan speed controller raises the fan speed to maximum for a few minutes in order to push this hot air off the ceiling and cirulate it through the room.
  • Another feature of the present invention is its demand period function.
  • the utility of this feature stems from the fact that any given electric bill is a function of two variables, total usage and peak usage. Peak usage is the maximum amount of electricity used within any given cycle window during the billing period. Thus, an entity that can spread its demand for electricity more evenly over time will have a lower electric bill even if its total usage remains constant.
  • the present invention employs a control loop which monitors cycle periods equal in duration to the cycle window used by the electric company. During the last few minutes of each cycle period this control loop turns the fan speed down to a minimum fan speed. This operation, while not reducing the total energy already being consumed the basic fan control system, reduces the peak usage of the system thereby significantly cheapening the cost of operation.
  • Another feature available with the present invention is a night setback function.
  • This feature allows for the adjusting of temperature during the night when the site of the system may not be in use. With the basic controller in place, this feature can be accomplished simply by slowing the circulation fan down to its minimum speed thereby letting the ambient temperature move to the edge of its allowable setback range. This setback temperature is maintained during the setback period by increasing the fan speed only as needed to keep the temperature within this setback range.
  • the night setback feature of the present invention is a vast improvement over the setback systems which have been tried in connection with present systems. These setback systems operated by toggling the circulation fans on and off during the setback period.
  • the fan occasionally remained off for long periods of time resulting in hot and cold regions within the zone. In some applications, these hot and cold regions proved harmful to products, plants, or animal life stored within the zone. These hot and cold regions are eliminated by the setback system of the present invention because the fans controlled by the present system are always maintained at a certain predetermined minimum speed.
  • control system and method may be implemented in a programmed general purpose microprocessor system such as a microcomputer employing an Intel iAPX microprocessor, together with peripheral support circuitry comprising random access memory, read-only memory, input/output circuits, timers, and the like.
  • a Compaq Model Deskpro 286/20 may be employed.
  • special-purpose microprocessor systems, together with sensors and support circuitry may be employed.
  • the method of the present invention may be implemented in a high-level programming language such as "C", or may be implemented in other languages such as assembly language.
  • a further alternative embodiment may employ discrete circuitry such as operational amplifiers, timers, gates and the like.
  • FIG. 1 describes how the heating, cooling and dehumdification functions of the present invention could be employed in connection with a system where return air passed first through a cooling unit and next through a heating unit before being circulated back into the ambient environment as supply air.
  • the present fan controller could also be employed in connection with a system where the heating and cooling units were reversed in order.
  • the present invention could be employed solely in connection with a cooling unit to perform only cooling, soley in connection with a heating unit to perform only heating, or in connection with a heating unit and cooling unit where both heating and cooling are controlled, but humidity is not.
  • the present invention could be employed in connection with a heating unit and a cooling unit solely to control humidity.
  • the air passing through the system is tested for temperature at various points. This testing may be accomplished by any conventional temperature sensor such as National Semiconductor's LM 34.
  • the return air entering the system is tested by a sensor located prior to the cooling unit. In an alternative embodiment the temperature of the return air is sensed at a control point within the zone or simply at the thermostat. The temperature of this return air is hereinafter referred to as the return air temperature.
  • the air exiting the cooling unit is tested by a sensor located between the cooling unit and the heating unit. The temperature of this cooled air is hereinafter referred to as the cooling air temperature.
  • the air is tested a final time after it passes through the heating unit, the temperature of this air being hereinafter referred to as the heating air temperature.
  • the heating air temperature is compared against the cooling air temperature (“CAT”) to determine whether the heating unit is being used. If HAT is greater than CAT then the heating unit is on and the algorithm moves to block 2.
  • CAT is compared against the return air temperature (“RAT”) to determine whether the cooling unit is on. If CAT is less than RAT then the cooling unit is on and the system is running in its dehumidification mode with both the heating and cooling units functioning.
  • the algorithm moves to block 3 where the temperature differential (“DT”) across the cooling coil is calculated by subtracting CAT from RAT.
  • the target delta temperature which is the desired temperature differential across the cooling unit for dehumidification is set. This TDT value is set at the dehumidification delta temperature (“DDT”) which is predetermined and a function of the particular cooling unit being used.
  • the temperature differential across the heating unit is calculated by subtracting RAT from HAT.
  • the target temperature differential across the heating unit is set at the heating delta temperature ("HDT"), which like DDT is predetermined and a function of the particular heating unit being used.
  • HDT heating delta temperature
  • the system next tests in block 5 to see if CAT is equal to RAT. If CAT and RAT are not equal this indicates that the system is in its cooling mode.
  • the temperature differential across the cooling unit is calculated for the cooling mode by subtracting CAT from RAT.
  • the target temperature differential across the cooling unit for the cooling mode is set at the cooling delta temperature ("CDT"), which like the DDT is predetermined and a function of the particular cooling unit being used.
  • the system moves to block 9 where the fan speed is adjusted.
  • the current speed is adjusted up or down according to whether DT is greater or less than TDT. If DT is greater than DT the fan speed is increased in an amount equal to (DT-TDT)*SPDF, where SPDF is a predetermined constant. If DT is less than TDT, the result of the calculation of (DT-TDT)*SPDF will be negative and the fan speed will be slowed accordingly.
  • the amount of fan speed adjustment is determined in a derivative fashion according to rate DT changes with time.
  • the amount of fan speed adjustment is determined by inputting the value of (DT-TDT) into a proportional integrated and derivative ("PID") control function.
  • MIN-SPEED mimimum speed
  • this minimum speed is determined in accordance with the relationship between KW and CFM for the particular fan being employed.
  • the fan speed is decremented by a predetermined "STEP”.
  • the fan speed is then compared with the MIN-SPEED. If the fan speed is below the MIN-SPEED the fan speed is set at the MIN-SPEED at block 10.
  • the fan speed is compared first to MIN-SPEED. If the fan speed is greater than MIN-SPEED, the fan speed is subsequently decremented by the predetermined STEP. If the fan speed is less than MIN-SPEED, the fan speed is set at MIN-SPEED. In yet another embodiment, if the system is not heating, cooling or dehumidifying the fan speed could simply be set at MIN-SPEED, as opposed to being brought down to that speed in a gradual or stepwise fashion.
  • an alternative embodiment of the present invention might employ a standard multi-stage thermostat or a multi-stage humidistat, instead of testing for RAT, CAT and HAT.
  • the fan speed is varied incrementally depending of the stage called for by the thermostat or humidistat.
  • the fan speed controller of the present invention might adjust the fan speed as follows: COOLING STAGE FAN SPEED First stage Fan speed set at 25% of maxspeed Second stage Fan speed set at 50% of maxspeed Third stage Fan speed set at 75% of maxspeed Fourth stage Fan speed set at 100% of maxspeed
  • the fan speed controller of the present invention might adjust the fan speed as follows: HEATING STAGE FAN SPEED First stage Fan speed set at 25% of maxspeed Second stage Fan speed set at 50% of maxspeed Third stage Fan speed set at 75% of maxspeed Fourth stage Fan speed set at 100% of maxspeed
  • the fan speed controller might adjust the fan speed as follows: DEHUMIDIFICATION STAGE FAN SPEED First stage Fan speed set at 20% of maxspeed Second stage Fan speed set at 40% of maxspeed Third stage Fan speed set at 65% of maxspeed Fourth stage Fan speed set at 90% of maxspeed
  • a microprocessor based control means is employed in connection with a variable speed motor to control fan speeds.
  • multiple motors with different horsepowers and different sized pulleys could be employed in connection with a blower to achieve the desired variation in fan speed or air velocity speed.
  • the motors in the above diagram might have horsepowers and pulleys sized as follows: MOTOR HORSEPOWER PULLEY SIZE DIAMETER (INCHES) M1 5HP 2.5 M2 10HP 5.0 M3 20HP 10.0
  • fan speed or air velocity is varied as desired by toggling the various motors on or off.
  • a multiple speed motor i.e, a two speed or three speed motor, could be employed to achieve the desired variation in fan speed or air velocity.
  • FIG. 2 depicts the operation of the control point satisfaction function
  • ST store temperature
  • MNT minimum allowable temperature
  • this pulsing is accomplished by increasing the fan speed in a stepwise fashion up to MAX-SPEED during the predetermined interval of time at the end of each cycle. In yet another embodiment, this pulsing could be accomplished without regard to cyclical intervals simply by increasing the fan speed until the warm had recirculated.
  • CDP the amount of time which is remaining during the cycle period
  • MSP the number of time which is remaining during the cycle period
  • CDP cycle period
  • MSP the number of time which has elapsed during the cycle period. If the condition in block 12 is false, the system moves to block 13 to see if CDP is zero. If CDP is not zero then in block 15 the fan speed is increased to MAX-FAN. Otherwise the system moves to block 14 and CDP is reset to CPP and MSP is reset to CPFSP, which represents CPP minus the pulse period.
  • FIG. 3. illustrates the demand period function of the present invention.
  • the utility of this feature stems from the fact that an electric bill is a function of two variables, total usage and peak usage. An entity that can spread its demand for electricity more evenly over time will have a lower electric bill even if its total usage remains constant.
  • the present invention employs a control loop which monitors cycle periods equal in duration to the cycle window used by the electric company. During the last few minutes of each cycle period this control loops turns the fan speed down to a predetermined minimum fan speed. This operation reduces the peak usage of the system thereby cheapening the cost of operation.
  • the fan could simply be shut off during the last few minutes of the cycle period or it could be reduced in some stepwise manner either down to a predetermined minimum speed or down to zero.
  • block 16 the amount of time which is remaining in the cycle period ("CDP") is tested to see if it is positive and MSP is tested to see if it equal 0.
  • MSP represents the length of the time remaining in the cycle period minus the interval of time where the fan speed will be reduced to MIN-SPEED in order to lower peak usage (5 minutes in the illustrated example). If the result of block 16 is true, this indicates that it is time to lower the fan speed and in block 19 the fan speed is reduced to MIN-SPEED where it will stay for the remainder of the cycle period. If the result of block 16 is false, CDP is tested to see if it is zero in block 17. If CDP is zero, this indicates that a cycle period has ended and in block 18 CDP and MSP are reset.
  • CDP is reset to a value representing the length of the cycle period used by the supplying electric utility to monitor peak usage (15 minutes in the illustrated example).
  • MSP is reset to a value representing the length of the cycle period used by the supplying electric utility to monitor peak usage minus the interval of time where the fan speed will be reduced to MIN-SPEED in order to lower peak usage.
  • MSP is set at 10 minutes (15 minutes minus 5 minutes).
  • FIG. 4 illustrates the night setback function of the present invention.
  • this feature allows for the adjusting of temperature during the night when the site of the system may not be in use and less comfortable conditions may be tolerated. This feature is accomplished by slowing the fan to is minimum speed thereby letting the ambient temperature move to the edge of its allowable setback range.
  • the setback temperature range is maintained during the setback period by increasing the fan speed only as needed to keep the temperature within the desired setback range.
  • the store temperature (“ST") is compared against the minimum allowable store temperature (“MNT”) and the maximum allowable store temperature (“MXT”) to see whether it falls within their range. If ST is within this range, the fan speed is lower by a predetermined amount (“STEP") in block 21.
  • the fan speed is compared against the minimum fan speed (MIN-SPEED). If the fan speed is below MIN-SPEED then the fan speed is set at MIN-SPEED. If in block 20 ST is not within the range between MNT and MXT, the fan speed is increased by the predetermined STEP amount in block 24.
  • the fan speed is then compared against the maximum fan speed ("MAX-SPEED"). If the fan speed is greater than MAX-SPEED, then in block 26 the fan speed is set at MAX-SPEED.
  • the fan speed is compared first to MIN-SPEED. If the fan speed is greater than MIN-SPEED, the fan speed is subsequently decremented by the predetermined STEP. If the fan speed is less than MIN-SPEED, the fan speed is set at MIN-SPEED. In yet another embodiment, if ST is within its desired range, the fan speed could simply be set at MIN-SPEED, as opposed to being brought down to that speed in a gradual or stepwise fashion.
  • the fan speed is compared first to MAX-SPEED. If the fan speed is less than MAX-SPEED, the fan speed is subsequently incremented by the predetermined STEP. If the fan speed is greater than MAX-SPEED, the fan speed is set at MAX-SPEED. In yet another embodiment, if ST is not within its desired range, the fan speed could simply be set at MAX-SPEED, as opposed to being brought up to that speed in a gradual or stepwise fashion.
  • FIG. 5 is a fan control algorithm incorporating the algorithms illustrated in FIGS. 1 through 4.
  • TOD time of day
  • ESD evening setback time
  • MSU morning start-up time
  • TOD is compared against the start of the demand period ("SDP") and the end of the demand period ("EDP"). If TOD is after SDP and before EDP, then the demand period function of FIG. 3 is triggered.
  • block 29 triggers the control point satisfaction function of FIG. 2 and block 30 triggers the heating, cooling and dehumidification function of FIG. 1.
  • block 31 the fan speed is set according to the updated fan speed value and CDP and MSP are decremented.
  • the present invention may be useful in the reduction of energy demand of a building environmental control system.
  • the system and method of the present invent ion may be used to reduce both energy consumption and cost in a conventional HVAC system, in dehumidification systems, and in combinations involving those systems.

Landscapes

  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Air Conditioning Control Device (AREA)
EP19900310205 1989-09-19 1990-09-18 System and method for fan speed control Ceased EP0419214A3 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US40955589A 1989-09-19 1989-09-19
US409555 1989-09-19

Publications (2)

Publication Number Publication Date
EP0419214A2 true EP0419214A2 (fr) 1991-03-27
EP0419214A3 EP0419214A3 (en) 1991-12-11

Family

ID=23621007

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19900310205 Ceased EP0419214A3 (en) 1989-09-19 1990-09-18 System and method for fan speed control

Country Status (2)

Country Link
EP (1) EP0419214A3 (fr)
JP (1) JPH03207955A (fr)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6684944B1 (en) 1997-02-18 2004-02-03 Hoffman Controls Corp. Variable speed fan motor control for forced air heating/cooling system
US6695046B1 (en) * 1997-02-18 2004-02-24 Hoffman Controls Corp. Variable speed fan motor control for forced air heating/cooling system
CN109959112A (zh) * 2019-03-31 2019-07-02 广东美的制冷设备有限公司 加湿控制方法、空气调节设备和计算机可读存储介质
CN117718725A (zh) * 2023-11-14 2024-03-19 徐州万卓五金工具制造有限公司 一种钢丝钳组合加工装置

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4324288A (en) * 1980-02-11 1982-04-13 Carrier Corporation Level supply air temperature multi-zone heat pump system and method
EP0097607A2 (fr) * 1982-06-21 1984-01-04 Carrier Corporation Appareil de chauffage à débit d'air variable pour différentes zones chauffées
FR2554216A1 (fr) * 1983-10-26 1985-05-03 Hitachi Ltd Conditionneur d'air

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4324288A (en) * 1980-02-11 1982-04-13 Carrier Corporation Level supply air temperature multi-zone heat pump system and method
EP0097607A2 (fr) * 1982-06-21 1984-01-04 Carrier Corporation Appareil de chauffage à débit d'air variable pour différentes zones chauffées
FR2554216A1 (fr) * 1983-10-26 1985-05-03 Hitachi Ltd Conditionneur d'air

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6684944B1 (en) 1997-02-18 2004-02-03 Hoffman Controls Corp. Variable speed fan motor control for forced air heating/cooling system
US6695046B1 (en) * 1997-02-18 2004-02-24 Hoffman Controls Corp. Variable speed fan motor control for forced air heating/cooling system
US7191826B2 (en) 1997-02-18 2007-03-20 Hoffman Controls Corp. Variable speed fan motor control for forced air heating/cooling system
CN109959112A (zh) * 2019-03-31 2019-07-02 广东美的制冷设备有限公司 加湿控制方法、空气调节设备和计算机可读存储介质
CN117718725A (zh) * 2023-11-14 2024-03-19 徐州万卓五金工具制造有限公司 一种钢丝钳组合加工装置

Also Published As

Publication number Publication date
EP0419214A3 (en) 1991-12-11
JPH03207955A (ja) 1991-09-11

Similar Documents

Publication Publication Date Title
CA1164970A (fr) Dispositif a microprocesseur pour controler la temperature de l'air fourni par un appareil de chauffage ou (et) de refroidissement multi-etage et controleur d'utilisation de l'air exterieur
US6408228B1 (en) Hybrid finite state machine environmental system controller
CA1142624A (fr) Dispositif de controle a micro-ordinateur pour pompe a chaleur commandee par un inverseur
Braun Reducing energy costs and peak electrical demand through optimal control of building thermal storage
US7640761B2 (en) System and method for controlling indoor air flow for heating, ventilating and air conditioning equipment
US11092371B2 (en) System and method of controlling a variable-capacity compressor and a variable-capacity fan using a two-stage thermostat
US5318104A (en) Error based zone controller
US5791408A (en) Air handling unit including control system that prevents outside air from entering the unit through an exhaust air damper
US6481635B2 (en) Environmental control method
EP0072982B1 (fr) Méthode et appareillage de commande d'une unité de conditionnement d'air avec ventilateur à plusieurs vitesses et économiseur
US7398821B2 (en) Integrated ventilation cooling system
US5447037A (en) Economizer preferred cooling control
US20060161306A1 (en) Method and apparatus for converting constant-volume supply fans to variable flow operation
WO2016176344A1 (fr) Système et procédé de commande d'un compresseur à capacité variable
US20070261422A1 (en) Humidity control for air conditioning system
EP0192140A2 (fr) Méthode de conditionnement d'air
US10767887B2 (en) System and method for thermal comfort control
AU1320399A (en) Method and apparatus for controlling supplemental heat in a heat pump system
US20080277488A1 (en) Method for Controlling HVAC Systems
US5131236A (en) Air handling system utilizing direct expansion cooling
CA1172338A (fr) Reduction de la consommation globale d'energie des installations de conditionnement de l'air
Seem et al. A new sequencing control strategy for air-handling units
US5138842A (en) Air handling system utilizing direct expansion cooling
EP0419214A2 (fr) Système et procédé de régulation de la vitesse d'un ventilateur
Krarti et al. Analysis of the Impact of CO 2-Based Demand-Controlled Ventilation Strategies on Energy Consumption.

Legal Events

Date Code Title Description
PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

AK Designated contracting states

Kind code of ref document: A2

Designated state(s): AT BE CH DE DK ES FR GB GR IT LI LU NL SE

PUAL Search report despatched

Free format text: ORIGINAL CODE: 0009013

AK Designated contracting states

Kind code of ref document: A3

Designated state(s): AT BE CH DE DK ES FR GB GR IT LI LU NL SE

17P Request for examination filed

Effective date: 19920609

17Q First examination report despatched

Effective date: 19930715

GRAG Despatch of communication of intention to grant

Free format text: ORIGINAL CODE: EPIDOS AGRA

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: THE APPLICATION HAS BEEN REFUSED

18R Application refused

Effective date: 19960908