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V. REFERENCES:[1] Müller, H.: Technische Thermodynamik, Wismar, 2000.[2] Dövényi, P. – Tóth, Gy.: A Kárpát-medence geotermikus éshévízföldtani adottságai, 2008.[3] Gyné., Halász: Geothermal Energy in Building Energy Supplywith Exergy Theory, XIV. Building Services and MechanicalEngineering Professional Days, 2008.[4] Gyné., Halász: Utility of Geothermal Energy in Building EnergySupply with Exergy Theory, Mechanical Engineering Letters,Selected Collection from the Research Results of Year 2010,Szent István University, 106-120 p. 2011.[5] Halász Gyné., Kujbus A.: Hazai földhőtermelés éskörnyezettudatosság, 2011.[6] Magyarország Megújuló Energia Hasznosítási Cselekvési Terve,Nemzeti Fejlesztési Minisztérium, 2010.[7] (Hungarian National Renewabe Energy Action Plan, Ministry ofNational Development, 2010.)[8] Dietrich Schmidt: Methodology for the Modelling of ThermallyActivated Building Components in Low Exergy Design, DoctoralThesis Stockholm, Sweden ISSN 1651-5563, ISRN KTH-BYT/R—04/194-SE, ISBN 91-7283-737-3, 2004.[9] Halász Gy-né.-Kalmár T.: Különböző hőtermelővel ellátott fűtésirendszerek exergetikai összehasonlítása I.-II. rész, MagyarÉpületgépészet, vol. L VI. 12 sz. vol. L VII. 1-2 sz., 2007-2008.62
Error in Water Meter Measuring at Water FlowRate Exceeding Q minLajos Hovány **PhD, assistant lecturer, Faculty of Civil Engineering, Subotica, Republic of Serbiae-mail address: hovanyl@gf.uns.ac.rsAbstract—The duration of consumption in households isshorter than 1 minute in 95% of consumption cases. Theprimary aim of this paper is to define the error inmeasuring consumption shorter than 10 (for Q min =0,03m 3 /h), 12,5 (for Q t =0,12 m 3 /h) and 4 minutes (for Q n =1,5m 3 /h) for B class water meter with rated diameter of 20 mm,installed in the water supply network of a single household.Error changes in the operation of the water meter weretested by the method of switching off the water meter andby the method without switching off the water meter.During accuracy measurements, water meter readings wereas follows: 2,5 centilitres and 1 decilitre. Through testing ithas been established: a) that during consumption shorterthan the time the meter was calibrated for, the watermeter's ranges of measuring error are larger than theranges of permitted errors, and b) that the biggest errorsoccur during Q min flow rate.Key words: water meter, consumption duration, operationerrorI. INTRODUCTIONIn line with the Measurement Protocol for WaterMeters in the Republic of Serbia, a water meter for waterconsumption in households is qualified for operation witherror below the permitted values, i.e. from ±5% (for Q min )and ±2% (for Q n and Q t ) from the actual water volume[6]. During calibration, water meter operation errors arechecked for the foreseen water volumes. Through thiswater volume and discharge, the time for which the meteris calibrated was calculated.TABELE 1.TIME FOR WHICH THE WATER METER IS CALIBRATED WITH 20 MMRATED DIAMETER, CLASS B (SOURCE:“POTISKI VODOVODI”LTD. FROMHORGOS)Water Discharged Permitted Time betweendischarge water error twovolume limit readingsm3/h litres ±% ±litres minutesQmin=0,03 5 5 0,25 10Qt=0,12 25 2 0,5 12.5Qn=1,5 100 2 2 4To eliminate the effects of opening and closing the flowswitch to measuring errors during calibration, the standardin force in the Republic of Serbia stipulates the following:„The uncertainty introduced into the volume may beconsidered negligible if the times of motion of the flowswitch in each direction are identical within 5% and if thistime is less than 1/50 of the total time of the test” [7]. Thesame recommendations are given by other standards aswell [4, 5]. Based on that, the following is recommended:„Should there be doubts about whether the operation timeof the valve affects the results of the tests, it isrecommended that the tests should be made longer, andnever under 60 seconds” [1]. That is to say, for neglectingthe impact of flow switch manipulation on the watermeter’s measuring errors the standards offer a solutionduring the calibration of water meter only.Water consumption in a single household isimplemented by the use of taps, washing machine,dishwasher-machine and shower in the bathroom, likewisethe flushing cistern of the toilet and the like. Eachconsumption is characterised by the opening and closingof flow switch and the duration of water discharge fromthe pipeline in order to satisfy needs. The duration ofconsumption in households is shorter than 1 minute in95% of consumption cases [2]. The error in measuringconsumption by water meter, due to manipulating the flowswitch, practically manifests as an error due to theduration of consumption shorter than the time the meterwas calibrated for.Owing to this fact, the primary aim of this paper is todefine measuring errors of consumption shorter than 10(for Q min ), 12,5 (for Q t ) and 4 minutes (for Q n ) of class Bwater meter with 20 mm rated diameter and flow ofQ n =1,5 m 3 /hour, installed in the water supply pipeline of asingle household.Water meter operation error depends on water meterreading accuracy [3]. The further aim of this paper is todefine water consumption measuring error in householdsshorter than the time the meter was calibrated for, in thefunction of water meter reading accuracy.II.DESCRIPTION OF THE TEST RIGA water supply pipeline was set up in the HydraulicLaboratory of the Faculty of Civil Engineering inSubotica, gravitationally supplied from a tank withconstant water level, i.e. for 16,25 m higher than the levelof the water meter axis. According to both water flow andthe water supply pipeline characteristics, the water supplypipeline corresponds to the one of a single household.For the test rig for a water supply system, new,calibrated multi-jet propeller water meters with wetmechanism were installed for water temperature of 30 o C,and with rated diameter of 20 mm, class B, with thefollowing typical flow rates: Q min =0,03 m 3 /h, Q t =0,12m 3 /h and Q n =1,5 m 3 /h. The water meters weremanufactured by Potiski vodovodi Ltd. from Horgos.63
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