Mirja Tiitinen 1 Dimensioning standard for domestic hot water Euroheat&Power RTD Workshop Brussels Mirja Tiitinen Finnish Energy Industries

Mirja Tiitinen 2 Research project, years 2004 – 2005 “The design flow and temperature criteria of hot tap water in respect of the microbiological water quality in district-heated residential buildings” Finnish Energy Industries Ministry of the Environment Helsinki Energy E.On Finland Oyj Vantaa Energy Helsinki University of Technology

Mirja Tiitinen 3 Objectives To establish temperature criteria for hot tap water based on the growth temperatures of microbes in the hot-water network To supplement and specify earlier studies carried out on the subject To produce a new design principle for the design flow of hot tap water as the basis for an official standard To compare the new design principle with criteria used in Finland and Sweden

Mirja Tiitinen 4 Number of bacteria colonies of Legionella as a function of temperature and time Increase Decrease Number of bacterial colony pmy/l] Time [h] Example of increase / decrease in various temperatures

Mirja Tiitinen 5 Research locations 26 locations in the Helsinki region Different types of residential buildings with district heating –Number of apartments –9 terraced houses, 5 small apartment buildings, 6 medium-sized apartment buildings and 6 large apartment buildings

Mirja Tiitinen 6 Measurements HelenMetering DVD Measuring data PC Sofware HUT Data analysis Tele network Apartment building Copper ADSL modem District heating heat exchanger Domestic hot water

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Mirja Tiitinen 9 Flow duration curves Flow l/s Time [%] Over – Under 20 Number of apartments:

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Mirja Tiitinen 12 Equation for the new design principle qAS.MAX is the mean location-specific maximum flow (Usually 0.5 l/s,location or 0.6 l/s,location) Θ is the probability that qAS.MAX is used during maximum consumption (0.005) Q is the sum of the standard flow of the connected water taps A is the factor that takes into account how often design flow q is exceeded (2.8) Suggested design flow

Mirja Tiitinen 13 Summary of the research project The design flows currently used in Finland don't correspond with the measured flows –in smaller buildings measured flows were higher –in bigger buildings measured flows were lower The maximum flow, the 30-second maximum flow and the 1- minute maximum flow were very close to one another The mean values of the water temperatures going into the network were reasonably good The return temperature of circulation was too low in most locations

Mirja Tiitinen 14 Dimensioning of the dhw control valve, example : Effect310 kW Flow1,65 l/sec. Pressure difference available250 kPa (in normal operational conditions) -heat exchanger 20 kPa -pipelines 5 kPa Available for the valve225 kPa

Mirja Tiitinen 15 ”Old” dimensioning custom Effect310 kW Flow1,65 l/sec. Pressure difference given60 kPa -heat exchanger 20 kPa -pipelines 5 kPa Dimensioning pressure difference for the valve35 kPa

Mirja Tiitinen 16 Valve: flow 1,65 l/sec, 35 kPa

Mirja Tiitinen 17 Result

Mirja Tiitinen 18 Valve: flow 50 % = 0,83 l/sec,35 kPa

Mirja Tiitinen 19 Result

Mirja Tiitinen 20 “Correct” dimensioning Effect310 kW Flow1,65 l/sec. Pressure difference given250 kPa -heat exchanger 20 kPa -pipelines 5 kPa Dimensioning pressure difference for the valve225 kPa

Mirja Tiitinen 21 Valve: flow 1,65 l/sec, 225 kPa

Mirja Tiitinen 22 Result

Mirja Tiitinen 23 Conclusions Domestic hot water valve shall be dimensioned with correct flow and correct pressure difference Correct flow is the actual maximum flow which can be expected to occur during normal conditions Correct dimensioning Δp is the pressure difference during normal operational conditions