European guidelines European guidelines for the preparation of domestic hot waterfor the preparation of domestic hot water

Janusz Różalski,OPEC Gdynia, Poland

EHP TF

Euroheat & Power XXXII. Congress, Berlin, "CHP/DHC: The Whole Picture"

Tuesday, 7 June 2005 - Parallel sessionsTECHNICAL ISSUES

Volume of hot water installation serviced by heat substation is different and balances between several kW

(when refers to one family house) to several MW ( in case of heat exchange group substation).

Process of production of domestic hot water is a dynamic

process carried out in different network water temperature

conditions appearing during a year.

Domestic Hot Water heat demand for 50 flats [KW]

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90

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Heat power consumption on chosen substationsduring the 12.05.2005

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hours

He

at p

ow

er f

or

90 f

lats

an

d 5

00 f

lats

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at p

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P (

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) an

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s (K

W)

Heat demand for 90 flats Heat demand for 500 flats Heat demand for 200 flats CHP heat demand

Incorrect volume of hot water consumed by heat substation installation taken into consideration during its dimensioning, To low or to high network pressure disposal taken into consideration during control valves dimensioning, Tendency to taking into account during design preparation bigger valves and pumps than it resulted from calculations, Wrongly dimensioned heat exchangers, Overestimated investment costs, Too high return temperature of network water, Too high level of electricity consumption, Problems with hot water stability during its differentiated consumption, Increased failure frequency of control valves, Too high sensitiveness of heat substation for changes in network parameters, Generating of sound permeability into house buildings, Luck of detailed measurements of small and short lasting energy consumption for example for hand washing, Legionella appearance within hot water circulation.

Common failures occurred during hot water substation designing and maintenance process are as follows:

Too high dimensions of hot water pipes and circulation, Too long hot water expectation time after tap opening, Fluctuations of DHW temperature during its consumption, Lack of hydraulic control valves in installation, Too high temperature decreases in hot water circulation – danger of Legionella appearance, Too high flows within DHW circulation, Noises in installation, Irregular temperature level in different parts of installation, Lack of water circulation at its ends – good conditions for Legionella incubation, Penetration of existing installation by cold water resulted from lack of check valves ( especially in wash machines connected to hot water installation ) and high pressure differences between hot and cold water, Lack of vertical insulation pipes in existing old hot water installations and circulation.

Common failures occurred during hot water installation designing and maintenance process of are as follows:

Guidelines worked out by “task force” will be an important aid during correct investment process for DH and designing

companies that prepare modernization works of heat substation and hot water installations.

Pressure Equipment EU Directive Measurement Instrument EU Directive

Buildings EU DirectiveEnergy Services EU Directive

Eco-design EU DirectiveEnergy End Use Efficiency EU Directive

Energy Performance of Buildings EU Directiverelevant CEN standards

Guidelines will be executed according to:

Country Temperature (Max/Min) ˚C

Pressure (MPa)

Austria 120/70 2.5

Denmark 120/70 1.6

Finland 120/70 1.6

France 110/70 1.0

Germany 130 1.6

Hungary 125 1.6

Italy 120/70 1.6

Poland 125/70 1.6

Slovenia 125/70 1.6

Sweden 120 1.6

Temperature and pressure differences existing in European DH systems

EHP recommended Temperature -120˚C

EHP recommended Pressure – 1.6 MPa

DISTRICT HEATING NETWORK

Country Temperature (Min) ˚C(standards established for comfort and disinfections

against legionella)

Temperature (Max) ˚CStandard established to secure against the burning skin)

Austria - 50

Denmark 50 65

Finland 50 60

France 50 60

Germany 50 55-60

Hungary 40 65

Italy 48 53

Poland 45(before 15.06.02)/55(after 15.06.02)

55(before 15.06.02)60(after 15.06.02)

Slovenia - 60

Sweden 50 65

National Building codes for Domestic Hot Water

EHP recommended Max hot tap water temperature - 60˚C

EHP recommended Min hot tap water temperature - 50˚C

Country Pressure for cold water (MPa)

Austria -

Denmark 1.0

Finland 1.0

France 0.7

Germany

Hungary 1.0

Italy 0.5

Poland 0.6

Slovenia 0.6/1.0

Sweden 1.0

Pressure for cold water

Simultaneously there are countries where designprinciples require to take into account

110-130 liters / day/ person.

It causes a significant over dimensioning of heatsubstation and internal installation and increases

unreasonably investment costs.

There are much more such differences and there is notechnical and economical use to keep them further.

An average European consumption is 36 liters per dayand per person at 60°C starting from cold water at

10°C.

Guidelines will contain principles for dimensioning of heatsubstations including the network from the substations to the hot water tap, domestic hot water circulation systems,

choice of heat exchangers and hot water storage tanks together

with functional requirements and control valves, with paying special attention for balance of DHW consumption.

Technical recommendations for conventional connection principles will be created, too.

Heat exchangers for heating

Pumps

Safety equipment: safety valves

Heat meters

Valves: by-pass valves, back-flow valves, shut-off valves drain valves

Other equipment: strainers , temperature meters and expansionVessels

Service and maintenance

Quality Control

Guidelines will include also recommendations for:

“ Euroheat & Power recommendations of technicalrequirements for the district heating substation “

The final result will be the

which is planned to be completed till the end of 2006.

DHW temperature diagram from heat substation with oversized control valve.

DHW Temperature chart for correctly and oversized regulating valwes

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Tem

per

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eg.C

Asigned temperature for DHW - case I

Obtained temperature of DHW - adequate valve case I

Obtained temperature of DHW - oversized valve case II

Asigned temperature - case II

Biofilm is composed of populations or communities of microorganismsadhering to environmental surfaces.

Biofilm may be found on essentially any environmental surfacein which sufficient moisture is present.

Their development is most rapid in flowing systems whereadequate nutrients are available.

Biofilm - common problem in DHW installations

A. Bacteria are depositing on a surface of water together with organicand inorganic compounds in the form of the coat

B. Reversible process of binding of bacteria with a membraneC. Depositing of bacteria in an irreversible process and their further

development D. Forming the micro colony as a result of reproduction of bacteriumE. Forming the biofilm consisting of various microorganisms F. Biofilm shaped completely

Example of effective modernization of heat substation.

Results were as follows:

● stable DHW temperature, ● all hot water tanks were eliminated, ● returned water temperature was decreased of 60%, ● water flow decreased and were obtained very good ● results of disposal pressure for all DH system sections.

Positive effects were possible to obtain due to consequent dimensioning of control valves based on utilization of full assuming disposal pressure

(installation of sometimes 2- 4 times smaller valves in relation to previous ones) and detailed estimation of hot water consumption in heat substations.

3062

2942

3112

2009

1986

1913

1493

1386

1303

500,0

700,0

900,0

1100,0

1300,0

1500,0

1700,0

1900,0

2100,0

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2500,0

2700,0

2900,0

3100,0

3300,0

3500,0

[t/h]

Jun

e 19

90

July

199

0

Au

gu

st 1

990

Jun

e 19

96

July

199

6

Au

gu

st 1

990

Jun

e 20

02

July

200

2

Au

gu

st 2

002

AVERAGE HOURLY FLOW FOR THREE SUMMER MONTHSIN 1990; 1996; 2002 YEARS

June 1990 July 1990 August 1990 June 1996 July 1996 August 1990 June 2002 July 2002 August 2002

BEFORE

AFTER

BEFORE

AFTER

Annual consumption of electric energy in OPEC Gdynia

0

5 000

10 000

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20 000

25 000

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40 000

1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003

YEAR

[MW

h]

Guidelines can have a direct impact for increase in technical levelof investment projects and significant decrease in investment costs.

In this way DH companies will be able to compete effectively with gasand oil supplied heat only boilers.

Correctly carried out investment process will assure very high levelof offered by us services and simultaneously will cause reductionof maintenance costs.

Guidelines can become basis for implementation of conventional technical solutions which will allow to minimizing costs of heatsubstations designing and production costs of compact heat substations.

OPEC Gdynia is a good example that guidelines can be an excellenthandbook for carrying out effective modernization processof existing heat substations.

A total effect will bring rational reduction of primary fuel utilization and greenhouse gases emission.

Conclusions:

Task Force creating European guidelines for the preparation of domestic hot water recognized it as very significant from

technical and economical point of view .So Task Force would

be grateful for any comments and conclusions from DH companies whose knowledge and experience could be

effectively used within the framework of project.

In case of any comment and conclusions please contact Task Force’s Secretary Mrs. Norela Constantinescu

[norela.constantinescu@euroheat.org]