district heating substation guidelines presentation

7/29/2019 District Heating Substation Guidelines Presentation

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Presentation on:

GUIDELINES FOR

DISTRICT HEATINGSUBSTATIONS


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The Guidelines address

Those who are running and maintainer a DH system Those who design, purchase, test, install and

manufacture substations

Those who own or maintain a building connected tothe district heating network

Those who are responsible for contacts between thedistrict heating utility and the customers

Chapter 1:GENERAL


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The Guidelines

Aid for investment process in DH

Aid for modernization works of heat substation and warmwater installations

Aid for avoiding technical misstakes during design andcalculation

Contain principles for dimensioning of heat substationsincluding:

domestic warm water,domestic warm water circulation systems,choice of heat exchangers,warm water storage,functional requirements and control valves

Chapter 1: General


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Guidelines are prepared in accordance with...

Pressure Equipment Directive (97/23/EC)

Measuring Instruments Directive (2004/22/EC)

Energy Performance of Buildings Directive (2002/91/EC)

Machinery Directive (2006/42/EC)

Energy Services Directive (2006/32/EC)

Eco-design Directive (2005/32/EC)

EN/CEN standards: EN 1434, CEN 311, etc.

Chapter 1: General


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DH companies recommended to build all new systems,including new parts in older systems, in accordance withlevels provided below

Good cooling of the DH water (i.e. the more heatabstracted) and good performance of the districtheating substation are in the interests of both thecustomer and the heat supplier.

District Heating systems

District Heating system Operating data Design data

High-temperature system(HTS system)

100C; 1,6 MPa

differential pressure 0,8 0,10Mpa

110C; 1,6 MPa

Low-temperature system(LTS system)

Max 85C; 0,6 Mpa

differential pressure 0,35 0,3MPa

90C; 0,6 MPa

Chapter 1: General


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District heating substations

HTS systems normally operate with a differentialpressure in the range of: 0,1 to 0,8 MPa [common rangeis 0,1 to 0,6 MPa]

For overall substations efficiency in a big DH network0,10 MPa is recommended

Technical energy supply conditions defined by local DHutility

DH temperature curveDH maximal and average pressureDH maximal and minimum pressure- difference

Installation of DP valves recommended at first on thebranches of the network to avoid interaction betweennumber of DP valves located in the same area.

Chapter 1: General


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DH system must be as far as possible protectedagainst oxygen and cold water intrusion to preventcorrosion

Recommended to avoid oil and fat use in the DHsystems

High pH values protect DH pipes against corrosion Recommended not using chemical treatment for waterhardness

District Heating water quality

Electrical

conductivityS/cm 100-1500

pH-value 9,5-10

Oxygen Mg/L


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Chapter 2:THE DOMESTIC WARM WATER SYSTEM

Domestic Warm Water general

Directive 98/83/EC: European standard for the safetyof water for human consumption.

In all warm water systems special actions should betaken to prevent the development of bacteria andLegionella (not a problem specific to district heating).


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Domestic Warm Water Production

Production of DWW either by a heat exchanger orstorage tank (with internal or external heat exchanger).

Primary side

(DH)

Secondary side

(DWW)

Differential Pressure

(max.)25 kPa 50 kPa

Calculating

Temperature65C 10C

CalculatingTemperature for LTS

60C 10C

Return Temperature,

multi family houses


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Domestic Warm Water dimensioning

Choice of flow recommended for dimensioning(best results is obtained closest to the lower line)

Apartment

Flow(

l/s)

Chapter 2: The domestic warm water system


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Domestic Warm Water control system

Stable DWW temperature

Fast control system is needed

electronically, temperature or flow-controlled


Possibility to have priority over space heating


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Domestic Warm Water circulation system

To keep the DWW-system active and the temperatureon such a level, that both comfort and health

requirements are satisfied

Especially recommended for multi family houses To ensure, that the DWW-return temperature never

goes below 50 C.

This can be ensured through a variable pump,thermostatic valves and balancing valves



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Choice of materials for domesticwarm water system

Materials should be selected taking into accountthe following criteria:

Pressure and temperatureCorrosion (galvanic corrosion), the contributionof poisonous substance and development ofbacteria

The same care has to be taken in choosinggaskets for the installationBeware of national regulations andrequirements.



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Guidelines deal with:

Heat exchangers (types, functional requirements),Choice of materials,Control system,Dimensioning,Valves and sensors

Radiator and ventilation systems should be built so thatthe return temperature of the DH water is as low aspossible.

Chapter 3:RADIATOR AND VENTILATION SYSTEM


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Choice of materials of radiators andventilation systems

A number of criteria addressed to ensuresafe and reliable operation:

PressureTemperature

Mix of materialsWater quality

Chapter 3: Radiator and ventilation system


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Control system

Should assure stable space heatingtemperature according to customer needsduring the whole year, independent ofchanges in the outside weather conditionsor inside heat loads

It is an advantage to install a controller

with temperature trend log that enables toregister controllable parameters in orderto carry out technological optimization



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Dimensioning of heat exchangers for radiatorand ventilation system

When determining the design parameters we have toconsider the DH system as a whole:

Heat losses,Production efficiency,Pipe capacity / construction cost,Pumping capacity,The cost of heat installations,Advantage of low return temperature in all aspects

When dimensioning heat substations the operatingmode with the highest heating power requirementsshould be considered



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Target design temperature

Max. district

heating supply

temperature,

HT/LT system

Max.

district

heating

return

temp.

Max.

radiator and

ventilation

system

supply

temp.

Max.radiator

and

ventilation

system

return

temp.

Max.

floor

heating

system

temp.

Heating

systems100/80C 43C 70C 40C

28 -

35C

Ventilation

systems100/80C 33C 60C* 30C

All systems

Max. pressure drop in

district heating side

Max. pressure drop in radiator

and ventilation side

25 kPa 20 kPa



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Energy saving pumps (electrical controlled)should be considered in all positions to save

energy and to reduce life time operation cost ofthe system. These kind of pumps also help tomaintain a right flow for all situations,providing better space heating conditions

The flow for a DWWC-pump should be at least 20%of the total flow for DWW heat exchanger

All pumps in the system should have so low noiselevel that no noise is transferred into the livingquarters of the building

Chapter 4:PUMPS, SAFETY EQUIPMENT AND OTHER

COMPONENTS


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Domestic Warm Water circulation pumpshave to be in operation continuously

For all choices of pumps the use of low

energy pumps is strongly recommend

For sensitive customers (hospitals,retirement homes etc.) where it is crucial toensure continuous good functioning, it isrecommended to use double pumps with

automatic start function for the secondmotor

Chapter 4: Pumps, safety equipment ...

PUMPS


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Valves and other components

Check valvesThermostatic radiator valvesHydraulic balancing and balancing valves

Shut-off valvesDrain, vent and pressure meter valvesStrainers (filters)Temperature metersPressure metersBooster pumps

Chapter 4: Pumps, safety equipment ...


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Chapter 5: CONNECTION PRINCIPLES

Why recommend connections ?

To ensure safe and reliable useTo maintain good quality of DHTo minimize energy consumptionTo simplify design work

To utilize the most cost efficientsolutions


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Connection principles: main differences

DOMESTIC WARM WATER HEATING

Suitable for DHsystem

Size ofbuilding Heat exchanger

Pre-heater

Storagetank

Type ofconnection

HTS, LTS LargeTwo stage heatexchanger YES NO

Indirect,prim.return >=45C

HTS, LTS LargeOne stage heatexchanger NO NO

Indirect,prim.

return

district heating substation guidelines presentation

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