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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
Chapter 2: The domestic warm water system
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
Chapter 2: The domestic warm water system
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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.
Chapter 2: The domestic warm water system
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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
Chapter 3: Radiator and ventilation system
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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
Chapter 3: Radiator and ventilation system
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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
Chapter 3: Radiator and ventilation system
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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