substation guidelines presentation
TRANSCRIPT
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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 to
the district heating network
Those who are responsible for contacts between the
district heating ut ility 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 warm
water installations
Aid for avoiding technical misstakes during design andcalculation
Contain principles for dimensioning of heat substations
including:
domestic warm water,domestic warm water ci rculation 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 with
levels provided below
Good cooling of the DH water (i.e. the more heat
abstracted) and good performance of the district
heating substation are in the interests of both the
customer and the heat supplier.
District Heating systems
District Heating system Operating data Design data
High-temperature system
(HTS system)
100°C; 1,6 MPa
differential pressure 0,8 – 0,10
Mpa
110°C; 1,6 MPa
Low-temperature system
(LTS system)
Max 85°C; 0,6 Mpa
differential pressure 0,35 – 0,3
MPa
90°C; 0,6 MPa
Chapter 1: General
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Distr ict heating substations
HTS systems normally operate with a differential
pressure in the range of: 0,1 to 0,8 MPa [common range
is 0,1 to 0,6 MPa]
For overall substations efficiency in a big DH network
0,10 MPa is recommended
Technical energy supply condit ions defined by local DH
utility
DH temperature curve
DH maximal and average pressure
DH maximal and minimum pressure- difference
Installation of DP valves recommended at fi rst on the
branches of the network to avoid interaction between
number 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 prevent
corrosion
Recommended to avoid oil and fat use in the DH
systems
High pH values protect DH pipes against corrosion
Recommended not using chemical treatment for water
hardness
Distr ict Heating water quality
Electrical
conductivityµS/cm 100-1500
pH-value 9,5-10
Oxygen Mg/L <0,02
Alkal ine mmol/L <0,02
Chapter 1: General
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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 be
taken to prevent the development of bacteria and
Legionella (not a problem specific to district heating).
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Domestic Warm Water Production
Product ion of DWW either by a heat exchanger or
storage tank (with internal or external heat exchanger).
Primary side
(DH)
Secondary side
(DWW)
Differential Pressure
(max.)25 kPa 50 kPa
Calculating
Temperature65°C 10°C
CalculatingTemperature for LTS
60°C 10°C
Return Temperature,
multi family houses<22°C
Supply temperature
55°C
Return Temperature,
single family houses
<25°CSupply temperature
50°CChapter 2: The domestic warm water system
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Domestic Warm Water dimensioning
Choice of f low recommended for dimensioning
(best results is obtained closest to the lower line)
Apar tment
F l o w ( 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
Possibi lity to have priori ty over space heating
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Domestic Warm Water circulation system
To keep the DWW-system active and the temperature
on such a level, that both comfort and health
requirements are satisfied
Especially recommended for mult i 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 account
the following criteria:
Pressure and temperature
Corrosion (galvanic corrosion), the contribut ion
of poisonous substance and development of
bacteria
The same care has to be taken in choosinggaskets for the installation
Beware of national regulations and
requirements.
Chapter 2: The domestic warm water system
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Guidelines deal wi th:
Heat exchangers (types, functional requirements),Choice of materials,
Control system,
Dimensioning,
Valves and sensors
Radiator and venti lat ion systems should be built so that
the return temperature of the DH water is as low as
possible.
Chapter 3:
RADIATOR AND VENTILATION SYSTEM
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Choice of materials of radiators and
venti lation systems
A number of criteria addressed to ensure
safe and reliable operation:
Pressure
Temperature
Mix of materialsWater quality
Chapter 3: Radiator and ventilation system
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Control system
Should assure stable space heating
temperature according to customer needs
during the whole year, independent of
changes in the outside weather conditions
or inside heat loads
It is an advantage to install a controller
with temperature trend log that enables toregister controllable parameters in order
to carry out technological optimization
Chapter 3: Radiator and ventilation system
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Dimensioning of heat exchangers for radiator and ventilation system
When determining the design parameters we have to
consider 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 operating
mode with the highest heating power requirements
should be considered
Chapter 3: Radiator and ventilation system
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Target design temperature
Max. distri ct
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
systems100/80°C 43°C 70°C 40°C
28 -
35°C
Ventilation
systems100/80°C 33°C 60°C* 30°C
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 (electr ical 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 to
maintain a right flow for all situations,
providing better space heating condit ions
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 noise
level that no noise is transferred into the living
quarters of the building
Chapter 4:
PUMPS, SAFETY EQUIPMENT AND OTHER
COMPONENTS
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Domestic Warm Water circulation pumps
have 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 to
ensure continuous good funct ioning, it is
recommended 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 valves
Thermostatic radiator valves
Hydraulic balancing and balancing valves
Shut-off valves Drain, vent and pressure meter valves
Strainers (filters)
Temperature meters
Pressure meters
Booster pumps
Chapter 4: Pumps, safety equipment ...
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Chapter 5: CONNECTION PRINCIPLES
Why recommend connections ?
To ensure safe and reliable use
To maintain good quality of DH
To minimize energy consumption
To simpl ify design work
To uti lize the most cost efficientsolutions
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Connection principles: main differences
DOMESTIC WARM WATER HEATING
Suitable for DH
system
Size of
building Heat exchanger
Pre-
heater
Storage
tank
Type of
connection
HTS, LTS Large
Two s tage heat
exchanger YES NO
Indirect,
prim.
return >=45°C
HTS, LTS Large
One stage heat
exchanger NO NO
Indirect,
prim.
return <45°C
HTS, LTS Small house
One stage heat
exchanger, max 60
kW NO NO
Indirect,
max 20 kW
HTS, LTS Large
One stage heat
exchanger NO NO Direct
HTS, LTS Large
One stage heat
exchanger NO YES
Charging
system
LTS, Small house
One stage heat
exchanger, max 40
kW NO NO
Direct, max
8 kW
LTS Small house
Heat exchanger
inside tank, max 25
kW NO YES
Direct, max
8 kW
Chapter 5: Connection principles
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Connection principles: in-/direct
Indirect connection Direct connection
With heat exchanger:
Separated waters in primary
and secondary sides
Without heat exchangers:
Same water in primary and
secondary sides
Recommended to use leakage
alarm system
Chapter 5: Connection principles
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Connection principles: in-/direct
Indirect connection Direct connection
Design Temperatures up to 110°C
less than 90°C –
generally 80°C
Design pressures 1.6 MPa 0.6 MPa
Cooling of district
heating water
max 3°C higher as
secondary return
temperature
same temperature as
secondary return
Differential pressure
controller normally not needed
needed to decrease
pressure in secondary
side
Risk of damages and
leakages
no risks because of
hydraulic separated
networks
Excessively high
pressure may cause
pipe or radiator
damages and water
leakage
Chapter 5: Connection principles
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Connection principles: 1-/2-step connection
1-step connection 2-step connection
1-step connection (parallel) 2-step connection
Design Temperatures No differences, normal values are valid.
Design pressures No differences, normal values are valid.
Cooling of district
heating water Pre-heater improves the cool ing of
district heating.
Total pressure loss
over substation
No extra pressure drops due to
separated flows f rom DWW and
space heating.
Pressure drop on the primary side can
become high: i f the flow from the space
heating side is greater than the
dimensioned flow through the DWW heat
exchanger.
Chapter 5: Connection principles
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Connection principles: warm water
productionInstantaneous water
heatersHeaters withaccumulation
Design Temperatures No differences, normal values are valid.
Design pressures No differences, normal values are valid.
Cooling of district heating
water Safe solution to keep good
cooling of district heating.
Normal cooling of district
heating if:
- inlet temperature for heatexchanger is normal cold
water temperature;
- running of charging pump is
controlled by temperature in
bottom of storage tank.
Safety in consumptionIn normal district heatingcircumstances no problems to
get enough DWW.
- there is a lack of appropriate
flow capacity from the DH
- momentary exceptionally
high use of DWW
- low energy one-family
houses
EHP recommends using instantaneous water heaters
Chapter 5: Connection principles
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Customer satisfaction is essential for DH
Substations are extremely reliable and have a long
lifetime, but for smooth and economicallyefficient operation, regular inspection and
maintenance are recommended
Specif ied periods of t ime are not prescr ibed
Qualified personnel is indispensable
Chapter 6:
SERVICE AND MAINTENANCE
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Service and Maintenance
Guidelines offer tool for space heating and
domestic warm water
Check lis ts contain all necessary steps for a
comprehensive inspection and maintenance
DH supply companies can develop individual
inspection and maintenance plans and
calculations
Chapter 6: Service and maintenance
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Example of check list
Pos.Working hours
look over [h]
Working hours
test function
[h]
Remark
3 Domestic warm water system
3.1 Pipe system
3.1.1 Check for corrosion (look over)
3.1.2 Check of insulation (look over)
3.1.3Potential equalisation available
(look over)
3.1.4Check of fill-, drain -, und air
escape valves
(look over)
3.1.5 Check of mounting (look over)
3.1.6 Check non return valves
3.2 Shut off - armatures
3.2.1 Test function (practicability)
3.2.2 Check for leaks (look over)
Chapter 6: Service and maintenance
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A tool for...
Energy saving byInvoicing the real consumption of energy
Supervision the function of the substation
Customer service by
Reporting back suspicious levels of
consumption
Meter contributes to optimizing operation
By knowing what happens in the network
Chapter 7:
HEAT METERING
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Main components of a heat meter
Calculator Temperature sensor pair
Flow sensor or combinations thereof
The used meters or sub-assemblies must be conform to MID
EHP recommends to use EN 1434 to ensure the
conformity
Chapter 7: Heat metering
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Functional requirements
Use standardised types and dimensions toensure compatibility and replacing ability
Measuring range
Temperature: One range fit most needs
Flow: Select carefully to avoid over sizing
Some flow sensors require a flow conditioner
package
If you have short peak loads
Use fast response flow sensors
Use short response time on sensorsUse high resolution on flow signal
Check the requirements for mains or battery
Chapter 7: Heat metering
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Selecting / dimensioning of meters
Temperature sensor pair
select to fit the pipe dimensions
Flow sensor
select to fit the expected flow levels
Calculator select to fit the wanted functions
info in display
info in data logger opt ioninfo in data output option and power
supply (mains or battery)
Chapter 7: Heat metering
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Documentation requirements
What documents you shall require
What information is needed to ensure that you
Can select the suitable units
Can mix sub-assemblies of different brandsCan install the units in a correct way not
damaging the metrological function
Can check and recalibrate units
Chapter 7: Heat metering
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Installation of heat meters
Planning the meter posit ion
so that the meter can do its job
Piping installation
Electrical installation
following electrical security rules as
well as metrological demands
Identity checking
Installation inspection
with an inspection report to be filed
Chapter 7: Heat metering
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Conformity to MID
Examination of type and design
Inspection of produced meters
Control system
Reverification of meters
Life time cost
Different scenarios, need to
perform own calculations
Chapter 7: Heat metering
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Guidelines have direct impact on improvingtechnical performance of DH systems and on
significantly decreasing both life-time costs as
well as installation costs
Correctly carried out installation assures high
levels of services and simultaneously reduce
maintenance costs
Guidelines allow to significantly decrease return
temperatures in the DH network
Such rationalization wil l lead to a reduced use of
primary energy sources and less greenhouse
gases emission
CONCLUSIONS