substation guidelines presentation

7/21/2019 Substation Guidelines Presentation

http://slidepdf.com/reader/full/substation-guidelines-presentation 1/38

Presentation on:

GUIDELINES FOR

DISTRICT HEATINGSUBSTATIONS



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



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



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



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



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



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



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).



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



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



Domestic Warm Water control system

Stable DWW temperature

Fast control system is needed

electronically, temperature or flow-controlled


Possibi lity to have priori ty over space heating



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




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.




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



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



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




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




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




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



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



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 ...



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



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



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




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




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.




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




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



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



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



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



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



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




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)




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




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




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




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

substation guidelines presentation

Documents