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 HOT WATER SUPPLY 

• Hot water can either be generated by thecentral boiler plant and stored, or producedclose to the point of use by using asecondary fuel

Central

heatingboiler

Indirect

heating HotWaterCylinder

Return

FlowFuel

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 HOT WATER SUPPLY 

COLD

WATERTANK

HOT WATER

STORAGE

TANK

HOT AND COLD

WATER USAGE

SERVICEPIPE

AIR VENT

Fuel(Direct Heating)

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 HOT WATER SUPPLY 

HOT WATER

STORAGE

TANK

AIR VENT

DEAD LEGS

DEAD LEGS:

Connections from thehot water source (orsecondary flow) to thetaps are known asdead-legs.

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 HOT WATER SUPPLY • In central systems there are pipework linking the

central supply with the draw-off points.

• In its simplest form a single pipe serving the outletsform a dead leg.

• Between draw-offs the water in the pipe will cool andthe next draw off will involve running the cold water towaste before it reaches the tap, creatingdissatisfaction, waste of water and heat.

• In these systems in order to keep consumption withinreasonable limits dead legs of pipework serving hot-water taps are governed to following maximum

lengths:• 12 m for pipes not exceeding 20 mm diameter

• 7.6 m for pipes not exceeding 25 mm diameter

• 3 m for pipes exceeding 25 mm diameter

• 1 m for pipes serving spray taps

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 HOT WATER SUPPLY 

Estimation of hot-water storageCode of Practice 342 (Centralized Hot-Water Supply, UK)

Type of Building Storage per person(litres)

Type of Building Storage per person(litres)

Colleges & Schools:

Boarding

Day

23

4.5

Dwelling houses 45.5

Factories 4.5

Flats 32 Hostels 32

Offices 4.5

Sports pavilions 36

Hotels (Average) 35

Hospitals:

General

Infectious

Maternity

Nurses’ homes

27

45.5

32

45.5

By use of the table, a dwelling with 3 occupants will require

45.5 x 3 = 136.5 litres of hot water-storage.

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 HOT WATER SUPPLY 

Estimation of hot -water storageIf the number of occupants is not known the following table may be used

APPLIANCE VOLUMES OF HOT

WATER (Litres)

WASH BASIN

Hand wash

WashHair wash

1.5

36

SHOWER 13

BATH 70

WASHING MACHINE 70

SINK

Wash up

Cleaning15

5

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 HOT WATER SUPPLY 

1

23

4

6

5

1. Thermostat2. Flue pipe

3. Cold water feed

4. Hot water outlet5. Burner6. Buffer

Storage-type gas water heater

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 HOT WATER SUPPLY 

Instantaneous gas water heater

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 HOT WATER SUPPLY 

Instantaneous electrical water heater

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 HOT WATER SUPPLY 

Water Heating by Solar Energy

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ThermosiphonThermosiphon

ActionAction

Air vent pipe

Cold Water Tank

Hot Water Cylinder

Collectors

Cold Water Feed

Circulation of Waterby THERMOSIPHON

action

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 HOT WATER SUPPLY 

Indirect heater-type hot water cylinder

Coil

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 HOT WATER SUPPLY 

Solar Collectors integrated into the roof structure

COLD

WATER

TANKSOLAR

ENERGY

HOTWATERTANK

INCLINED

ROOF

AIR

VENT

Cold

feed

Hot

water

SOLAR

COLLECTORS