HOT WATER SUPPLY

• Hot water can either be generated by the central boiler plant and stored, or produced close to the point of use by using a secondary fuel

Central heating

boiler

Indirectheating Hot

WaterCylinder

Return

FlowFuel

HOT WATER SUPPLY

COLDWATERTANK

HOT WATERSTORAGETANK

HOT AND COLDWATER USAGE

SERVICEPIPE

AIR VENT

Fuel(Direct Heating)

HOT WATER SUPPLY

HOT WATERSTORAGETANK

AIR VENT

DEAD LEGS

DEAD LEGS:

Connections from the hot water source (or secondary flow) to the taps are known as dead-legs.

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 outlets

form a dead leg.• Between draw-offs the water in the pipe will cool and

the next draw off will involve running the cold water to waste before it reaches the tap, creating dissatisfaction, waste of water and heat.

• In these systems in order to keep consumption within reasonable 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

HOT WATER SUPPLYEstimation of hot-water storage

Code 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

Day234.5

Dwelling houses 45.5

Factories 4.5

Flats 32 Hostels 32

Offices 4.5

Sports pavilions 36

Hotels (Average) 35

Hospitals:General

InfectiousMaternity

Nurses’ homes

2745.53245.5

By use of the table, a dwelling with 3 occupants will require 45.5 x 3 = 136.5 litres of hot water-storage.

HOT WATER SUPPLY

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

APPLIANCE VOLUMES OF HOTWATER (Litres)

WASH BASIN

Hand washWash

Hair wash

1.536

SHOWER 13BATH 70WASHING MACHINE 70SINK

Wash up Cleaning

155

HOT WATER SUPPLY

OUTLETPIPE

HEAT

ER E

LEM

ENT

340

mm

H =

700

mmO 470 mm

INLET PIPE

60 m

m

INSULATION 35 mm

VENTPIPE

Storage-type electrical water heater

The following figure shows the typical dimensions used in Cyprus

HOT WATER SUPPLY

1

2 34

6

5

1. Thermostat2. Flue pipe3. Cold water feed4. Hot water outlet5. Burner6. Buffer

Storage-type gas water heater

HOT WATER SUPPLYInstantaneous gas water heater

HOT WATER SUPPLYInstantaneous electrical water heater

HOT WATER SUPPLY

Water Heating by Solar Energy

ThermosiphonThermosiphonActionAction

Air vent pipe

Cold Water Tank

Hot Water Cylinder

Collectors

Cold Water Feed

Circulation of Waterby THERMOSIPHONaction

HOT WATER SUPPLYIndirect heater-type hot water cylinder

Coil

HOT WATER SUPPLYSolar Collectors integrated into the roof structure

COLDWATERTANK SOLAR

ENERGYHOT

WATERTANK

INCLINEDROOF

AIRVENT

Coldfeed

Hotwater

SOLARCOLLECTORS