Worcester 35CDI II Service Manual download pdf (Page 3)

A combi (or combination boiler) is a compact and

highly efficient unit giving all the heating and hot

water you need, with significant savings on running

and installation costs.

Unlike a conventional heating and hot water system,

a combi boiler system does not store domestic hot

water. It heats water directly from the cold mains –

as you use it. There’s no hot water cylinder, no tank in

the loft (and so less risk of freezing and flooding),

and none of the connecting

pipe work. So you not only

save space, but also reduce

hot water costs – which can

account for up to 60% of a

typical domestic fuel bill.

A combi also supplies hot

water at mains pressure,

giving you exhilarating power

showering without the need for a pump. And as, on

average, a shower uses considerably less water than

a typical bath, the savings on hot water costs and

water consumption can be significant.

Room

Thermostat

GREENSTAR CDi

Combi Boiler

Hot to

Baths,

Showers

and Basins

Hot to Basins

and Appliances etc.

Cold Water

Storage

Cistern

Feed and

Expansion

Cistern

Hot

Water

Tank

Programmer

Boiler

Room

Thermostat

Motorised

Valve

Pump

Hot to Baths, Showers

and Basins etc.

Hot to

Basins and

Appliances

etc.

COMBI SYSTEM

CONVENTIONAL SYSTEM

LAYOUT

The advantages of a combi boiler

The Greenstar CDi condensing combi boiler series

A condensing boiler is more efficient due to its ability to extract

more heat from the flue gases normally lost to the environment

through the flue system.

All the Greenstar CDi models use the same Aluminium-Silicon heat

cell with an extra large surface area.

As the flue gases pass through the heat exchanger this extra

surface area cools the flue gases to around 55°C whereupon the

latent heat within, which would normally be lost to the atmosphere,

is instead released and applied to the system.

It is this ability to extract as much heat as possible from the gas it

burns that gives the Greenstar CDi series an exceptionally high level

of operating efficiency.

This higher efficiency is recognised within section L of the Building

Regulations, subsequently achieving a higher SAP or NHER rating.

Key features of the Greenstar CDi condensing boilers include the

separate plate domestic hot water heat exchanger, which is

guaranteed for 5 years.*

This, combined with the ‘keep hot’ facility, ensures that hot water is

delivered instantly to the tap.

*Subject to conditions

The CDi series design benefits

in operation

Hot water mode

Whenever a hot water tap is turned on the incoming mains water will

activate a flow turbine which, via the electronic control system,

ignites the pre-mix burner. Boiler output is automatically boosted to

maximum to heat the incoming cold water as it passes through the

heat exchanger. Electronic controls modulate the boiler output

downwards to ensure the hot water temperature remains between

40 and 60ºC (as set by the consumer).

Keep hot facility

All the Greenstar CDi combi models have an in-built keep hot facility

which will keep the primary water within the heat cell hot. This will

ensure that hot water is delivered instantly to the opened outlet.

Eco mode

With the Eco mode button activated the keep hot facility is

de-energised and the hot water will be heated from cold. A slight

delay should be expected before the hot water is at full temperature

when in the Eco mode.

Central heating mode

On a Central Heating demand, the boiler will initially fire at minimum

output before modulating upwards to meet the actual system

requirement. Electronics within the boiler continually monitor the

heating flow temperature increasing or decreasing output on demand.

An anti-cycling device makes the Greenstar CDi range particularly

suitable for use on systems with TRV’s (Thermostatic Radiator Valves).

Options

Fluing

The Greenstar CDi series features 2 different sizes of

multi-directional RSF flue systems, 100mm or 125mm.

The flue can be run horizontally or vertically with additional 90 or

45 degree in-line bends allowing changes of route or direction,

providing an extremely flexible and versatile fluing system enabling

the appliance to be sited virtually anywhere.

More details are shown on page 13.

Versatility

Gas

The Greenstar CDi series is manufactured in both natural gas and

LPG variants (40CDi LPG launch date to be confirmed).

Controls

The CDi Series feature:



Power on/off switch.



Central heating variable temperature control selector.



An integral facia with status display lights and a digital display

which also operates as a fault diagnosis display.

Optional plug-in controls

The Greenstar CDi series of condensing combi boilers is available

with a comprehensive range of easy-to-use controls, ranging from

a simple mechanical timer to a choice of sophisticated radio-

frequency digistats. All fascia mounted controls offer simple

plug-in connection to the boiler circuit board.

MT10 mechanical timer

A simple easy-to-operate mechanical

timer with 15 minute switching points

over a 24 hour period. The timer

features a clock face with raised

hands to facilitate setting by visually

impaired users.

MT10RF mechanical RF thermostat

A simple, easy-to-operate 24 hour

mechanical timer combined with a

radio frequency room thermostat. The

thermostat features individual higher

and lower temperature sensors.

DT20RF digital RF thermostat with twin

channel programmer

A wall-mounted RF room thermostat

with digital display, combined with a

twin channel digital timer in the boiler

fascia. The fascia mounted

programmer benefits from automatic

time and date setup, automatic

summer/wintertime changeover

and a backlight for use in low light

conditions.

DT20 twin channel digital programmer

A versatile, easy-to-learn, 7 day,

digital programmer offering up to

3 on/off settings per day. The

programmer has a host of innovative

features including automatic setup,

which sets the correct time and date

at power-up, automatic summer/

wintertime changeover and a green

backlight for use in low light

conditions.

BBT180 Gstar CDi T&S Iss B 4/5/06 12:50 Page 4

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