Technical data

54
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
pipework. 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 Si
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 Si 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 Si 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 Si 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 Si 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 Si series design benefits
in operation
Hot water mode
Whenever a hot water tap is turned on the incoming mains water will
activate a flow switch 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 Si 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.
A built-in bypass and anti-cycling device makes the Greenstar Si
range particularly suitable for use on systems with TRV’s
(Thermostatic Radiator Valves).
Options
Fluing
The Greenstar Si 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 Si series is manufactured in both natural gas and
LPG variants.
Controls
The Si Series feature:
●
Power on/off switch.
●
Central heating variable temperature control selector.
●
An integral facia with status display lights which also operate as
a fault diagnosis display.
Optional plug-in controls
The Greenstar Si 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.