Section 1: IntroductionPage 4
1.1 HOW A CONDENSING BOILER OPERATES
During the combustion process, hydrogen and oxygen combine
to produce heat and water vapour. The water vapour produced
is in the form of superheated steam in the heat exchanger. This
superheated steam contains sensible heat (available heat) and
latent heat (heat locked up in the fl ue gas). A conventional boiler
cannot recover any of the latent heat and this energy is lost to the
atmosphere through the fl ue.
The Grant condensing boiler contains an extra heat exchanger
which is designed to recover the latent heat normally lost by a
conventional boiler. It does this by cooling the fl ue gases to below
90°C, thus extracting more sensible heat and some of the latent
heat. This is achieved by cooling the fl ue gases to their dew point
(approximately 55°C).
To ensure maximum e ciency, the boiler return temperature
should be 55°C or less, this will enable the latent heat to be
condensed out of the fl ue gases.
The boiler will achieve net thermal e ciencies of 100%.
To achieve maximum performance from the Grant boiler, it is
recommended that the heating system is designed so that a
temperature di erential of 20°C between the fl ow and return is
maintained.
The Grant boiler will however still operate at extremely high
e ciencies even when it is not in condensing mode and
therefore is suitable for fi tting to an existing heating system
without alteration to the radiator sizes. The boiler is capable of a
maximum fl ow temperature of 75°C.
1.2 BOILER DESCRIPTION
The Grant Boiler House range of automatic pressure jet oil boilers
have been designed for use with a fully pumped central heating
system with indirect domestic hot water cylinder.
They are not suitable for use with either a direct cylinder or a
‘primatic’ cylinder or gravity hot water.
The boilers are suitable for use on open vented or sealed central
heating systems. Refer to Section 7.
The boilers are supplied with a separate burner and dual
thermostat.
The dual thermostat is supplied factory fi tted on the 46/70 models.
All the models in the current Grant range of boilers are designed
to comply with the maximum NOx emissions* under the Energy-
related Products Directive (ErP).
* From the 26th September 2018, the maximum NOx emissions
for all new oil fi red boilers (up to and including 400kW for both
new build and replacement boiler installations) is 120mg/kWh.
1.3 FLUE OPTIONS
The boilers can be connected to either a conventional fl ue system
or a balanced fl ue system, as required.
1.3.1 FOR CONVENTIONAL FLUE
APPLICATIONS
Where a chimney is to be lined - Grant recommends the use
of the Grant ‘Orange’ fl ue system, specifi cally designed for the
range of condensing boilers. Refer to Section 9.2 for further
details.
Where a rigid conventional fl ue - either internal or external - is
required, Grant recommends the use of the Grant ‘Green’ and
‘Orange’ fl ue system components. As no fl ue adaptor is supplied
with the boiler it will be necessary to purchase the Grant CF
adaptor kit in order to correctly connect this system to the boiler.
Flue adaptor kit (Grant product code: CFA15/70) is used for all
models as they all use the 100 mm ‘Green’ and ‘Orange’ system
components to construct a fl ue of maximum vertical height 19
metres.
! NOTE !
The fl ue system materials and construction MUST be
suitable for use with oil-fi red condensing boilers. Failure
to fi t a suitable conventional fl ue may invalidate the
guarantee on the boiler.
1.3.2 FOR BALANCED FLUE APPLICATIONS
The following fl ue kits are available from Grant. Refer to Section
9.4.
Yellow system
• Standard low level concentric balanced fl ue - components
available:
• Extensions 225 mm, 450 mm and 675 mm
• 90° extension elbow
• 45° extension elbow
• 45° elbow
• Plume diverter kits
Green system
• Standard external high level/vertical fl ue starter kit (room
sealed) - components available:
• External high level/vertical fl ue starter kit short (room sealed)
• Extensions 150 mm, 250 mm, 450 mm, 950 mm
• Adjustable extension 195 to 270 mm
• 45° elbow
• High level terminal
• Vertical terminal
White system
• High level and vertical concentric balanced fl ue kit-
components available:
• Extensions 225 mm, 450 mm, 950 mm
• Adjustable 275 to 450 mm
• Vertical concentric balanced fl ue kit
• Extensions 225 mm, 450 mm, 950 mm
• Adjustable extension 275 to 450 mm
• 45° elbow
Red system (15/21 and 21/26 only)
A fl exible vertical balanced fl ue system designed to be fi tted inside
an existing masonry chimney.
Consisting of three sections:
• Concentric white painted fl ue pipe connected to the boiler
• Vertical concentric fl exible fl ue (fl exible stainless steel fl ue liner
inside a stainless steel air inlet liner)
• Terminal assembly for chimney top mounting
Flue extensions and 45° elbows from the White system may be
used.
Fitting instructions for the Low level, High level and Vertical
balanced fl ue systems are supplied with the kits.
1.4 BOILER COMPONENTS
All burners are pre-set for use with kerosene and are supplied
ready to connect to a single pipe fuel supply system with a loose
fl exible fuel line and 3/8 to 1/4 BSP male adaptor supplied with
the boiler.
If required, an additional fl exible fuel line (630 mm) and 3/8”
to 1/4” BSP male adaptor are available to purchase from Grant
1 INTRODUCTION
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