1.1 How the Condensing Wood Pellet 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 locked
up in the flue gas). A conventional boiler cannot recover any of the
latent heat and this energy is lost to the atmosphere through the flue.
The Grant External Vecta contains a unique extra (secondary)
condensing heat exchanger which has been designed to capture
some of this lost heat energy that would otherwise be lost, so it
maintains extremely high efficiencies.
It does this by cooling the flue gases to their dew point (below 55°C)
thus extracting more sensible heat.
The boiler has been independently tested to BS EN 303-5:2012
and BS EN 12809:2001+A1:2004 and will achieve the following net
efficiencies when both the boiler and system are correctly set:
Operating Condition
Full load efficiency
Part load efficiency
Condensing
101.5%
97.5%
To ensure maximum efficiency from the Grant External Vecta boiler,
the boiler return temperature should be 55°C or less (but NOT less
than 40°C) at maximum operating temperature. This will enable
the latent heat to be condensed out of the flue gases. The boiler is
capable of a maximum flow temperature of 80°C.
To achieve the required return temperature (55°C or less), it is
recommended that the heating system is designed and balanced
to operate with a temperature differential of 20°C between flow
and return. The use of modulating circulating pumps (now widely
available) and effective control systems should be considered.
The Grant External Vecta condensing wood pellet boiler will still
operate at extremely high efficiencies even when not in condensing
mode and are therefore suitable for fitting to an existing heating
system without alteration to the radiator sizes.
1.2 Boiler Description
Grant External Vecta wood Pellet boilers have an insulated
weatherproof enclosure made of galvanised steel with a powder
coated finish, and are designed for external installation, either against
a wall or free standing some distance away from the property, as
required.
The boiler is suitable for use on a sealed or open vented central
heating system. When commissioned and set correctly, the Grant
External Vecta wood pellet boiler will operate automatically, using a
typical heating control system.
The boilers are not designed specifically for operation on a system
with a buffer tank/ thermal store, however when used on such a
system there is no effect on the boiler performance.
Refer to Section 4 for boiler installation.
1.3 access
The External Vecta wood pellet boiler enclosure is fitted with the
following means of access:
•
A hinged door (with lockable door catch*) at the front - for
access to the boiler for routine cleaning (emptying the ash pan)
and access to boiler/burner controls.
•
A hinged top hopper lid (with lockable door catch*) - to allow
pellets to be tipped into the hopper by the user and for access to
the top of the boiler for commissioning and servicing.
•
A removable side access panel (with lockable door catch*) on
the left hand side - to allow access to the electrical wiring/PCB
enclosure, photocell ignition heater element, etc., and also the
water and condensate connections.
* These door catches can be fitted with a small padlock (not supplied)
if required.
To unlock and open any of the above, unlock/remove the padlock (if
fitted). Rotate the knob of the catch clockwise to unlatch and open the
front door, top hopper lid or side access panel.
Close and lock the door, lid or panel using the reverse of the above
procedure.
1.4 Flue System
The Grant External Vecta wood pellet boiler must be connected to a
conventional flue system.
the OnLY flue suitable for use with the Grant Vecta wood pellet
boilers is the Grant ‘Biomass’ conventional flue system. this
is a 125mm (5”) diameter twin wall insulated, powder coated
stainless steel flue system. Refer to Section 7 for details.
nOtE
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Section 1: introduction
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