Graphite GR910-B, Instruction Manual

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SYSTEM INSTALLATION:
GENERAL GUIDELINES
Central heating systems
A pumped central heating circuit combined with a
gravity hot water circuit is generally the accepted
specification for multi fuel boiler systems which are
not linked to another system. However, achieving
the correct balance between the pumped and gravity
flows in such a system is critical to the efficient
performance of the boiler stove and should be left
to an experienced Hetas wet installer or appropriate
specialist registered on a Competent Persons scheme.
Increasingly new systems are specified as ‘fully
pumped’ to provide improved operational control and
this is a feature that we would recommend for your
system.
Dual fuel linked systems
You may have purchased your new Graphite Boiler
stove with the intention of adding it to an existing
heating system powered by a different fuel type. This
is likely to be to a non-pressurised oil or gas system,
but could also be solar powered, probably in a new
pressurised system.
Linking two such systems requires specialist
knowledge to ensure a fully functioning system which
is efficient, safe and legal. Such systems require the
installer to possess a knowledge and understanding
which will be beyond the provisions and intentions of
these general installation and operating guidelines.
The United Kingdom’s Solid Fuel Association
through their website
www.solidfuel.co.uk , provides
informative downloads on various link-up system
solutions.
The most common problem with link-up systems is
a failure to understand the existing system which
may have faults which are then exacerbated by the
new link. Our advice when linking this boiler stove
to any system is therefore to consult the appropriate
installation expert who will develop an understanding
of your requirements and provide you with a
thorough survey of any existing system.
There are various Government competent persons
schemes listing installers trained in designing and
installing linked systems:
• Hetas
www.hetas.co.uk
• Association of Plumbing & Heating Contractors
(Certification)
www.aphc.co.uk
• Building Engineering Services Accreditation
www.besca.org.uk
• NICEIC www.niceic.org.uk
BASIC SYSTEM ESSENTIALS
The basic system diagram shown overleaf should
be used for general guidance purposes only and is
included here to demonstrate basic system principles.
Combined with the at-a-glance list below this should
provide you with a basic understanding of the
essential requirements your system should have. As
each system and its requirements will vary the list
below is by no means meant to be comprehensive.
A good system should adhere to the following:
• Systems using two tappings must use diagonally
opposite system ports
• Adjustable flow circulating pump
• High and low limit thermostats
• Cold feed pipework must be minimum 22mm dia’
• Open vent pipework must be minimum 22mm dia’
• Overflow pipe must be 22mm dia’ copper
• All pipework must be able to operate at
above 100ºC
• Feed / expansion tank must be galvanised steel
or copper
• Float valve should also be copper
• No automatic or manual valves on cold feed
or open vent pipework
• Heat leak radiator fitted to gravity circuit
• Exposed pipework (eg lofts) must be insulated
to prevent freezing
• Hot water cylinder and thermostat
• System should be capable of being completely
drained
Heat leak radiator
A heat leak radiator with a minimum rating of 10%
of the boiler’s total output to water should be fitted
to the gravity circuit. Heat leak radiators rated at
approximately 2kW (6,800BTU) tend to be the norm
in most systems. Pipes to and from the heat leak
radiator can be reduced to 15mm diameter provided
the run is no further than 300mm (12”) away from
the 22mm gravity circuit. No thermostatic or manually
adjusted valves should be fitted to the heat leak
radiator to ensure that it can never be shut down. If
a thermostatic control over-heat valve, which controls
the flow when the water in the hot water cylinder
has reached a predetermined unsafe temperature, is
specified as part of the system then you must ensure
that the heat leak radiator has a rating to cope with
the extra demands made on it when the hot water
cylinder is isolated.
Adjustable circulating pump
It is important that the system flow can be adjusted
via the circulating pump to ensure the best operation.
A system flow which is too slow could potentially
over-heat or at the very least take a long time to
warm the house. One that is too fast could reduce the
time it takes for the water pass through the boiler and
absorb heat, thus reducing the overall effectiveness
of the system. Ensure that isolation valves are fitted