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HD25Bi 22/09/15
The gravity circuit should connect to a domestic indirect hot water cylinder of minimum 135lt capacity,
using 28mm flow and return pipes, rising continuously from the boiler to the cylinder. Any nominally
horizontal runs of gravity pipework should slope upwards at not less than 1:30. The base of the hot water
cylinder should be located at least 150mm above the top of the stove. The gravity circuit must not contain
any shut off valves and should be fully lagged to minimise heat loss. The pipes should not exceed 7.8 meters
(25ft) in length to/from the cylinder. In general, the shorter the run of pipework the less heat loss and the
more efficient the water heating.
A heat soak radiator of at least 2kW must be used on the same gravity circuit, positioned above the stove.
This is used to dissipate heat when the central heating is switched off or the HW cylinder is fully heated.
Link Up:
On heating and hot water installations, a semi-pumped system should be used to the central heating system
with gravity circulation to the hot water cylinder. For optimum performance of the boiler we recommend
that all 4 tappings are used when using separate gravity and pumped heating loops. The flow and return
pipes should be taken from diagonally opposite sides of boiler.
Injector Tee:
If only two tappings are used on a common flow system, they should be taken diagonally opposite and the
remaining tappings should be plugged. An injector Tee should be fitted to join the gravity feed and central
heating circuits back to the stove, which should be situated as close to the stove as possible. The tee
connection encourages the stable flow of water through both circuits and prevents priority being given to the
stronger flow, typically the pumped circuit.
Pipe Thermostats
A HIGH LIMIT thermostat should be fitted to the gravity flow pipe close to the boiler and set at 90°C.This
should override any pump control, switching the pump on and dissipating any excess heat around the
radiator circuit. To prevent boiler corrosion due to condensation it is necessary to maintain the return water
temperature above 45°C. This can be achieved by the use of a LOWLIMIT thermostat on the return pipe
from the hot water cylinder, close to the boiler. The thermostat should make on temperature rise, preventing
the circulating pump from operating until the gravity circuit is up to temperature.
FAILURE TO COMPLY WITH THE ABOVE REQUIREMENTS WILL INVALIDATE THE GUARANTEE
Commissioning and Handover
Upon completion of the installation, allow a suitable period of time for any fire cement and mortar to dry
out. A small fire may then be lit and checked to ensure the smoke and fumes are taken from the stove up the
chimney and emitted safely to atmosphere. Do not run the stove at full output for at least 3 – 4 days.
On completion of the installation and commissioning, ensure that the operating instructions and operating
tools for the stove are left with the customer. Ensure to advise the customer on the correct use of the
appliance with the fuels likely to be used on the stove and warn them to use only the recommended fuels for
the stove.
Advise the user on what to do should smoke or fumes be emitted from the stove. The user
should use a suitable fireguard in the presence of children, aged and/or infirm persons.
All connections to the boiler should be checked to ensure there are no leaks during operation and that the
flow and return water connections are working properly. The stove should be fired up initially by the
Plumber / Heating Engineer to ensure that it is operating safely with the rest of the heating system.
