gledhill Torrent GreenHeat TGH140-OV Design, Installation & Servicing Instructions page 26

INSTALLATION
Gravity Flow Solid Fuel Boiler Pipe Layout
Solid
fuel
vent
Pipe
stat 2
Normally
closed
2 port valve
Normally open
Pipe
2 port valve
stat 1
Multi-fuel stove
Solid Fuel Option
All models of the Torrent GreenHeat shown in this installation manual have the tappings
included as standard for a solid fuel boiler. In the absence of recommendations from
HETAS or the solid fuel boiler manufacturer, we would advise the following pipe layout
to achieve the best performance from your solid fuel system and our thermal store.
This diagram represents a good example of a gravity circulation pipe layout. Points to
note are;
• All pipework rises towards the cylinder and the heat sink radiator and fall back
towards the solid fuel burner.
• The heat source is below the cylinder which gives the layout a good system height.
• All gravity circulation pipework is recommended to be 28mm or above pipe
diameter, at low fl ow speeds the pipe resistence is negligible in this pipe diameter.
• Avoid long horizontal runs and try to make the ratio horizontal:vertical to be a
maximum of 20:80.
SOLID FUEL BOILERS
Feed and expansion tank sized to include
the expansion of solid fuel boiler, open vented
boiler and open vented central heating
Min. 250mm
Heat sink radiator
(ensure lockshields
are left fully open)
This circuit usually uses gravity circulation.
Good circulation depends on the system
height and the temperature difference
between the hot flow and the cool return
to provide the motive force to overcome
the frictional resistance in pipe and
fittings and provide circulation.
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To ensure that the solid fuel boiler does not
overheat the thermal store during its operation
and prevent gravity circulation cooling the
thermal store when it is not, the following
controls can be used. Other methods of
control can be used; HETAS and/or the solid
fuel boiler manufacturers instructions should
be consulted. This control system is fed from
a dedicated fuse spur to enable safe isolation
for changing components. All wiring should
comply with BS7671 Requirements for Electrical
Installations 17th edition.
Typical components (not supplied);
• 1 x Honeywell V4043B1265 - 28mm
compression normally open 2 port valve
• 1 x Honeywell V4043H1106 - 28mm
compression normally closed 2 port valve
• 2 x Honeywell L641B1012 - High limit pipe
thermostat
When the boiler is lit, the water temperature
raises. When the temperature is above pipe
thermostat 1 set point, the contacts close
signalling the normally closed valve to move
open. Once it is fully open, it signals the normally
open valve to motor there by closing it. The
thermal store now receives heat from the solid
fuel boiler via gravity circulation.
If pipe stat 2 set point is exceeded then the
power to the normally closed valve is cut which
in turn cuts the power to the normally open
valve. Excess heat from the solid fuel boiler is
then circulated around the heat sink radiator.
Careful selection of the pipe thermostat
switching temperatures should be made during
commissioning to get the best performance
from the system.
There are 2 solid fuel returns on the Sol
cylinder range to enable the whole store water
volume to be used to store heat when the solar
contribution is negligible. For example, a solid
fuel boiler that is used for space heating would
only be used in the winter months when the
solar contribution is small. Connecting it to
lower return enables the store to hold more heat
when the sun cannot provide as much.
Alternatively an Aga which runs 24 hours 365
days a year would need to be connected to
the upper return when the solar contribution
is greatest and the lower when the solar
contribution is least. A pair of simple isolation
valves may be used to switch from summer to
winter mode or more sophisticated control
methods used.
Please note, the Torrent Greenheat should
not be held at temperatures above 85˚C for
prolonged periods.