Page 26
Gravity Flow Solid Fuel Boiler Pipe Layout
Min. 250mm
Normally open
2 port valve
Pipe
stat 1
Control
stat 2
Solid
fuel
vent
Feed and expansion tank sized to include
the expansion of solid fuel boiler, open vented
boiler and open vented central heating
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.
Normally closed
2 port valve
Heat sink radiator
(ensure lockshields
are left fully open)
Multi-fuel stove
Normally open
2 port valve
Solid Fuel Option
All models of the Torrent ECO 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 flow 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.
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 but available to purchase from Gledhill Spares Ltd);
• Honeywell V4043B1265 (XB165) - 28mm compression normally open 2 port valve
• Honeywell V4043H1106 (XC012) - 28mm compression normally closed 2 port valve
• Honeywell L641B1012 (XC016) - High limit pipe thermostat
• (XC010) - Control 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.
INSTALLATION
SOLID FUEL BOILERS
If control 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 and control
thermostat set points should be made during
commissioning to get the best performance
from the system. To comply with building
regulations control stat 2 should be set at a
temperature which prevents the contents of the
thermal store exceeding 100°C. If temperatures
in store exceed 85°C then secondary protection
will be required in accordance with Part G3 of
Building regulations.
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.
With regards to the domestic hot water
overheat protection, please refer to page 25 in
this installation manual.
Feed and Expansion Tank
A feed and expansion cistern supplying a system
heated by wet solid fuel appliance should either
be of metal construction (copper, stainless
steel etc.) of manufactured of a material
that has been certified as being suitable for
temperatures up to 110
°
C. These are available
to order from Gledhill at the time of purchase.
The capacity of the cistern should be at least
one twentieth of the total system volume.
The cistern should be fitted with a brass float
operated valve that is manufactured to BS1212
Pt. 2 and is fitted with an appropriately sized
copper float. The overflow pipe should be either
made of metal or manufactured from a material
that has been certified as being suitable for
temperatures up to 110
°
C. The overflow pipe
must have appropriate support – for plastics
this may require continuous support.
