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9. Pump Assisted Central Heating
9.1 The most common arrangement is to have a pumped
central heating circuit combined with a gravity hot water
circuit. This arrangement requires careful balancing of the
two in order to avoid the gravity circuit being starved when
the pump is running.
To overcome this problem it is common practice to fit
an injector tee where the pumped central heating return
re-joins the gravity return from the hot water cylinder. This
injector tee induces a much stronger gravity flow when the
pump runs.
Only use proprietary injector tees, homemade ones are
difficult to get right.
9.2 When installing a system that has pumped central heating
and gravity hot water it is recommended to use all 4
boiler tappings. Each flow and return should be diagonally
opposite each other.
10. Fully Pumped System
10.1 In many installations (especially new build) a fully pumped
system is the best choice to give increased control.
WARNING - To prevent the risk of boiling it is essential
to arrange the pipe work and position the hot water
cylinder and heat leak radiator so that gravity circulation
can take place when the pump is not running. Any
motorised valves fitted in this circuit must return to the
fully open position when the power is interrupted.
11. Sealed (Pressurised) System
11.1 Do not fit this appliance to sealed or pressurised systems or
an unvented hot water cylinder.
12. Pipe work Diagrams
12.1 See over for a typical layout of a pumped central heating
and gravity hot water circuit.
6. Pump
6.1 Where a pump is fitted into the circuit it should be
adjustable so that the flow can match the system
requirements. Fit isolation valves to enable removal for
servicing. The pump must have at least 1.5 meters of static
head.
7. Electrical Supply
7.1 Electrical connections must meet the requirements of
national Building Regulations* and standards**, along with
any European, local regulations and working practices that
may apply. Should conflict occur between these instructions
and these regulations then the regulations must be followed.
The connection to the mains supply should allow
complete electrical isolation and only serve the heating
circuit pump.
All water connections should be completed by a competent
person to meet the requirements of local water authority
by-laws.
CONVENTIONAL PIPE WORK SYSTEMS
All pipe work must be able to operate at above 100
degrees Celsius. Any pipe work installed in an exposed
position e.g. loft space must have provision to prevent
freezing.
Ensure the pipe work system has sufficient drain
points to enable the complete removal of water for the
purposes of servicing.
8. Gravity Pipe Circuit
8.1 To prevent the risk of boiling it is essential to arrange the
pipe work and position the hot water cylinder and heat
leak radiator so that gravity circulation can take place when
the pump is not running. Position the cylinder and the
radiator vertically above the boiler with sufficient height to
encourage gravity flow.
8.2 Horizontal pipe work in a gravity system must have an
incline of at least 5mm in every 1000mm and a minimum
diameter of 28mm. Vertical pipe must have a minimum
diameter of 22mm.
8.3 Any motorised valves fitted in this circuit must return to the
fully open position when the power is interrupted.
INSTALLATION INSTRUCTIONS