10
ALPHA 700
14.0 minimum
water flow rate
15.0 circulating
water
The minimum water flow
rate must be provided at all
times either via the main
system pump/s or via shunt
pumps. The boiler and burner
must be interlocked to the
pumps and the burner must be
prevented from firing in the
event of water flow failure.
In the case of multiple
boilers with individual shunt
pumps, it is important to install
non return valves upstream of
the return connection to avoid
parasitic flows between
boilers. See diagram opposite.
Alpha boilers must always be installed on closed systems, whether they are of open vented or sealed
and pressurised type. All systems should be thoroughly cleaned prior to the installation of the boiler and
the system water must be treated to prevent the deposition of scale or sludge in the boiler waterways. The
system water must be of a sufficient quality to maintain the following requirements:
●
pH between 7.5 and 8.5
●
maximum hardness between 8 and 12 grammes of calcium carbonate per 100 litres of water.
16.0 flue
systems
The diameter of the flue pipe used must not be less than the diameter of the flue connection on the
boiler. Due consideration must be given to the requirements of the Clean Air Act Memorandum on
Chimney Heights (3rd Edition) when designing flue systems and selecting terminal positions. Detailed
guidance and recommendations for flue design are given in BS6644 and British Gas Publication IM11. Similar
guidance for oil fired appliances may be found in BS5410 Part 3.
Any brick built chimney used must be swept clean, cleared of any obstructions and where not internally
coated with an impervious barrier, must be lined with a suitable liner and insulated as necessary.
The chimney must be designed to provide the negative draught requirement as detailed in the technical
data section of this publication. Where the generated draught exceeds the maximum figure quoted, then
gas fired installations can be fitted with a draught stabiliser.
Exposed, prefabricated flue systems should be adequately insulated to maintain flue gas buoyancy and
reduce condensation.
Flue terminals should have minimum resistance and terminals such as GLC and GC1 types are not
considered suitable.
Flue pipe routes should allow for the shortest possible horizontal run to the main vertical chimney. The
use of tight radius bends and square tees should be avoided.
For detailed guidance, assistance and quotations on flue systems, contact MHS Boilers
Flue Department.
Non Return Valves
