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4.9 (a) CENTRAL HEATING CONNECTIONS, DESIGN & REQUIREMENTS
This boiler is designed for fully pumped sealed systems only.
Treatment of Water Circulating Systems
All recirculatory water systems will be subject to corrosion unless an appropriate water treatment is applied. This means that
the system efficiency will deteriorate as corrosion sludge accumulates within the system. This causes a risk to the pump and
valves and can result in boiler noise and circulation problems. When installing heating systems, flux will be evident in the system
which can lead to damage of boiler and system components.
All systems must be thoroughly drained and flushed out using corrosion inhibitors and cleansing agents/descalers that are
compliant with BS7593 requirements. In all cases, they should be used following the manufacturer’s instructions.
Failure to flush and add an inhibitor to the system will invalidate the manufacturer’s warranty of the boiler.
It is also important that the inhibitor concentration is checked for correctness after installation, modification and during every
service in accordance with the relevant manufacturer’s instructions. Test kits specifically for this purpose are available from
inhibitor stockists.
Heating Flow & Return
These connections are ¾ “ for connection to 22mm pipe using the tails provided. Service valves should be installed in the
pipework directly below the boiler with drain-off points above to allow the boiler to be isolated for maintenance without the
need to drain the entire system. The valves should be of sufficiently large bore so not to restrict the heating circulation.
The boiler is not suitable for single pipe heating systems, only a twin-pipe heating system should be used.
It is recommended that a
minimum
of 2m of 22mm diameter pipework is present to/from the flow and return connections
on the boiler as reduction in size prior to this may result in the system flow rate being below the minimum level required,
resulting in error E3.
Drain Point
As detailed above, drain points should be installed directly above the service valves on the flow and return pipe work to
enable the removal of water from within the boiler for servicing and maintenance, preventing the need to drain the entire
system.
A drain point must also be fitted at the lowest point of the system. It is not acceptable to drain the boiler through the safety
valve as debris and deposits will prevent correct operation of the valve.
Heating System By-pass
The heating water flow switch requires a minimum flow rate through the boiler of 7 L/min for correct operation. Systems
fitted with Thermostatic Radiator Valves on every radiator
must
have a bypass circuit installed.
The bypass circuit must be in 22mm pipe work, is recommended to have at least 2m of continuous pipework and must
incorporate an automatic bypass valve. This is required in order to maintain sufficient flow through the boiler should all of
the valves be closed. (See 7.3 Heating System Flow Switch - E3 Error & System Bypass Requirements).
To alleviate potential flow issues, especially on smaller systems, it is recommended that all installations be fitted with a bypass
circuit as described above.
System Expansion
An integral 6 L expansion vessel provides for expansion of the heated system water under normal conditions however a
system with larger volumes of water may require extra expansion capacity to be provided.
