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        Why should I fit a Low Loss Header?

  • 1. Your boiler, particularly the heat exchanger in you boiler, will only function at it's peak efficiency when the water velocity passing through it is maintained within prescribed parameters. Boiler manufactures should tell you what the specs are for each make and model.
    In some cases the flow rate through the system circuit will exceed the recomended maximum flow rate through the boiler, or it may be that the system flow rates are simply unknown. In other cases the reverse is true, where the boiler flow rate exceeds the maximum system flow rate (particularly true in some multi boiler systems). Fitting a Low Loss Header allows the creation of a primary circuit, within which water velocity can be maintained at the required constant, regardless of changes or requirements in the secondary circuits.
    To sum this up in plain English: The amount of water going around the system (radiators, cylinder etc) might be to much or to little for the boiler.

  • 2. Not only is the water velocity important, but also water temperature. There are two potential problems: the first is "thermal shock". If the temp difference between the flow and return is to great, it puts a huge strain; through thermal expansion and contraction, on the heat exchanger. Also the temperature of the water passing through the heat exchanger is important, particularly with condensing boilers, these have there own specific requirements to operate at maximum efficiency. For a boiler to go into "condensing mode" the return temperature should not be higher than about 55'C. So in some cases temperature sensors are fitted on the header to allow control over the primary circuit temperature.
    Again in plain English: The temperature of the water coming from the system, might be to hot or to cold for the boiler.

  • 3. Because of the reduced water velocity, the header is an ideal place for siting an automatic air vent for removing air and a drain point for removing sediment and debris. These are generally fitted as standard on most headers

  • 4. The header allows separation of primary and secondary circuits for easier diagnosis when problems occur.

  •    To sum this up, the primary cicuit is acting like a circulating reservoir of hot
       water into which the secondary circuits can dip as needed.
       Secondary circuits are therefore normally pumped.

       This example shows a system where the primary circuit currently
       has a higher flow than the secondary circuits.
       Flow connections are usually at the top and the return at the bottom.


    small manifold.


    Quit a complicated small unit. 67mm dia body with one 54mm port coming off and a number of 22mm and 28mm stub pipes.

    with flanges.

    with flanges

    Two units with a 67mm main body and bi-metal PN16 flanges at one end.

    219mm dia.

    219mm dia unit

    A large diameter header with two flanged stub pipes and four 2" BSP female brass fittings. .

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