What are low loss headers?
The heat exchanger in any boiler will only function at peak efficiency when the water velocity passing through it is maintained within prescribed parameters.
In some heating installations the flow rate through the heating system may exceed the recommended flow rate through the boiler, or the reverse may be true where the boiler flow rate exceeds the maximum heating system flow rate.
Fitting a Low Loss Header prevents this from happening by the creation of a primary circuit whereby water velocity may be maintained at the required rate, regardless of changes in demand of the heating system.
Not only is the water velocity important, but also water temperature. There are two potential problems: the first is “thermal shock”. If the temperature difference between the flow and return legs are too great, it can shorten the life of the heat exchanger.
Secondly, the water passing through the heat exchanger is also important, particularly with condensing boilers, maximum efficiency can only be maintained if they function within prescribed temperature parameters.
For a boiler to go into “condensing mode” the return temperature should not be higher than about 55’C and a low loss header fitted with temperaure controls can facilitate this.
To sum up, the primary cicuit or low loss header is acting like a circulating reservoir of hot water into which the secondary circuits can dip as required.