How does the modulation system in Endurance work?
The Endurance modulation system senses the boiler return water temperature indirectly and adjusts the input by varying the combustion air blower speed. Proper combustion is maintained by the ratio gas valve, which senses blower suction pressure and adjusts gas flow accordingly. The full output is provided when the return water temperature is low. As the return water temperature increases, the firing rate modulates downward and is a minimum just prior to limit operation. This type of modulating system is ideal for low mass boilers.
