Hewlett-Packard, a top computer manufacturer in Houston has recently upgraded their hydronic heating Central Utility Plant from a steam/indirect system to a direct hydronic system. The steam/indirect system consisted of (1) 500 HP steam boiler and a steam-to-water heat exchanger. This system had a set point for the hot water loop of 180 deg F.
The system was replaced with a “hybrid” hydronic heating system consisting of (2) Hydrotherm KN-20 condensing boiler and (3) RBI Futera III 2000 non-condensing boilers (all rated at 2,000 MBH each) totaling 10 MBTU with a turn-down ratio of 22-to-1. All boilers are connected together using CAT5 cabling using the standard on-board HeatNet® controls. This allows all five boilers to be controls by the master (main) boiler using one sensor in the main header piping and one outdoor sensor for system reset. The master boiler is tied to the buildings automation system by way of Bacnet MSTP protocol. The master boiler, by way of HeatNet® control, stages and modulates boilers as the load changes in the hot water loop. The hybrid boiler system can vary the hot water loop temperature from 110 degrees to 180 degrees depending on the outdoor air temperature. The new hybrid boiler system should save the company a minimum of 25% to 35% on their fuel consumption each year over the prior system.
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