The Hybrid Boiler System

GOES has always been “green” oriented even before it became a worldwide trend.  We proudly represent the equally progressive and innovative Mestek boiler brands of Hydrotherm and RBI.  With the volatility of today’s energy prices, we continue to be innovative and design the most energy efficient boiler systems based on local usage patterns and climate.  With the recent economic recession, we are cognizant of building owner’s budget concerns.  The Hybrid Boiler System achieves this goal by incorporating condensing boilers together with non-condensing boilers to maximize energy efficiency and longevity while minimizing the upfront equipment and long term operating costs.

Not every heating system is designed or operated under the same conditions which is the reason the Hybrid Boiler Systems work very well in our market.  In the design of a Hybrid Boiler System, the condensing boiler is sized for 20 to 25% of the total heating capacity and the non-condensing boilers are sized for the remaining 75 to 80%.  Only 20% of the heating capacity in most cases is used 80% of the time during the heating season.  80% of the total capacity is only used 20% of the time.  This results in the more durable and efficient condensing boiler carrying most of the load thus resulting in a much longer lifespan for the complete system.  Within most markets in these uncertain economic times, we are seeing that the replacement of heating systems is growing at a much faster rate than new construction projects.  Older systems that were designed for 20°ΔT with 160° to 180° degree fan coil units will not sustain the lower temperatures necessary to justify using all condensing boilers in most cases.  Another general rule of thumb when designing Hybrid Boiler Systems is to size the pump on the condensing boiler for a 60°ΔT and the non-condensing boilers at a 30°ΔT.  Using a higher ΔT in the condensing boiler will prevent short cycling when only minimal heat is required.  We find that most existing heating systems are not designed with adequate flow rates when all heating zones are satisfied or when variable frequency drives are added to existing secondary pumps.

We have recently incorporated the use of hydraulic separators to the Hybrid Boiler System concept.  The hydraulic separator assists in not only matching the flow rate to the system but also to protect the low velocity condensing boilers from air and dirt present in the system piping.  Regardless of secondary loop operational flow rates or the interruption of system flow due to repairs or additional maintenance, the boilers are protected.  With the constant upgrading of Mestek’s HeatNet® controls to distinguish between high mass (Hydrotherm KN's) and low mass (RBI Futera III) boilers, the Hybrid Boiler System will far exceed the return on investment over systems using only condensing boilers.