Hybrid heating systems are becoming more and more common today as building owners, engineers and facility managers seek ways to reduce heating costs in both current facilities and new builds. Combining a large mass, non-condensing boiler with a high efficiency-condensing boiler – or “hybrid system” – ensures that a heating system is running at optimum efficiency to minimize operating costs over the course of a heating season.
Why do condensing and non-condensing boilers make such a good pair? Non-condensing boilers are ideal for the core heating season months of December through February. That’s because these boilers are designed to run at higher return water temperatures above 130 degrees to maximize longevity. The average efficiencies of non-condensing boilers, such as cast iron boilers, range from 80-85 percent thermal efficiency.
Condensing and non-condensing boilers
Running condensing boilers in high return temperature applications reduces their operating efficiency
In comparison, condensing boilers reach their maximum efficiency – upwards of 95 percent –when the return water temperature is below dew point and are ideal for operation during the milder heating season shoulder months of October, November, March and April. Running condensing boilers in high return temperature applications reduces their operating efficiency to marginally higher than non-condensing boiler designs.
By combining non-condensing and condensing boilers in a hybrid system boiler plant, users can reset building set points, reduce fuel consumption to lower operating costs and create comfortable, consistent building temperatures throughout the heating season.
Hybrid boiler systems
So why not just use an all high efficiency boiler plant? Consider the following benefits of a hybrid boiler system:
- Boiler Replacement Applications: Installing a hybrid system makes sense in existing, non-condensing replacement boiler applications. Most often, there are at least two high mass, non-condensing boilers in older boiler plants. Installing a high efficiency, condensing boiler in place of one of the failing high mass boilers now enables the efficiency benefits of the hybrid system. Further, this approach enables an incremental step in financing the overall boiler replacement capital outlay over time.
- New Build Applications: In short, condensing boilers cost more - upwards of 30-40 percent more than non-condensing boiler systems because of the non-corrosive heat exchanger materials required. Installing a hybrid system is more cost effective to purchase upfront and often achieves the greater portion of the energy savings of replacing an entire boiler plant with high-efficiency condensing boilers.
- Product Life / Longevity: Inherent to their design, non-condensing boilers have a longer product life, up to two times that of condensing boiler designs because of their thicker cast iron design and wider water pathways. Installing a hybrid system ensures a longer life of the boiler plant dedicated to the coldest heating season months.
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| Hybrid heating systems are becoming more and more common today |
Multiple industries
Consider an elementary school with two large cast iron boilers – one of which needs to be replaced after many years of dependable operation. In this scenario, the cast iron boiler is replaced with a new, high efficiency condensing boiler to match the heating requirement. A hybrid system can be utilized in many facilities across multiple industriesOnce installed, the condensing boiler controller allows for the assignment of an alternating, lead/lag boiler plant so that it serves as the primary boiler over the milder heating season months and the existing non-condensing boiler is operational more for colder days.
A hybrid system can be utilized in many facilities across multiple industries. More frequently, commercial buildings such as medical facilities, apartment complexes, churches, schools, colleges, nursing homes and corporate campuses, are standardizing on hybrid system boiler designs.
Combining a durable cast iron boiler with a high efficiency condensing boiler can reduce wasted energy, lower utility costs and protect the environment with a smaller carbon footprint, while extending the life of the existing heating system at a lower acquisition cost.
