Cleaver-Brooks - Complete Boiler Room Solutions

Hydronic Boilers Yield Significant Savings

Tip Sheet: March 2012

Key Facts

  • Condensing hydronic boilers can achieve efficiencies in the mid- to high - 90s
  • Hydronic boilers can be used for either building heat or for process hot water applications
  • It is often advantageous to use multiple boilers in condensing applications

Get up to 99% boiler efficiency with a condensing hydronic boiler.


Before condensing boiler technology was introduced, boilers operated at 80% to 85% efficiency. Today, condensing hydronic boilers can operate at efficiencies in the mid - to high - 90s. Hydronic boilers can be used for either building heat or for process hot water applications.   


A condensing boiler extracts latent heat in addition to sensible heat from combustion exhaust, and the results can be dramatic. Some facilities experience an energy savings of up to 50% in systems that make proper use of outdoor reset schedules, aggressive night/weekend setback schemes and larger system temperature differentials.  

Non-modulating (on-off) boilers operate at full fire all the time. Whereas older design units are typically most efficient at higher firing rates, the same does not hold true for today’s modular boilers. These new designs tend to be more efficient at lower fire compared to high (or max) fire. The modulation helps achieve the lower firing rate. The longer a modular boiler can run at lower fire, the more efficient it is. Also, each time a boiler cycles off and on, it loses efficiency. Modulating boilers can also run longer at lower temperatures, which minimizes excessive cycling.  

Modern controls such as the Cleaver-Brooks Falcon, available on ClearFire® boilers, use a variety of sensors to monitor the boiler system and modulate the output of the boiler to meet a facility’s demands. This modulation allows the boiler to run at lower firing rates for longer intervals while still maintaining the desired temperature.  

The temperature of the return water is an important factor to consider when evaluating new modular units. Some models cannot take return water below 140° F, and other condensing models are designed to go lower. With a 130° to 135° F single return water flow, the ClearFire-C, a condensing boiler, can achieve efficiencies as high as 90%. However, if the return water flow is 140° F or above, it is not low enough to cause condensing, and a better choice is to use a near-condensing boiler such as the ClearFire-W.  


It is often advantageous to use multiple boilers in condensing applications. Multiple boilers with turndown capabilities facilitate better overall system load matching. By installing smaller and multiple condensing boilers, a facility manager can stage the boilers depending upon heating load, which will help in fuel savings compared to one larger boiler.   

To learn more about modular boilers and the associated controls that can help your company reduce costs, watch the Hydronic Boilers Yield Significant Savings webinar or visit cleaverbrooks.com/clearfire.