Hybrid Boiler Plants w/ Jim Devlin (Podcast)

Jim Devlin from Weil-McLain joins us to talk about high-efficiency and cast-iron boilers. He also explains how to use them together in a “hybrid” configuration to serve your customers.

Cast-iron boilers are standard-efficiency boilers. These boilers are “standard-efficiency” because they have higher return water temperatures; you typically measure about 330 degrees in the flue. Conversely, high-efficiency boilers have much lower return water temperatures, only around 180-190 degrees in the flue. The goal of a high-efficiency boiler is to get more BTUs out of the fuel, so your flue gases will be cooler. However, the standard boiler can be better for thermal transfer and gives us more leeway for our flue temperatures.

Hybrid boiler plants aim to eliminate inefficiencies by using cast-iron and high-efficiency boilers together. These hybrid configurations usually exist in older constructions, but you also see them in new constructions with dual-fuel burner systems or where high-efficiency boilers won't have a good value on their own. You will often see a greater ROI on systems that use cast-iron and high-efficiency boilers together than on systems with multiple high-efficiency boilers. Hybrid configurations usually set up dissimilar boilers in series with a primary-secondary loop. The controls usually use sensors and 1-10v DC output signals, so these controls can modulate the burners.

Many people make mistakes when piping these boilers; they don't understand the parallel positioning of the tees. When installers make these mistakes, the boilers lose efficiency. Jim recommends drawing out the piping to avoid making those errors.

Jim and Bryan also discuss:

  • Sulfuric acid and condensate
  • Boiler metals
  • Dual-fuel burner systems
  • Boiler controls
  • Hybrid vs. Combi-boilers
  • Comparing utility reports and checking ROI
  • Energy savings on cast-iron boilers
  • Heat exchangers
  • Future geothermal and solar hybrid systems

Visit to learn more.

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