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Hydronic (Water) Boilers

Residential hydronic boiler systems heat a home by warming water (or sometimes an antifreeze solution) and circulating it to deliver heat through radiators, baseboards, or radiant flooring. These systems are commonly classified by fuel type, boiler design, venting method, and heat delivery method.

Natural draft cast iron mid efficiency boiler system

1. Conventional (Cast Iron) Boilers

A traditional and widely used boiler type.

  • Description: Use heavy cast iron heat exchangers to heat water, which is then circulated through the home. Use a natural draft method for exhausting flue gases without an induced draft motor.

  • Efficiency: Low to moderate.

  • Advantages: Extremely durable, long service life, simple design.

  • Limitations: Slow response time, lower efficiency.

  • Typical use: Older homes with radiator or baseboard heating.

2. Non-Condensing Boilers

A modern version of traditional boiler design.

  • Description: Use heavy cast iron heat exchangers to heat water, which is then circulated through the home. Use an induced draft motor to push flue gases into the chimney or flue piping.

  • Efficiency: Moderate (typically up to ~85% AFUE).

  • Advantages: Reliable and less complex than condensing boilers. Faster heat distribution than a traditional natural draft boiler system.

  • Limitations: More heat loss through exhaust.

  • Typical use: Replacement systems where existing venting is used.

3. Condensing Boilers

The most efficient residential hydronic boilers.

  • Description: Capture additional heat from exhaust gases by condensing water vapor, allowing much higher efficiency.

  • Efficiency: High to very high (90–98%+ AFUE).

  • Advantages: Lower fuel consumption, compact size, environmentally friendly.

  • Limitations: Higher upfront cost; requires condensate drainage and increased maintenance frequency.

  • Typical use: New installations and high-efficiency upgrades.

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