Published on November 21, 2017
1. Hydronic Systems – Condensing and Non-Condensing Boiler Overview Catie VanWormer, PE, LEED AP – Product Sales Manager, ClearFire Products Cleaver-Brooks, Inc.
2. To Condense or Not to Condense? Hydronic Heating ?
3. • Firetube Boiler – hot flue gases pass through one (or multiple) tube passes through a pressure vessel that contains water (and/or steam) • Watertube Boiler – tubes contain water that are externally heated by the boiler flue gases • High Mass Condensing Boiler - more than 50 gallons of water volume per MMBTU • Low Mass Condensing Boiler - less than 20 gallons of water volume per MMBTU • Condensing Mode – boiler operating below the flue gas dew point • Non-condensing Mode – boiler operating above the flue gas dew point 3 Boiler Definitions
4. Hydronic Heating Non Condensing Boiler Types 4 Fire Tubes Fire Box Flexible Watertube Cast Iron Sectional Modular watertube
5. 5 Quality Segmentation Firetube / Flextube High Mass Cast Iron Sectional High Mass Modular Low Mass Modular Atmospheric Firetube – Long life, best efficiencies (84-85%) Flextube – Long life, 80-85% eff., wider Delta T, thermal shock resistant Cast Iron – Medium life, higher maintenance, primary-secondary pumping H/M Modular – medium life, lower return temp, pumping flexibilty Low mass – Shorter life, high press. drop high minimum flow requirements, primary-secondary pumping, 80-85% eff. Atmospheric – Low efficiency (60-80%) Value System Impact Hydronic Heating Non Condensing Boiler Types
6. Hydronic Boilers Non-Condensing Pros and Cons 6 Advantage • Most have Higher Temp limit • Higher Pressure designs • Larger Capacities • Fuel oil and alternative fuel back-up • Lower Initial Equipment Cost Disadvantage • Larger footprint • Standard Efficiencies • Less than 85% • Rust Corrosion • Minimum operating/return temperatures • Thermal Shock • Cast Iron / Firetube • Piping/pumping limitations • For Boiler Protection
7. Hydronic Boilers Condensing Performance 7 Questions: #1 – What makes a boiler a Condensing Boiler? #2 – What physically allows/promotes boilers to condense?
8. 8 The Science Behind Condensing Non-condensing boilers Available energy in flue gas is lost 80-87% eff. at very best
9. 9 The Science Behind Condensing Boiler Efficiency Improves Dramatically with Condensing Available Energy is recovered before it is allowed to go up the stack Efficiencies now: 90% to 99%
10. 10 • Operating at LOW Temperatures • Effective Heat Exchanger Boiler Efficiency Improves Dramatically with Condensing Condensing Efficiency Drivers The Science Behind Condensing
11. 11 Efficiency Characteristics with Condensing The Science Behind Condensing
12. 12 • Operating at LOW Temperatures • Effective Heat Exchanger Boiler Efficiency Improves Dramatically with Condensing Condensing Efficiency Drivers Counter-flow Heat Exchanger Effective Heating Surface to promote condensing The Science Behind Condensing
13. Condensing Technology Condensing Boiler Types 13 Modified Firetube [SS] Cast Aluminum Cast iron w/ add-on HX Copperfin w/ add-on HX Firetube [SS]
14. 14 Hydronic Boilers Condensing Boilers High Mass Firetube Mid-mass Firetube & Watertube Low Mass High mass – Long life, high ∆T limit, large water volume, premium operational efficiencies Designed for primary variable flow Mid-mass – Medium life, 30-60 F ∆T limit, limited water volume, high efficiency Capable of limited primary variable flow Low mass– Shorter life, 20F-30F ∆T limit, little water volume Primary-secondary ONLY Quality Segmentation Value System Impact
15. Hydronic Boilers Condensing Considerations 15 Why Condensing? • Highest efficiencies • Thermal shock resistant • Lower temperature designs • Venting flexibility • Smaller footprint • Modular system design solutions • Often includes low emission burner technology Limitations? • Limited alternative fuels • Category IV flue requirement • Limited water side inspection • Some designs • Piping/pumping limitations • Some designs
16. System Considerations OR To Condense or Not to Condense?
17. Hydronic System Design – Piping, Pumping, Control What drives the design? Types of Piping System arrangements: • Primary secondary • Variable flow pumping 17 Piping, pumping & control: Is the design for protecting the boilers or is the design for optimizing system efficiency?
18. Hydronic System Design – Piping/Pumping Primary-Secondary with Bypass Line & Blending Valve Primary-Secondary pumping with blend valve – maintain minimum return water temperature to boilers 22
19. Hydronic System Design & Control StrategiesPrimary Pumping Only (Reverse Return) Low Pressure Drop, Large Mass Boilers are Ideal for Variable Flow Pumping Applications No minimum return temperature → Greater Efficiency Hydronic System Design and Control Strategies Primary Pumping Only 24
20. Hydronic Heating Boilers Decision Guide 20 When to Condense? • New construction • Varied set point – lower return temps • Variable flow pumping – wider Delta T, result in lower return temps (caution low mass) • Can accommodate Category IV venting • Rising energy costs • Lower emission requirements • Life cycle costs: Short term vs. long term • Rebates, future potential for condensing • Willingness to invest in higher efficiency, lower carbon footprint
21. 21 When not to Condense? • Retrofit – 50/50 • Fuel type – fuel oil, alternative fuels • Like-for-like replacement – value/quality • Venting considerations • Low energy costs • Minimal emission regulations • Life cycle costs: Short term vs. long term • Remaining equipment life/maintenance costs • Hybrid approach Hydronic Heating Boilers Decision Guide
22. 22 What is a Hybrid System? Hybrid Hydronic Heating System
23. 23 How Hybrid Systems Work Effective Hybrid System Control
24. Summary • Product segmentation – understand customer requirements and specify appropriate equipment -- recall the “Value Pyramid” • Life Expectancy – Total Cost of Ownership • Customer Goals – anticipate future needs • Keep existing equipment when it makes sense • System Design Flexibility – present and future Condensing and Non-condensing
25. Thank you for the opportunity to present today!