Case Study: 1920s Boiler-to-High-Efficiency Conversion in Dundee, Omaha
This case study documents a substantial boiler conversion project completed for a 1924 Tudor Revival home in the Dundee Historic District of Omaha. The work involved removing a 1968 atmospheric cast iron sectional boiler and installing a modern modulating condensing boiler with primary-secondary piping, while preserving the original cast iron radiators throughout the home. The conversion produced substantial efficiency improvement (estimated 28% gas consumption reduction) while maintaining the home’s hydronic heating character and original architectural elements.
Customer Situation
The property is a 1924 Tudor Revival home in the Dundee Historic District, approximately 2,950 sq ft across two main floors plus partial third-floor attic conversion, with original cast iron radiators throughout (24 radiators total) serving five hydronic zones organized by the home’s living spaces. The home retains substantial original character including leaded glass windows, hardwood floors, original interior trim, and the original boiler venting through brick chimney shared with gas water heater.
The 1968 boiler had served the home for 56 years — remarkable longevity for atmospheric cast iron sectional equipment, but substantially beyond useful life. Symptoms prompting replacement consideration:
- Boiler short-cycling throughout the heating season regardless of weather
- Gas consumption substantially higher than comparable Dundee homes
- Two of five zones with reduced output suggesting circulation issues
- Boiler exterior showing rust and insulation deterioration
- Customer concerned about reliability for upcoming winter
- Customer aware of substantial federal tax credits and OPPD rebates for high-efficiency installations
Diagnostic Assessment
Initial consultation by Ryan Kowalski (Service Lead, 14 years hydronic specialization). Assessment time approximately 3 hours including detailed boiler inspection, hydronic distribution analysis, and conversion feasibility evaluation.
Boiler Inspection
- 1968 Weil-McLain CGi atmospheric cast iron sectional boiler, 175,000 Btu/hr input
- Estimated 65-70% AFUE in current condition (rated 78% AFUE new)
- Substantial scale accumulation on water-side surfaces from 56 years of service
- Combustion analysis: 78 ppm CO (elevated), 9.5% O2 (excessive)
- Heat exchanger sections showing thermal stress patterns but no failures yet
- Original 1968 controls with manual override
- Atmospheric venting through brick chimney shared with gas water heater
Hydronic Distribution Assessment
- Five zones controlled by original zone valves (3 of 5 still operational)
- 24 cast iron radiators total, all original 1924 installations
- Original piping (mix of black iron and copper, both functional)
- Two zone valves stuck in partially closed positions explaining reduced output
- Original expansion tank with substantial waterlogging
- Original circulator with bearing wear
Conversion Feasibility
- Modern condensing boiler installation requires PVC venting (sidewall) and condensate drainage
- Chimney liner installation required for orphaned gas water heater after conversion
- Primary-secondary piping arrangement appropriate for modulating boiler with multiple zones
- Existing zone distribution adaptable to modulating boiler with zone valve replacement
- Original radiators ideal for condensing boiler operation (cast iron mass allows lower water temperatures with extended cycles)
Equipment Selection
Premium modulating condensing boiler selected for substantial property and customer’s interest in maximum efficiency:
- Lochinvar Knight WHN155 modulating condensing boiler — 95% AFUE rated, 155,000 Btu/hr input (right-sized from existing 175,000 based on heat loss calculation), modulating from 31,000 to 155,000 Btu/hr matching actual load
- Primary-secondary piping — appropriate for modulating boiler with multiple zone configuration
- Five new motorized zone valves — Taco Zone Sentry replacing original 1968 valves
- New Taco 007 circulator — primary loop circulation
- Expansion tank, air separator, system fill — complete replacement of supporting components
- Outdoor reset control — varies water temperature based on outdoor conditions for maximum efficiency
- Chimney liner — for orphaned water heater
Project Execution
Three-day conversion project given substantial scope:
Day 1 (8 hours) — Old boiler removal: water-side drainage, gas disconnection, electrical disconnection, removal of cast iron sectional boiler in sections (substantial weight required disassembly for stairway transport from basement). Primary mechanical room preparation including new floor protection and equipment positioning planning.
Day 2 (10 hours) — New boiler installation: Lochinvar Knight positioning, primary-secondary piping fabrication and installation, expansion tank and air separator installation, new circulator installation, gas piping connections, electrical connections including outdoor reset sensor installation. Sidewall venting penetration through basement window header. Condensate drainage installation with condensate neutralizer. Chimney liner installation for orphaned water heater.
Day 3 (6 hours) — Zone valve replacement (5 valves), system fill and pressure testing, leak testing, combustion analysis on new boiler, outdoor reset calibration, customer walkthrough including operation explanation, maintenance schedule, smartphone monitoring setup, and warranty registration.
Results
- Heating efficiency dramatically improved — 95% AFUE vs prior estimated 65-70% AFUE produces estimated 28% gas consumption reduction (subsequent heating season confirmed 26% reduction)
- Modulating operation — boiler firing rate continuously adjusts to actual load (31K-155K Btu/hr range), producing dramatically more even heat delivery than single-stage atmospheric equipment
- Outdoor reset benefit — water temperature varies with outdoor conditions; lower water temperatures during mild weather produce better condensing efficiency
- Original radiators perform better — cast iron mass with lower modulated water temperatures produces extended steady-state cycles with more even radiant heat than prior short-cycle atmospheric operation
- Zone balance restored — new zone valves operating properly, all five zones receiving appropriate heat distribution
- Combustion analysis — 6 ppm CO with new condensing boiler vs 78 ppm prior; substantially safer combustion
- Federal Section 25C tax credit — $600 (30% × $600 max furnace/boiler)
- OPPD high-efficiency rebate — $400 for qualifying condensing equipment
Pricing
Total project cost: $13,500
- Lochinvar Knight WHN155 modulating condensing boiler: $5,800
- Primary-secondary piping fabrication and materials: $885
- Five Taco Zone Sentry motorized zone valves: $485
- Taco 007 circulator, expansion tank, air separator: $385
- Chimney liner installation: $1,485
- Sidewall venting and condensate drainage with neutralizer: $585
- Outdoor reset control and sensor: $285
- Old boiler removal and disposal (substantial weight): $485
- Installation labor (24 hours over 3 days, primarily Ryan Kowalski): $2,800
- Materials, supplies, miscellaneous: $310
Net cost after rebates and credits:
- Project cost: $13,500
- OPPD high-efficiency rebate: -$400
- Federal Section 25C tax credit: -$600
- Net cost: $12,500
Why Conversion Made Sense vs Replacement With Forced-Air
Some customers consider converting hydronic homes to forced-air during major boiler replacement. For this Dundee property, hydronic conversion to high-efficiency boiler was substantially better than forced-air conversion:
- Forced-air conversion would have cost $45,000-$80,000+ for ductwork addition in pre-1930 home with limited chase space
- Forced-air conversion would have damaged substantial original interior character (cutting plaster walls, dropping ceilings for ducts, removing radiators)
- Cast iron radiator heat distribution is fundamentally superior to forced-air in pre-1930 homes (massive thermal mass produces even radiant heat without convection drafts)
- Hydronic system zoning is simpler and less expensive than forced-air zoning
- Boiler conversion preserves substantial architectural and functional character at a fraction of forced-air conversion cost
Lessons from This Project
- Pre-1930 historic homes with hydronic heating benefit substantially from boiler conversion rather than forced-air replacement
- Modulating condensing boilers achieve substantially higher efficiency than even modern single-stage condensing equipment
- Outdoor reset control provides additional efficiency through water temperature optimization across heating season
- Cast iron radiator distribution actually improves with modulating low-temperature operation (thermal mass benefits)
- Primary-secondary piping is standard for modulating boiler installations with multiple zones
- Chimney liner installation is required for orphaned water heater after condensing boiler conversion
- 56-year-old boiler service life is remarkable but substantially beyond average; planned replacement before failure provides better outcomes
Contact Omaha Heating and Air Conditioning
For Dundee historic home boiler conversion, modulating condensing boiler installation, primary-secondary piping, outdoor reset, or hydronic system service, call our 24/7 line.
- Emergency Line (24/7): (402) 258-6703
- MUD Gas Emergency: 402-554-7777 (suspected gas leaks)
- 911: for CO detector alarms or fire/smoke situations
- Address: Lake Regency Building, 450 Regency Pkwy #370, Omaha, NE 68114
- Email: info@omahaheatingairconditioning.xyz
- City of Omaha Mechanical Contractor License: #MC-2014-08847
- EPA Section 608 Universal: #608U-2014-227841