Clayton St Denver: Historic Boiler Restoration & Efficiency Upgrade

A Success Story Facilitated by EmergencyHVACs Network

Within the EmergencyHVACs Network, we focus on referral management for leading specialty HVAC contractors in Denver. The Clayton Street project exemplifies the level of expertise, diagnostic acuity, and specialized lift knowledge we seek in our network partners. This case demonstrates the potential of our network when working with true specialists, especially Philip Wyatt, whom we highly recommend.

Network Quality Assurance: Why This Case Study Matters

This project was completed in large part thanks to Philip Wyatt’s use of advanced, non-invasive methodologies on a delicate 116-year-old system. His success in restoring 15 percentage points of efficiency without replacing the boiler demonstrates the high standards of both technical expertise and sensitivity to the historical structure of the HVAC system that the EmergencyHVACs Network brings. This case illustrates the precision of our network partners in relation to our selection system and the quality assurance we enforce.

Residential Building Profile & Baseline Context

The historic Denver Square (3,200 sq ft, 4 bedrooms) occupies a corner lot in Congress Park. Built in 1908, this home features a well-preserved boiler room from the coal era. The house was heated exclusively by a 60-gallon cast-iron hot-water boiler (installed in 1994) for nearly three decades. The hydronic heating system covers three floors of the house and serves seven radiator zones.

The owners prioritized making the house age-appropriate, reliably heating the home, and reducing energy consumption in the context of Denver’s 5,280-foot elevation and harsh winter climate of -10°F. The house must be comfortable year-round.

Basic climate context: Congress Park has an average annual winter heating load of 8,800 degree days. Atmospheric pressure is 83.5% of sea level, making natural draft through boiler flues much more difficult. Denver’s groundwater is hard (180-220 ppm) and mineral-rich, making scaling more common in hydronic systems, especially cast iron systems.

Initial Diagnostic Assessment & Root Cause Analysis

The system was suffering from a decline in functionality (cold radiators upstairs, irregular cycling, large bills). When Philip Wyatt arrived, he understood it as a 30-year compounding system degradation along with the complications that come with Denver’s elevated geology.

Diagnostic Assessment Details:

The thorough technical analysis undertaken by our vetted partner, Philip Wyatt, led to the below findings:

Combustion Analysis (at full load):

• Carbon monoxide (CO): 185 ppm (unsafe; safe threshold <50 ppm per EPA)
• Excess oxygen (O2): 8.1% (indicating excess combustion air and heat loss to flue)
• Flue gas temperature: 510°F (excessive, indicating heat waste)
• Calculated boiler efficiency: 68.2% (vs. 82% nameplate, indicating significant degradation)

Hydronic System Water Analysis (Digital Photometer Results):

• Hardness: 201 ppm CaCO3 equivalent (very hard; >150 ppm considered problematic)
• Alkalinity: 168 ppm (elevated; ideal 80-120 ppm for boiler systems)
• pH: 11.2 (too alkaline; optimal 8.5-9.5 for cast iron)
• Dissolved solids: 1,310 ppm (high; indicates years of mineral accumulation)
• Iron content: 3.2 ppm (evidence of internal corrosion and scale shedding)

Circulator & Room Inspection:

• Circulator impeller (3450 rpm rated, sea-level design) vibrating excessively; performance reduced at altitude.
• No combustion air intake; boiler drawing from unconditioned basement (efficiency penalty in winter).
• Radiators with heavy sediment buildup inside; several bypass valves inoperative.

Engineering Solution: Four-Phase Altitude-Optimized Retrofit

The network professional designed a non-invasive, retrofitted system as a diagnostic solution that did not involve/remove/replacing the existing cast iron boiler. This solution had four phases, demonstrating the requisite mastery needed for working at this high-altitude, historic environment: hydronic loop restoration, combustion tuning, circulation optimization, and smart controls integration.

Phase 1: Hydronic Loop Restoration & Water Treatment:

Instead of the aggressive industrial acid used on commercial sites, we utilized a pH-neutral chelating cleaner to protect the 1908 pipe joints. The system was circulated for 4 hours at 130°F. This process successfully suspended and filtered out approximately 18 pounds of magnetite (black iron oxide) sludge, which had been restricting flow to the upper-floor radiators.

• New Fill & Expansion System: Installed a combination automatic fill valve (set to 18 psig). Expansion tank bladder was replaced and re-charged to 17 psig (per altitude-corrected formula: 0.75 x 22 psig).
• Water Treatment Protocol: Dosed the system with a proprietary boiler water treatment inhibitor (nitrite-based, 800 ppm active) and added a polyphosphate threshold inhibitor.
• Filtration: Installed inline cartridge filter (50-micron) on return line.

Phase 2: Combustion Tuning & Boiler Room Upgrades:

• Altitude-Corrected Gas Orifice: Replaced the original #45 gas orifice with a #50 orifice (Denver-rated).
• Dedicated Combustion Air Intake: Installed a 4-inch insulated ductwork run from outside wall. This eliminated the energy penalty of drawing cold basement air into the combustion zone.
• New Combustion Readings: CO: 12 ppm (safe), O2: 4.8% (optimal), Flue temp: 385°F (design range). Calculated efficiency: 83.1% (improvement of 15 percentage points).

Phase 3: Circulator & Distribution Optimization:

Calculated required pump head and flow using affinity laws to compensate for lower air density.

• Required performance: 14.1 GPM at 12 feet head (to compensate for lower air density).
• New Circulator: Installed a new variable-speed ECM circulator rated for 14-16 GPM at altitude. The pump automatically reduces speed on mild days.
• Radiator Balancing: Manually balanced each of the seven radiators using calibrated thermostatic radiator valves (TRVs). Repaired three inoperative bypass valves.

Phase 4: Controls Integration & Commissioning:

• Honeywell XL500 System Controller: Paired the boiler with a modern WiFi-enabled smart thermostat featuring a Denver-specific heating season curve calibrated for 5,280-foot elevation.
• Commissioning: Full-load pressure test at 80 psig confirmed no leaks. Radiator thermographic scan confirmed all seven zones reaching design surface temperature within 45 minutes.
• Final Verification: Gas combustion analyzer final verification showed CO <5 ppm and efficiency 83.1%.

Installation & Project Timeline

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Network Service Reliability: Proven Results

The following data detail the performance results and show the expertise and level of quality control our network partners have. We connect you with experts who present actual measurable improvements in efficiency and comfort.

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Energy Efficiency Gains:

Long-Term Impact & Owner Experience

Owner Feedback & Comfort Improvements:

The retrofit performed by an experienced member from our network achieved comfort, reliability, and cost savings.

• 18% reduction in annual heating fuel consumption translates to $122/year savings on a 3,200 sq ft home. Payback period is 3.5-4 years.
• Historic preservation: All changes remain invisible or reversible; the 1908 cast iron boiler remains in place.
• Safety: Zero carbon monoxide risk; system now complies with current safety standards.
• System Response: Radiator thermographic scan confirmed all seven zones reaching design surface temperature within 45 minutes.

Owner Quote:

“I used to set the thermostat, then wait for it to heat, and then adjust it a lot, especially if the upstairs was too cold. Now the whole house of radiators and the boiler heats quietly and evenly. It’s over a $100 savings in the winter months. Philip explained everything including the importance of altitude with step. It was critical to keep the old boiler and radiators. It was the right investment for an old house.“

Maintenance Protocol for Long-Term Operations

The following plan is set out to maintain the 83.1% efficiency gain over the long term:

Quarterly Schedule:

• Visual inspection of boiler room for leaks, corrosion, or moisture.
• Check system pressure gauge (should remain 20-24 psig in winter, 18-22 psig in summer).
• Test low-water cutoff by gently reducing system pressure; valve should engage at 18 psig.

Annual Service (Fall):

• Combustion analysis with Bacharach Fyrite kit (verify CO <25 ppm, O2 4-6%).
• Boiler water sampling: pH, hardness, alkalinity, dissolved solids (confirm inhibitor effectiveness).
• Circulator impeller inspection and vibration check.

3-Year Deep Service:

• Replacement of inline cartridge filter on return line.
• Full system pressure test at 80 psig.
• Update water treatment inhibitor concentration (maintain 800 ppm active).