Emergency Medical Center Boiler Replacement & Redundancy – Denver Case Study

Facility Profile

This medical center operates as a 250-bed acute care teaching hospital serving the Denver metro area. The facility maintains 24/7 critical care operations across 450,000 square feet, including 180 patient rooms, two operating theaters, a 24-bed ICU, emergency department, diagnostic imaging centers, and administrative offices.

The complex elevation of 5,280 feet presents unique HVAC design challenges, requiring 3.5% capacity adjustment for high-altitude air density loss. Winter heating loads in Denver are substantial—with 6,282 annual heating degree days (base 65°F)—making boiler reliability mission-critical for patient safety and regulatory compliance.

Initial Assessment & Problem Identification

The Challenge:

In early October 2024, the hospital’s facilities management team discovered catastrophic failure in their primary boiler system. The facility operated two older firetube boilers (Cleaver-Brooks units from 1998, approximately 26 years old) feeding a 120-ton per hour distribution system serving patient care areas, operating theaters, and domestic hot water. During the first major cold front of the season (temperatures dropping to 12°F overnight), the lead boiler experienced a complete loss of combustion efficiency, triggering low-water cutoff safeties.

Richard Ruiz was dispatched for emergency diagnosis. Upon arrival, he identified multiple critical issues:

• Primary Boiler Failure: Scale and sediment accumulation inside the firetube passages (typical calcium carbonate buildup in high-altitude Denver water with 180 ppm hardness) had reduced heat transfer efficiency to 73% (down from design 80%). Combustion analysis showed excess oxygen at 6.2% (target: 3-4%), indicating air infiltration through door gaskets and bleeder valve degradation.
• Backup Boiler Limitations: The secondary boiler was undersized at 75 tons/hour capacity, insufficient to maintain building comfort during peak demand (estimated 110 tons/hour at -10°F design day). System pressure relief settings had drifted, showing 85 psig instead of the required 75 psig setpoint.
• System Vulnerabilities: Single-point-of-failure piping configuration with no zone isolation capabilities. Expansion tank was 30 years old (Flexcon model, likely depleted of pre-charge nitrogen due to lack of service history). No temperature reset controls on supply water—system maintained constant 180°F regardless of outdoor air temperature, causing standby losses estimated at 8-12% annually.
• Regulatory Risk: Hospital must maintain heated spaces above 68°F per state health department regulations; any extended outage risks non-compliance and potential patient safety violations.

Technical Diagnosis & Root Cause Analysis

Richard’s comprehensive diagnostic approach included:

• Boiler Water Analysis: Sent samples to Nalco water treatment lab. Results showed: Hardness 178 ppm CaCO₃ equivalent, Alkalinity 156 ppm (too high), pH 10.8 (should be 8.5-9.5), Dissolved solids 1,240 ppm. This combination created aggressive scale formation.
• Combustion Testing: Using a Bacharach Fyrite and oxygen meter at full load:
  • CO (carbon monoxide): 120 ppm (unsafe; should be <50 ppm)
  • O₂: 6.2% (excess air causing heat loss to flue)
  • Flue gas temperature: 438°F (higher than expected 380°F design)
  • Calculated boiler efficiency: 72.3% (vs. 80% nameplate)
• Pressure Testing: Hydrostatic test revealed slow weeping at a tube joint—insufficient for immediate shutdown but progressive deterioration within 2-3 heating seasons.
• System Hydraulics: Flow test across old expansion tank showed only 2 gallons usable volume (original 86-gallon tank pre-charge lost to normal diffusion over 30 years).

Root Causes:

• Deferred water treatment (no inhibitor added for 5+ years)
• No temperature reset or outdoor air sensor integration
• Lack of preventative maintenance (last tube cleaning: 2019)
• Inadequate primary-secondary boiler sizing for Denver’s heating extremes

Engineering Solution & System Design

Richard and his engineering team designed a three-phase replacement strategy:

Phase 1 – Primary Boiler Replacement

• New Equipment: Two matching Lochinvar Crest II condensing boilers, each rated 125 GPM at 80 psig, 85% AFUE minimum. These high-efficiency units recover latent heat from flue gas condensation, reducing oxygen trim to 2.5% and flue gas temperature to 290°F.
• Configuration: Primary-secondary piping with 3-way motorized mixing valve (Caleffi 145 series) maintaining zone-specific supply temperature. Each boiler has dedicated 3-inch circulator (Grundfos MAGNA3 40-120F) with variable frequency drive (VFD) for demand-responsive operation.
• High-Altitude Optimization: Burners rated for 5,280-foot elevation operation; air intake through certified combustion analyzer feedback to maintain 2.0-3.0% oxygen setpoint automatically using electronic trim.
• Redundancy: Both boilers plumbed in lead-lag configuration with automatic switchover. If primary fails, secondary activates within 30 seconds via dual-pressure transmitters and logic controller.

Phase 2 – Water Treatment & System Conditioning

• Water Softening: Installation of Autotrol 255/740 automated softener (30,000-grain capacity, treating all system makeup water) reducing incoming hardness from 178 ppm to <5 ppm.
• Filtration: 100-micron magnetic strainer (Amtrol ACV-M60) on system return to trap iron oxide particles—critical for protecting VFD drives and control valves.
• Chemical Treatment: Nalco Thermacare 7000 corrosion inhibitor dosed at 2,500 ppm alkalinity reserve and 800 ppm dissolved solids target (typical for hospital systems). Quarterly analysis protocol implemented.

Phase 3 – Intelligent Control & Monitoring

• Outdoor Air Reset: Honeywell XL500 Logic Controller with OAT sensor (-40°F to 120°F range) calculates optimal supply water temperature setpoint:
  • At -10°F (design day): 180°F supply
  • At 32°F: 140°F supply
  • At 55°F: 110°F supply
  • At 65°F+: 90°F supply (keeping boiler in condensing mode)
• Expansion Tank Upgrade: New Flexcon HC-120 with proper pre-charge of 12 psig nitrogen (matching system pressure at 75 psig setpoint), providing 48 gallons usable volume for thermal expansion plus safety margin.
• Monitoring & Alarms: Integration with hospital SCADA system via Modbus TCP:
  • Real-time boiler efficiency monitoring
  • Pre-emptive alerts for scale formation (pressure differential across primary circuit rising >0.3 psi/day)
  • Water treatment depletion warnings
  • Lead-lag boiler switchover events logged with 1-minute resolution

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Installation & Commissioning

Timeline & Execution:

• Week 1: Boiler room preparation. Removed old boilers under controlled hot shutdown (cooling system to 80°F before isolation). Acid flush of entire hydronic loop using Nalco hot chemical descaler—circulated for 6 hours at 140°F to remove 18 years of scale and iron oxide (approximately 340 pounds of sludge removed and filtered out).
• Week 2: New boiler installation. Positioned dual Crest II units on reinforced concrete pads, aligned flue venting (direct outdoor intake at 8 feet above roof, per NFPA code for high-altitude Denver location), and installed dual gas trains with backflow preventers and isolating ball valves.
• Week 3: Piping & Hydronic Integration. Installed 2-inch copper main lines with swing-check valves, compression connections throughout. Circulator impellers sized for Denver altitude using affinity laws: calculated 2,800 rpm vs. sea-level 3,450 rpm for 100 GPM demand at 35 feet head.
• Week 4: Controls & Commissioning. Programmed Honeywell XL500 with Denver-specific heating season curves (September 1 – May 31, with shoulder-season optimization). Field-calibrated OAT sensor using certified thermometer. Conducted full-load firing tests at 80 psig with combustion analyzer showing final efficiency 87.2% (vs. design 85%, exceeding expectations due to high-altitude optimization).
• Week 5-6: System balance testing and handover documentation. Verified lead-lag switchover by deliberately shutting down primary boiler under controlled 20°F outdoor conditions—secondary boiler engaged, supply temperature maintained within 2°F setpoint. Loop thermometers confirmed even heat distribution to all zones.

“At this altitude, healthcare systems require a whole different way of thinking. A 26-year-old boiler failing amid the first cold snap is not strange in Denver. What matters is having redundancy and enough smart controls to measure up to Denver’s horrendous temperature changes. We didn’t just replace equipment. We created a system to guard against patients even when the mountain temperatures drop to double digits below zero.”

Richard Ruiz

Technical Performance Results

Energy Efficiency Gains:

Cost Savings:

• Annual Natural Gas Savings: 860 MMBtu @ $8.50/MMBtu = $7,310/year

• Equipment & Installation Cost: $187,500 (dual boilers, controls, commissioning)
• Simple Payback Period: 25.6 years (offset by hospital regulatory compliance premium and avoiding 1-3 day outage cost of ~$450,000)

Reliability Improvement:

• Mean Time Between Failures (MTBF): Projected 15+ years with preventative maintenance (vs. 6-8 years for old system)
• Redundancy: 100% uptime during single-boiler failure scenarios (per design)
• Regulatory Compliance: Full alignment with CMS CoPs (Conditions of Participation) for hospital heating and hot water reliability

Key Technical Innovations for Denver

• Altitude-Specific Burner Calibration: Factory recalibration at 5,280 feet elevation ensured stoichiometric oxygen ratio and prevented excessive flue gas loss—critical for high-altitude efficiency.
• Outdoor Air Reset Strategy: Denver’s variable thermal swings (daily 30°F+ fluctuations) make reset control 2-3× more valuable than at sea level. Condensing boilers achieve 87%+ efficiency only when return water is <130°F; reset prevents unnecessary energy waste during mild periods.
• Water Treatment Specificity: Denver municipal water’s moderate hardness (180 ppm typical) requires targeted softening to prevent scale—generic “inhibitor-only” approaches fail in this climate.
• Magnetic Filtration: High-altitude air contains higher particulate concentration; magnetic filtration protects VFD drives that fail prematurely in unfiltered systems.

Recommended Maintenance & Long-Term Operations

Quarterly Schedule:

• Water analysis (hardness, alkalinity, dissolved solids, inhibitor reserve)
• Boiler combustion efficiency test
• Lead-lag switchover functional test
• Expansion tank nitrogen pressure verification (maintain 65 psig)

Annual Service:

• Tube inspection via borescope
• Circulator impeller cleaning and bearing pack lubrication
• Control valve seat cleaning and stroke verification

3-Year Deep Service:

• Tube bundle acid soak and flush
• Circulator impeller replacement
• Expansion tank replacement (preventative at 10-year mark)

Client Impact & Long-Term Outcomes

The hospital’s boiler system now operates with uninterrupted patient care capability, meeting 100% of winter demand even during design day conditions (-10°F). The 30% energy reduction translates to approximately $7,300 annual savings and reduced carbon footprint. More importantly, the redundant design eliminated the single-point-of-failure risk that previously threatened compliance and patient safety.

Hospital maintenance staff report significantly reduced alarm frequency and improved system predictability. The outdoor air reset integration has become a model for other Denver healthcare facilities seeking altitude-optimized heating solutions.

“I’ve seen a reduced number of alarms and more stable heating performance since the new boiler system was put in place. Other hospitals in Denver must consider the outdoor air reset.”

Hospital Maintenance Supervisor