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

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.

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.