Common Boiler Sizing Mistakes Engineers Still Make (And How to Avoid Them)
Jan 16
3 min read
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Boiler sizing may feel routine, but it remains one of the most common sources of inefficiency, short cycling, and budget overruns in commercial projects. Even experienced engineers can fall into familiar traps—especially when schedules are tight or legacy designs carry forward.
At VHF Sales, we regularly review boiler selections during design and value engineering, and many issues trace back to the same handful of sizing mistakes. The good news? Modern boiler solutions—particularly Camus Hydronics and Precision Boilers—are designed to help engineers avoid them when applied correctly.
1. Oversizing “Just to Be Safe”
Adding excessive safety factors is still common practice, especially when future loads or unknowns are involved.
Why it’s a problem:
Oversized boilers short cycle
Efficiency drops at part load
First cost and operating costs increase unnecessarily
How Camus and Precision help:
Camus modular water-tube and fire-tube boilers allow engineers to size closer to actual loads while maintaining redundancy
Precision electric and steam boilers can be staged precisely, eliminating the need to oversize a single large unit
2. Designing for Peak Load Only
Many boiler plants are designed to meet extreme design days, even though buildings operate at partial load most of the year.
Why it’s a problem:
Boilers spend most of their life operating inefficiently
Shoulder-season performance suffers
Control issues become more noticeable
How Camus and Precision help:
Camus boilers offer wide turndown ratios, allowing the system to closely match real-time demand
Precision electric boilers excel in applications where loads vary significantly or where peak demand occurs infrequently
These solutions perform just as well at 20–40% load as they do at peak.
3. Overlooking Minimum Turndown Requirements
Total capacity is often the focus, while minimum firing rate is overlooked.
Why it’s a problem:
High minimum firing rates lead to cycling
Increased wear on components
Reduced comfort control
How Camus and Precision help:
Camus water-tube boilers are designed for excellent modulation and low minimum firing rates
Precision boilers can be staged in small increments, particularly beneficial for low-load or electrification-focused projects
This makes them well-suited for schools, offices, healthcare facilities, and other buildings with wide load swings.
4. Not Accounting for Distribution Losses & System Design
Boiler sizing decisions are sometimes made without fully considering the distribution system.
Common oversights include:
Long piping runs and distribution losses
Terminal unit limitations
Control valve and pump interaction
How Camus and Precision help:
Both manufacturers offer configurations that integrate well into modern hydronic systems, supporting:
Primary-secondary or variable primary flow designs
Precise temperature control
Stable system operation across varying loads
Proper boiler selection supports the entire system, not just the mechanical room.
5. Using Outdated Rules of Thumb
Building envelopes, controls, and usage profiles have changed—but boiler sizing habits don’t always keep up.
Why it’s a problem:
Modern buildings rarely need the capacity older rules assume
Energy codes penalize oversized, inefficient systems
How Camus and Precision help:
Camus high-efficiency boilers align well with today’s lower-load, high-performance buildings
Precision electric boilers support decarbonization and low-load applications where traditional sizing methods fall short
Revisiting assumptions often leads to smaller, smarter boiler plants.
6. Forgetting About Future Phases or Expansion
Future-proofing is important, but oversizing day one is rarely the best solution.
Why it’s a problem:
Higher upfront cost
Reduced efficiency during early years of operation
How Camus and Precision help:
Modular Camus boiler plants can be expanded as building demand grows
Precision boilers allow additional units to be added without major system disruption
This keeps current performance optimized while maintaining flexibility for future phases.
7. Selecting Equipment Before Confirming Loads
Under schedule pressure, boiler selections sometimes happen before loads are fully validated.
Why it’s a problem:
Limits value engineering opportunities
Makes later adjustments more costly
How Camus and Precision help: Early collaboration allows engineers to:
Validate loads
Confirm turndown and staging strategies
Align performance goals with budget realities
This is where early rep involvement adds real value.
The Takeaway
Most boiler sizing mistakes don’t come from lack of expertise—they come from time pressure, outdated assumptions, or oversimplified safety margins.
When properly applied, Camus and Precision boilers give engineers the tools to:
Size closer to actual demand
Improve part-load efficiency
Reduce cycling and maintenance
Balance performance, redundancy, and budget
Need a Second Set of Eyes?
At VHF Sales, we work closely with engineers to support load validation, boiler selection, and early budget pricing using proven solutions like Camus and Precision. Our goal is to help you design boiler plants that perform as intended—not just on paper, but in the field.
If you’re working through boiler sizing on an upcoming project, we’re here to help you size, select, and budget with confidence.
