- Steam and hot-water boilers require different maintenance approaches — mixing service practices between them causes problems.
- High-efficiency condensing boilers (95%+ AFUE) can replace aging 60–70% units with significant Nicor rebates for qualifying equipment.
- Uneven radiator heating is almost always a water, air, or pressure balance issue — rarely a sign the boiler itself has failed.
Radiators aren't heating evenly across floors
In a hot-water system, trapped air prevents flow to distant radiators. In a steam system, improper pitch, failed steam traps, or a water level issue creates cold zones. Both are diagnosable without replacing the boiler.
Boiler is over 20 years old and repair costs are climbing
Cast-iron boiler sections crack, gas valves fail, and controls age. When annual repair costs approach 30% of replacement cost, a flat-rate assessment of current high-efficiency options makes sense.
Steam vs. hot-water systems — what distinguishes them
Steam systems run at low pressure and cycle water through a single pipe or two-pipe arrangement — radiators are sized to condense steam, not just warm up. Hot-water (hydronic) systems circulate water continuously via a pump; baseboard radiators and in-floor tubing are common. The two systems are not interchangeable.
High-efficiency boiler replacement and Nicor rebates
Modern condensing boilers extract heat from flue gases, achieving 95%+ AFUE versus a typical older unit's 70–80%. Nicor offers rebates on qualifying high-efficiency gas boilers — Legendary verifies current program requirements at the time of your estimate.
Waterlogged steam boiler loses efficiency rapidly
Steam boilers require precise water levels — too high floods the system, too low causes dry-firing that cracks sections. Automatic water feeders can mask a leak that gradually corrodes the boiler from inside.
Failed pressure relief valve creates a safety hazard
The pressure relief valve is the boiler's primary safety device. A valve that weeps or seals completely are both warning signs — weeping indicates over-pressure; a seized-shut valve means no protection. Either condition warrants immediate service.
Questions homeowners ask
- Can I add zones to my existing boiler system?
- Hot-water systems can often be zoned with additional circulators and zone valves. Steam systems are harder to zone due to pipe sizing constraints — Legendary assesses what's feasible without disrupting the existing distribution.
- Are cast-iron radiators energy-efficient?
- Cast-iron radiators store and radiate heat gently, which pairs well with outdoor reset controls that lower boiler temperature on mild days. Properly maintained radiant systems can be very efficient — the boiler efficiency is what matters most.
- Is a Free Second Opinion available on a boiler replacement quote?
- Yes — if you've received a replacement proposal elsewhere, Legendary will review it and provide an independent flat-rate assessment at no charge.
Editorial provenance
Content by Legendary Service editorial team
Updated:
Methodology
Guidance compares the stated system factors, applicable utility program rules, and the conditions that must be confirmed in the home. Figures are planning ranges, not quotes; Legendary Service provides an upfront flat-rate price after diagnosis.