Cast-iron and mod-con boiler service.
From a century-old cast-iron radiator system to a brand-new wall-hung modulating-condensing unit, we service the hydronic heat that keeps Duluth's older housing stock warm.
What we cover.
Boiler work is its own craft. Hydronic and radiant systems do not behave like forced-air furnaces, and the wrong service tech can do real damage with the wrong assumption. Our crew knows cast-iron sectionals, copper-fin units, mod-cons, and radiant manifolds.
We service, repair, and replace boilers across Duluth, Hermantown, Superior WI, Two Harbors, and Cloquet. Banging at startup, weeping sections, kettling scale, low-water cutoffs, expansion tanks, circulator pumps, mixing valves, the full system.
Signs you need boiler service.
If one of these is happening at your house, do not wait. The longer you run it, the more it costs to fix.
Banging on startup
Usually scale or sediment causing localized boiling. Fixable with a flush. Not catastrophic, but worth a fall service.
Water on the floor below the boiler
Relief valve, expansion tank, pump seal, or a cracked section. We pressure-test the water side to isolate.
Cold rooms or one cold zone
Air in the loop, stuck zone valve, dying circulator, or expansion tank failure. All quick fixes when caught early.
Kettling (teakettle whistle)
Always scale on the heat exchanger. Catching it early is a descale, ignoring it is a partial rebuild.
Low water cutoff trips
Real safety device working. Tells us about a leak somewhere in the loop. Worth tracking down rather than just resetting.
Boiler is 30+ years old
Cast-iron can run 50+ years with care. Mod-con is 15 to 20. We give you a straight repair vs replace answer at the diagnostic.
Four steps from your call to a comfortable home.
System read-out
Manometer on the gas, combustion analyzer, water-side pressure, temperature drop across each zone.
Real diagnosis
Banging at startup vs throughout the cycle. Weeping vs cracked sections. Kettling vs short-cycling. Each one is a different fix.
Flat-rate repair
Real price in writing for the actual problem. No throwing parts at it.
System commissioning
Final water pressure, expansion tank precharge, mixing valve set, then a walk-through with you.
Real numbers, before you call.
We are not afraid to publish prices. Final quotes are flat-rate, written, and itemized after we see your system.
Diagnostic visit
- Manometer on gas inlet and manifold
- Combustion analyzer on flue
- Water-side pressure, expansion tank, low-water cutoff test
Common boiler repair
- Circulator, expansion tank, or zone valve
- Relief valve, pressure-reducing valve, mixing valve
- Aquastat or low-water cutoff replacement
New boiler install
- Cast-iron sectional $7,500 to $12,500
- Wall-hung modulating-condensing $8,500 to $15,000
- Includes near-boiler piping rebuild + permit + commissioning
Steam boilers, oil-fired boilers, and large multi-zone hydronic systems quote separately. Radiant manifold and snowmelt work priced on site.
Why homeowners pick Northland Air for boiler.
Boiler-specific tools and training
Manometers, combustion analyzers, hydronic flowmeters. The right tool for the right system, not just a multimeter and guesswork.
Cast-iron experience
Plenty of Duluth homes still run cast-iron. We know how to service them without cracking sections.
Mod-con expertise
Modulating-condensing units are efficient but unforgiving of bad setup. We commission them right the first time.
What homeowners say about our boiler work.
Our cast-iron boiler is from 1956 and most contractors will not touch it. Northland Air not only services it, they walked us through what it would take to keep it running another 20 years vs converting to a modern boiler. Honest, patient, no pressure.
Brands we service and install: Weil-McLain · Burnham · Lochinvar · Triangle Tube · Buderus · Navien · Viessmann
The sound or the leak tells us the fix.
Boilers are diagnostic. The when and where of the symptom tells us what is actually wrong, before we charge for parts.
Banging only at startup, then quiets
Scale or sediment causing localized boiling and water-hammer when the burner first kicks on. Chemical or mechanical flush, sometimes a sectional inspection.
Banging throughout the heat cycle
Usually a circulator pump on the way out, a stuck zone valve, or an expansion tank that lost its precharge. Single-component swap, not a boiler replacement.
Cold radiator on one floor, others fine
Air in the loop. Common after a power outage or a low-pressure event. Purge the affected zone, check the auto-fill valve for leaks.
Water pooling under the boiler
Look at the relief valve first ($40 part). Expansion tank second. Cracked cast-iron section is rare and last on the list.
Teakettle-style whistle (kettling)
Always scale on the heat exchanger. Catching it early is a descale. Ignoring it for a season turns into a partial rebuild.
Soot at the flue or yellow flame
Incomplete combustion. CO concern. Combustion analyzer reading first, then burner adjustment or replacement.
Boiler questions, answered.
Banging at startup is usually scale or sediment causing localized boiling, fixable. Banging throughout the cycle is usually a circulator or expansion-tank issue. We diagnose first, not throw parts.
Cast-iron replacements typically run $7,500 to $12,500. Wall-hung mod-cons run $8,500 to $15,000 depending on BTU and zoning. Itemized written quotes always.
Cast-iron boilers commonly last 30-50 years. Mod-cons typically last 15-20 years with annual service. The radiators and piping often outlive the boiler itself by decades.
Yes. We service radiant manifolds, mixing valves, circulators, and zone valves for both new and legacy radiant systems.
Usually a relief valve, expansion tank, or pump-seal issue, sometimes a cracked section. We pressure-test the water side to find the source before quoting a repair.
Once a year, every fall. A real tune-up includes combustion analysis, water-side pressure check, expansion tank, low-water cutoff test, and a flue-gas read.
Available across the Twin Ports.
Same-day boiler service in your neighborhood.