What is a boiler?
A boiler is a heating appliance that heats water and distributes it through pipes to baseboards, radiators, or radiant floor tubing. It is the heart of a hydronic heating system, which is the most common type of heating in older New Hampshire homes. While the name suggests boiling water, most modern residential boilers actually heat water to between 140°F and 180°F without bringing it to a boil.
At A.J. LeBlanc Heating, we install and service residential boilers across Manchester, Bedford, Concord, Nashua, Salem, and Auburn.
How a forced hot water boiler works
A typical residential boiler operates in a closed loop:
- A burner (gas, propane, or oil) heats a metal heat exchanger.
- Water flowing through the heat exchanger picks up heat.
- An electric circulator pump moves the heated water through supply piping to the home's emitters (baseboards, radiators, or radiant tubing).
- The water transfers heat to the room and returns to the boiler via the return piping.
- The cycle repeats.
An expansion tank, pressure relief valve, air separator, and combustion controls round out the basic system.
Types of boilers used in NH homes
Cast-iron sectional boilers
Traditional, robust, often last 25 to 30+ years. Typically 80 to 87 percent efficient. Common in older NH homes built before the 1990s.
Condensing modulating boilers
Modern wall-mounted units that achieve 95 percent AFUE or higher by extracting additional heat from flue gases. Use stainless steel or aluminum heat exchangers. Lifespan typically 15 to 20 years. Most common in newer NH installations and retrofits where the existing system can run at lower water temperatures.
Combi (combination) boilers
A single unit that provides both space heat and on-demand domestic hot water. Common in smaller homes and condos where mechanical room space is limited.
Oil-fired boilers
Still common in rural and central NH where natural gas is not available. Modern oil boilers reach 87 to 90 percent AFUE. Cast-iron sectional designs from manufacturers like Biasi, Burnham, and Buderus are widely installed, along with low-mass welded steel designs like the Energy Kinetics System 2000.
What hydronic distribution looks like in NH homes
The boiler is just the heat source. The water it heats is then distributed through one of several emitter types:
- Fin-tube baseboard: the most common in NH homes built after the 1950s. Inexpensive, easy to install, requires hotter water temperatures.
- Cast-iron radiators: common in homes built before the 1950s. Hold heat well, comfortable on a cold morning, can operate at lower temperatures.
- Radiant floor tubing: tubing embedded in concrete slabs or attached under floor joists. Very comfortable, operates at low temperatures, ideal pairing with condensing boilers.
- Hydro-air handlers: a coil of hot water tubing inside an air handler, used to heat air for forced-air distribution. Combines hydronic heat source with ducted distribution.
Why hydronic heat is popular in NH
NH homes lean toward hydronic for several reasons:
- Older housing stock built with hydronic distribution from the start
- Quiet, even heat without the air movement of forced-air systems
- Easy room-by-room zoning
- Long equipment life (especially cast-iron boilers)
- Works well with traditional emitters and radiant floors
Boiler service and maintenance
Annual boiler service is essentially required for:
- Maintaining manufacturer warranty
- Confirming clean, efficient combustion (especially for oil)
- Inspecting the heat exchanger
- Verifying expansion tank pressure and relief valve operation
- Testing safety controls and aquastats
- Checking the system for air, sediment, and water quality issues
Schedule boiler service or replacement
If you have a boiler that has not been serviced in over a year, or you are considering a replacement for an aging cast-iron system, contact A.J. LeBlanc Heating. Serving New Hampshire families since 1928.
Frequently Asked Questions
Is a boiler the same as a furnace?
No. A boiler heats water and distributes it through pipes. A furnace heats air and distributes it through ducts. Different fluid, different distribution, different equipment.
Does a boiler actually boil water?
Most residential boilers do not. They heat water to between 140°F and 180°F, well below boiling. The name is a historical holdover from older systems that did produce steam.
How long does a boiler last?
Cast-iron boilers typically last 25 to 30+ years with good maintenance. Modern condensing boilers typically last 15 to 20 years. Their stainless or aluminum heat exchangers are more efficient but more sensitive to water chemistry.
Can a boiler provide both heat and hot water?
Yes. A boiler paired with an indirect water heater uses the boiler to heat domestic hot water in addition to space heat. A combi boiler does both in a single wall-mounted unit.
How often should I have my boiler serviced?
Annually, ideally in late summer or early fall. For oil-fired boilers, annual service is essentially required to maintain clean combustion.