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The burner, heat exchanger, and ignition system in a Merrimack County furnace carry load for almost the entire calendar year. Homes in Merrimack County, NH run heat about nine months a year, from September through May. A contractor quoting a repair here checks those cycling components first, because that is where wear concentrates when a system rarely gets extended rest. Cracked heat exchangers and worn ignitors are more common findings than failed secondary controls, and a repair estimate that skips those components before pricing the job is likely to miss the main problem.
Furnace parts fail in ways that the unit's exterior does not predict. A cracked heat exchanger looks the same from the front as a clean one, and a burner assembly that has been swapped once or twice carries wear the original install date does not explain. Half the homes in Merrimack County, New Hampshire were built in 1977 or earlier (2020-2024 ACS 5-year). That history of successive equipment in unchanged housings means a contractor opening a furnace here is tracing what has actually been run, replaced, and left in place, not working from a single generation of decisions. Whether a part is still made depends on which generation of equipment is sitting in the system right now.
The Parts of a Furnace a Contractor Checks First
The furnace cabinet sits in the basement, utility room, or closet and holds most of the parts a contractor looks at. Inside it, the heat exchanger is the piece that fails silently and matters most: cracks there let combustion gases into the airstream. The burners, igniter, and flame sensor are the first stops when a furnace runs briefly and shuts off or refuses to start.
The blower motor and fan sit in the lower section of the cabinet and move conditioned air out through the supply side of the house. The flue pipe runs from the cabinet to an exterior wall or chimney and removes exhaust; a contractor checks it for blockages and deterioration alongside the cabinet components. The filter housing sits at the air-return entry point and is often where airflow problems begin.
The drawing shows a typical furnace layout, and a licensed contractor determines which components apply to the specific system and situation in your home.
Find a contractor in Merrimack CountyMerrimack County, by the numbers
138 severe weather events were recorded in Merrimack County, New Hampshire between 2015 and 2024.
NOAA National Centers for Environmental Information, Storm Events Database, bulk CSV export, events 2015-01-01 through 2024-12-31.Half the homes in Merrimack County, New Hampshire were built in 1977 or earlier (2020-2024 ACS 5-year).
U.S. Census Bureau, 2020-2024 American Community Survey 5-Year EstimatesMerrimack County, New Hampshire holds 66,497 housing units (2020-2024 ACS 5-year).
U.S. Census Bureau, 2020-2024 American Community Survey 5-Year EstimatesOwners occupy 73.5% of the occupied homes in Merrimack County, New Hampshire (2020-2024 ACS 5-year).
U.S. Census Bureau, 2020-2024 American Community Survey 5-Year EstimatesCodes & Standards Covering Furnace Repair in Merrimack County, New Hampshire6 sourced rules and standards
What furnace repair looks like in Merrimack County
Non-weatherized gas furnaces manufactured on or after November 19, 2015 must reach 80.0 percent AFUE.
Non-weatherized oil-fired furnaces manufactured on or after November 19, 2015 must reach 83.0 percent AFUE.
Mobile home gas furnaces manufactured on or after November 19, 2015 must reach 80.0 percent AFUE.
Non-weatherized gas furnaces manufactured on or after December 18, 2028 must reach 95.0 percent AFUE, up from the 80.0 percent minimum that applies to units manufactured before that date.
Licensing and Legal Requirements in Merrimack County, New Hampshire
New Hampshire's mechanical licensing board issues nine credentials — hearth system, four fuel gas endorsements, domestic appliance technician, and master, journeyman and apprentice plumber — and a licensee may not work outside the specialty their licence names. None of the nine is an HVAC licence.
New Hampshire does not license HVAC as a trade, and says so where it matters: the plumbing licence expressly does not reach a person installing heating, cooling, air conditioning or domestic water heating systems, whether solar, oil, gas or electric. The gas piping on a gas-fired system is a separate matter and needs a fuel gas fitter licence.
Severe Weather Events in Merrimack County
Extreme weather puts real load on furnace components, and New Hampshire winters are not gentle on equipment that was already running hard. How much stress a furnace absorbs over its lifetime is a local question, and the record below shows what the weather in this county has actually looked like.
138 severe weather events, 2015–2024. Source: NOAA National Centers for Environmental Information, Storm Events Database.