HVAC in Connecticut is, in most older houses, a boiler and a loop of pipe. Steam still knocks in New Haven and Bridgeport three-families. Hot-water baseboard runs the perimeter of ranches built later. Oil is common, and so are tanks that have been in the ground or in the cellar longer than anyone now living there remembers. Say what is in the basement before you name a system you wish you had.
Short-cycling, a cold radiator at the end of a wing, and a chimney that is the wrong size for the burner are separate problems. A fuel smell at the foundation is a reason to talk about the tank, not the filter. Buried tanks leak without a dramatic puddle. Basement tanks weep at the legs and the fittings. Note soot on the front of the boiler and whether the heat dies on the coldest mornings.
Ductless heads get bolted onto colonials that never had ducts, especially on enclosed porches and third floors. They do not purge air from a steam main, and they do not fix a leaking boiler. Condensate lines freeze if they dump outside without a thought for January. Salt air on the shore is hard on outdoor coils. Tell the caller which rooms were added after the original heat.
August humidity in this state loads a stone cellar until the stairs feel damp. A dehumidifier may matter as much as another ton of cooling. Inland nights in the Litchfield hills drop harder than a shore evening, and a heat pump with no backup will struggle there. Window units drip into clapboard and rot the casing they hang on. Ask what the house can live on if the power drops.
Have the fuel, the kind of system, and the room that fails. Say whether this is no heat, a fuel smell, a leak at a valve, or a plan to cool a house that has only radiators. Mention the tank if you know it is buried. Call the number on this page.