Furnace replacement and installation

When replacement makes more sense than repair

Most furnaces last somewhere around 15 to 20 years. Once yours is in that range, a large repair is harder to justify. Many contractors suggest replacing the furnace when the repair would cost a big share of a new unit, when repairs are becoming frequent, or when the heat exchanger is cracked. A cracked heat exchanger can let combustion gases into the air you breathe, and most technicians will recommend replacement rather than repair.

Other good reasons to replace: rooms that never get warm, a system that was oversized or undersized for the house, or plans to add central air. If you are going to replace the furnace anyway, it is a good time to ask about a heat pump or a dual-fuel setup.

Sizing and the house you actually have

A new furnace should be sized from a load calculation, not by copying the old unit's label. Older Westchester homes have often had new windows, insulation or additions since the original system was put in, and the right size may be smaller now. Ask the contractor how they sized the system. A furnace that is too large heats in short bursts, wears out sooner and leaves some rooms uneven.

• Ask for a load calculation (often called a Manual J)
• Ask about the efficiency rating and how it affects the price
• Ask whether the ductwork, venting or chimney liner needs changes
• Ask who pulls the permit, and get the warranty terms in writing

Oil to gas conversions

Many older homes in this part of Westchester were built with oil heat. When the old oil furnace or boiler fails, some owners switch to natural gas if a gas line reaches their street. Most oil furnaces cannot be converted to burn gas, so a conversion usually means new equipment, new venting and a gas line, plus removal or abandonment of the oil tank by someone who handles tank work. Angi puts a typical conversion at about $5,000 to $12,000, and it can run higher when a new gas service line is needed.

Your gas utility decides whether service is available to your address, so check with them early. The contractor should handle the permits. Many villages and towns require one for this kind of work.

What happens on install day

A typical furnace swap takes a day, sometimes two if venting or ducts need work. The crew disconnects the old unit, sets the new one, connects fuel, venting, ducts and wiring, then starts it and checks combustion and safety controls. Ask the installer to show you the filter, the shutoffs and the warranty registration before they leave.

Questions homeowners ask