Furnace tune-ups in Aldie.

Natural gas heats about 86 percent of Stone Ridge’s owner homes, and the association lists Washington Gas as the supplier. Across all of 20105 it’s about 78 percent, because the houses outside Stone Ridge lean more on propane and electric heat. The checks are the same on either fuel, but the numbers they’re held to aren’t, so say which yours burns when you book.

About one Aldie owner home in twenty burns propane, most of them outside Stone Ridge. A propane furnace is a gas furnace set up for a different fuel, with narrower orifices at the burners and a different spring in the gas valve, running at a manifold pressure well above natural gas. The tech reads it against the propane figure on the furnace’s label, and a missing conversion label goes in the write-up. The tank and its regulator are often the propane company’s; our part starts at the furnace.

In houses this young the furnace is often the high-efficiency kind, with two plastic pipes leaving through a wall or the roof and a small drain line beside it. Outside, leaves, a bird’s nest or a mulch pile can end up against those pipes. Inside, one of the safeties on the list is a pressure switch that has to prove the vent is drawing before the burners are allowed to fire, so a half-blocked pipe or a sluggish condensate trap shows up in the readings first.

Stone Ridge’s houses skew older, from a 2009 median against 2013 for the whole ZIP. On a furnace past fifteen, the parts that light the burners, the igniter, the flame sensor and the inducer motor, tend to tire first, and watching it light, run and shut down through full cycles is where that shows. Book in September or early October, while a part the visit turns up can be swapped on a mild day.