Most of 20151 went up in the 1980s and 90s, and a little over 4 in 10 owners there heat with electricity, usually a heat pump in a Chantilly house that age. The first warm afternoon you switch the thermostat to cool, it goes straight from a winter of heating into its first long cooling run, and that’s when a weak part shows itself, as warm air on a cooling call. A spring tune-up runs the system in cooling before you need it, so that surprise comes on a mild day.
In the gas houses the furnace usually stands in the basement, with the cooling coil on top. A basement often has no floor drain low enough for the water that coil makes, so a small condensate pump lifts it to the laundry sink. When one quits, the first sign is a wet floor. Part of the tune-up is clearing that drain, and the tech follows it to the pump or the sink.
South Riding, across the county line in 20152, is younger: the typical house went up around 2006, and nearly half are townhouses. In many of those the cooling coil is upstairs, in the attic or a closet off the top hall, drain pan and all, over the bedrooms. Few people climb up there between visits, so April’s tune-up is the one time a year anyone sees that pan before July puts it to work.
The bigger South Riding houses often have a second outdoor unit for the upstairs; each one is a separate $99 tune-up. Many builder units from the mid-2000s are still running, close to twenty summers on, and the label on the side gives the year and the refrigerant. Already blowing warm? That needs a repair, and our Chantilly AC repair page lists the prices.