Nearly half of Centreville’s owner-occupied homes are townhouses, and about seven in ten went up between 1980 and 1999. In the usual townhouse from those years, one system cools all three floors from the bottom: the indoor coil sits on top of the furnace in the utility room, and the condenser stands on a pad out back.
That coil wrings water out of the air all summer. On an unfinished lower level it usually runs to a floor drain; where the lowest floor became a family room, it more often drains to a small condensate pump beside the furnace. Plenty of these houses have since gone to a high-efficiency furnace, which makes water of its own all winter and often empties into that same pump, so the pump never gets a season off. Every tune-up cleans the drain line, and a pump that’s slow to empty goes in the write-up.
About three in ten homes here are single-family houses, and the bigger ones often cool the bedroom floor with a second system in the attic. Up there the coil drains into a pan right over a bedroom ceiling, usually with a backup pan below it and a float switch that stops the cooling when water backs up. That’s two systems and two tune-ups at $99 each, and the attic one deserves the trip up the ladder: nobody sees its drain until there’s a stain on the ceiling.
Electric heat, in a quarter of Centreville’s owner homes, mostly comes from a heat pump, where one outdoor unit cools in July and heats in January, so a spring visit sees only its cooling half. In the gas homes, close to three in four, the condenser sits idle from October to May, and the first warm week is when an ant colony or a wasp nest that wintered in its electrical box sometimes turns up.