Time the starts: why a World Golf Village system shuts off every six minutes, and what each cause costs

Count the starts with your phone

Stand near the outdoor unit with the stopwatch open. Start it when the compressor kicks on, stop it when the unit goes quiet, and note the gap before the next start. A healthy system on a St. Augustine afternoon runs fifteen minutes or more and rests for a while. Three or more starts in an hour, each run under ten minutes, is short cycling. Write down the numbers; they tell us more than “it keeps turning on and off” does.

Why six-minute cycles hurt more in this humidity

The compressor is the most expensive part of the system, and starting is the hardest thing it does. A unit cycling eight times an hour starts about seventy times a day; a unit running proper cycles starts a dozen. Over a summer that difference is years of compressor life.

Then there is the water. From May to October the dew point here lives in the mid-70s, and the only thing removing moisture from the house is a coil that has been cold for a while. A short cycle cools the air and stops before much water has condensed. The thermostat says 74; the hygrometer says 65 percent; the house smells like the inside of a cooler. And a system that starts seventy times a day draws more from FPL than one that runs steadily, because every start is a surge.

The causes, from most to least common in St. Augustine

1. An oversized unit. The boom-era default in World Golf Village, Murabella and the newer parts of St. Augustine Shores: builders went a size up to avoid callbacks, and a later contractor went up again. The house never asks for the full capacity, so the unit sprints and stops.
2. A badly placed thermostat. Afternoon sun through a glass door, a supply register overhead, a lamp beneath it. Common in two-story floor plans with a front hall.
3. Low refrigerant or a dirty coil. Pressures fall out of range, a safety switch stops the compressor, it resets, and the cycle repeats. More common on coastal units at Vilano and Crescent Beach, where coils leak.
4. A clogged drain and float switch. The switch opens, the system stops, water drains a little, the switch closes, the system starts. Looks like short cycling from the thermostat; sounds like it from the garage.
5. A failing capacitor or contactor. The unit tries to start, cannot, and tries again. Usually loud about it.
6. An iced coil. Airflow drops, the coil freezes, pressure switches trip, it thaws, it restarts.

The fix ladder, cheapest first

Shade or move the thermostat. Clear the drain and add a float switch if there isn’t one. Replace the filter and clean the coil. Replace the capacitor or contactor. Find and fix the refrigerant leak, then recharge. Set a longer minimum run time on the thermostat. Then, and only then, talk about equipment. We work up the ladder and quote each step before taking it.

Ask for a cycling diagnosis

When the right fix is a smaller system

If the stopwatch says six minutes, the house says 65 percent humidity, and every step on the ladder has been checked, the equipment is oversized for the structure. Nothing short of replacement fixes that, and the replacement should be sized by a load calculation run on today’s version of the house, with its current windows, insulation and shade. In most of the 2005 subdivisions that comes out a half-ton to a ton smaller than what is there, and a two-stage or variable unit at that size runs long, quiet cycles that finally dry the house. We say that plainly when it is true, and we quote the repairs first when it isn’t.