Controls & Thermostats

Converting a furnace to hydronic heating with a boiler and indoor-outdoor reset seemed like a great idea — until the family complained it was cold. Lower supply water temperatures meant cooler air from the registers, longer fan cycles, and a different comfort perception. Sometimes the technologist learns the hardest lessons at home.

Pressure-independent control valves were being blamed for a building's pumps running at 80% speed regardless of load. The real problem was the differential pressure sensor installed right at the pumps instead of out in the system — feeding garbage information to the variable speed pump controller.

A modulating-condensing boiler connected to a radiant garage slab was short-cycling badly despite being properly set up. The culprit was hidden in the manual's fine print: the controller was adding 10°F to whatever operating differential temperature was entered, causing the burner to overshoot and cycle repeatedly.

A mother's condo heating system got hotter the more she turned it down. The problem: her brother had replaced the thermostat with a direct-acting model, but hydronic zone valves are normally open and require a reverse-acting thermostat. Diagnosed from 800 kilometres away over the phone.