Boilers

Condensing boilers can reach 98% efficiency — but only when return water is around 80°F. Above 130°F the boiler won't condense at all, making it an expensive mid-efficient unit. Designing the connected system to consistently deliver low return temperatures is essential to realizing the efficiency promise.

A condo building's new modular boiler appeared undersized but was actually firing at half capacity due to a plugged strainer in the primary loop. The contractor said they'd blown it down, but pulling the screen revealed it was still plugged. Don't assume strainers are clean — open them up and check.

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 boiler short-cycling like it was possessed turned out to be an injection pump issue in a primary-secondary radiant floor system. The globe valve in the injection return was wide open, causing the radiant supply to match boiler temperature, which repeatedly triggered the controller to shut down and restart the boiler.