Articles

Side-stream filters keep hydronic systems healthy like kidneys clean blood, yet almost nobody knows the actual flow rate through them. For consistent filtration regardless of variable pump head and filter loading, an automatic flow limiter in the side-stream circuit is the practical solution.

A frantic call about a malfunctioning humidifier led to a long climb up the stairs of a high-rise — only to discover the unit hadn't been purchased from them at all. The novelty greeting card sent in response became a memorable lesson in checking the basics before calling for help.

A recreation complex's domestic hot water was lukewarm despite the boiler system running. The piping arrangement allowed boiler water to flow backwards through the shell-and-tube heat exchanger, feeding it return water instead of supply. The facility manager's parting question — 'How could they balance it when it's flowing backwards?' — remains unanswered.

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.

New automatic flow limiters were blamed when a heating coil produced no heat, but zero pressure drop across the limiter proved it wasn't plugged. The real culprit was a butterfly valve with a cleanly broken shaft — the handle moved but the disc didn't. Sometimes the simplest components fail in unexpected ways.

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.

An expansion tank connected on the discharge side of the pump caused the pump inlet pressure to drop below atmospheric, turning the air separator into an air intake. The fix was simple — move the tank connection to the pump inlet. The glycol everyone blamed was never the problem.

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.

Logarithmic mean temperature difference (LMTD) is the driving force behind heat transfer, and counter-flow arrangements produce a higher LMTD than parallel flow. For installers, the rule is simple: hot-to-hot, cold-to-cold — or for coils, air in where water goes out. Follow the labels.

Using a pump curve to estimate flow is a useful technique, but only if the gauge piping is correct. In this case, the gauge was connected upstream of the suction diffuser instead of at the pump flange, making the pump appear to be overflowing when it was actually close to spec.