Hydronic Design

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.

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.

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.

Of the essential components every modern hydronic system needs, the air separator is the one most often missing. Without one, automatic air vents won't work properly, and the result is noise, poor circulation, and poor heat transfer. High temperature, low pressure, and low water velocity are the keys to effective air separation.

Albert Einstein's word 'schlembe' — an improvement that makes things worse — perfectly describes what happened when an energy performance upgrade left a school freezing. Incorrectly installed monoflo tees and added control valve head loss combined with a revised ventilation schedule to kneecap the heating system.

A 15-storey apartment building with chronic cold complaints had most of its pump flow short-circuiting through an oversized, unbalanced unit heater in the penthouse mechanical room. Closing one ball valve brought immediate improvement — and a tenant confirmed the problem had existed for 22 years.

Primary-secondary piping doesn't have to be mysterious. Drawing a capital H captures every P-S connection's four arms and decoupler pipe, making it easy to map out flow rates, temperatures, and blending direction for both design and troubleshooting purposes.