Articles by John Siegenthaler, P.E.

An installer is asked to provide a relatively simple single-zone floor heating system supplied by a mod/con boiler. He’s heard that a hydraulic separator is a good component in such systems

Well-designed and properly installed hydronic radiant heating systems have earned a deserved reputation for superior comfort. Even so, many people hesitate on using these systems because they can’t just push a button on their thermostat to change the system from heating to cooling.

The system was intended to supply one high-temperature heating zone, a couple of medium-temperature zones and two zones of floor heating for a garage and breezeway where antifreeze protection was needed.

All closed-loop hydronic systems require an air space to absorb the increased volume of water as it warms during system operation. In most hydronic systems, this task is handled by an expansion tank. In most modern hydronic systems, it’s handled by a diaphragm-type expansion tank.

A homeowner asks his local heating installer if a geothermal heat pump can be combined with radiant floor heating. The system he creates is meant to supply a dozen independently controlled zones of low-temperature floor heating.

A homeowner wants to use a wood-gasification boiler as his primary source of space heating. He also wants a propane-fueled boiler to automatically come on for backup should he decide not to tend the fire, or if he is away. The owner has read that a generously sized thermal storage tank is necessary to allow a gasification boiler to operate at consistent high efficiency.

Last fall, I taught my first online course dealing with designing hydronic heating systems. The course was titled “Mastering Hydronic System Design.” It was a collaborative effort between HeatSpring Learning Institute, BNP Media’s CE Campus and myself.

A hydronic system is to supply four panel radiators, each with its own thermostatic radiator valve, and an indirect water heater from a gas-fired sectional cast-iron boiler. The system is designed using primary/secondary piping.

In past columns, we’ve discussed geothermal water-to-water heat pumps and air-to-water heat pumps via hydronic heat sources. Both can be a great match to low-temperature hydronic distribution systems.

The hydronic system shown above was created to connect three gas-fired, cast-iron boilers to a low-temperature distribution system that supplies 12,000 ft. of 3/4 in. PEX tubing embedded in the floor slab.The installer spends several frustrating hours attempting to get the air out of the system. He finally gets it purged to the point that the distribution circulator is at least moving some water through the floor-heating circuits.