The Glitch & The Fix

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An installer is asked to add a monobloc-style air-to-water heat pump to an existing hydronic system that is supplied by a mod/con boiler.

A technician encounters a system installed in the 1980s when radiant floor heating was relatively new in North America.

A homeowner hires a heating contractor to upgrade his propane-fired cast-iron boiler to a mod/con boiler. The cast-iron boiler is only 15 years old and in good shape. 

A multiple boiler system using sectional cast-iron boilers has been configured to supply two loads as shown below. A “crossover pipe” is installed in case the flow rate in the primary circuit is different from the flow through the boilers. There are several piping errors in this proposed design. Can you spot at least five of them?

Sometimes multiple mistakes show up in small portions of hydronic systems.

An installer is asked to provide a system that supplies two zones of fin-tube baseboard and two zones of floor heating.

An installer is asked to connect a single speed geothermal water-to-water heat pump to a highly-zoned low temperature hydronic distribution system.

Figure 1 shows the piping layout for an actual installation. It uses two boilers, fired in stages, to supply three areas of a building. 

An installer recently read about the benefits of piping a buffer tank in a “2-pipe” configuration.  

A heating designer is asked to create a three zone radiant floor heating system using a 5-ton (60,000 Btu/h) geothermal heat pump as the primary heat source, and a mod/con boiler as the auxiliary heat source.