We’re only human, and most humans like to put off things until they absolutely have to be done. 

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. 

A zone is any area of a building for which indoor air temperature is controlled by a single thermostat (or other type of temperature controller). 

An installer pipes up the system shown in Figure 1. Its purpose is to provide two zones of space heating.