National Oilheat Research Alliance 19
from the primary loop. The tees that connect
the secondary circuit should be no more than
12″, or 4 pipe diameters – whichever is less,
apart. If the secondary circuit is piped in ¾",
the tees should be 3" apart.
Because the water temperature drops as
it circulates through the primary loop, it’s
important to connect the secondary circuits
that require the hottest water (baseboard) at the
beginning of the primary loop and those that
require lower temperatures (radiant) towards
the end.
When there is a call for heat, both the
primary and secondary circulators operate and
the secondary circulator pulls water from, and
returns it to, the primary loop.
Figure 8
Figure 9