Install Instructions

23
IM-PR 566442 1114 (Design Manual)
1.8.1 Primary/secondary
When sizing primary piping, maintain a fluid velocity
of 2.0 to 4.0 feet per second at a temperature drop
that will satisfy the total design heat load of the
system. This velocity range is ideal for two reasons.
The first is that maintaining fluid flow through
the piping above 2 feet per second will facilitate
separation of air from the fluid – extending its useful
life. Also, to enable the primary piping to operate
quietly, fluid flow should not exceed 4 feet per
second by any significant amount. Higher fluid flow
velocities can contribute to the erosion of copper
components within the system.
To optimize control of water temperatures,
maintain design flow rates and properly size
circulators, it is important to design the piping
system to provide hydraulic separation between
primary and secondary piping. Designing for
hydraulic separation permits greater control over
heat delivery and reduces interference that could
otherwise result between circuits. Options to
achieve hydraulic separation include:
• Hydraulic separators with air and sediment
separation functions: See manufacturer
literature for sizing guidance.
Figure 1-18 Hydraulic separator
• Closely spaced tees: Space tees less than
4 pipe diameters apart and less than 6
pipe diameters from the closest change of
direction to achieve design ow rates through
secondary piping. See Figure 1-17.
Figure 1-19 Closely spaced tees
5 gpm
10 Gallons
per minute
5 gpm
10 Gallons
per minute
8 gpm
10
Gallons
pe
r minute
2 gpm
10 Gallons
per minute
0 gpm
10 Gallons
per minute
10
g
pm
10 Gallons
per minute
50'-0"
50'-0"
75'-0"
25'-0"
98'-0"
2'-0"