Bryant 50YEW Design Manual page 46

Water-to-Water System Design Guide
Part III: Source Side Design / Closed Loop Installation Guidelines
Headers that utilize large diameter pipe feeding the last circuits
should not be used. PE 1-1/4" IPS pipe requires 9.5 gpm [36 l/m]
to attain 2 fps [0.6 m/s] and since increasing the fl ow through
the last circuit would also require increasing the fl ow through the
other circuits at an equal rate as well, we can estimate the fl ush
fl ow requirements by multiplying the number of circuits by 9.5 gpm
[36 l/m] for 1-1/4" IPS. For instance, a 5 circuit loop would require
5 circuits x 9.5 gpm/circuit = 47.5 gpm [5 circuits x 36 l/m per
circuit = 180 l/m or 3.0 l/s] to attain fl ush fl ow rate. This is clearly is
a diffi cult fl ow to achieve with a pump of any size.
Figure 3-4b: Typical Header Through 5 Tons
Figure 3-5: Typical "Laydown" Header
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Header Layout - Generally header layouts are more cost effective
with short headers. This requires centrally locating the header to
all circuits and then bringing the circuits to the header. One of the
easiest implementations is to angle all trenches into a common
pit similar to a starburst. This layout can utilize the laydown or
'L' header and achieves reverse return fl ow by simply laying the
headers down in a mirror image and thus no extra piping or labor.
Figure 3-5 details a "laydown" header.
Bryant: Whatever It Takes.