UFC 3-440-01
14 June 2002
4-2.2.7
Collector Sub-System Plumbing Details. The collector banks must be
able to be valved off for maintenance, repair, or replacement. It is recommended that
ball valves be used in this capacity instead of gate or globe valves. Manually operated,
calibrated balancing valves are also to be located at the outlet to each collector bank to
adjust for any flow imbalances present after construction. Drain valves should be
located at all low points in the collector sub-system to allow the collectors to be drained
if necessary. Pressure relief valves should be located on each collector bank that could
be valved off accidentally and allowed to stagnate. Finally, manual air vents should be
located at the high points of the collector loop to allow air to escape during the filling
process. Ensure that adequate room is provided for expansion of the internal manifold
and absorber plate assembly within the collector casing. The differential expansion
between the system flow paths and the system and the support structure must be
considered in the design.
4-2.2.8
Thermal Expansion. Thermal expansion control becomes important when
long lengths of pipe are present or when pipes must be secured at a given location.
Other locations for which pipe movement can be critical are in pipe chases and near
pumps, where expanding pipe could cause shifts in pump alignment. The preferred
method of accounting for thermal expansion is to construct a U-shaped bend in the pipe
run that can absorb the anticipated movement at a given location. When necessary,
these loops should be located horizontally and supported properly so that the fluid
contained within can be drained. Figure 4-8 shows the change in length of copper pipe
with temperature change. When long pipe runs are required, the designer will ensure
that the resulting expansion or contraction will not harm system components or cause
undue stress on the system or the building. If the plumbing geometry cannot withstand
the length changes or if the plumbing must be anchored at certain locations, pipe
supports and guides must be designed to allow freedom of movement in the direction of
motion.
4-3
STORAGE SUB-SYSTEM
4-3.1
Storage Tank Construction. Solar storage tanks must be insulated to a
value of R-30 or better, to minimize loss of collected solar energy. The storage tank
should be equipped with a minimum of four pipe connections, two located near the top
of the tank and two located near the bottom. To take advantage of storage tank
stratification, pipes supplying the collector array and the cold-water inlet should be
connected to the bottom penetrations, and the pipes returning to the tank from the
collector array and hot water supplied to the load should be connected to the
penetrations near the top. Instrumentation openings will be required as well as
openings for relief valves, drains, and the like. Since copper is to be used for all system
plumbing, the designer should ensure that a dielectric coupling is included in the design
of any necessary penetrations of the storage tank.
4-13
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