| Criterion
6.5.8
Structural Supports
Criterion
text:
Neither
wind loading (including uplift) nor the additional weight of filled
collectors shall exceed the live or dead load ratings of the building,
roof, roof anchorage, foundation or soil. Collector supports shall
not impose undue stresses on the collectors. The design load shall
be as specified by the codes in force at the installation site
and shall include an additional load due to snow accumulation
for applicable locations.
Comments:
The system has been certified based on manufacturer's specifications
and instructions.
SRCC
reviews the manufacturer's structural design, but does not conduct
a detailed analysis. It is the manufacturer's responsibility to
properly design the structural supports.
Installers
must use the structural design, materials and installation instructions
that the manufacturer outlines in the SRCC approved installation
manual.
Figure
1
The
manufacturer has designed the system (and its components) for
specific loads. Nevertheless, installers must be aware of local
conditions and resulting wind load and structural requirements.
In specific geographical areas, such as coastal Florida, the winds
load requirements are much greater due to periodic hurricanes.
In addition, coastal areas require different types of hardware
due to the ocean environment and its affect on various metals.
As
always, follow local code requirements.
Figure
2 indicates the various wind forces that are placed on a mounted
solar collector. In this instance, the collector has been mounted
using extension struts to provide a greater tilt. This in turn
also impacts the structural considerations. In light of this,
manufacturers have designed the mounting hardware to withstand
anticipated loads.
Figure 2
Figure
3 through 6 provide illustrations of the various collectors and
systems that have unique mounting designs and materials provided
by the manufacturer. Figure 3 shows a common flat plate type system
installation that is almost flush to the roof. Wind loads on the
collector would be reduced by mounting the collector down further
from the roof peak. Compare this with the flat plate installation
in Figure 6. Which collector is more susceptible to wind loads?
Correct, Figure 6.
Figure
3
Integral
Collector Storage (ICS) systems (Figure 4) have their own unique
structural mounting design and materials. The manufacturer has
obtained SRCC approval for these and therefore, the installer
must follow the manufacturer design and installation procedures
and use the manufacturer provided hardware.
Figure 4
Thermosiphon
systems have unique structural requirements due to the specific
design characteristics of this type of system.
Figure 5
The
collector shown in Figure 6 was installed on a back roof facing
south since the owner did not want to see a solar collector on
the street side. Compare this installation with that presented
in Figure 3.
Figure
6
The
solar industry has developed collector mounting methods that are
used by most manufacturers and installers. These include the following:
Figure
7 shows the most common mounting method used in the industry -
the lag bolt into the roof truss member. Care must be taken to
ensure that the lag bolt is screwed
into the direct center of the truss.
Figure
7
Figure
8 illustrates the spanner method which is also quite popular and
is actually the method preferred by many building officials.
Figure
8
Note
that some jurisdictions allow only spanner mounting using metal
braces (Figure 9). It is the installer's responsibility to be
aware of local requirements.
Figure 9
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