After laying out the sloped chalk line, mark the position of the feet along the line. Drill a
1/4" pilot hole through the roof to locate the position of the purlin underneath. Secure
the purlin underneath, then redrill through the hole for a 3/8 in. bolt. Figure 3.5 shows
different options for the roof mounting structure.
Be sure to caulk under the bolt head and under the feet with silicone sealant to keep
water out. Make sure to point the narrow dimension of the feet up and down the roof to
prevent damming rain water and trapping leaves and debris. The collectors should be
held at least 2 in. off the roof to clear debris and allow air flow.
Figure 3.6 shows the collector to tank piping concepts. The return line should be the
shortest to conserve energy.
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Solar Installation Manual
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Figure 3.5. Different kinds of under roof fastening methods
a) hit rafter
b) Near miss
c) spanner and blocks
d) purlin
