23
Direct solar systems should not use plastic pipe to feed cold water to the tempering valve. The
water from the collector can melt the pipe from the valve. High temperature CPV plastic pipe
may be used down line of the tempering valve if a six foot copper stub is installed in the
tempering valve before the plastic pipe.
The flow control valve for pre-heater systems (direct solar systems do not need a flow control
valve) is used to by-pass the collector so that it may be drained for severe winter shutdown or in
the unlikely event of a problem with the collector. The by-pass mode will allow the conventional
water heater to continue to provide hot water for the house. The recommended flow control
valve is a 3-way ball valve. For FSEC certified two-way systems the flow control valve is the 3-
way ball valve identified as valve #2 in the plumbing schematics. In the SRCC schematic it is
valve #2B.
All systems must have a 150 psi pressure relief valve installed in the solar loop piping between
the collector and the flow control valve. The valve may be installed in the supply side of the
solar loop piping, the return side of the solar loop piping, or at the collector on either the inlet or
the outlet pipe connection. The supply side pipe is the recommended preferred location as is
shown in both the FSEC and SRCC approved system schematics. Some local codes may
require the pressure relief valve to have a drain line. If the valve is installed in the supply line as
shown in the plumbing schematics, its drain line can follow the same route as the drain line from
the T&P valve on the conventional water heater. Some local codes will allow both valves to
share the same drain line, some will not.
A check valve is used only if a freeze prevention valve is installed. It should be installed in the
return solar loop piping below the boiler drain to prevent short circuiting of the freeze prevention
valve during cold weather. Use a check valve that is designed for back-flow prevention when
installed in a vertical position.
XI.
SYSTEM INSULATION
All piping, fittings, valves, and the conventional water heater must be well insulated. Even small
sections of bare pipe will cause substantial heat loss at elevated temperatures. The cold water
supply line will also conduct heat away from the system unless it is insulated. Only Direct
Systems installed in tropical or low latitude areas should have un-insulated supply lines. Use a
¾” wall, closed-cell tube insulation such as Rubatex, Armaflex, or Insul-tube in mild climates. In
cold climates, where freezing occurs, 1.5” wall insulation
must
be used. The
chart on page 24
illustrates the freezing characteristics of various copper pipe and insulation configurations.
Remember, TCT’s warranty does not cover freeze damage to any system piping. All tube
insulation exposed to sunlight must be protected from UV degradation. Use pipe insulation
jackets or a coating of exterior grade latex paint, or metal tape. Do not use duct tape because it
will quickly deteriorate when exposed to outdoor conditions. If the solar system is retrofitted to a
pre-existing conventional water heater, the water heater should be insulated with an extra super
insulation jacket. At least two inches of fiberglass batt is recommended
see Detail W in the
Appendix.
If the conventional water heater is of the high efficiency type insulated with R-12 or
better foam insulation, it will not need additional insulation
Summary of Contents for ProgressiceTube
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