Specifications

prevent the pump from operating when the collector is above a certain limit. This function is most
commonly used with drain-back systems as circulating water through the collector when hot would cause
large volumes of steam (depending on pressure setting) resulting in a pressure increases and potential
dumping of water/steam from the drain-back tank.
c) Low Temperature Limits: The low temperature limits of all components in the system must be known
and cannot be exceeded. In every climate region, all materials exposed to winter freezing conditions must
be able to withstand such conditions. This is particularly important for any synthetic materials, such as
plastics or rubbers that may become brittle when extremely cold. The following are examples of
components that should be able to withstand the coldest conditions experienced in the installation location:
- High-point ball valve (used for auto-air vent during system charging)
- Pipe insulation (either high temp EPDM or fiberglass)
- Roof flashing, if in direct contact with copper pipe
- Washers or seals used in any quick-connect, compression or threaded fittings etc.
- Heat transfer fluids, if closed loop
- Rubber/plastic components on solar collectors, particularly if they are
structural.
Apricus uses silicone rubber components which are able to maintain good
flexibility even during freezing conditions.
d) Ultraviolet (UV) degradation: Any components installed outside must be
able to withstand UV radiation without significant degradation. Color fading is
common, but cracking, peeling and other severe degradation should not occur
during the design-life of any component in the system.
e) Structural Loads: Components must be able to withstand environmental
forces such as wind loading, snow loading, rain and hail. They must also be
securely and positively fastened to the structure.
- Wind loading refer to section 3.13.
- Snow loading refer to section 3.14.
- Hail refer to section 3.16.
3.11. Fluid Expansion
a) Thermal Expansion of Water: Water can expand in volume by up to 2%
from cold to hot in a solar thermal system. In the past, most water heaters
utilized the cold supply inlet as a vessel to accept this increase in fluid volume;
in other words, they literally pushed the excess volume backward against
incoming water pressure. Many codes now require back-flow prevention devices
that prohibit this method. In these cases, an expansion tank is necessary to
accept increased fluid volume, otherwise the T/P Valve will discharge frequently.
If there is already an expansion tank present, you will need to install another one
or a larger one, as necessary. For example, a direct flow system with an 80
gallon tank and 2 gallons in the solar loop needs between 1.5-2 Gallons of
additional volume. The expansion tank needs to be able to accept that amount of fluid. A potable expansion
tank is required for direct flow systems.
b) Expansion Tank (potable AND direct flow): Direct flow systems AND closed systems that have a check
valve or back-flow preventer on the incoming cold potable supply must have an expansion tank installed to
accept the potable water’s thermal expansion. The expansion tank must be potable water rated and sized to
accept the maximum thermal expansion possible for the entire volume of water heated in any and all the
tanks in the system. Contact the expansion tank manufacturer to confirm, which model is necessary given
the system fluid type, fluid volume, pressure and operating temperature range. The expansion tank for
direct flow systems must be rated for use in potable water systems.
c) Expansion Tank (closed loop): For closed loop systems, an appropriately-sized, expansion tank must
be installed in the solar loop to accept the heat transfer fluid’s thermal expansion. The expansion tank must
be sized to accept the maximum fluid expansion possible for the specific heat transfer fluid and rated for
Apricus Solar Collector Installation & Operation Manual - USA
Copyright © 2011 – Apricus Inc Doc: A7-05.4.12-PB Page 21 of 129