
Refer to section 11.3 for more details on tube replacement.
✖ Hail related damage to the collector is not eligible for warranty claims.
3.17. Lightning Protection
It is advisable to earth-ground the copper circulation loop of the collector to avoid lightning related damage,
or electrical safety issues. It may also help to prevent galvanic corrosion of the copper pipe which can
result in blue staining of basins/baths etc.
3.18. Thermo-siphoning
a) Thermo-siphoning (convection) can occur if the solar loop pump is off and a low outside air temp makes
the collector manifold colder than the fluid or water in the mechanical room. Thermo-siphoning occurs when
hot fluid rises up the Return Lines toward the cooler collector and external piping. After it dissipates its heat
and cools, it falls back down the Supply (Feed) Line and cools the tank. This can occur with direct flow
systems or closed loops with a coil heat exchanger inside the tank. Thermo-siphoning only occurs when
the collector is cooler than the tank, so normally at night. If not controlled it can cause considerable heat
loss.
The following methods can be employed to stop thermo-siphoning:
i) Normally, a check valve can be installed on the Supply (feed) Line after the pump and is enough to
stop thermo-siphoning. Some pumps have integral check valves, which provide the same benefit.
ii) If thermo-siphoning occurs even with a check valve installed, a heat trap should be formed in the
return line (line back from collector) close to the tank. The heat trap should be a U-shaped section of
pipe, extending downward 8-10” and then back up. Since heat rises, this downward section of pipe will
trap hot water and prevent migration of heat up the piping. This section of pipe in particular should be
well-insulated.
3.19. Pressure and Temperature Control and Relief
a) Direct Flow Max Incoming Pressure: For direct flow systems, the normal operating pressure should be
no greater than 72.5 psi (500 kPa), if necessary a pressure limiting (pressure reduction) valve should be
installed on the main cold feed line.
b) Closed Loop Max Incoming Pressure: For closed loop systems, the solar loop must operate at no
greater than 50 psi (350 kPa) and have an expansion tank installed to accept fluid expansion. If a single
wall heat exchanger is used, the solar loop operating pressure must be below the water main pressure. The
solar controller should have a “max tank temp” function to protect the tank from being overheated. All
Apricus controllers provide such this function as standard. Refer to section 6 for more information.
c) Maximum Allowable Pressure: The maximum allowable operating pressure for the solar collector in any
system configuration (domestic or commercial) is 116 psi (800 kPa) with pressure relief valve discharge
rating at no more than 123 psi (850 kPa) or lower as specified by local codes and regulations. Also, check
the maximum pressure ratings for all components of the system and only use products that can handle the
operational temperatures and pressures of the system design.
d) Stagnation: For direct flow systems and closed loop systems with suitable heat transfer fluid, it is
acceptable for the system design to allow the solar collector to stagnate (i.e. stop the pump) to prevent
overheating of the storage tank above ~177
°
F (~80
°
C). An expansion tank must be properly sized and
installed to accept the increase in fluid volume due to thermal expansion and potential steam formation, in
order to minimize or prevent release of fluid from the pressure relief valve.
e) Heat Transfer Fluid: In a closed loop system, it is important to use a heat transfer fluid that is rated to at
least 320
°
F (160
°
C) to minimize fluid degradation during periods of stagnation (see above). Depending on
the pressure of the closed loop the fluid may vaporize (boil) during stagnation causing some degradation of
the fluid. If stagnation happens on a regular basis due to excessive heat production (heat supply > demand)
or power outages, an inspection of the fluid should be completed. Contact the manufacturer for more
information on how to check the fluid. Refer to Section 3.31 and Appendices 11-17 for heat transfer fluid
information.
✖ System pressures that exceed those requirements outlined above will void the warranty.
Apricus Solar Collector Installation & Operation Manual - USA
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