STIEBEL ELTRON SOL 25 PLUS - Manual (Page 62)

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7. The second phase of the leak test detects smaller leaks and
requires a wait time. Pressurize the system to 80 psi and watch
the pressure gauge over a period of 15-60 minutes to see if any
pressure loss occurs.
8. After any leaks have been repaired, repeat this test. If pressure
appears steady, line up the red dial of the pressure gauge with the
needle indication. Check again to see if the pressure holds,
relative to the lowest pressure previously indicated by the red dial.
Small leaks may be detected by covering suspected locations with
soapy water and looking for bubbles.
9. After all known leaks have been repaired, the final phase of
the leak test requires waiting a day or more to see if pressure
is holding steady. Use the red dial to mark the pressure
and see that the gauge returns to the same indication each
evening. Remember that the air pressure will vary based on
the temperature of the loop, so it will be necessary to read the
pressure at night, after the system cools down.
At the conclusion of the leak test, check all fittings and vent the
system.
8.2 Setting the Expansion Tank Pre-charge Pressure
While the leak testing (described above) is being performed, the
installer should set the expansion tank’s precharge pressure. Make
sure that the “wet” side of the expansion tank (pipe connection)
is vented to atmosphere. Using a compressor, pre-charge the tank
with air (or use pressurized nitrogen) to a final pressure of 5 psi
less than the target system pressure. For example, if the final target
system (solar loop) pressure is to be 50 psig, fill the expansion
tank to 45 psig (which is the recommended default value). When
complete, cap the Schrader valve fitting and re-attach the tank to the
pump station. Make sure the expansion tank always faces up (the
Schrader valve must be pointed down).
8.3 Flushing the System
The next step of the commissioning process involves flushing the
solar loop to purge contaminants and air.
Preparations:
• Use only 50/50 Dowfrost propylene glycol solution for flushing
the system. Use of water or any other fluid may adversely affect
the operation of the system.
• Wear protective gloves and goggles when handling propylene
glycol mixtures. Never fill the system when it is subject to strong
solar irradiation. This could lead to steam hammer inside the
collectors and possible burns from escaping steam. If the sun
shines during start-up, cover the collectors or wait until there is
some shade.
8. COMMISSIONINg ThE SYSTEM
WARNING: PRESSURE TEST SYSTEM ONLY WITH
COMPRESSED AIR.
NEVER FILL AND PRESSURE TEST THE SYSTEM WITH WATER
WHERE THERE IS A RISk OF FROST. (COLLECTORS CAN FREEZE
AT TEMPERATURES SIGNIFICANTLY ABOVE AIR TEMPERATURE IF
RADIATIONAL COOLING IS STRONG, SUCH AS WITH CLEAR SkIES.)
After the installation is complete, the system may be commissioned
for service. Commissioning involves the following procedures, which
are explained in detail in this section:
• Pressure and Leak Test (Section 8.1)
• Setting The Expansion Tank Pre-charge Pressure (Section 8.2)
• Flushing The System (Section 8.3)
• Final Charging and Venting The System (Section 8.4)
• Start-up (Section 8.5)
8.1 Pressure and Leak Test
After the pipework has been installed and the collectors have been
connected it will be necessary to pressure-test the system to detect
leaks before filling the solar loop with heat transfer fluid. Propylene
glycol solutions can leak from much smaller gaps than can water,
so such testing is critical to assuring a successful installation.
Recommended test pressure is 80 psi. The thermal insulation should
be installed only after the leak test has been successfully completed.
It is recommended that compressed air be used to test the system
for leaks, as it is very easy to make repairs and it will prevent
loss of solar medium, spills, property damage, and messy clean-
up problems. Air is also capable of revealing very small leaks,
that water may not reveal, through which propylene glycol will
often leak. Leaks will be evident from the sound of escaping air,
observation of bubbles emanating from fittings and other leak-prone
components that are coated with soapy water, and watching the
pressure gauge over time. Bear in mind that the pressure gauge
will vary based on temperature of the air, so one must try to read
the pressure on successive nights when the system cools down to
ambient temperature. The following procedure is recommended:
1. Isolate the Purg-O-Mat and expansion tank by shutting their
isolation valves.
2. Turn check valves in the pumping station to their 45° position
to allow two-way flow.
3. Close the bottom fill & drain valve.
4. Connect hose with a Schrader valve to the upper fill & drain
valve.
5. Connect an air compressor and raise the solar loop system
pressure to 80 psi.
6. The first phase of the leak test, which detects gross leaks or
inadvertently open valves, involves listening for leaks or observing
if pressure does not immediately reach 80 psi. Repair any such
gross leaks.