STIEBEL ELTRON SOL 25 PLUS - Manual (Page 30)

30 | SOL 25 PLUS WWW.STIEBEL-ELTRON-USA.COM
gross leaks.
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 longer time to see if pressure is
holding steady. Use the red dial to mark the pressure and see tha
the gauge returns to the same indication. Remember that the air
pressure will vary based on the temperature of the loop, so it may
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 pre-charge 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.
• Never fill the system when it is subject to strong solar
irradiation or if the collectors are significantly hotter than the
ambient air. This could lead to steam hammer inside the collectors
8. COMMISSIONING THE SYSTEM
WARNING: PRESSURE TEST SYSTEM ONLY WITH DOWFROST
50/50 OR 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 pipe work 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 some based on temperature of the air, so one must
try to read the pressure at nights when the system cools down to
ambient temperature or when covered. The following procedure is
recommended:
1. Isolate the expansion tank by shutting the isolation
valve.
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