Oil-filled loops must never be flushed with water. Water is a
contaminant that can never be completely removed.
Flush the system until the fluid coming from the "drain" fitting is clean. Make sure
the fluid is moving through all parts of the loop. On a sunny day, all the collectors
should be at the same temperature. Their temperature will rise slightly throughout
Refilling (Recharging) Glycol or Oil Loops
Before recharging the system, make sure the expansion tank capacity is adequate
for the system and fluid. This is especially important if the system has a history of
relief valve blow-off. Information on expansion tank sizing can be found in Diamond
reference 1, in the bibliography.
It may be necessary to adjust the air pressure of diaphragm-type expansion tanks
before filling the system. The correct air pressure is listed in Table 5-4.
Before introducing a new fluid, pressure test the piping system with compressed air.
Use air rather than water to prevent damage to pipe insulation or building
components if leaks appear. Also, water must never be introduced into an oil loop.
Test at 75 PSI for a period of two to three hours. If pressure relief valves or other
components cannot withstand this pressure, isolate them or remove them from the
system. A lower test pressure can be used for a longer period of time, but it is not
as good a test.
During the test, the pressure will fluctuate slightly (5 to 10 PSI) as the system heats
up and cools down. Leaks can be found by spraying or brushing a liquid soap and
water solution on joints and looking for bubbles. Commercial leak detection fluids
can be used instead.
If there is any doubt about the system leaking, continue the test overnight.
After the test is complete, let the air out of the system.
5.2 REPAIR PROCEDURES