During operation on a sunny day, the solar fluid entering the heat exchanger from
the collectors should be higher in temperature than the fluid leaving the heat
exchanger going back to the collectors.
Under the same conditions, the water leaving the heat exchanger should be hotter
than the water entering from the tank.
Many tube and shell heat exchangers have a sacrificial anode in the tube manifold.
Check the anode by unthreading it, if it is accessible from outside the heat
exchanger. If not, remove the bonnet to check it. Use teflon tape on the threads
when re-installing the anode. This will aid removal for future inspections. Also,
attach a note to the tank indicating the condition of the anode and the date it was
last replaced, if known.
Draindown Tank/Heat Exchanger
The collector fluid reservoir of a draindown system should be inspected for leakage,
corrosion and appropriate flow rates and temperature changes.
In addition, the water level in the reservoir should be checked. For most systems,
this is done while the solar loop pump is off. Check with a sight glass, a dip stick
(sometimes using a real stick!) or by simply filling the tank until it overflows when the
solar loop pump is off.
3.1.6 Solar Fluids. Solar loops will work only if they have adequate fluid in
them. Drainback reservoir tanks must be filled to the correct level. Closed-loop
systems must have adequate pressure.
Check for the recommended liquid level or pressure from the system's operation
and maintenance manual. If no such manual exists, Section 5.2.6 in the Repair
chapter of this manual includes a chart of recommended glycol and oil fill pressures.
Draindown systems use city or well water in the collector loop. If water quality is
poor, water treatment equipment may be used. The product water from the
treatment equipment should be checked.
3.1 INSPECTION PROCEDURES