Specifications

www.aetsolar.com Open Loop / PV - Page 17
OPEN LOOP START-UP
After visual inspection of the complete system, it is ready for filling and pressure testing. All drain valves
should be closed, all other valves opened. The air vent caps should be loosened two turns to allow air to
escape the system. The cold water inlet valve should then be opened slowly and system checked for
leaks as it fills. When the system is completely full, indicated by water escaping from the air vent when
the valve is depressed it should be pressure checked with normal pressure for 30 minutes.
Once the system has been pressure tested and repaired if required, the control system can be energized.
On an A/C controlled system, plug the controller into a 115/120 VAC outlet. Set the “ON DIF” dial to 10
and the “HI LIM” to 135. Move the “RELAY” (pump) override switch to the “AUT” (automatic) position. On
a PV controlled system, switch the toggle to the “ON” position. If the sun is shining and the storage tank is
cool, the pump should come on and water should flow through the collector. The first water through the
collectors will be very hot but should stabilize in about 15 minutes. The return lines from the collectors
should be hotter than the inlet lines and the collector glass should be slightly warmer than ambient
temperature.
If the differential temperature control offers a freeze protection mode, testing of the sensor can be made
at night when the pump is not normally working. A piece of ice set on the collector sensor should be
sufficient to turn the pump on. The pump should turn off as soon as the sensor has a few seconds to
warm back up when the ice is removed. Caution should be exercised when working on the roof at night.
OPEN LOOP MAINTENANCE
Maintenance of an open loop system is straightforward. The tank should be partially drained every 6
months to allow minerals to be removed preventing scale build up (this is recommended for all water
heaters). The wye strainer should be cleaned at least once a year or more often if harsh water conditions
exist. The power should be switched off, the piping drained, and the screen removed and cleaned.
The collector glass should be kept clean for best system performance. Rainwater will usually suffice but a
garden hose can be used during dry weather. The air vent caps should be loosened two turns for proper
operation and best system performance.
OPEN LOOP PV SYSTEM
The single photovoltaic module, attached to the top of the solar collector (Figure 18) operates a brushless
12 VAC or 24 VAC pump at a speed relative to the amount of available sun. When clouds pass over, the
pumping operation slows to allow the water to remain in the collector longer for continued heating. When
the sun goes down in the evening the pumping action will stop.
The solar system is installed as per the open loop installation manual. The photovoltaic module will
replace the differential control and sensors. Be sure to mount the panels on the same plane as the solar
collector. A toggle switch is to be installed, as per the “Direct PV System” diagram, to serve as a service
disconnect should the solar system require maintenance or for purposes otherwise directed in this
manual.
When wiring the photovoltaic module to the circulating pump use 16 gage stranded double exterior PVC
jacketed wire for lengths up to 85 feet for 10 and 25 watt modules. Use 14 gauge for over 85 feet for a
module over 1.4 amps. When wiring the module to the pump, remember that the black wire is always
ground and the red wire is the hot wire. Do not reverse the polarity.