The Fault + Bank OVh condition indicates that one or more of the 2, 4 or 8 transistor banks that provide the output current is overheating. Inside the power supply are banks of transistors that are cooled by water flow through a copper block that the banks are mounted on. Each of the banks is equipped with a temperature sensor mounted on the copper block that is wired in series with the other banks. If the temperature of any bank exceeds 60 °C, the sensor opens the circuit that produces the OVh alarm. This overheating is usually the result of restricted water flow caused by a buildup in the plumbing that connects the banks to each other.
To troubleshoot this issue:
Disconnect the power supply from the AC circuit.
Disconnect the water output.
Connect a short hose to the hose barb on the water output.
Run water into a bucket to confirm that you have the proper flow through the power supply.
The power supplies require a continuous water flow with a temperature between +15 °C and +25 °C as follows:
Model 662: 1.5 gal/min (5.7 L/min)
Model 665: 2.2 gal/min (8.0 L/min)
Model 668: 2.2 gal/min (8.0 L/min)
If you find that the flow rate is below the listed minimum, you need to verify that the source is flowing at that value. If the source is flowing at that value, you can assume that you have blockage within the power supply.
To clear a blockage in the power supply:
Remove the covers so you have access to the banks in question. On each bank mounting are two hose fittings that connect the plastic hose between the water source and each bank. The most common place where the blockage occurs is in the 90° elbows.
Remove each of the fittings and clean them out with a wire brush.
If the buildup is excessive, the internal walls of the copper mounting adapters might also need to be cleaned in the same manner as the fittings to obtain proper thermal transfer.
Note: Mark and label all wiring that you remove in this process. This will help you to ensure proper reconnection to the banks once you have cleared the blockage.