pianotuna wrote:
They are powered by the inverter. But if you turn off the inverter the fans cease to run. Or, if 120 volt shore power is being used to charge the battery bank via the Magnum, is disconnected, the fans also stop running.
The inverter is either running forward inverting making 120v or running in reverse charging using 120v. If it is doing neither than there is no need to actively cool the fets or transformer.
The inverter has temp sensors on the fets and transformer, it will run the fans based on temp alone so long as it has at least 9.5v at the battery terminals:
From the manual:
The inverter contains two internal cooling fans that are automatically controlled. The speed of
these fans is determined either by the internal temperature of the inverter or by the load on the
inverter. The inverter’s fans will come on under the conditions listed below:
• Fans run full speed if the internal transistors (FETS) or the power transformer reaches 176°F
(80°C), or the inverter is running at 100% of its rated load.
• Fans run medium speed if the internal transistors (FETS) or the power transformer reaches
140°F (60°C), or the inverter is running at 50% of its rated load.
• Fans run low speed when the inverter is running at 25% of its rated load.
The fans shut down if none of the above conditions are met, or if the battery voltage is < 9.5V.
Whenever the inverter is first connected to the battery, the fans start for about one second.
