Wiring a Fan to Expansion Board using the Relay

When connecting to the controlled Outputs (that are using mosfets) make sure that these loads   do not have large inrush currents. The typically DC-DC or other components have capacitors can draw large inrush currents when first switched on, compared to their continuous running consumption.  The WatchMon supervisor and expansion boards outputs are rated to 3A (default), they will fail when the inrush currents exceed their rating (x2 even for micro/milliseconds).  We recommend to reduce complexity by sticking to a single voltage rather than using DC-DC (i.e. if powering from 48V pack use a 48V fan to avoid the need for DC-DC, or if 24V pack then 24V fan, contactor etc) only use if you have sufficient expertise.  If you have an expansion board it is best practice to use the relays rather than mosfets for a fan

For large (or unknown) loads make sure you use an external relay/SSR (solid state relays) that is appropriate for the rated purpose.  

Connecting a Fan to the Relays on an Expansion Board

Locating Relay connector on the Expansion Board

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