Wiring Fan to On-Board Output - 4 pin Output
This relates to WatchMon4.2 or WatchMon5.1 or earlier that have 4 pin output.
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.
For large (or unknown) loads make sure you use a external relay/SSR (solid state relays) that is appropriate for the rated purpose.
Wiring a Fan to On-board Output WatchMon - 4pin
If powering WatchMon using your battery pack, the fan should be the same voltage as the battery pack voltage.
Wiring a Fan using Supply DC-DC to On-board Output WatchMon - 4pin
Note that DC-DC should be used to power WatchMon at the voltage you need for your outputs. Therefore if using a 24V fan or contactor then use the appropriate DC-DC to feed 24V into the WatchMon.
The DC-DC should be before the power not between the WatchMon and load. Placing the DC-DC after the output voids the warranty.
Locating Input & Output Connections on WatchMon4
The inputs and outputs on the WatchMon4 can be configured on the Hardware - Expansion settings as inputs and Outputs A. See the Hardware Configuration - Expansion Settings
The options for what to trigger the fan is Cooling Required