Current specifications for parallel circuit from two cross connected power supplies
There's quite a bit of confusion here, sorry.  

The way you show the supplies you have only +24 available, not 48. There are two +24 outputs and one return, so you can connect 24V loads to either (or both) supplies. 

Whether they are 'floating' or not depends on how the supplies are made internally, nothing to do with how they are connected. 

If you can use a resistor for the fan, the resistor will depend on the actual (not nameplate) fan current draw, not on the rating of the supplies. If the fan is anything like amperes current draw, using a resistor is not very practical (a 2A 12V fan run from 24V will require a large power-wasting 24W+ resistor). Better to get another supply to run the fan.