Hi, don´t worry I found the way to do it (I guess).
P(BTU/hr) = 3.412141633 × P(W)
On the 650 datasheet specifies
Power Specifications
• Maximum power consumption: 126 watts
• Power-over-Ethernet total capacity: 78 watts
• Power-over-Ethernet capacity per port: 19.5 watts
So I take the max power and substract the total PoE.
126watts - 78watts = 48 watts
This is valid for a controller that is no using the PoE
If you use a port with PoE you should add 19.5 watts
The we have to calculete the BTU
P(BTU/hr) = 3.412141633 x 48 watts = 163.78.27
Thanks for the help.