Heat dissipation is measured in British Thermal Units (BTUs). This reflects the maximum (i.e. worse case) amount of heat that can be generated by the equipment and assumes that none of the input power is used to power circuitry and all power is converted to heat, whether from the PSU itself, the system unit, expansion module or cabling.
A heat value expressed in Watts can be converted to BTU/hr by multiplying by 3.41297
Based on the wattages from the product description, you can calculate the notional BTU for IP Office
You use the max power input of 115 VA (rather than the 45W output) of each power supply to calculate this most accurately
Using the conversion factor, BTU/hr = 115W* 3.41297 = 392.5
The metric equivalent to BTU is/are Joules. Convert @ 1,055.
This is number per power supply. So the max BTU per system is calculated by the number of power supplies installed per system
So for a 412, this would be 1 for the base unit; up to 12 for the expansion modules; up to 7 for WAN modules = 20 * 392.5 = 7,850 BTH/hr.
Whereas a Small Office Edition would be rated at 392.5 BTU/hr
The total BTU would also need to consider any outboard equipment (mid-span power for IP Phones; Server PC for apps etc)
