Late response, but still a useful question.
The Avaya manual states that a "unit load" is equal to 1.9 watts of electrical consumption. Standard physics tells us that pretty much all the power consumed by an electrical appliance is converted to heat, unless it is doing other useful work. You may assume between 50 - 60% of the "work" is done in each circuit card, and the rest of the work is done in the telephone (and the electrical loss in the wiring.) Some cards, such as Voice Mail, don't power any remote telephones, so become nearly 100% efficient heaters.
So, assume in the Magix system cabinet, roughly 1 watt for each unit load.
The metal carrier uses a 491D1 power supply, capable of providing 96 unit loads. So a full chassis is generating at most (1.9 * 96) watts of heat, plus any heat from the power supply itself. Assume roughly another 20 watts there, as the power supply is an efficient switching-type power supply.
=John=
