For Heating the NB181608-1HFS-UL includes two thermostat-controlled 200W (400W total) heaters. Each 200W heater is controlled by L-com's exclusive solid state thermostat controller. The heaters turn on when the internal temperature of 93° F (33.8°C) and a heat turn-on temperature of 16° F (-8.8° C). The heaters do not require the use of any of the AC outlets, leaving them all available for your equipment. No extra room for the heaters is required since they are mounted underneath the plate. For Cooling the NB181608-1HFS-UL model includes L-com's exclusive solid state temperature controller connected to dual 12W (24W total) fans. The high airflow, low noise fans used allow warm air to be actively pushed out the top vent while the second fan on the lower vent actively pulls in outside air into the enclosure. Filters for both ports prevent foreign objects or debris from entering the enclosure. The controller features improved temperature set point accuracy. The fans turn on when the internal temperature rises to 90° F (32° C) ±5° and turn off at 81° F (27° C) ±5°. The cooling fans do not require the use of any of the AC outlets, leaving them all available for your equipment.