Rooms containing electrical power distribution equipment require attention to hvac. Due to their location in the building, electrical closets are typically served by the building hvac system and provided with conditioned air to meet both heating and cooling requirements. Spaces containing substations or service switchgear are often located near the building perimeter and may be served by conditioned air or outside air ventilation. Because the cooling loads of this equipment can be very high, it is often desirable to avoid mechanical cooling and the associated capital and energy costs.
In most cases, only the upper limit on temperature represents a challenge. Unless serious extremes of temperature are anticipated, heating requirements are limited to maintaining equipment surfaces above the dewpoint to avoid condensation, and providing an acceptable work environment for service. Often the former can be accomplished using electrical resistance heaters installed inside the enclosures, making it possible to install even medium-voltage (over 600 V and less than 72,000 V) equipment in unheated space or outdoors.