It is said that the stock of knowledge doubles every eight years. This is more so in regard to scientific knowledge. Anergy is marketing a number of products-mainly control system components for HVAC industry. To understand HVAC Control system, an engineer need to have reasonable exposure to many branches of engineering like air-conditioning, refrigeration, mechanical, electrical, electronics, instrumentation etc. It is a Herculean task to keep abreast with the latest developments in all these branches of engineering which have a bearing on HVAC Systems and controls. Taking into account this challenge, Anergy’s endeavour is to progressively disseminate broad theoretical knowledge necessary for the understanding of control applications in HVAC systems through these pages. New topics will be added to this section periodically in brief modules that can be understood not only by the practicing engineer but other technicians as well.