HVAC Control and Direct Digital Controls 2 - An HVAC technician who knows nothing about HVAC control systems would wonder how these HVAC control systems work. To understand HVAC controls, one must understand basic electricity and circuits.
Variable Air Volume Systems - Variable Air Volume (VAV) systems are the best way to zone especially in large buildings. A VAV system with the proper controls and setup will help the building owner realize large savings in energy usage. There are many VAV systems out there set up in different ways. The most common set-up (for DDC) is, of course, usually the cheapest to install.
They have an air handler (DX or Chilled Water) which supplies the VAV Boxes with fixed pressure and temperature of the conditioned air. The VAV Boxes have electric reheat which will heat the air if that particular zone calls for heat (it is not uncommon to also find VAV boxes that have hot water reheat although this usually costs more to install but can save in energy costs). More on how VAV boxes work.
How Cooling Towers Work - Cooling towers use evaporation cooling to cool condenser water from a chiller. Water is pumped to the top of the cooling tower, where the water flows down some flow plates to the cooling tower basin. As the water is flowing down the flow plates air is pulled through the plates and over the water where it releases heat through evaporation. (more…)
DDC Programming Logic 3 - DDC control logic blocks have practically an unlimited way of arranging the blocks for HVAC control. Below is an example of a line of logic blocks arranged for static pressure control of a VAV air handler supply fan using a variable frequency drive. This same arrangement could also be used for static pressure control using a bypass damper instead of a VFD. (more…)
York Variable Frequency Drives VFDs | HVAC Control - Variable Frequency Drives or VFDs have added a whole new dimension to energy efficiency and control. These drives, or VFDs, are hooked up to two different York VAV air handlers that have two three-phase motors a piece. (more…)
