Variable Air Volume Box with Hot Water Reheat – The variable air volume box or VAV box is a commercial solution to adding multiple zones to large buildings. VAV boxes offer zoning solutions so that separate zoning demands or temperature selections can be maintained in different areas of the building.
If the president of the company wants the temperature in their office to be 70 degrees Fahrenheit but the vice president wants their office to be 74 degrees Fahrenheit then it is possible with the VAV zoning system as long as their VAV boxes are on different zones. (more…)
DDC Control Module for an Air Handling Unit – This is a direct digital controls control module for an air handler that serves some VAV boxes in office spaces for a Data Center. This DDC control module includes analog and digital inputs and analog and digital outputs to handle all the control functions necessary to control the devices and components on a large commercial air handler. (more…)
VAV Air Handlers are ideal for providing zones in a commercial building. Office space typically has several offices and open areas that need to be conditioned for the comfort of the people working in those areas or offices. By installing VAV boxes and zoning the ductwork from those VAV boxes these areas and offices can be kept comfortable using a VAV air handler system. More on how VAV boxes work. (more…)
DDC Controlled Chilled Water Actuator | HVAC Automation. This chilled water actuator is attached to a valve which supplies chilled water to the air handling unit. The air handling has a chilled water coil. The actuator modulates the valve based on a set point inside the DDC program. If the program has trim and respond capabilities the set point will rise up and down based on demand. Demand from the VAV boxes or the HVAC zones. Most DDC controlled actuators work off of a DC volt or current signal. (more…)
VAV Box Types Fan Powered and Shut Off VAV Boxes - When attempting to name the different types of VAV boxes we find there are different names given to VAV boxes by different people and we find that no one is on the same page when VAV boxes are definitively defined.
We have fan-powered VAV and non-fan-powered VAV’s and we have series and parallel VAV’s and we have VAV boxes with a hot deck and a cold deck that mixes and one of the last projects I worked on some of the VAV’s were referred to as shut-off vavs. Variable Air Volume Boxes (VAV Boxes) regulates airflow into zones using a primary air source from a VAV air handler.
VAV Box Types Fan Powered and Shut Off
Cool only single ducted series
Fan-powered single duct series with reheat
Fan-powered single ducted parallel with reheat - uses plenum air before using reheat for energy efficiency
Aside from the control aspect of VAV boxes, pneumatic, electric, electronic, or DDC, there are many different variations to VAV Boxes and we will attempt to define each type of VAV including offering a diagram of each type and matching it with a specific application. VAV boxes are simply an assembly of a damper, damper controls, and sometimes reheat such as electric heat strips or a hot water coil. VAV boxes get their primary air source from a central VAV air handler and then distribute air throughout a specific zone the VAV box controls.
HVAC Control Transformer Bank - This bank of transformers is being used to power several VAV box controllers. One of many VAV boxes is powered by one of these transformers. In most VAV box applications, the power for the control system is at the box and a properly sized transformer for VA load is used to power the controller. In this application, the VAV boxes were not fan-powered and line voltage was not available in the boxes. So a central transformer bank was used and a wire for control power was pulled to each VAV box. (more…)
Air Handling Unit Components 2: Heat - There are many different types and arrangements of heating systems for air handling units and these types of heating systems and arrangements of heating systems vary from commercial to residential. Some air handling units do not have any heat source inside them at all but have remote heat for zoning. The air handling unit provides the airflow and the remote heaters provide heat for zoning.
Sometimes the air handling unit is a VAV air handling unit and other times it is just to provide air for a duct heater whether the duct heater is gas-fired or electric. For air handling units which some have heating systems inside the five main ways of providing heat for air handling units are:
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.
Alerton BTI DDC Controller Building Automation - This is the main DDC controller for Alerton. It communicates with all the other controllers in the field serving the building automation system and connects those systems with a computer or modem. (more…)
Programming DDC Logic 2 - The analog network input is similar to an analog input except this input is not hardwired to the local controller but on a remote controller in the network. It is very important that the communication works effectively for this analog network input to work. An example of this is the outside air temperature which is hardwired to a DDC controller in the penthouse of a multistory building.
The building engineer only wants the boilers to fire if the outside air temperature is less than 55° F. Instead of having an outside air temperature device hardwired to the boiler controller an analog network input can be placed into the boiler controller program and linked to the outside air temperature reading which is in the penthouse controller where the outside air temperature thermistor is hardwired. This saves devices and wires necessary for optimum control.
HVAC Tip - Having the proper humidity levels in your home or business is important not only for your health but also the amount of energy your HVAC systems use to keep you comfortable. If the humidity level is high in the summer you will not feel comfortable. If the humidity level is low in the winter you will not feel warm when the thermostat is set for an average temperature. This will result in turning the thermostat up to compensate and you will use more energy to stay comfortable. A properly designed and installed HVAC system will keep the proper levels of humidity in your home or business and save you money in energy costs by reducing the amount you use the HVAC system. For more information on humidity and maintaining the proper levels of humidity in your home please visit our humidity technical pages.
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DDC Control Module for an Air Handling Unit – This is a direct digital controls control module for an air handler that serves some VAV boxes in office spaces for a Data Center. This DDC control module includes analog and digital inputs and analog and digital outputs to handle all the control functions necessary to control the devices and components on a large commercial air handler. 
VAV Air Handlers are ideal for providing zones in a commercial building. Office space typically has several offices and open areas that need to be conditioned for the comfort of the people working in those areas or offices. By installing VAV boxes and zoning the 
HVAC Control Transformer Bank - This bank of transformers is being used to power several 
Alerton BTI DDC Controller Building Automation - This is the main DDC controller for Alerton. It communicates with all the other controllers in the field serving the 
