Rooftop Economizer CO2 | HVAC Control – This damper is part of a free cooling system for a rooftop economizer. It is part of an economizer damper system that allows free outside air cooling when the outside air temperature and humidity are ideal. This economizer also works on CO2 control so that if the CO2 levels inside the space rise above a set point the economizer damper opens allowing fresh outside air into the building while venting the air laden with CO2 to the outside. (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 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.
DDC Outside Air Economizer System - Outside louvers allow the DDC control system to open dampers and introduce fresh air into the building. Building automation system, or the energy management system as it is sometimes called, monitors outside air temperature and humidity and based on a calculation and opens the outside air dampers when this calculation determines a precise set point. (more…)
Outside Air Temperature-Humidity Sensor - The outside air temperature sensor uses a thermistor to read the outside temperature. This sensor also senses humidity using a humidity transducer. The temperature and humidity readings are collected by a direct digital control system and used in a program. Aside from using this information for user interfaces, the information is also used in a control program to open and close an outside air damper. (more…)
HVAC Tip - Carbon monoxide detectors are important to own for those people who burn fossil fuels for heat. Carbon monoxide is a flammable, colorless, odorless, tasteless toxic gas produced during incomplete combustion of fuel - Natural Gas, Oil, Coal, Wood, Kerosene, etc. Someone suffering from carbon monoxide poisoning generally has severe headaches, nausea, and sinus problems. These symptoms generally begin with mild effects and people usually remain unaware of what the exact problems are until, sometimes, it is too late. How many cracked heat exchangers or faulty furnaces are out there that no one knows anything about except a slight headache and nausea? Don't take any chances, get your carbon monoxide detector and call your local heating and air conditioning company for a heater inspection today. Read more on this subject on the Furnace Page.
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Rooftop Economizer CO2 | HVAC Control – This damper is part of a free cooling system for a rooftop economizer. It is part of an economizer damper system that allows free outside air cooling when the outside air temperature and humidity are ideal. This economizer also works on CO2 control so that if the CO2 levels inside the space rise above a set point the economizer damper opens allowing fresh outside air into the building while venting the air laden with CO2 to the outside. (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. 
DDC Outside Air Economizer System - Outside louvers allow the DDC control system to open dampers and introduce fresh air into the building. 
Outside Air Temperature-Humidity Sensor - The outside air temperature sensor uses a thermistor to read the outside temperature. This sensor also senses humidity using a humidity transducer. The temperature and humidity readings are collected by a 