High duct-static pressure creates problems during a building fire when fire dampers close. Closed fire dampers cause downstream duct sensors to detect a drop in pressure. The duct pressure sensors in turn send signals to crank the air handler even faster to get back up to normal operation. Because the fire dampers are closed, when the air handler ramps up, the duct pressure upstream of the fire dampers will increase to a point where a high static pressure switch will cut power to the VFD (variable frequency drive) and send a signal to the DDC (direct digital control). Switches in this application — by specification — are all manual reset and require two outputs: one for cutting power to the VFD and one for sending the signal to the DDC.
Traditionally, there have been three tactics to address this issue, each with its own problems. Continue reading “Solve High Duct-Static Cutout Problems with the Series 1831”
Stability is defined as a change (or lack of change) in accuracy over a period of time.
Drift is commonly used as a specification to illustrate the stability, or change in accuracy over a period of time, commonly shown as X%/year where X = a number; i.e. 0.25%/year. In this scenario, a device with a ±1% accuracy, would be expected to have an accuracy of ±1.25% (1%+0.25%) after a period of one year. Depending on the design, brand, and range of the sensing instrument, the stability can vary widely. Continue reading “What is Stability and Why is it Important?”
Most local regulations for indoor air quality are designed around ASHRAE Standard 62. This standard specifies the minimum amount of outdoor air flow into an occupied space to be between 15 to 60 CFM per person, but more commonly building regulations require 15 to 20 CFM per person. Besides actually measuring the air flow, ASHRAE also defines indoor air quality using the concentration of carbon dioxide gas in the air. Carbon dioxide is recommended to be less than 1000 PPM. When sizing the air handling unit for a building, engineers will make the design exceed the maximum occupancy in the building or space to ensure that they will always be able to meet the minimum air requirements. In most cases, buildings or mix used spaces rarely are occupied at these maximum levels, thus the amount of conditioned air supplied is usually much greater than what is required. As building owners aim to reduce energy costs and operate buildings more efficiently, wasted energy of conditioning unneeded outside air has been a good place to start. Continue reading “Energy Savings from On-Demand Ventilation”
What is a Paint Booth?
Aerospace paint spray booths provide the ideal environment to paint aircrafts, such as fighter jets, commercial airplanes, and helicopters. The paint spray booths regulate humidity, temperature, airflow, and pressure for proper coating application and curing. The booths are categorized by three different designs, which are: air pressure, cabin, or airflow.
The air pressure design booth will either have a negative or positive pressure. The positive pressure means that the pressure inside the booth is greater than the air pressure outside of the cabin. The air pressure inside the booth is provided by an air make-up system and replaces the air being exhausted by the fan. Continue reading “Aerospace Application: Paint Spray Booth”
Water chillers are nothing new, with nearly an estimated 100,000 units operating in North America alone. Chillers are the cooling machines of choice to condition industrial, commercial, and institutional facilities. They are used to lower the temperatures of all kinds of equipment and processes such as: robotic machinery; semiconductors; injection and blow molding machines; welding equipment; die-casting and machine tooling; paper and cement processing; power supplies; power generation stations; compressed air and gas cooling systems; medical imaging machines; chemical, drug, food and beverage production; even simply to cool potable water to desirable levels. Whether for office comfort, keeping data server centers from overheating, or specialized industrial processes, water temperature control plays a vital role in many of the behind-the-scenes activities that affect our everyday lives. Continue reading “Proving Flow Through Chillers”