Nailor Airwaves is your source for content on relevant topics concerning Nailor Industries, Inc. and the HVAC industry. New product releases, case studies, product & project spotlights, employee interviews, trade publication articles, and general announcements are some of the content types you can expect to find in the Nailor Airwaves.
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HVAC Ins & Outs with Dan Int-Hout - What is wrong with ADPI?
The Air Diffusion Performance Index (ADPI) was developed at Kansas State University in the 1960’s as an ASHRAE project to assist in understanding air diffuser layout and performance. The basic concept is that the ratio of the discharge air projection, defined by the diffuser’s throw, and the separation distance between air outlets, could be used to define the resulting air mixing in a space. The percentage of points in the “occupied zone” in a space that meet a criterion for acceptable “draft temperature” determined the ADPI. An ADPI of 80% was determined to be a minimum acceptable value for most of the occupants in a space, with certain assumptions regarding the uniformity of activity and clothing levels of the occupants.
The draft temperature was… Read more
VAV Systems: Ground Control to Major Tom
Choosing the right equipment for your VAV system is critical, but it is only part of creating the right solution. The specified control sequences for each terminal unit will ultimately have the largest impact on eliminating any SPACE ODDITIES. ASHRAE has issued standard control sequences for terminal units in Guideline 36: High-Performance Sequences of Operation for HVAC Systems. The goal of the guideline is to provide uniform sequences the industry can use to optimize HVAC system performance. The selection of control sequence for each piece of equipment affects the overall performance of the system.
Air Handling Unit (AHU) Control
AHUs in VAV systems are controlled using Trim and Respond control logic. A static pressure sensor in the primary ductwork that monitors pressure delivered to… Read more
HVAC Ins & Outs with Dan Int-Hout - Measuring Air Speeds
The 1962 Air Diffusion Council Test Code 1062 required that room airspeed measurements be taken with an Anemotherm Air Meter. This was a battery-powered analog highly shielded hot wire anemometer, made by Reeves Hoffman, a sister company to Anemostat, located in Scranton Pa. It was the required instrument in the ADC 1062 test code, which was ”the bible” for air outlet measurements. It was also the most popular and most readily available instrument for many years. It was, however, not without issues.
The Anemothern sensor was a wand about ½” in diameter with a couple of looped shielded wires located behind a couple of holes in a tube. In an evaluation conducted as part of the Owens Corning Fiberglas response to a GSA lawsuit on measured air motion in a GSA construction project (which… Read more
VAV System Design: What is your style?
The Houston, Seattle, and Washington DC markets largely specify systems that utilize series fan-powered terminal units in all zones. Dallas and Portland, OR, specify parallel fan-powered units on the exterior with single duct units in the interior. The equipment and configuration of selected terminal units appear to be a matter of style. There are many reasons why different areas could have different design standards. Regardless, analyzing why you would select one style over the other could provide some value.
Equipment Reminder
Terminal units are used within a Variable Air Volume (VAV) System to control the airflow and temperature delivered to a zone. Single duct, parallel fan-powered, and series fan-powered units are connected to an air handling unit (AHU) that supplies the terminal… Read more
VAV Diffusers: The solution to some issues but the cause of others?
Over-cooling in the summer or over-heating in the winter can impact occupant comfort. There are several solutions for this issue. These include rebalancing the system, adding Terminal Units for those spaces, or adding a VAV Diffuser. The use of a VAV Diffuser requires an understanding of the design, how they work, limitations, and system considerations associated with the product.
VAV Diffuser
The Nailor UNI VAV diffuser enables the control of airflow into a room with a connected thermostat. The diffuser includes an actuator, linkage, plate damper, and diffuser. The ductwork from the air handling unit is connected to the diffuser in the same way it connects to a standard diffuser. The associated thermostat is in the space and is wired to the UNI VAV controller. The diffuser controls… Read more