- Video Introduction of the New Aztec AMC Evaporative Cooling Air Turnover System
- Designing Data Centers as Thermos Bottles
- A New Video on YouTube Describing How the Aztec Evap System Works
- Aztec To Be In Capacity North America Exhibit Hall
- Virtual Reality
- A Simple Concept That Saves Big Dollars
- Indirect Evaporative Cooling Research Project Launched
- Canadian Patent Granted for Mestex Digital High Turndown Burner
- So You Think Your Critical HVAC System Is Reliable?
- Aztec Provides Fresh Air Intake Penthouses for Data Centers in Northwestern US
- Shading and Make-Up for Building Designers
- Credibility and Trust
- How I Spent My Summer Vacation
- Too Hot to Handle? A Simple Reminder.
- Preaching to the Choir
- Evaporative Cooling Anaysis for Data Modules in Two Diverse Climates
- Aztec Indirect Evaporative Cooling System on Display at DFW ASHRAE Golf Outing
- How We Used To Do It
- Air Pollution and HVAC
- Mestex, Division of Mestek YouTube Channel
- Aztec Evaporative Cooling for Data Centers at Data Center World
- GreenBuild Toronto
- Trane Division of Ingersoll-Rand in Lawsuit Over Wireless Technologies
- New BIM Objects From The Aztec Brand
- DOE Proposes Building Rating System
- Instant Online Document Lookup Using Microsoft Tags
- Do Evaporative Cooling Systems Use Too Much Water?
- Sustainability at Mestek Dallas
- Facebook Offers Their Outside Air Cooling Solution To All Data Center Owners
- Restaurant Energy Saving Idea That Can Be Used Anywhere
- Planning for Volatility
- Ever Wonder Where the Power Goes in a Data Center?
- ASHRAE TC 9.9 Expands Data Center Temperature Ranges Again
- Green Buildings Get Another Boost
- ASHRAE Show Report
- The Story of SHR or Why My Classroom is Stuffy
- CFD, Air Turnover, and the Pharmaceutical Industry
- It is not sustainable if it is not maintainable... or if it breaks down
- Accounting Rule Change Might Impact HVAC
- Reduce electrical demand load with an Aztec indirect evaporative cooling unit
- Lower Cost of Ownership with the Applied Air FAP
- Everything You Want to Know in a Flash
- Data Centers and Evaporative Cooling Webinar August 23
- New "Green" Product Announcement
- DDC Application Case Studies
- PowerPoint showing the importance of gas pressure, static pressure, and voltage
- Webinar: 'The Importance of Correct Gas Pressure, E.S.P. and Voltage'
- An Old Solution to a New Problem
The Importance of Correct Static Pressure for Direct Fired Make-Up Air Equipment
This particular article might get a little more technical than some previous articles but a recent visit to California prompted me to put this together.
During a meeting with a consulting engineer I was told of a problem that he was having with a direct fired make-up air unit…not one of ours but the principles are the same. The issue was a burner that would shut down for “unknown reasons” shortly after coming on-line. After some discussion the engineer stated that his estimate of external static pressure was wrong because the unit was not installed as he had originally designed. The duct system attached to the unit had several more bends in it than he designed and thus the external static pressure was higher than he estimated and higher than the manufacturer was told at the time of production. This was the clue we needed to help the engineer understand what was going on.
Almost 10 years ago the safety standards for direct fired equipment were changed. As a result most certified direct fired equipment provides heated air that is extremely safe from carbon monoxide, carbon dioxide, and other gaseous contaminants. That is because the direct fired product is designed to meet a specific set of operating conditions, by code, that assure a velocity across the burner that is roughly 2,800 to 3,200 feet per minute. When a direct fired product operates in that range then the combustion is “clean” and harmful byproducts are not produced in any significant amount.
In order to assure the user that the direct fired burner is operating in the proper range the manufacturer uses the total static pressure that is calculated for the unit (including the external static pressure) to size the airflow opening across the burner to stay within the target range. Most manufacturers will size the opening to land in the middle of the range so that there is some room for minor errors in the estimates.
In order to make this even more fool-proof the safety standard required manufacturers to add pressure switches to the units that would shut down the burner if the velocity across the burner was either too high or too low. In the case that this engineer was describing the overly high external static pressure was causing the velocity across the burner to be too low and the burner would shut down.
Because the code and testing standards required manufacturers to be very specific you will find that the acceptable range between high and low is unique to each model and size in a product line. Some of these ranges are very narrow…less than 0.25 inches of static from the high set point to the low set point. This gives the equipment only 0.125 inches of static from the midpoint to the trip point in either direction. Too many bends in the ductwork can easily add that much static to the system and cause the premature shutdown of the system.