Damper leakage limits free cooling

Sidebar: Consulting-Speciyfing Engineer HVAC Technology Report

03/18/2009


Most people familiar with HVAC equipment would be quick to recognize the benefits afforded by low-leakage dampers applied to mixed-air plenums in the context of the outdoor air damper. After all, a leaky outdoor air damper in a cold or hot and humid environment can lead to energy waste by imposing an unnecessary outdoor air conditioning load on the system, either when it is on minimum outdoor air or during unoccupied hours. Furthermore, the leakage in a cold environment can lead to frozen coils and subsequent water damage issues and repairs.
However, another factor comes into play when you consider the economizer dampers in a mild environment and look at what happens if the return damper does not seal well. Economizer-equipped systems in mild environments tend to spend a lot of time near or at the 100% outdoor air position. This is because the ambient temperatures are frequently in the range of the required discharge temperature.
For example, in San Francisco, there are 7,896 hours per year (out of a total of 8,760 hours) where the temperature is 50 to 75 F and the enthalpy is low enough to make it advantageous to cool a 100% outdoor airstream versus a recirculated airstream with minimum outdoor air. In a situation like this, outdoor air damper leakage, while a problem in theory, is not much of an issue from a practical standpoint. But a return damper leaking 10% to 15% when it is supposed to be fully closed, compromises the ability of the economizer to provide free cooling because it elevates the return temperature above the current outdoor air temperature.
For example, on a 55 F day, with 75 F return air and a 55 F discharge temperature requirement, a system leaking 10% of its return air when it is supposed to be on 100% outdoor air is delivering a 57 F mixed air temperature (not a 55 F mixed air temperature). As a result, many control systems would stage on mechanical cooling when it is not actually necessary if the damper quality was improved.





No comments
The Top Plant program honors outstanding manufacturing facilities in North America. View the 2015 Top Plant.
The Product of the Year program recognizes products newly released in the manufacturing industries.
The Engineering Leaders Under 40 program identifies and gives recognition to young engineers who...
Your leaks start here: Take a disciplined approach with your hydraulic system; U.S. presence at Hannover Messe a rousing success
Hannover Messe 2016: Taking hold of the future - Partner Country status spotlights U.S. manufacturing; Honoring manufacturing excellence: The 2015 Product of the Year Winners
Inside IIoT: How technology, strategy can improve your operation; Dry media or web scrubber?; Six steps to design a PM program
Getting to the bottom of subsea repairs: Older pipelines need more attention, and operators need a repair strategy; OTC preview; Offshore production difficult - and crucial
Digital oilfields: Integrated HMI/SCADA systems enable smarter data acquisition; Real-world impact of simulation; Electric actuator technology prospers in production fields
Special report: U.S. natural gas; LNG transport technologies evolve to meet market demand; Understanding new methane regulations; Predictive maintenance for gas pipeline compressors
Warehouse winter comfort: The HTHV solution; Cooling with natural gas; Plastics industry booming
Managing automation upgrades, retrofits; Making technical, business sense; Ensuring network cyber security
Designing generator systems; Using online commissioning tools; Selective coordination best practices

Annual Salary Survey

Before the calendar turned, 2016 already had the makings of a pivotal year for manufacturing, and for the world.

There were the big events for the year, including the United States as Partner Country at Hannover Messe in April and the 2016 International Manufacturing Technology Show in Chicago in September. There's also the matter of the U.S. presidential elections in November, which promise to shape policy in manufacturing for years to come.

But the year started with global economic turmoil, as a slowdown in Chinese manufacturing triggered a worldwide stock hiccup that sent values plummeting. The continued plunge in world oil prices has resulted in a slowdown in exploration and, by extension, the manufacture of exploration equipment.

Read more: 2015 Salary Survey

Maintenance and reliability tips and best practices from the maintenance and reliability coaches at Allied Reliability Group.
The One Voice for Manufacturing blog reports on federal public policy issues impacting the manufacturing sector. One Voice is a joint effort by the National Tooling and Machining...
The Society for Maintenance and Reliability Professionals an organization devoted...
Join this ongoing discussion of machine guarding topics, including solutions assessments, regulatory compliance, gap analysis...
IMS Research, recently acquired by IHS Inc., is a leading independent supplier of market research and consultancy to the global electronics industry.
Maintenance is not optional in manufacturing. It’s a profit center, driving productivity and uptime while reducing overall repair costs.
The Lachance on CMMS blog is about current maintenance topics. Blogger Paul Lachance is president and chief technology officer for Smartware Group.
This article collection contains several articles on the vital role that compressed air plays in manufacturing plants.
This article collection contains several articles on the Industrial Internet of Things (IIoT) and how it is transforming manufacturing.
This article collection contains several articles on strategic maintenance and understanding all the parts of your plant.
click me