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 2013 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...
The true cost of lubrication: Three keys to consider when evaluating oils; Plant Engineering Lubrication Guide; 11 ways to protect bearing assets; Is lubrication part of your KPIs?
Contract maintenance: 5 ways to keep things humming while keeping an eye on costs; Pneumatic systems; Energy monitoring; The sixth 'S' is safety
Transport your data: Supply chain information critical to operational excellence; High-voltage faults; Portable cooling; Safety automation isn't automatic
Case Study Database

Case Study Database

Get more exposure for your case study by uploading it to the Plant Engineering case study database, where end-users can identify relevant solutions and explore what the experts are doing to effectively implement a variety of technology and productivity related projects.

These case studies provide examples of how knowledgeable solution providers have used technology, processes and people to create effective and successful implementations in real-world situations. Case studies can be completed by filling out a simple online form where you can outline the project title, abstract, and full story in 1500 words or less; upload photos, videos and a logo.

Click here to visit the Case Study Database and upload your case study.

Maintaining low data center PUE; Using eco mode in UPS systems; Commissioning electrical and power systems; Exploring dc power distribution alternatives
Synchronizing industrial Ethernet networks; Selecting protocol conversion gateways; Integrating HMIs with PLCs and PACs
Why manufacturers need to see energy in a different light: Current approaches to energy management yield quick savings, but leave plant managers searching for ways of improving on those early gains.

Annual Salary Survey

Participate in the 2013 Salary Survey

In a year when manufacturing continued to lead the economic rebound, it makes sense that plant manager bonuses rebounded. Plant Engineering’s annual Salary Survey shows both wages and bonuses rose in 2012 after a retreat the year before.

Average salary across all job titles for plant floor management rose 3.5% to $95,446, and bonus compensation jumped to $15,162, a 4.2% increase from the 2010 level and double the 2011 total, which showed a sharp drop in bonus.

2012 Salary Survey Analysis

2012 Salary Survey Results

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.