The energy efficiency provisions proposed for the new Section-J of the BCA (2005) will require HVAC systems to be designed to maintain a temperature range between 20°C and 24°C for 98 percent of the system operating time.
Title: HVAC Equations, Data, and Rules of Thumb, Third Edition
Publisher: McGraw-Hill Education: New York, Chicago, San Francisco, Athens, London, Madrid, Mexico City, Milan, New Delhi, Singapore, Sydney, Toronto
Copyright / Pub. Date: 2016 McGraw-Hill Education
ISBN: 9780071829595
Authors: Arthur A. Bell, Jr., PE is a registered professional engineer and certified mechanical, plumbing, fire, and energy-conservation code official in the Commonwealth of Pennsylvania with more than 31 years of experience in the design of HVAC systems. In addition, he has been involved in the design of plumbing systems, fire protection systems, and construction field engineering-mechanical systems. Mr. Bell is also the author of HVAC Design Portfolio, published by McGraw-Hill. W. Larsen Angel, PE is a registered professional engineer in the State of Maryland with more than 25 years of experience in the design of HVAC systems. In addition, he has been involved in the design of plumbing systems and electrical systems. Mr. Angel is also the author of HVAC Design Sourcebook, published by McGraw-Hill.
Description: 'Tricks of the Trade' for State-of-the-Art HVAC Design on Construction Jobs of Any Size!This fully revised, industry-standard handbook presents a wealth of HVAC design information encompassing all types of facilities—from offices and hospitals to commercial spaces and computer rooms. Written in an outline format for ease of use, this practical reference offers hundreds of field-tested equations and rules of thumb and features all-new coverage of the latest building components and materials. HVAC Equations, Data, and Rules of Thumb, Third Edition, reflects all the latest changes to the codes and standards used in the industry—including ASHRAE, ICC, NEC, and NFPA—and clearly shows how to interpret them and put them to use.This thoroughly updated Third Edition covers:• Definitions• Equations• Rules of Thumb for Cooling, Heating, Infiltration, Ventilation, Humidification, People/Occupancy, Lighting, and Appliances/Equipment• Cooling and Heating Load Factors• Design Conditions and Energy Conservation• HVAC System Selection Criteria• Air Distribution Systems• Piping Systems, Including Plastic Piping• Central Plant Equipment (Air-Handling Units, Chillers, Boilers, Cooling Towers, Heat Exchangers)• Sustainability Guidelines• New Technologies for HVAC• Noise and Vibration Control• Architectural, Structural, and Electrical Considerations• Properties of Air and Water• Auxiliary Equipment (Fans, Pumps, Motors, Controllers, Variable-Frequency Drives, Filters, Insulation, Fire-Stopping)• Automatic Temperature Controls/Building Automation Systems• Building Construction Business Fundamentals• Architectural, Structural, and Electrical Information• Conversion Factors• Designer's Checklist• Professional Societies and Trade Organizations• References and Design Manuals• Cleanroom Criteria and Standards
Every summer we have to shut down some equipment due to a combination of outside temperature and high load. The air conditioners just can't keep up. As we cycle in new equipment and cycle out old, it would be nice to know if we are making our cooling problem better or worse. Even better, I'd like to be able to calculate a rough estimate of the amount of cooling we'll need to support our equipment at high load.
Is there any rule of thumb or calculation to determine how much cooling capacity will be required?
Computer room/CRAC/HVAC cooling is typically measured in 'tons' (for instance, my company's data centers has 15, 20 and 30 ton cooling units depending on room design). The general rule of thumb formula is:
12,000 BTUs per hour per 1 ton of cooling
The number of watts is written on the back of the power supply (and in the server's technical specs). The formula to get from watts to BTUs is:
BTU/hr = W * 3.415
So, say you have a 500 Watt PSU operating at an estimated 80% capacity. You would need:
500 * .8 * 3.415 / 12,000 = .11 tons of cooling.
OK, so now say you have a data center full of 400 of the same servers using the same PSUs:
This is all back of napkin, but it's surprisingly difficult to get hard and fast rules for this stuff. This is all 'tons of cooling', but how you have you machines arranged affects this a lot too. Hot/Cold row design helps a ton. If you get really overloaded, the special cabinets that have duct work in the front door and a heat vacuum in the back can really cram more heat into an area.