Hi Top 10 HVAC! How to Assure ‘Right-Sizing’ HVAC Systems for Efficient Operation!.

Hi Top 10 HVAC! How to Assure ‘Right-Sizing’ HVAC Systems for Efficient Operation!. 

“Right sizing” an HVAC system improves efficiency, reduces noise, offers greater cooling/heating comfort and SAVES MONEY. 

An oversized system increases installation costs, wastes energy, and costs more in overall operating costs than correctly sized systems.

If you consider the worst-case scenarios when sizing your HVAC SYSTEM, such as maximum occupancy, lighting needs and weather conditions, you’ll probably install an oversized system. And an oversized system can reduce the cooling capacity. 

That results in the compressors short cycling, which in turn affects the system’s ability to dehumidify the building effectively.

Most HVAC systems are sized to meet HEATING AND COOLING loads occurring around 1% to 2.5% of the time, but an efficient system works most effectively for the conditions occurring 97.5% to 99% of the time, according to the National Institute of Building Sciences.

Over sizing is common in commercial as well as residential applications because contractors use the rule-of-thumb sizing – a load calculation based on square footage, says Terry Townsend, president of the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE).

Understanding how each system affects the others offers the best ENERGY SAVINGS. 

The whole building design concept emphasizes designing a building’s HVAC system taking into account how one system affects another. 

It uses a systems approach rather than a component-based approach, considering the overall system configuration and the low load operation strategy. 

Whole building design, coupled with a right-sized, efficiently performing HVAC system results in as much as a 30% reduction in annual energy costs.

An efficient whole building design should plan for expansion without over sizing the equipment. 

The plan should not offer so much excess that it exceeds current required capacity and accounts for future loads that may never occur. 

Instead, the plan should build in physical space for adding equipment such as pumps, boilers and cooling towers. 

Use systems that can be modified, so additional equipment can be added later to expand the system.

‘Right Sizing’ HVAC SYSTEM Considerations and Tips 

for Efficiency:

According to the National Institute of Building Services and the Building Energy Codes Resource Centre:

• Do not rely on rules-of-thumb load calculations when sizing HVAC equipment. Obtain updated equipment load data matching the usage;
• Calculate HVAC SYSTEM design loads in accordance with accepted engineering standards and use handbooks such as the ASHRAE Handbook – Fundamentals;
• Calculate an accurate load estimate, using established design data from ASHRAE.
• The Air Conditioning Contractors of America (ACCA) publishes the Manual J, the standard for performing load calculations, for residential applications. For commercial facilities, the U.S. Small Business Administration recommends using the ACCA Manual N.
• Use HVAC safety factors and pick-up load allowances in ASHRAE/IES 90.1 as the maximum limit;
• Use safety factors sparingly. On the hottest or coldest day of the year, it’s unlikely the building would contain the maximum occupancy with every light and piece of machinery operating.
• Choose cooling equipment meeting/exceeding the SEER (seasonal energy efficiency ratio) or EER (energy efficiency ratio) for the capacity requirement, advises the Building Energy Codes Resource Centre. Additionally, choose cooling equipment meeting/exceeding the IPLV (integrated part-load value).
• Use computer analysis tools to simulate how the building operation affects loads to prevent over sizing. Utilize tools provided by UTILITY COMPANIES and the U.S. Department of Energy’s Building Energy Software Tools.