According to ACCA Manual S, furnace size should be within what percent of the peak heating load requirement?

• A. 100%
• B. 120%
• C. 140%
• D. 150%

Answer: (B)

The correct choice aligns with the guidelines established in the Air Conditioning Contractors of America (ACCA) Manual S, which specifically provides standards for load calculations and equipment selection. According to the Manual, the recommended sizing of a furnace should be no more than 120% of the calculated peak heating load requirement.

Choosing a furnace size that is 120% of the peak heating load ensures that the system can adequately meet heating demands during the coldest times without excessive cycling. It balances efficiency and comfort, preventing the furnace from short-cycling, which can lead to increased wear and tear, reduced efficiency, and potentially higher utility bills.

Oversizing a furnace (beyond 120% of the load) increases the likelihood of inefficiency and discomfort, as oversized units may produce more heat than required, causing rapid temperature fluctuations and increased operational costs. This standard is in place to promote optimal performance and energy efficiency for residential and commercial heating systems.