What is the correct spacing of a heat detector listed for 25 feet and a ceiling height of 25 feet?

What is the correct spacing of a heat detector listed for 25 feet and a ceiling height of 25 feet?

• A. 11'6"
• B. 9'0"
• C. 12'0"
• D. 13'0"

Answer: (A)

Heat detectors need to be spaced so that their coverage matches the way heat rises and reaches the sensing element. The listing on a detector often assumes a certain ceiling height, and as ceiling height increases, the effective distance heat must travel to reach a detector grows if you keep the same center-to-center spacing. To maintain the same level of coverage on a taller ceiling, you reduce the spacing between detectors. In this case, the detector is listed for 25 ft spacing, and the ceiling height is also 25 ft. To preserve similar coverage density at that height, the spacing is effectively reduced to about half. Half of 25 ft is about 12.5 ft, and the closest standard spacing that achieves this on practice installations is 11'6". This keeps detectors within reach of rising heat so the system detects a fire promptly. So, the correct spacing is 11'6". The other options would place detectors too close or too far for a 25 ft ceiling with a listing of 25 ft, risking either excessive detectors or insufficient coverage.

Heat detectors need to be spaced so that their coverage matches the way heat rises and reaches the sensing element. The listing on a detector often assumes a certain ceiling height, and as ceiling height increases, the effective distance heat must travel to reach a detector grows if you keep the same center-to-center spacing. To maintain the same level of coverage on a taller ceiling, you reduce the spacing between detectors.

In this case, the detector is listed for 25 ft spacing, and the ceiling height is also 25 ft. To preserve similar coverage density at that height, the spacing is effectively reduced to about half. Half of 25 ft is about 12.5 ft, and the closest standard spacing that achieves this on practice installations is 11'6". This keeps detectors within reach of rising heat so the system detects a fire promptly.

So, the correct spacing is 11'6". The other options would place detectors too close or too far for a 25 ft ceiling with a listing of 25 ft, risking either excessive detectors or insufficient coverage.