What is the detector time constant for a 135° heat detector with a listed spacing of 50 ft?

What is the detector time constant for a 135° heat detector with a listed spacing of 50 ft?

• A. 45
• B. 44
• C. 46
• D. 43

Answer: (B)

Understanding how a heat detector responds over time is key. For fixed-temperature detectors like a 135°F device, the listing provides the expected response time (time constant) for different ceiling spacings. The 50 ft spacing corresponds to a time constant of about 44 seconds, which is why that value is the best match. This time constant comes from the detector’s thermal characteristics combined with the spacing to ensure reliable activation across the protected area. The other nearby numbers are just close points in the same table and don’t match the 50 ft spacing listing.

Understanding how a heat detector responds over time is key. For fixed-temperature detectors like a 135°F device, the listing provides the expected response time (time constant) for different ceiling spacings. The 50 ft spacing corresponds to a time constant of about 44 seconds, which is why that value is the best match. This time constant comes from the detector’s thermal characteristics combined with the spacing to ensure reliable activation across the protected area. The other nearby numbers are just close points in the same table and don’t match the 50 ft spacing listing.