Thermal Imager Delta-T Reference
Typical surface-temperature differentials for moisture, insulation, and electrical hotspots.
Reference
Scenarios
- Moisture intrusion behind drywall 2 to 5Note: Wet substrate cools the surface relative to surrounding dry areas; difference grows with evaporation.
- Missing or compressed insulation 3 to 10Note: Heat-flow gradient through the assembly creates a visible thermal pattern at the cavity boundary.
- Active leak around penetration 3 to 8Note: Cool tail downstream of the leak path; reflects evaporative cooling and conductive loss.
- Electrical hotspot (loose lug, overloaded conductor) 10 to 50+Note: Compare phase to phase under load; a single hot lug indicates a loose or oxidized connection.
- Bearing or motor overheating 10 to 30Note: Compare to ambient and similar units; trend over time matters more than a single reading.
Details, formula, and sources
(reference page; no compute) Thermal-imager delta-T interpretation: compare inspected component temperature against an unloaded reference of the same construction; ≥ 1 °C above reference flags moisture migration, ≥ 5-10 °C flags an active issue per IR-imaging engineering practice.
ASTM C1153 (Standard Practice for Location of Wet Insulation in Roofing Systems) by name; FLIR / Fluke published thermography training materials.
ASTM licensed; training overviews free at flir.com / fluke.com / infraredtraining.com.
Estimate. AHJ and licensed professional govern.