User Guide

Plumbing Design Assistance Manual l Appendix F – Pipe heat loss and surface temperature l 183
1. All calculations based on cylindrical thermal resistance methodology (ASHRAE).
2. Based on uid velocity of 8 ft./sec. at 160°F/71.1°C (maximizing heat transfer from 100% water).
3. Pipe convection set to be 1.761 Btu/hr•ft²•°F (based on standard value for free convection of air).
4. This heat loss comparison uses 0.24 Btu•in/(hr•ft2•°F) as the insulation thermal conductivity.
This is a standard value for berglass pipe insulation at a 100°F/37.8°C mean temperature.
Pipe heat loss and surface temperature
2½" Uponor PEX surface
temperature at 90°F/32.2°C ambient
Water
temp
(ºF)
Surface temperature (°F)
No insulation
½" insulation
1" insulation
1½" insulation
2" insulation
30 37.6 73.0 80.8 83.9 85.6
40 46.3 75.9 82.3 84.9 86.3
50 55.0 78.7 83.8 86.0 87.1
60 63.8 81.5 85.4 87.0 87.8
70 72.5 84.3 86.9 88.0 88.5
80 81.3 87.2 88.5 89.0 89.3
90 90.0 90.0 90.0 90.0 90.0
100 98.7 92.8 91.5 91.0 90.7
110 107.5 95.7 93.1 92.0 91.5
120 116.2 98.5 94.6 93.0 92.2
130 125.0 101.3 96.2 94.0 92.9
140 133.7 104.1 97.7 95.1 93.7
150 142.4 107.0 99.2 96.1 94.4
160 151.2 109.8 100.8 97.1 95.1
170 159.9 112.6 102.3 98.1 95.9
180 168.7 115.4 103.9 99.1 96.6
190 177.4 118.3 105.4 100.1 97.3
200 186.1 121.1 106.9 101.1 98.1
2½" Uponor PEX heat loss
at 90°F/32.2°C ambient
Water
temp
(ºF)
Heat loss (btu/hr·ft)
No insulation
½" insulation
1" insulation
1½" insulation
2" insulation
30 -36.0 -16.1 -11.2 -8.9 -7.6
40 -30.0 -13.4 -9.3 -7.5 -6.4
50 -24.0 -10.7 -7.5 -6.0 -5.1
60 -18.0 -8.0 -5.6 -4.5 -3.8
70 -12.0 -5.4 -3.7 -3.0 -2.5
80 -6.0 -2.7 -1.9 -1.5 -1.3
90 0.0 0.0 0.0 0.0 0.0
100 6.0 2.7 1.9 1.5 1.3
110 12.0 5.4 3.7 3.0 2.5
120 18.0 8.0 5.6 4.5 3.8
130 24.0 10.7 7.5 6.0 5.1
140 30.0 13.4 9.3 7.5 6.4
150 36.0 16.1 11.2 8.9 7.6
160 42.0 18.8 13.1 10.4 8.9
170 48.0 21.5 14.9 11.9 10.2
180 54.1 24.1 16.8 13.4 11.5
190 60.1 26.8 18.6 14.9 12.7
200 66.1 29.5 20.5 16.4 14.0