User Guide

Plumbing Design Assistance Manual l Appendix F – Pipe heat loss and surface temperature l 175
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 70°F/21.1°C ambient
Water
temp
(ºF)
Surface temperature (°F)
No insulation
½" insulation
1" insulation
1½" insulation
2" insulation
30 35.0 58.7 63.8 66.0 67.1
40 43.8 61.5 65.4 67.0 67.8
50 52.5 64.3 66.9 68.0 68.5
60 61.3 67.2 68.5 69.0 69.3
70 70.0 70.0 70.0 70.0 70.0
80 78.7 72.8 71.5 71.0 70.7
90 87.5 75.7 73.1 72.0 71.5
100 96.2 78.5 74.6 73.0 72.2
110 105.0 81.3 76.2 74.0 72.9
120 113.7 84.1 77.7 75.1 73.7
130 122.4 87.0 79.2 76.1 74.4
140 131.2 89.8 80.8 77.1 75.1
150 139.9 92.6 82.3 78.1 75.9
160 148.7 95.4 83.9 79.1 76.6
170 157.4 98.3 85.4 80.1 77.3
180 166.1 101.1 86.9 81.1 78.1
190 174.9 103.9 88.5 82.1 78.8
200 183.6 106.7 90.0 83.2 79.5
2½" Uponor PEX heat loss
at 70°F/21.1°C ambient
Water
temp
(ºF)
Heat loss (btu/hr·ft)
No insulation
½" insulation
1" insulation
1½" insulation
2" insulation
30 -24.0 -10.7 -7.5 -6.0 -5.1
40 -18.0 -8.0 -5.6 -4.5 -3.8
50 -12.0 -5.4 -3.7 -3.0 -2.5
60 -6.0 -2.7 -1.9 -1.5 -1.3
70 0.0 0.0 0.0 0.0 0.0
80 6.0 2.7 1.9 1.5 1.3
90 12.0 5.4 3.7 3.0 2.5
100 18.0 8.0 5.6 4.5 3.8
110 24.0 10.7 7.5 6.0 5.1
120 30.0 13.4 9.3 7.5 6.4
130 36.0 16.1 11.2 8.9 7.6
140 42.0 18.8 13.1 10.4 8.9
150 48.0 21.5 14.9 11.9 10.2
160 54.1 24.1 16.8 13.4 11.5
170 60.1 26.8 18.6 14.9 12.7
180 66.1 29.5 20.5 16.4 14.0
190 72.1 32.2 22.4 17.9 15.3
200 78.1 34.9 24.2 19.4 16.5