User Guide

Plumbing Design Assistance Manual l Appendix F – Pipe heat loss and surface temperature l 179
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
1" 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 33.5 74.3 82.1 85.0 86.4
40 42.9 76.9 83.4 85.8 87.0
50 52.3 79.5 84.7 86.7 87.6
60 61.7 82.1 86.0 87.5 88.2
70 71.2 84.8 87.4 88.3 88.8
80 80.6 87.4 88.7 89.2 89.4
90 90.0 90.0 90.0 90.0 90.0
100 99.4 92.6 91.3 90.8 90.6
110 108.8 95.2 92.6 91.7 91.2
120 118.3 97.9 94.0 92.5 91.8
130 127.7 100.5 95.3 93.3 92.4
140 137.1 103.1 96.6 94.2 93.0
150 146.5 105.7 97.9 95.0 93.6
160 155.9 108.3 99.3 95.9 94.2
170 165.3 110.9 100.6 96.7 94.8
180 174.8 113.6 101.9 97.5 95.3
190 184.2 116.2 103.2 98.4 95.9
200 193.6 118.8 104.6 99.2 96.5
1" 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 -16.6 -8.7 -6.5 -5.4 -4.8
40 -13.9 -7.3 -5.4 -4.5 -4.0
50 -11.1 -5.8 -4.3 -3.6 -3.2
60 -8.3 -4.4 -3.2 -2.7 -2.4
70 -5.5 -2.9 -2.2 -1.8 -1.6
80 -2.8 -1.5 -1.1 -0.9 -0.8
90 0.0 0.0 0.0 0.0 0.0
100 2.8 1.5 1.1 0.9 0.8
110 5.5 2.9 2.2 1.8 1.6
120 8.3 4.4 3.2 2.7 2.4
130 11.1 5.8 4.3 3.6 3.2
140 13.9 7.3 5.4 4.5 4.0
150 16.6 8.7 6.5 5.4 4.8
160 19.4 10.2 7.6 6.3 5.6
170 22.2 11.7 8.7 7.2 6.4
180 25.0 13.1 9.7 8.1 7.2
190 27.7 14.6 10.8 9.0 8.0
200 30.5 16.0 11.9 9.9 8.8