User Guide

Plumbing Design Assistance Manual l Appendix F – Pipe heat loss and surface temperature l 171
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 70°F/21.1°C ambient
Water
temp
(ºF)
Surface temperature (°F)
No insulation
½" insulation
1" insulation
1½" insulation
2" insulation
30 32.3 59.5 64.7 66.7 67.6
40 41.7 62.1 66.0 67.5 68.2
50 51.2 64.8 67.4 68.3 68.8
60 60.6 67.4 68.7 69.2 69.4
70 70.0 70.0 70.0 70.0 70.0
80 79.4 72.6 71.3 70.8 70.6
90 88.8 75.2 72.6 71.7 71.2
100 98.3 77.9 74.0 72.5 71.8
110 107.7 80.5 75.3 73.3 72.4
120 117.1 83.1 76.6 74.2 73.0
130 126.5 85.7 77.9 75.0 73.6
140 135.9 88.3 79.3 75.9 74.2
150 145.3 90.9 80.6 76.7 74.8
160 154.8 93.6 81.9 77.5 75.3
170 164.2 96.2 83.2 78.4 75.9
180 173.6 98.8 84.6 79.2 76.5
190 183.0 101.4 85.9 80.0 77.1
200 192.4 104.0 87.2 80.9 77.7
1" 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 -11.1 -5.8 -4.3 -3.6 -3.2
40 -8.3 -4.4 -3.2 -2.7 -2.4
50 -5.5 -2.9 -2.2 -1.8 -1.6
60 -2.8 -1.5 -1.1 -0.9 -0.8
70 0.0 0.0 0.0 0.0 0.0
80 2.8 1.5 1.1 0.9 0.8
90 5.5 2.9 2.2 1.8 1.6
100 8.3 4.4 3.2 2.7 2.4
110 11.1 5.8 4.3 3.6 3.2
120 13.9 7.3 5.4 4.5 4.0
130 16.6 8.7 6.5 5.4 4.8
140 19.4 10.2 7.6 6.3 5.6
150 22.2 11.7 8.7 7.2 6.4
160 25.0 13.1 9.7 8.1 7.2
170 27.7 14.6 10.8 9.0 8.0
180 30.5 16.0 11.9 9.9 8.8
190 33.3 17.5 13.0 10.8 9.6
200 36.1 18.9 14.1 11.8 10.4