User Guide

Plumbing Design Assistance Manual l Appendix F – Pipe heat loss and surface temperature l 161
Appendix F:
Pipe heat loss and surface temperature
½" Uponor PEX surface
temperature at 50°F/10°C ambient
Water
temp
(ºF)
Surface temperature (°F)
No insulation
½" insulation
1" insulation
1½" insulation
2" insulation
30 30.7 45.2 47.7 48.6 49.0
40 40.4 47.6 48.8 49.3 49.5
50 50.0 50.0 50.0 50.0 50.0
60 59.6 52.4 51.2 50.7 50.5
70 69.3 54.8 52.3 51.4 51.0
80 78.9 57.1 53.5 52.1 51.5
90 88.6 59.5 54.6 52.9 52.0
100 98.2 61.9 55.8 53.6 52.5
110 107.9 64.3 56.9 54.3 53.0
120 117.5 66.7 58.1 55.0 53.5
130 127.2 69.0 59.2 55.7 54.0
140 136.8 71.4 60.4 56.4 54.5
150 146.5 73.8 61.5 57.2 55.1
160 156.1 76.2 62.7 57.9 55.6
170 165.8 78.6 63.8 58.6 56.1
180 175.4 81.0 65.0 59.3 56.6
190 185.1 83.3 66.1 60.0 57.1
200 194.7 85.7 67.3 60.7 57.6
½" Uponor PEX heat loss
at 50°F/10°C ambient
Water
temp
(ºF)
Heat loss (btu/hr·ft)
No insulation
½" insulation
1" insulation
1½" insulation
2" insulation
30 -3.2 -2.0 -1.6 -1.4 -1.2
40 -1.6 -1.0 -0.8 -0.7 -0.6
50 0.0 0.0 0.0 0.0 0.0
60 1.6 1.0 0.8 0.7 0.6
70 3.2 2.0 1.6 1.4 1.2
80 4.7 3.0 2.4 2.0 1.8
90 6.3 4.1 3.2 2.7 2.4
100 7.9 5.1 4.0 3.4 3.1
110 9.5 6.1 4.7 4.1 3.7
120 11.1 7.1 5.5 4.8 4.3
130 12.6 8.1 6.3 5.4 4.9
140 14.2 9.1 7.1 6.1 5.5
150 15.8 10.1 7.9 6.8 6.1
160 17.4 11.1 8.7 7.5 6.7
170 18.9 12.2 9.5 8.2 7.3
180 20.5 13.2 10.3 8.8 8.0
190 22.1 14.2 11.1 9.5 8.6
200 23.7 15.2 11.9 10.2 9.2
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.