User Guide

Plumbing Design Assistance Manual l Appendix F – Pipe heat loss and surface temperature l 165
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
1½" 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 31.6 44.5 47.1 48.2 48.7
40 40.8 47.3 48.6 49.1 49.3
50 50.0 50.0 50.0 50.0 50.0
60 59.2 52.7 51.4 50.9 50.7
70 68.4 55.5 52.9 51.8 51.3
80 77.5 58.2 54.3 52.7 52.0
90 86.7 60.9 55.7 53.7 52.6
100 95.9 63.7 57.1 54.6 53.3
110 105.1 66.4 58.6 55.5 53.9
120 114.2 69.1 60.0 56.4 54.6
130 123.4 71.8 61.4 57.3 55.2
140 132.6 74.6 62.8 58.2 55.9
150 141.8 77.3 64.3 59.1 56.5
160 151.0 80.0 65.7 60.1 57.2
170 160.1 82.8 67.1 61.0 57.9
180 169.3 85.5 68.5 61.9 58.5
190 178.5 88.2 70.0 62.8 59.2
200 187.7 91.0 71.4 63.7 59.8
1½" 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 -7.8 -3.8 -2.7 -2.2 -1.9
40 -3.9 -1.9 -1.4 -1.1 -1.0
50 0.0 0.0 0.0 0.0 0.0
60 3.9 1.9 1.4 1.1 1.0
70 7.8 3.8 2.7 2.2 1.9
80 11.7 5.6 4.1 3.3 2.9
90 15.6 7.5 5.4 4.4 3.9
100 19.5 9.4 6.8 5.5 4.8
110 23.4 11.3 8.1 6.6 5.8
120 27.3 13.1 9.5 7.8 6.7
130 31.2 15.0 10.8 8.9 7.7
140 35.1 16.9 12.2 10.0 8.7
150 39.0 18.8 13.5 11.1 9.6
160 43.0 20.6 14.9 12.2 10.6
170 46.9 22.5 16.2 13.3 11.6
180 50.8 24.4 17.6 14.4 12.5
190 54.7 26.3 18.9 15.5 13.5
200 58.6 28.1 20.3 16.6 14.5