User Guide

Plumbing Design Assistance Manual l Appendix F – Pipe heat loss and surface temperature l 163
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 50°F/10°C ambient
Water
temp
(ºF)
Surface temperature (°F)
No insulation
½" insulation
1" insulation
1½" insulation
2" insulation
30 31.2 44.8 47.4 48.3 48.8
40 40.6 47.4 48.7 49.2 49.4
50 50.0 50.0 50.0 50.0 50.0
60 59.4 52.6 51.3 50.8 50.6
70 68.8 55.2 52.6 51.7 51.2
80 78.3 57.9 54.0 52.5 51.8
90 87.7 60.5 55.3 53.3 52.4
100 97.1 63.1 56.6 54.2 53.0
110 106.5 65.7 57.9 55.0 53.6
120 115.9 68.3 59.3 55.9 54.2
130 125.3 70.9 60.6 56.7 54.8
140 134.8 73.6 61.9 57.5 55.3
150 144.2 76.2 63.2 58.4 55.9
160 153.6 78.8 64.6 59.2 56.5
170 163.0 81.4 65.9 60.0 57.1
180 172.4 84.0 67.2 60.9 57.7
190 181.9 86.7 68.5 61.7 58.3
200 191.3 89.3 69.8 62.6 58.9
1" 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 -5.5 -2.9 -2.2 -1.8 -1.6
40 -2.8 -1.5 -1.1 -0.9 -0.8
50 0.0 0.0 0.0 0.0 0.0
60 2.8 1.5 1.1 0.9 0.8
70 5.5 2.9 2.2 1.8 1.6
80 8.3 4.4 3.2 2.7 2.4
90 11.1 5.8 4.3 3.6 3.2
100 13.9 7.3 5.4 4.5 4.0
110 16.6 8.7 6.5 5.4 4.8
120 19.4 10.2 7.6 6.3 5.6
130 22.2 11.7 8.7 7.2 6.4
140 25.0 13.1 9.7 8.1 7.2
150 27.7 14.6 10.8 9.0 8.0
160 30.5 16.0 11.9 9.9 8.8
170 33.3 17.5 13.0 10.8 9.6
180 36.1 18.9 14.1 11.8 10.4
190 38.8 20.4 15.2 12.7 11.2
200 41.6 21.8 16.2 13.6 12.0