User Guide

Plumbing Design Assistance Manual l Appendix F – Pipe heat loss and surface temperature l 181
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 90°F/32.2°C ambient
Water
temp
(ºF)
Surface temperature (°F)
No insulation
½" insulation
1" insulation
1½" insulation
2" insulation
30 34.9 73.6 81.4 84.5 86.1
40 44.1 76.3 82.9 85.4 86.7
50 53.3 79.1 84.3 86.3 87.4
60 62.5 81.8 85.7 87.3 88.0
70 71.6 84.5 87.1 88.2 88.7
80 80.8 87.3 88.6 89.1 89.3
90 90.0 90.0 90.0 90.0 90.0
100 99.2 92.7 91.4 90.9 90.7
110 108.4 95.5 92.9 91.8 91.3
120 117.5 98.2 94.3 92.7 92.0
130 126.7 100.9 95.7 93.7 92.6
140 135.9 103.7 97.1 94.6 93.3
150 145.1 106.4 98.6 95.5 93.9
160 154.2 109.1 100.0 96.4 94.6
170 163.4 111.8 101.4 97.3 95.2
180 172.6 114.6 102.8 98.2 95.9
190 181.8 117.3 104.3 99.1 96.5
200 191.0 120.0 105.7 100.1 97.2
1½" 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 -23.4 -11.3 -8.1 -6.6 -5.8
40 -19.5 -9.4 -6.8 -5.5 -4.8
50 -15.6 -7.5 -5.4 -4.4 -3.9
60 -11.7 -5.6 -4.1 -3.3 -2.9
70 -7.8 -3.8 -2.7 -2.2 -1.9
80 -3.9 -1.9 -1.4 -1.1 -1.0
90 0.0 0.0 0.0 0.0 0.0
100 3.9 1.9 1.4 1.1 1.0
110 7.8 3.8 2.7 2.2 1.9
120 11.7 5.6 4.1 3.3 2.9
130 15.6 7.5 5.4 4.4 3.9
140 19.5 9.4 6.8 5.5 4.8
150 23.4 11.3 8.1 6.6 5.8
160 27.3 13.1 9.5 7.8 6.7
170 31.2 15.0 10.8 8.9 7.7
180 35.1 16.9 12.2 10.0 8.7
190 39.0 18.8 13.5 11.1 9.6
200 43.0 20.6 14.9 12.2 10.6