Heating

Heating pipes

Pipe

28 × 1,5

Velocity

0,33m/s

Pressure gradient

57Pa/m

Heating pipes select the nominal size from heat output or volume flow. Dimensions follow EN 10255 up to DN 100 and EN 10220 up to DN 300, and pressure loss follows Darcy–Weisbach. The result is velocity, friction and the matching size.

Nominal size

28 × 1,5

Copper

Velocity

0,33

m/s

k = 0,0015 mm

Internal
25,0mm
Flow rate
584l/h
Mass flow
573kg/h
Pressure gradient R
57Pa/m
SeriesNearby sizes
  • 12 × 1,02,07 m/s · 4.573 Pa/m
  • 15 × 1,01,22 m/s · 1.297 Pa/m
  • 18 × 1,00,81 m/s · 480 Pa/m
  • 22 × 1,00,52 m/s · 165 Pa/m
  • 28 × 1,50,33 m/s · 57 Pa/m
  • 35 × 1,50,20 m/s · 18 Pa/m
  • 42 × 1,50,14 m/s · 7 Pa/m
  • 54 × 2,00,08 m/s · 2 Pa/m
  • 76,1 × 2,00,04 m/s · 0 Pa/m
  • 88,9 × 2,00,03 m/s · 0 Pa/m
  • 108 × 2,50,02 m/s · 0 Pa/m

Given

Pipe

Save in —

How it's calculated

Heating pipes pick the smallest size that meets both the target velocity and the maximum pressure gradient. Volume flow comes from the heat output through specific heat and density, or it is entered directly. Friction is Darcy–Weisbach with the Colebrook-White friction factor and the roughness of the chosen series. Steel follows EN 10255 up to DN 100 and EN 10220 from DN 125. If no size meets both limits, the largest size stays visible and is marked as not acceptable.

Worked example

10 kW, 70/55 °C, steel, 0.5 m/s and 150 Pa/m: DN 20, 0.44 m/s, R = 132 Pa/m.

FAQ

Why is a larger size chosen?
If the fast size exceeds the pressure gradient, the next size that meets both limits is used. The note names that case.
What value of R is usual?
150 Pa/m is the starting value for distribution pipes. Branches may be higher and quiet networks lower. The value is an input, not a limit in the standard.
Does EN 10255 apply above DN 100?
No. Up to DN 100 it is medium-weight threaded tube, and from DN 125 the series 1 sizes of EN 10220.
Does this include the pump head?
No. It shows the friction gradient and, if a length is entered, the loss of that run without fittings.