Product(s):	Hevacomp Mechanical Designer
	Version(s):	V8i
	Environment:	N/A
	Area:	Netsys
	Subarea:	Pipe Sizing

Overview

Bentley Hevacomp V8i v26 now includes the option to implement the BS EN 806-3:2006 standards for pipe sizing.

This applies to HWS and CWS systems in both Netsys and System Builder.

Method

Loading units and flow rate calculation methods specified by BS EN 806-3 differ to that of the preceding BS 6700. Both of these standards are available in Hevacomp v8i v26.

The Pipes>Defaults menu now displays options for BS 6700 and BS EN 806-3, as in image below.

Existing projects from previous versions of Hevacomp will remain set to BS 6700.
All new projects created in Hevacomp v26 will default to BS EN 806-3 automatically.

If changing the standards on your project, ensure you recalculate your system.

Information

BS EN 806-3 uses both different loading units and a different flow rate calculation method to that of BS 6700.

• Loading Units:
  These are detailed in BS EN 806-3, Table 2. Taking a Basin as an example, the difference between the two standards in this regard can be seen in the following side-by-side comparison:

 
Should you wish to specify a specific flow rate at your outlet rather than use these loading units, then you can instead enter a figure for Continuous flow, as below.

• Flow rate calculation method:
  Each final pipe connecting to an outlet is sized using the maximum flow rate (l/s) for that outlet.
  
  For diversity in distribution pipes feeding groups of outlets the total of connected Loading units of the outlets fed by that pipe are used. BS EN 806-3 considers the highest single loading unit connected to that run and uses the appropriate line on the graph of Figure B.1, BS EN 806-3 (below) to calculate the diversified flow rate at that point. This process is repeated at each distribution pipe using the highest connected outlet Loading unit.

Example

The effect of the new standards on flow rate results is best shown by example. Consider the following system:

 
Note that the pipe properties in the example above represent:

Looking at section one, for example, the key figures are:

• Total flow rate (in Loading units) = 1 + 1 + 1 + 4 = 7 
   
• Highest single Loading Unit at any outlet supplied (i.e. outlet H4) = 4

The Design flow rate can then be obtained from Figure B.1, BS EN 806-3, which plots Total flow rate (x-axis, LU) vs Design flow rate (y-axis, l/s), alongside values for the highest single Loading unit. Below, the total flow rate is highlighted in yellow, and the highest single loading unit is highlighted in red:

The point of intersection between these two lines shows the corresponding Design flow rate on the y-axis, in this case 0.483 l/s.