BS EN 806 -2006

Hi Liam

It is quite a complex procedure. You need to consider that there are two equations. One that works exclusively with the LU of the outlet, the second that works with the peak outlet in a section.

For LU's larger than 300:

dim = loading units

m = (log(9)-log(1.7)) / (log(5000) - log(300))

c= log(1.7)-m*(log(300)

flowrate  = exp(m * log(dim) +c)

For LU's smaller than 300:

pdim = peak loading units for section

m = (log(1.7) - log(pdim)/10)) /(log(300)-log(pdim))

c = log(pdim/10) - m * log (pdim)

flowrate  = exp(m * log(dim) +c)

This differs substantially from BS 6700:

For LU's larger than 2000:

dim = loading units 

flow = specified flow rate (if any)

m = 11.2 + (dim-2000) * 0.0039

flowrate = flow + m

For LU's smaller than 2000:

dim = loading units 

flow = specified flow rate (if any)

m = .0.0532 * dim ^ 0.7

flowrate = flow + m

For further information on the pipe sizing standards, please consider this document. For more information about the methods considered by BS 6700, please see this document. 

Best regards,

Duncan Brown

Hi Duncan, 

Appreciate I am a little "late to the party" since this is a follow up to a question raised almost four years ago.

My question - I am looking for clarifcation on whether the formula you gave in this answer for BS EN 806 is 100% correct to the software?

Reason is that when I plug your formula into a rudimental excel sheet for QA'ing my teams Hevacomp BS EN 806 outputs - they do not match. I am wondering if it is how the brackets are displayed in your answer which are affecting the results?

What I am trying to do if have a basic Excel sheet where I am plug in the "dim" or "pdim" figures and it'll tell me the flow rate, and I use this when QA'ing outputs generated. 

Thanks for your help, and hope you had a good Christmas break.

Kind regards

Hi George, happy new year to you. This would be quite difficult to replicate in an excel spreadsheet as the calculation methodology for BS EN806 utilises the rather complex graph shown here. I would suggest perhaps using the graph to QA your results if suitable. I hope that helps.