Netsys is ignoring fixed duct sizes

I am doing a ductwork pressure drop through Netsys. I have manually fixed the ALL duct sizes but the software appears to be selecting new ones in a number of instances. How can I stop this from happening?

Many Thanks

Craig

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  • I did have fixed neck sizes in place which I have now un-ticked in all instances just in case but I don't think that has helped.

    I have no risers as such, I am using wall mounted grilles at the same height as the system.

    I think the problem may be related to duct size changes in the same section. For instance, where I have a 1400 x 200 transforming to 900 x 400, the whole section becomes 900 x 200 in the calculation. Is there a correct way of adding a reducer that I'm not using? I was considering "bodging" this by added a short branch with limited volume but hope there's a better solution!

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