Some more very useful points as I consider just how to install the duct system, thanks again.
Terry, I had hoped to do as you have but have so far not found a reasonable source of 125mm "flexi" and gates, please could you point me in the right direction if you have time. At the moment I can only find the very flimsy ventilation type.
MattRoberts, Mike is correct that I can't help with practical experience yet but if your purchase is not imminent then I will let you know how it works out. I still have to buy the ducting etc so will be a couple of weeks (my "slow weeks" I'm afraid).
It might be useful to give you a few clues on the rationale behind my choice if it helps, these are just my ramblings and I do not claim to have much expertise in this field. I suffer from severe non-allergic persistent rhinitis although up to a few months ago I managed with the various headgear (PPE) I mentioned before. As my condition is not responding to treatment I'm sad to say that pleasure in the hobby, for me, is greatly reduced. At the same time I have started to realise that my initial machinery could be improved which of course will need substantial investment from me which would be a waste if I cannot recover the enjoyment. My working background is as an aircraft engineer so I have a grasp of airflow and the various "laws" but am by no means an expert. With the great advice from the more knowledgeable here, I realised that I could not afford an "industrial" solution and it probably wouldn't work for me anyway. My first approach was to simplify my plans and reduce the duct run to a minimum for the dust and chip producers, possible about 6m now, and handle the fine dust tools with my HPLV and its' Hepa filters. I realise that this may not be entirely successful as it depends too much on the local collection capability of the sander, router etc. Not a major issue to me as I had already decided that I will have to use decent mask or Air fed hood for these tasks. With the larger chips it seems that the speed of the flow is the important issue and the matching of the duct and impellor properties is critical. To me an obvious example of the difference in impellor efficiency is the apparent suction of the machine, here I think the Jet 1100 Vortex scores more highly than the 300BC even with its' higher "free air" flow rate. All HVLP systems suffer a major loss of performance with any sort of drag in the airflow whether by reduction in duct cross section, by sharp changes in direction or just turbulence created by rough internal surfaces. The Jet is a fair bit more expensive though. So my current needs are to see if I can live with a system that I can afford, I feel that the 300BC is fit to trial my ideas but may not be the final extractor I buy if I am able to get back into the hobby. I am also planning to modify the extractor by removing the metal ducting and mounting the impellor directly on the filter/waste housing.
I have rambled enough (OK too much - sorry) but I wanted to let you see that my needs are specific and may not be right for everyone. I'm sure I will have many more questions to ask as I see what is possible particularly with improving the extraction on my 01332 table saw and the bandsaw which up till now has not had much use. With the great help and advice from this forum I am at least more positive that I may be able to return to the fold.
Best regards
Keith