Am I on the right track - Ventilation.

[beadysam]

Hiya all!
I'm just setting up my studio and want to clarify that I understand ventilation issues adequately. Can someone correct me if I'm wrong please? Or add any important issues I may have ommitted. Thanks

As I understand it the basics are:

Venting should be smooth not corrugated and preferably metal.
Rectangular is okay but circular is better.
The straighter the run the better.
Vent outlet should be at least 10feet away from make up air inlet.
Make up air inlet input should be at least equal to the extraction rate.
CFM should be approx 120 per sq foot, but this can lower to 80 cfm when using a Barley Box style set up (this will be my set up).
In a Barley Box set up the sq footage is the measurements of the opening of the box - the facing square/rectangle (am I making sense here?).
Generally squirrel cage or centrifugal fans are more suitable for lampworkers needs than standard bathroom type extractors or cooker hoods.

These are just the simple bits without all the complicated, case specific calculations - am I on the right track?

SAM xx

[Dale M.]

I would say generally you are on right track.... About round duct over square... Both can be used and they can be equal in performance. But round ducting is so much more available (home improvement centers) than square, and its so much easier to install for the non AC professional I would stay with round ducting.

Face opening for barley box is "height X width" with hood its "depth X width" ... So if your hood/box has opening of 2 ft X 3 ft that equals 6 sq ft... So with an acceptable rate of 100 cfm multiplied by 6 sqft your fan needs to be capable of moving about 600 cfm... Several factors come into play here like static pressure in your duct run and few other things but you have good understanding of basics.

Dale

[beadysam]

Thanks Dale
You explained the Barley Box opening MUCH better than I did! Its taken me ages to find the UK equivalent of CFM but now I have my biggest problem is finding a supplier of a fan with enough power. They all seem a bit pathetic over here unless you want to get really spendy and the squirrel cage fans only seem to be used in industrial settings! Still I have a few leads that I am working on and there is always ebay...
SAm xx

[MikeAurelius]

Yes - don't buy an american fan UNLESS it is capable of running on your voltage and frequency - if I recall correctly you have 50 hz power, correct?

The US, actually, all of North America, runs on 60 hz power and running a 60 hz motor on 50 hz will quickly lead to a burnout.

There are some fans capable of 50/60 hz operation but they are very expensive.