Quote:
Originally Posted by szglassy
Dennis...............
Do you mean 2-- 45 degree elbows together?
Will that not make the same turn as one 90??
Or.....do you mean 2 45's at different positions to get tot the same angle?
Going to be installing soon and wnat to clear up the confusion.
Thanks!
Sue
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I mean 2 - 45 deg elbows connected together to produce the 90 deg bend. The wider arc causes less air flow resistance. Even better would be a wide arc curve (these are available for metal ducting but are pretty pricey).
For at least 40 years, the plumbing code for drains and vents stated specifically that in any run of drain or vent, one only 90 was permitted but an unlimited number of 45's was allowed. If the experts insist that makes a critical difference for venting plumbing drains, it's reasonable to assume it'll make a significant difference for venting torching fumes.
Compare it to a road. A corner slows flow down more then a curve. The wider the curve, the less it slows down. On a really wide curve, you can travel the same speed as a straight run. When you install your ducting, think of it like building a road where you want traffic to keep moving steadily without having anywhere it has to slow down.
There has been extensive discussion on the needs for a high capacity fan. There are factors that will DEFINITELY reduce the size of fan needed:
1. The closer the hood is to the torch, the less fan capacity is needed.
2. The more enclosed the work area is, the less fan capacity is needed.
3. The lower the ducted air flow obstruction, the less fan capacity is needed.
4. The less other air movement, the less fan capacity is needed.
The 125 rule is a guideline only. It is NOT a commandment from God and it is NOT a legal requirement.