Static pressure of reverse 45 ?

4 years ago

I'm trying to figure out the static pressure of a reverse 45° Y. This is a 4" exhaust duct for a sauna using a 180 CFM fantech inline blower. The plan was to T in to the existing 4" duct but the guy doing it for me didn't have a 4" T so he's using a 4" 45 but had to install it in the reverse direction due to other stuff in the way.

My memory is that a reverse 45 like this is extremely high but I can't find a reference.

Thanks,

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Comments (3)

klem1
4 years ago
If I understand how the vent is configured,I don't believe there's a common need for such,therefore no standard established. Tools are available for testing air pressure,volume and volocity.
opaone thanked klem1
opaone
Original Author
4 years ago
Here's a very rough sketch of what they did. We added a 2.5x10 vertical exhaust vent in the wall so this is servicing that. The original plan was to come out of that straight in to a T in the existing duct. They didn't think they had enough room w/ the blower so they came out w/ to a 90 (actually about a 110 > a 20 > reverse 45) and then over to the reverse 45.

It would have been much better to have 45'd out of the 2.5x10 so that they could have done a 90° T in to the existing but, at least for now, what's done is done.
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opaone
Original Author
4 years ago
IIRC in equiv duct length a 90 is very roughly 10' of straight, a regular 45 is 4.5' but a reverse 45 is something like 80'.