No.
Just like the title says. Just curious.
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No.
it would take superhuman calculations...
The TRUE highest cost system is the system not installed properly...
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Do you go to a boat repairman with a sinking boat, and tell him to put in a bigger motor when he tells you to fix the holes?
I am yourmrfixit
Maybe... some cheap manometers have a "calibrated' plastic piece the slides on the end of the tube that creates a venturi which will allow you to roughly determine velocity based on the vacuum generated. It's won't be all that accurate, but better than nothing.
LOL. And that's what it is............. Better than nothing!
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An 'anemometer' is what you use; you need to know the (Ak) square foot free-air-area of the register. Many list the Ak on the their Internet sites; such as Hart & Cooley plus others.
It is Not physical area; it is the diffuser's free-air-area (or, Ak) Square Foot (sf) area * FPM Velocity = CFM.
Example: 0.21-sf * 600-FPM=126-CFM
This will only get you a ballpark fpm velocity & CFM; however, you can tell if flow is close to the ballpark volume number needed.
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udarrell
If you know the brand and model/style of the register. The manufacturer will have the specs for it. And you can determine the CFM by pressure drop across the register.
The only way to do it accurately with a garden variety manometer would be to traverse the duct or pipe with a pitot tube before the outlet. You would still need to convert the velocity pressure (square root of VP x 4005) to velocity and multiply by the internal free area of the duct or pipe. Otherwise, you need a hot wire anemometer or a rotating vane anemometer.
Don't pick the fly crap out of the pepper.
Good question. You should ask them. It likely has more to with duct system design and noise reduction than it does balancing. I have never recorded a pressure drop across any diffuser as part of a T&B report. IMO, I don't think it's a very reliable way to determine flow.
Don't pick the fly crap out of the pepper.
I come up with pretty much what the ESP at the air handler says I'm moving. Varying with the amount of duct leakage.
How do you compensate for vents that are partially closed? I assume their ratings are at 100% full flow. Do you think it makes a difference? As static increases, flow decreases.
Don't pick the fly crap out of the pepper.
I don't use register dampers to balance(talking residential). Dampers in the supply itself, so no problem balancing in that situation.
And checking for duct leakage isn't a problem in that case either.
If the register dampers are being used for balancing, then PD across the register won't work real well in most cases.