Couple Questions on Using my Thermo Anemometer


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Old 12-11-14, 09:03 PM
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Couple Questions on Using my Thermo Anemometer

Got a little EXTECH AN100 to get an idea what's happening with airflow in my place. I have a question on entering the Area. Say I have a 6" duct that hooks to a 4"X10" boot and then on top of that is my adjustable register. What do I enter for Area?

4"x10"=40"/12= 3.333 sq. ft??? or
3.14x9= 28.26 (pi x radius squared)???

And then the register - I should remove that while I'm taking the measurement, yes? So in other words I would just then have the unobstructed 4'x10" boot area that I'm holding my vane probe in front of. Do I just hold it directly over it, or try to shove it down in that boot a little ways, or ?

One last question - the fan blows harder in cooling mode and a friend suggested I should test in that cooling mode, even though I'm really trying to understand something about balancing the heating system - I've got some rooms that are up to 7 degrees colder than others - the basement was actually warmer than the main level, so I completely shut a couple registers down there and I did gain a couple degrees on the main level from doing that.

Anyway, thanks very much - just trying to get a little more savvy about this as I will be engaging with an HVAC contractor soon.

Pete
 
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Old 12-11-14, 09:14 PM
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Oops...my mistake, that first sq. footage calculation should be:

4"x10"=40"/144=0.278 sq. ft. , but doesn't even look like I can enter that small a number into the sq. ft. area field of the AN100.
 
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Old 12-12-14, 11:48 AM
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What are you trying to find out? This will help us. If your looking for cfm you will just use the size of the grill
 
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Old 12-13-14, 01:01 PM
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Well, I'm trying to "balance" things out a bit by comparing the actual CFMs for each register against the CFMs for each register listed on a drawing of my system, and then playing with the adjustment knob on the register to get them in the ballpark of what's on the drawing.

I've figured out the AN100 enough to use it; a support guy at Extech was actually quite helpful.

So I've checked things out and restricted some airflow from a few registers that were blowing way over what the drawing says they're supposed to, and now the master quarters are getting quite a bit more air than they were before (and the master quarters are definitely the cold zone of the house).

We'll see if this helps - I know airflow isn't the entire picture, but I needed to start somewhere.

Thanks for thinking of me airman - sometimes even one reply helps me feel not so alone!

Pete
 
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Old 12-13-14, 09:52 PM
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Your meter only asks for the area. It does the math.

"The meter has 16 memory locations (8 for CFM and 8 for CMM) that can be used to store
commonly used area sizes that you can recall at anytime.
1. Press the AREA button until meter beeps twice. A memory location number will
appear in the top right of the display indicating the memory location.
2. Push the NEXT button to scroll thru and select the desired location. Once you have
selected the desired memory location enter your dimension
Use the ▲ (UP) button to change the flashing digit
Use the ◄ (LEFT) button to move the decimal
Use ► (RIGHT) button to select the other digits. After all of the digits are entered,
press and hold the AREA button (until it beeps twice) to save the area into memory
and return to CFM or CMM measuring mode.
To select and use a previously stored dimension, press and hold the AREA button until it
beeps twice.
Press NEXT to scroll thru the 8 memory locations. Press and hold the AREA button until it
beeps twice to return to CFM or CMM measuring mode."
 
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Old 12-14-14, 02:39 AM
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Airflow adjustments should be made at balancing dampers installed at the beginning of the duct run, not at the register. Making the adjustments at the registers will lead to noise at the register.

Unfortunately, few homes built in the last twenty plus years have balancing dampers installed. You CAN install them your self.
 
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Old 12-15-14, 06:30 PM
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Yep Furd, you're absolutely right - I AM hearing noise at some of the registers now. But sheesh, there are so many noises in this new house. It's only got one big honkin' return in the hallway - the rest of the rooms use transfer grills or crossover ducts; anyway that return is LOUD - someone suggested some duct insulation - might try that. Then my radon was way over the recommended EPA limits - so that's another fan, and yes, I can hear that too! Then I heard chewing and scratching - rabbits and mice! - so I've got a critter control guy helping me trap and build some steel mesh around the deck (they're getting under and got into a cantilever and then some mice chewed into the basement from there). I think I want to go rent an apartment!
 
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Old 12-15-14, 08:13 PM
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You MAY be able to slow down the blower in your furnace and significantly reduce the noise level. We had quite a thread on that running a short while ago, let me see if I can find a link for you.

Here it is, the page order may be wrong. http://www.doityourself.com/forum/in...lations-2.html
 
 

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