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  1. Replies
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    Wrong context Andrew. HVAC operates at much...

    Wrong context Andrew. HVAC operates at much lower velocities than DC, hundreds of CFM not thousands. At those velocities the output of a Pitot-static tube is very low, it varies with the square...
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    Of course the velocity is different but Eric is...

    Of course the velocity is different but Eric is talking about flow rate, CFM, which is the same in either section. Read the first part of your link, the part titled "The basic continuity". It...
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    On the Australian site that Chris mentioned I...

    On the Australian site that Chris mentioned I posted some data comparing the Testo 405i that Thomas and I have to my pitot/manometer combo. Go to their advanced search usine keyword testo and user...
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    Dwyer makes well respected equipment but I use ...

    Dwyer makes well respected equipment but I use this lower cost pitot-static tube.

    I have a manometer that's an older version of this one and it's ok but I prefer this one, in part for it's...
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    Sorry, I wasn't clear. "That adapter" was...

    Sorry, I wasn't clear. "That adapter" was referring to the Hammer-to-Magport adapter previously discussed. That sort of thing supports a much higher price than $7, probably more like $170. I bet...
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    It looks like Magport 3D prints some of their...

    It looks like Magport 3D prints some of their newer fittings.

    "Production Volume" of that adapter is probably two or three a week. I'm sure something cheap, like an Ender 3, could easily keep up...
  7. Thanks for the opportunity to make dent in my...

    Thanks for the opportunity to make dent in my pile of "cutoffs" (nearly empty spools).

    PM me your shipping address.

    474204
  8. The Powermatic CFM claim is with an 8" inlet. ...

    The Powermatic CFM claim is with an 8" inlet. You won't get close to 1500 in actual shop use.

    The Powermatic specs do not include a fan curve so it's difficult to tell what you're really getting....
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    There's this...

    There's this or this.
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    I have 8' fluorescent fixtures that I've modified...

    I have 8' fluorescent fixtures that I've modified with retrofit kits that replace the two 8' tubes with six 4' LED tubes. I rewired the two lighting circuits so now one switch controls the center...
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    If you are prioritizing minimum enclosed...

    If you are prioritizing minimum enclosed footprint it might be best to focus on Core XY style printers, like the Voxel/Flash Forge you're looking at. A bed slinger needs a lot of space fore and aft...
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    I think hosting stl and CAD files might be a bit...

    I think hosting stl and CAD files might be a bit of a stretch for this site, both from a hardware and maintenance standpoint.

    I do like the idea of a 3D Printing for the Woodshop subforum though. ...
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    The fact that this thread exists answers that...

    The fact that this thread exists answers that question.:D
  14. That 1/2" could be a problem. ASHRAE spec...

    That 1/2" could be a problem. ASHRAE spec requires that it be flush with the wall. IME about an 1/8" protrusion caused around -0.2" wg error at decent flow rates. BTW, that's not a plenum; it's a...
  15. First point - Don't use DWV. That's just a foam...

    First point - Don't use DWV. That's just a foam core version of Schedule 40 and uses the same fittings. The appropriate spec for DC is ASTM 2729. That's a slightly smaller OD than schedule 40/80...
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    Typically no, but most will fit inside a 6"...

    Typically no, but most will fit inside a 6" coupling if you cut some threads for the wire spiral.

    468870
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    That seems a little low. I would expect about...

    That seems a little low. I would expect about double that on a 45° fitting.

    I see you have current measuring capability. Would you take some current readings, one with all blast gates closed and...
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    Expect the 6" duct to support about 16 pounds,...

    Expect the 6" duct to support about 16 pounds, half that for the 4". Should be done vertically.
  19. Keep in mind that the PM2.5 calculation from...

    Keep in mind that the PM2.5 calculation from Dylos particle counts is only a rough approximation. It's based on an "average" particle size of 1.5 micron and an assumed particle mass density of 1.3...
  20. PM values versus particle counts

    A particle counter displays it's measurements as number of particles GREATER in size than the reference value. So, for example, if the 2.5µm channel on the Dylos reads 26, that indicates 26...
  21. How to compare the readings

    Both the Dylos and the Plantower (manufacturer of the sensor) are particle counters and it's appropriate to compare the particle counts, especially since the Dylos counter doesn't provide PM...
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    Yes, it's an exponential decay. With a perfect...

    Yes, it's an exponential decay. With a perfect filter you would have 37% remaining after the first exchange time. With a 20% filter it would be 82%.

    You are also correct in using the average...
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    To me psf is more intuitive than psi.

    To me psf is more intuitive than psi.
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    With a perfect filter the number of changes need...

    With a perfect filter the number of changes need to drop to 10% of initial concentration is 2.3. If the filter is not perfect then simply divide by the filter efficiency. So for a 20% efficient...
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    Those MPR2200 filters exceed MERV 13 requirements...

    Those MPR2200 filters exceed MERV 13 requirements and are just short of being MERV 14.

    466574466575
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