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  1. #27
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    May 2009
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    Cumming, GA
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    I picked up these 1/2" plugs from TTT. They're perfect for plugging test holes in ductboard or metal from the SDP2 or STA2. Just thought I would share.

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  2. #28
    Join Date
    Jul 2007
    Location
    Delaware
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    Can you post of pic of the your system and the locations where you captured the data?

  3. #29
    Join Date
    Feb 2009
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    Tallahassee, FL
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    Hi brent been meaning to ask this - a lot of our systems are vertical indoors with free air return. I read that supply traverse are not accurate especially near blower. Would traversing between filter and coil be accurate?

    If you can picture just sliding the wand above the filter through opening.

  4. #30
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    May 2009
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    Cumming, GA
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    Quote Originally Posted by SBKold View Post
    Hi brent been meaning to ask this - a lot of our systems are vertical indoors with free air return. I read that supply traverse are not accurate especially near blower. Would traversing between filter and coil be accurate?

    If you can picture just sliding the wand above the filter through opening.
    SB,

    No. The air is too turbulent. The STA2 is not good for every application. When I come across a unit with a free air return, I use duct static and a blower curve.


    Energy,

    I will take a pic tomorrow and post.

  5. #31
    Join Date
    Feb 2013
    Location
    north georiga
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    Quote Originally Posted by Brent Ridley View Post
    I picked up these 1/2" plugs from TTT. They're perfect for plugging test holes in ductboard or metal from the SDP2 or STA2. Just thought I would share.

    Name:  image.jpg
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    Name:  image.jpg
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Size:  34.9 KB
    do you just use a regular drill bit in duct board?

  6. #32
    Join Date
    May 2009
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    Cumming, GA
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    Quote Originally Posted by davidj001 View Post
    do you just use a regular drill bit in duct board?
    Yes. I usually use a 1/2" step bit.

  7. #33
    Join Date
    Feb 2013
    Location
    north georiga
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    Quote Originally Posted by Brent Ridley View Post
    2 Fieldpiece tools + 10 mins = 1 easy BTUH calculations.

    I just wanted to make a post explaining how easy an actual output BTU calculation is using only two of Fieldpiece's tools. FP really has simplified some of the hardest HVAC calculations with the introduction of these tools.

    What I used:

    Fieldpiece SDP2 Dual In-duct psychrometer
    Fieldpiece STA2 In-duct hot wire anemometer
    Drill w/ 1/2" step bit.
    Tape measure.

    Attachment 380771

    Step 1:

    Operate your system in cooling mode. Drill one 1/2" hole in the supply and one 1/2" hole in the return. Using the SDP2, insert the probe marked with red in the return and the unmarked probe in the supply. After the system has ran for a bit and settled down, record the enthalpy. The SDP2 will display supply enthalpy and return enthalpy. Subtract the supply from return.

    My system.
    Return Enthalpy: 26.04
    Supply Enthalpy: 19.50
    Enthalpy change (Δh): 6.54


    Attachment 380781

    Attachment 380791

    Step 2:

    Using the tape measure - measure your return duct. Using the STA2, input your square duct measurements or round duct diameter. Refer to the table in the STA2 manual; mark and drill 1/2" holes in appropriate traverse locations. Take timed measurements.

    My system:
    Feet per minute: 556
    Cubic feet per minute: 988.4


    Attachment 380801

    Attachment 380811

    Step 3:

    Calculate.
    CFM x 4.5 x Enthalpy change (Δh) = BTUH

    My system:
    988.4 x 4.5 x 6.54 = 29,088 BTUH.


    I have a 2.5 ton (30,000) system. Not to bad. I would like to make a few adjustments and maybe get a little closer to the nominal tonnage. This whole process took no time at all. I stated 10 minutes and that is only due letting the system run and settle down. By performing this calculation on each system I service, I can tell exactly what changes need to be made produce more output BTU's.

    Hope this helps!

    Thanks.

    Brent A. Ridley
    was this done with the house already at "comfort conditions"? any rough idea what to expect if the house is not at those conditions?

  8. #34
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    May 2009
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    Cumming, GA
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    Quote Originally Posted by davidj001 View Post
    was this done with the house already at "comfort conditions"? any rough idea what to expect if the house is not at those conditions?
    Yes. The house was already at set temperature.

    Depending on the indoor/outdoor sensible and latent loads - the system capacity could vary as much as 25%.

  9. #35
    Join Date
    Feb 2013
    Location
    north georiga
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    Quote Originally Posted by Brent Ridley View Post
    Yes. The house was already at set temperature.

    Depending on the indoor/outdoor sensible and latent loads - the system capacity could vary as much as 25%.
    another question, i used my spd2 on a unit where the installer used a 2' box on top of the a/h then tapped a 14" collar off the top and a 12" off the side, this duct design is not the best for optimum results is it?

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