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  1. #1
    Join Date
    May 2006
    Posts
    134

    Measuring Humidity Levels

    As a maintenance person, all my units are fixed orifice, 1.5- 2 ton units, split systems.

    To acurately measure the charge and determine superheat I know I should be
    using a sling phychometer to determine wet bulb temp in an apartment.

    Is there any way to fake it ?

    For example if the weather report determines the humidity level in the area,
    is there a standard rule you can use , for example outside humidity + 5 percent more of humidity to determine inside wet bulb, or is this just rediculus ?

  2. #2
    Join Date
    Jun 2004
    Location
    4H: Hot, Humid Houston H.O.
    Posts
    3,304
    There must be some professional quality instrument which will deliver humidity conveniently and accurately. I understand the sling psychrometer is traditional and accurate, but it sounds like a bit of effort to use.

    I'm a homeowner who likes to monitor %RH using cheap thermometer gadgets from Walmart. Convenient but not all that accurate, I'm thinking you need something of quality about 10x more expensive.

    Based on my humidity measurements, I can most definitely promise you that outside humidity +5% has no relation to what's going on inside my house.

    Hope this helps -- Pstu

  3. #3
    Join Date
    Jul 2006
    Location
    NW burbs of Detroit
    Posts
    6,058
    Quote Originally Posted by summerblues View Post
    As a maintenance person, all my units are fixed orifice, 1.5- 2 ton units, split systems.

    To acurately measure the charge and determine superheat I know I should be
    using a sling phychometer to determine wet bulb temp in an apartment.

    Is there any way to fake it ?

    For example if the weather report determines the humidity level in the area,
    is there a standard rule you can use , for example outside humidity + 5 percent more of humidity to determine inside wet bulb, or is this just rediculus ?
    A sling is a pain to use for varying reasons. The biggest is you must take a whole bunch of reading and average it out if in a large area.

    Try the Yellow Jacket site as well as Testo.
    For 80 bucks you can buy an electronic hygrometer (fancy name for a RH meter)

    No u can't fake it. You either use the relevent data required or you take a SWAG.
    Last edited by hvaclover; 05-11-2007 at 07:48 PM.

  4. #4
    Join Date
    Apr 2007
    Posts
    6,285

  5. #5
    Join Date
    Apr 2007
    Location
    Ohio
    Posts
    31
    Wrap a wet paper towel around the end of your thermometer.Then put it in your return air grill.Try it, it works!

  6. #6
    Join Date
    Apr 2007
    Posts
    6,285
    How accurately?

  7. #7
    Join Date
    Jul 2006
    Location
    NW burbs of Detroit
    Posts
    6,058
    Quote Originally Posted by BigJon3475 View Post
    How accurately?
    Dig it.

  8. #8
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,347
    Get you one of these:



    A temperature/humidity stick. The probe is small enough to insert easily into a supply plenum while doing capacity checks. Measures temperature, humidity, and converts to wet bulb. I have one on order from National Comfort Institute. It's made by Testo. Last night at my RSES chapter meeting a fellow tech showed me his and it is the bee's knees.
    • Electricity makes refrigeration happen.
    • Refrigeration makes the HVAC psychrometric process happen.
    • HVAC pyschrometrics is what makes indoor human comfort happen...IF the ducts AND the building envelope cooperate.


    A building is NOT beautiful unless it is also comfortable.

  9. #9
    Join Date
    Jul 2006
    Location
    NW burbs of Detroit
    Posts
    6,058
    Quote Originally Posted by shophound View Post
    Get you one of these:

    [IMG]http:// Last night at my RSES chapter meeting a fellow tech showed me his and it is the bee's knees.
    ok i wont ...

  10. #10
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,347
    Quote Originally Posted by hvaclover View Post
    ok i wont ...
    Sheesh...get your mind out of the gutter, dude.
    • Electricity makes refrigeration happen.
    • Refrigeration makes the HVAC psychrometric process happen.
    • HVAC pyschrometrics is what makes indoor human comfort happen...IF the ducts AND the building envelope cooperate.


    A building is NOT beautiful unless it is also comfortable.

  11. #11
    Join Date
    Jul 2006
    Location
    NW burbs of Detroit
    Posts
    6,058
    Heh, yeah.

  12. #12
    wconell Guest
    Quote Originally Posted by shophound View Post
    Last night at my RSES chapter meeting a fellow tech showed me his and it is the bee's knees.
    Bee's have knee's?
    I shouldn't have slept thru biology!

  13. #13
    Join Date
    Jul 2006
    Location
    NW burbs of Detroit
    Posts
    6,058
    Quote Originally Posted by wconell View Post
    Bee's have knee's?
    I shouldn't have slept thru biology!
    Yeah and crickets have ears in their shins!

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