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  1. #14
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    Jan 2004
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    Lancaster PA
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    Thats a high PD for 1400CFM through a 5 ton coil.
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  2. #15
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    Apr 2008
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    Princeton, NJ
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    Quote Originally Posted by beenthere View Post
    Thats a high PD for 1400CFM through a 5 ton coil.
    Did not know I had a 5-ton coil.....thought it was matched to the condenser at 4-ton.

    If that PD is high does than mean something is not installed correctly? Or is it that there is a range and I am the unlucky one that got the high end of the range?

    Does Trane have specs. (Equipment specifications)...and if so would this PD fall outside of those specs?
    Key1

    Thanks.

  3. #16
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    Jan 2004
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    Lancaster PA
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    If I'm reading that mod number right, its a 5 ton coil.
    Which isn't unusual on 4 ton systems.

    A 4 ton running 1400 usually isn't that high.

    Could be just that model coil is restrictive.

    I would expect around .2 to .25 for a 4 or 5 ton coil at 1400 CFM.
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  4. #17
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    Apr 2008
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    Princeton, NJ
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    Quote Originally Posted by udarrell View Post
    You don't reduce static much by going from 8" back to 5" in the wall stacks.
    That is a no, no, it produces too much back pressure.

    The boots, the supply registers & everything must flow the velocity FPM & CFM volume with minimum static pressures rises.

    The Return Air filter Racks must be, way oversized, & all Return ducting with a low Fiction Rate. - Darrell
    Well.....there you have it......
    With a coil sitting at 0.37 SP...... leaving the available SP for the entire supply, filter, and return duct system at only 0.13......It is safe to say that with a 2 story house and 4 ton condenser....It is not realistic to think I can get down to the name plate max SP of 0.5. I checked the specs of the media filters including the Honeywell F100, F200, and aprilaire 2200 and all have PD of close to 0.2 at 1400-1600CFM.....which would imediately take me over the max SP even if all supply and return ducts were disconnected.....

    However, I am not one to walk away from a challenge .....(my wife calls this new HVAC system my obsession and wishes we stuck with the old one) I tell her the old one may have had high static also we just did not know about it.

    Anyway, I will have installed a very large return drop (from current 24x10 to new 24x20). I have been looking inside a lot of the new model homes lately and I have never seen one larger than 24x14.

    After that, I will have only the large 8" run to the master bedroom enlarged all the way to the register as this should increase comfort in that room.

    At that point, I'll live with what I have and go ahead and purchase the 10 year labor warranty (I was given 6 months to make up my mind so I did not rush it).

    Key1

  5. #18
    Join Date
    Jun 2004
    Location
    4H: Hot, Humid Houston H.O.
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    3,304
    Key1, I am a homeowner with Trane equipment. I wonder how much was saved by not going with the variable speed furnace. I replaced old Consolidated furnaces with Trane's 2-stage and variable speed, the deciding factor was no fan tables available (airflow vs. static pressure) and that annoying label on the equipment saying never operate above 0.5 ESP. My ESP had already been measured at 0.7, but the new air handler is rated up to 0.9. You show a degree of fanaticism which I admire.

    My original return was a bit restrictive and measured 0.45 inch vacuum using some medium quality pleated filters. Essentially added a whole lot of capacity via 2 additional returns and got that down to about 0.2. Still using pleated filters but there are two 20*30*1 ones for a 3-1/2 ton system, that makes for low airspeed at the filter face and therefore pretty low pressure drop.

    It is my understanding that Trane specs the same exact coil for 3, 4, and 5-ton systems. Maybe not all the time but sometimes. So your system would be pretty normal to use a 5-ton coil but I marvel that the pressure drop over your coil is supposed to be 0.37. Do I understand correctly this is calculated and not measured? My system has transitions before and after the coil and that makes room for pressure takeoff points so I could easily measure the pressure drop over the coil itself. The hot attic dissuades me from being too curious about that exact measurement though, that and the fact my total supply side static is about 0.35 or less (it varies greatly with airflow).


    Best of luck -- Pstu

  6. #19
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    Jan 2004
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    Lancaster PA
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    pstu

    Take a static reading with your blower at 1400 CFM, and 1600 CFM.
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  7. #20
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    Jun 2004
    Location
    4H: Hot, Humid Houston H.O.
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    Beenthere, is the message to say ESP varies with airflow? I totally agree if that is what you are saying. My system is set up for 350 cfm/ton, plus about 20% additional slowdown when the humidistat is above its setpoint. So I have watched ESP move between about 0.40 and 0.55 under those two conditions.

    There is a simple equation that fairly accurately relates static pressure as a function of airflow, is there not?

    Best wishes -- Pstu

  8. #21
    Join Date
    Aug 2002
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    Office and warehouse in both Crystal River & New Port Richey ,FL
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    Quote Originally Posted by key1cc View Post
    More pics

    I'd remove the supply plenum and return drop ,and start over with better fitting ,turning vanes ,etc..

  9. #22
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    Apr 2008
    Location
    Princeton, NJ
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    Quote Originally Posted by dash View Post
    I'd remove the supply plenum and return drop ,and start over with better fitting ,turning vanes ,etc..
    If I turn the unit horizontal (plenty of room) I would have much more room for a larger plenum after the coil, better filter intake options, and better/multiple return options........However I'm not that big of a fanatic .....yet

    Key1

  10. #23
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    Apr 2008
    Location
    Princeton, NJ
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    Quote Originally Posted by pstu View Post
    Key1, I am a homeowner with Trane equipment. I wonder how much was saved by not going with the variable speed furnace. I replaced old Consolidated furnaces with Trane's 2-stage and variable speed, the deciding factor was no fan tables available (airflow vs. static pressure) and that annoying label on the equipment saying never operate above 0.5 ESP. My ESP had already been measured at 0.7, but the new air handler is rated up to 0.9. You show a degree of fanaticism which I admire.

    Best of luck -- Pstu
    PSTU,
    I took the liberty to read through a few of the threads you started. I now understand why you admire my fanaticism on this subject (like-kind).

    Your system is pushing 1200 CFM on its current setting and mine is pushing 1400. To Beenthere's point, It would be interesting to know what your SP is at 1400 CFM.

    My main question for you is that you have a VS Trane blower as I do and you indicated that it is rated up to 0.9 SP. Does your nameplate state that or does it state 0.5 max like mine? And do you get your rating range numbers of 0.1 to 0.9 from the Service facts document that came with the equipment? What size Furnace (in btu) do you have again?
    Key1

  11. #24
    Join Date
    Apr 2008
    Location
    Princeton, NJ
    Posts
    581
    .....My duct pro is taking a little long to get my new 24x20 radius return drop (RD) so I called a sheetmetal shop closest to my house just to get an estimate on availabilty. It turns out the closest place that can fabricate the RD is the same place that installed my system. I put in a request with my measurments to the sheetmetal guy at that place through the phone....he said no problem I can make this in an hour or two...I or my boss will call you back with a price....15 minutes later the owner called me and asked are my measurements correct.....he said he had never heard of such a thing as a gigantic 24 x20 return drop...He said that thing will move 3500 CFM of air...he said what size system do you have...I told him XV95-100k btu/XL15i-4-ton....he said we usually put in a 24x10 for that....that is all you need because it will move 1600 CFM.....I replied I know, your guys installed it.... and I have high static pressure sitting at ~1....It got very quiet for a moment, then he asked what is your name again....I told him and he pulled my file and said he will call me back tomorow because he wants to talk to his guys first......the plot thickens...

    Key1

  12. #25
    Quote Originally Posted by key1cc View Post
    I told him XV95-100k btu/XL15i-4-ton....he said we usually put in a 24x10 for that
    Interesting. Another "rule of thumb?" lol. That would make sense as to why I was given 24x8 returns on 3 ton systems....

  13. #26
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    Aug 2002
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    Office and warehouse in both Crystal River & New Port Richey ,FL
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    Quote Originally Posted by key1cc View Post
    If I turn the unit horizontal (plenty of room) I would have much more room for a larger plenum after the coil, better filter intake options, and better/multiple return options........However I'm not that big of a fanatic .....yet

    Key1
    Horizontial,like this?

    http://www.hvac-talk.com/vbb/showthread.php?t=156408

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