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  1. #1
    Join Date
    Mar 2009
    Location
    Central Ky.
    Posts
    47

    Talking As Happy As I Can Be....(Almost)

    Hey Guys,
    I happened by this site about 2 wks. after a new install in my home. After reading this site for the past 2 months I feel my guy did me right. It appears properly sized for 1250 sq. ft. Goodman 2.5 Ton GSH130301 & ARUF303016 AH with HKR-15C Strips. (I know, a dinosaur by your standards, but a quantum leap from 15 yrs. of ceiling cable.) This unit has lowered my winter energy costs by at least 35-40% Woo-Hoo. I couldn't believe it. The reason I'm posting is about fan speed, Based on summer cooling (400 cfm per ton) I feel the ARUF3030 needs to run medium speed 1330/1239/980 @ .3 Static, but the specs. clearly states it must be on high with 15k strips. I have around a 60 degree Temp Rise on Emerg. Heat. I was curious if running on Med. speed if there was a danger with overheating, SA would probably 140+ in Aux. With that said smaller Air Handlers ARUF182416 have the same strips pulling the same amps with 1025/790/570 cfm. I know the strips aren't needed during cooling but I'd like to just leave it on Medium Speed year round cause you can't even hear it run. If it matters I have an 8"x14" trunk running left, right & up to 2nd Story Master Bdrm/Bath with a total of 10 6" supplies. Any Response Welcomed

  2. #2
    Join Date
    Jan 2008
    Location
    In the work truck
    Posts
    3,065
    Quote Originally Posted by MrDodge View Post
    Hey Guys,
    I happened by this site about 2 wks. after a new install in my home. After reading this site for the past 2 months I feel my guy did me right. It appears properly sized for 1250 sq. ft. Goodman 2.5 Ton GSH130301 & ARUF303016 AH with HKR-15C Strips. (I know, a dinosaur by your standards, but a quantum leap from 15 yrs. of ceiling cable.) This unit has lowered my winter energy costs by at least 35-40% Woo-Hoo. I couldn't believe it. The reason I'm posting is about fan speed, Based on summer cooling (400 cfm per ton) I feel the ARUF3030 needs to run medium speed 1330/1239/980 @ .3 Static, but the specs. clearly states it must be on high with 15k strips. I have around a 60 degree Temp Rise on Emerg. Heat. I was curious if running on Med. speed if there was a danger with overheating, SA would probably 140+ in Aux. With that said smaller Air Handlers ARUF182416 have the same strips pulling the same amps with 1025/790/570 cfm. I know the strips aren't needed during cooling but I'd like to just leave it on Medium Speed year round cause you can't even hear it run. If it matters I have an 8"x14" trunk running left, right & up to 2nd Story Master Bdrm/Bath with a total of 10 6" supplies. Any Response Welcomed
    it all depends on your static in YOUR system.. that needs to be calculated by the professional that installed the system. Also when your system runs it does not have to be at the same speed for both.. Thats all the info i can give w/o over stepping my boundaries. Call your contractor that you are happy with and let him tell you how its running and if it needs changes or what it needs... What sparked this interest? Why do you think it wrong?
    Gotta have the right tool for the job!

    Where is all the stuff MADE IN THE USA?

    "Thats what we do Troy. Incredible, Invisible, Imbelivable things. We are an Unseen, Unknown, Unvincible fraternity of craftsman.."

  3. #3
    Join Date
    Jan 2004
    Location
    PA
    Posts
    68,758
    If you have a 60F temp rise on 15KW of strip heat.
    Your only moving 790CFM.

    How did you figure you were at a .3" static(ESP).
    Last edited by beenthere; 03-23-2009 at 10:10 PM. Reason: Fixed typo
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  4. #4
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    34,590
    Ya gots a typo there been, had me cornfused. That's 60 rise!!!

    And that is a pretty healthy rise! Many brands don't allow 15kw in a 2 ton because running only 800 CFM is too little. Goodman didn't used to on the ARUF24 but I see it does now on the 1824.

    But if you are getting 60 rise and 790 CFM as been has calculated, you must have considerably higher static and risk cycling on limit. Having the pump on and 3 elements will make it worse. 15kw for 1250 sq ft seems high unless you are in a very cold area. How about turning off the smaller breaker and trying only 10kw?

    You have 1 14x8 supply? Or 3? Are the 10 6" supplies metal or flex?

  5. #5
    Join Date
    Jan 2004
    Location
    PA
    Posts
    68,758
    Quote Originally Posted by BaldLoonie View Post
    Ya gots a typo there been, had me cornfused. That's 60 rise!!!

    LOL... Fixed it.
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  6. #6
    Join Date
    Mar 2009
    Location
    Central Ky.
    Posts
    47

    Talking

    Guys Thanx 4 Your Replies,
    Pas,
    I'm not sure it is wrong, I've probably just been doin to much reading & it isn't even AC weather yet. By other posts Ive read 1350 cfm may be to much flow for 2.5 ton thats the main thing that sparked my interest.
    BT,
    thats the stats for airflow posted by the mfg.
    BL,
    I have three, each are about 12' in length running left,right, & up from supply plenum with 8- 6" & 2-7" Flex Ducts. Turning off the 2nd 30 AMP Circuit seems to be a viable option. I was uncertain if that was possible.
    4 All Who Replied,
    I spoke with my installer & he said just leave it on high I shouldn't have any problem which may be true. I was just thinking ahead to Mid August with short cycles, and 70% RH. I'm a worry-wart right?
    Last edited by MrDodge; 03-23-2009 at 11:25 PM.

  7. #7
    Join Date
    Dec 2007
    Location
    Ohio
    Posts
    2,876
    Quote Originally Posted by beenthere View Post
    If you have a 60F temp rise on 15KW of strip heat.
    Your only moving 790CFM.
    This could be the dumbest question ever.....but what is the formula for figuring that?? Not busting balls at all, just extremely curious!!
    I need a new signature.....

  8. #8
    Join Date
    Jan 2004
    Location
    PA
    Posts
    68,758
    In order to use the mfg fan data. You must measure the actual static(TESP) that the blower is working against.

    Then you would go to that static pessure column, and read how many CFM its moving, for the fan speed you have it running at, while your getting that reading.

    Your not moving any of the CFM's you posted.

    If after you turn off the 30 amp breaker, you get around a 40F rise, your moving roughly 790CFM, at what ever speed the blower is currently running at.
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  9. #9
    Join Date
    Jan 2004
    Location
    PA
    Posts
    68,758
    Quote Originally Posted by I_bend_metal View Post
    This could be the dumbest question ever.....but what is the formula for figuring that?? Not busting balls at all, just extremely curious!!

    BTU output/(temp rise*1.08)=CFM
    51195/(60*1.08=64.8)=790

    34130/(40*1.08)=790
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  10. #10
    Join Date
    Jul 2006
    Location
    NW burbs of Detroit
    Posts
    6,058
    Quote Originally Posted by I_bend_metal View Post
    This could be the dumbest question ever.....but what is the formula for figuring that?? Not busting balls at all, just extremely curious!!
    Fiddle with the equation to calculate CFM on an electric furnace and i think you'll get it.

  11. #11
    Join Date
    Jan 2004
    Location
    PA
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    68,758
    Quote Originally Posted by I_bend_metal View Post
    This could be the dumbest question ever.....but what is the formula for figuring that??

    You got mail.
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  12. #12
    Join Date
    Mar 2009
    Location
    Central Ky.
    Posts
    47

    Updated Readings

    Thanx Everyone,
    I've taken your advice & am running on 10k strips (turned off 30 amp Br.) & have opened all registers ( Mrs. had 2 bdrms. closed ) from original post. I have a 34-35 deg. temp rise in emerg. heat at supply plenum which is in line with the documentation I have. I was curious about capacity, with 26,800 btu cap. in heating would that mean approx. 26 deg. rise in a perfect world? I checked today & I have a 29 degree rise in heat mode @ 56 deg. ambient. Does this seem in the realm of ok?

  13. #13
    Join Date
    Jan 2009
    Location
    Keokuk, IA
    Posts
    5,520
    Quote Originally Posted by MrDodge View Post
    I checked today & I have a 29 degree rise in heat mode @ 56 deg. ambient. Does this seem in the realm of ok?
    If your flowing 1000 CFM, (400 CFM/ ton) you would be producing 31,300 BTU's. So if you think your capacity actually is 26,800 at 56F (is that from the product data sheets?) then you're flowing about 850 CFM or clsoe to 350CFM/ton which is nice for comfort, and will give good latent capacity in summer without freezing the coil.

    However, if this was measured with a clean air filter, keep in mind that if the filter gets dirty, you may have issues. I'm not sure I'd cut it that close with a PSC motor without a air flow switch.

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