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  1. #1
    Join Date
    Jan 2006
    Posts
    4

    Confused

    Background:
    I was in the process of having a humidifier installed on my Heil 5 ton Heat pump when the technician informed me that the supply line on my unit was too small. He indicated that based on his duct calculator, I would require a 18 inch round duct to provide 2000 CFM rather than the 14 inch that was installed. He also said the He indicated that he used a friction ratio of .1 in his calculation. I don't know what the friction ratio means. I called the original installer and he indicated that since the unit was in service for 5 years that it was probably ok. The original installer sent out a new tecnician and he indicated he uses a friction ratio of .5 in his calculations.

    Question:
    I don't know who to beleive or how to get to the bottom of this delima. I called the manufacture and they indicated that I need 2000 CFM but they said that they could not provide duct size information. What is the correct friction ratio and how does it affect the duct size? Any help or suggestions woule be greatly appreciated.

  2. #2
    Got a model number?

    The technician needs to measure the TEST (then by using the fan data) he will know the CFM that the blower is moving.

    BTW, .5 is too high, 14" is too small.

  3. #3
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,765
    Originally posted by jultzya
    Got a model number?

    The technician needs to measure the TEST (then by using the fan data) he will know the CFM that the blower is moving.

    BTW, .5 is too high, 14" is too small.
    I think you mean TESP.

    14" is way too small.
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  4. #4
    Join Date
    Jan 2006
    Posts
    4
    The model number is NFCX6000C1

  5. #5
    Originally posted by beenthere
    I think you mean TESP.
    Yes, I did... you do know that the T and P are so close together! LOL Or, they need to perform the TEST to get the TESP.

  6. #6
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    33,921
    I'm seeing lots of bad info.

    I see 18" round metal pipe as 1400 CFM at .1" static pressure or just under 800 FPM velocity.

    I have 14" flex return on my 2 ton system!

  7. #7
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,765
    I glad someone elses fingers type faster then they should.




    John, wouldn't 18" round metal be 2000 cfm at a .1 FR, and 1125 fpm.

    Not saying thats what should be installed.
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  8. #8
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    33,921
    You're right. Duh, I was looking at the flex duct wheel not the metal wheel Dang, those glasses are getting sooner & sooner

  9. #9
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,765
    LOL...

    I already have to use them to read.
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  10. #10
    Join Date
    Jan 2006
    Posts
    4

    Confused

    Thank you all for this information.
    Even if the supply line was increased from 14" to 18", since it ties into a 14" trunk line I don't see any advantage for increasing the size of the supply line. Incedently the supply line I am speaking about is about 10 feet long. Am I correct in my assumption?

    I have a few more details. I have 2 - 12" return lines leading into the unit. I should have mentioned that before, but I forgot. I also was told that this model, NFCX6000C1 has multiple blower speeds. I don't know if this is true, but if it was set to the lowest output perhaps my setup is ok. Any comments?

    What is TESP and how is it determined? Perhaps if I sounded more knowledgeble, I could get some tests run. My main worry now is that by not doing anything, the compressor will eventually fail.

    Since my home is already 5 years old, I don't see any recourse but to keep it as is since the lower level is finished. Any suggestions or comments are much appreciated. As you can see I really don't know where to turn.


  11. #11
    You would have had this before, but the Image Shack site was experiencing technical difficulties.

    The higher the speed, the greater the airflow.
    Once the TESP is found, you can use the chart to find the actual CFM being delivered.

    FCX60 is a 5-ton unit, 350 CFM (min)/ton would require 1750 CFM. As per the chart, you would need MED (for anything up to .4) or HI (for anything up to .5). Assuming your equipment is being provided 230 volts.



  12. #12
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,765
    Also check and post the model number of your outdoor unit, it could be a 4 ton unit.

    Why the chart julz posted, your tech needs to take the sp at the return at the A/h, and in the supply plenum, add them together, and you'll know how much air the AH is moving, and if it is enough for the outdoor unit.

    Your return sounds alittle small also, for 5 tons.

    Is it noisey when it runs.
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