Page 1 of 4 1234 LastLast
Results 1 to 13 of 40
  1. #1
    Join Date
    Sep 2012
    Location
    Orlando, FL
    Posts
    37

    Manual J/Blower Door/Duct Testing

    Time to replace my aging (18 years) AC systems in our 2 story house. Down stairs unit has stopped cooling completely and upstairs unit cannot keep up with demand, both are 2 1/2 ton Carrier units. I have received a couple of quotes and a Manual J was performed by one of the contracters, the other just eye balled everything and made recommendations.

    My question is after reading so many posts on here, is it necessary to do a Blower Door test and Duct blaster in order to properly size the new units? None of the contactors I called, including some of the larger businesses here in Orlando, offer this service or think its necessary for proper sizing.

  2. #2
    Join Date
    Oct 2010
    Location
    Anderson, South Carolina, United States
    Posts
    7,675
    Without a blower door test you have to guess on the infiltration rate of the house which is a major factor in sizing correctly, with a blower door test you know exactly what the infiltration rate is and know where you can improve to reduce the infiltration this allowing smaller size equipment. Duct leakage in a typical home is 25-40% of capacity lost, you don't necessarily need a duct blaster, the blower door can tell you if the duct system is leaky but a duct blaster test is good to do. A leaky duct system would be like going to the gas station and filling up your car at 3.50$+ a gallon and having a bunch of holes in your gas tank, not a very smart move.

  3. #3
    Join Date
    May 2012
    Location
    San Diego, CA
    Posts
    352
    You probably have to get a HERS (Home Energy Rater) aka third party to do the testing. Not bad though, they aren't usually contractors so no conflict of interest and trying to sell you stuff.
    You can call me Sam

    It should be a crime to be a mechanical engineer in San Diego
    Summer Design Temperature: 83 F Dry Bulb ~ 69 F Wet Bulb (California Climate Zone 7)

  4. #4
    Join Date
    Mar 2011
    Location
    Galveston Texas
    Posts
    530
    here a duct blaster test is required to pass inspection. it is done by a 3rd party to avoid conflict of interest.

  5. #5
    Join Date
    Sep 2012
    Location
    Orlando, FL
    Posts
    37
    Thanks for the responses, jtrammel your analogy makes sense. Now its just a matter of finding someone who does these tests.

    The only requirement, at least here, is that the contractor perform a Manual J. Interestingly enough, the contractor who actually did the J recommended downsizing the upstairs unit to a 2 ton and the guy who eye balled everything recommended upgrading to a 3 ton and adding another return.

  6. #6
    Join Date
    Oct 2010
    Location
    Anderson, South Carolina, United States
    Posts
    7,675
    www.bpi.org or www.comfortinstitute.org contractor locator on these sites

  7. #7
    Join Date
    Oct 2010
    Location
    Anderson, South Carolina, United States
    Posts
    7,675
    Florida power and electric will test, not sure how much testing they do but they do test

  8. #8
    Join Date
    May 2004
    Location
    south louisiana
    Posts
    3,291
    resnet.org is another source for an energy rater. we aren't called auditors.

    blower door using subtraction method can measure duct leakage.
    blower door measures house leakage also. different steps..same equipment.

    resnet raters use duct blaster or pressure pans to test
    ductwork you would have to request if you chose to test differently.

    usually houses are depressurized to get leakage amount.
    if you pressurize you can feel the air leaking out of ductwork
    so you know exactly where to seal.


    sealing house leakage means less of the great outdoors to heat and cool
    sealing ducts means all of air you pay to condition comes into the space
    where you live. return should also be tested.

    sealing both leakage areas (house & duct) can change how many
    tons of hvac is required.
    manual J would have to reflect reduced infiltration numbers.


    best of luck.
    The cure of the part should not be attempted without the cure of the whole. ~Plato

  9. #9
    Join Date
    Sep 2012
    Location
    Orlando, FL
    Posts
    37
    Quote Originally Posted by jtrammel View Post
    www.bpi.org or www.comfortinstitute.org contractor locator on these sites
    Thanks, only one contractor in the area listed on these sites, will call and see if they offer these services as part of a quote or installing new systems.

    Quote Originally Posted by jtrammel View Post
    Florida power and electric will test, not sure how much testing they do but they do test
    Not a FPL customer, we are OUC here.

    Quote Originally Posted by energy_rater_La View Post
    resnet.org is another source for an energy rater.
    Sure about this website? What comes up is some sort of Business referral network.

  10. #10
    Join Date
    May 2004
    Location
    south louisiana
    Posts
    3,291
    The cure of the part should not be attempted without the cure of the whole. ~Plato

  11. #11
    Join Date
    Oct 2010
    Location
    Anderson, South Carolina, United States
    Posts
    7,675
    Quote Originally Posted by scooterfj62 View Post
    Thanks, only one contractor in the area listed on these sites, will call and see if they offer these services as part of a quote or installing new systems.



    Not a FPL customer, we are OUC here.



    Sure about this website? What comes up is some sort of Business referral network.
    Most will charge a fee for the testing because it is rather involved, takes time and the testing equipment is very expensive some will discount the testing fee off the invoice if awarded the job. Even if it costs a couple hundred bucks its well worth it when making an hvac investment. You will be more comfortable, save more on utilities and improve your indoor air quality by implementing some or all of the solutions to the problems that are found by the testing, lots of what you will find can be done by the homeowner with minimal skill and little investment (a few tubes of caulk, weather stripping, receptacle gaskets etc.) others may need to be done by hvac pros, insulators, electricians etc.

  12. #12
    Join Date
    May 2004
    Location
    south louisiana
    Posts
    3,291
    how much are you willing/able to diy?
    The cure of the part should not be attempted without the cure of the whole. ~Plato

  13. #13
    Join Date
    Jun 2005
    Location
    SW Wisconsin
    Posts
    5,025
    Quote Originally Posted by jtrammel View Post
    Most will charge a fee for the testing because it is rather involved, takes time and the testing equipment is very expensive some will discount the testing fee off the invoice if awarded the job.

    Even if it costs a couple hundred bucks its well worth it when making an hvac investment.

    You will be more comfortable, save more on utilities and improve your indoor air quality by implementing some or all of the solutions to the problems that are found by the testing, lots of what you will find can be done by the homeowner with minimal skill and little investment (a few tubes of caulk, weather stripping, receptacle gaskets etc.) others may need to be done by hvac pros, insulators, electricians etc.
    Right-On, JT

Page 1 of 4 1234 LastLast

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Comfortech Show Promo Image

Related Forums

Plumbing Talks | Contractor Magazine
Forums | Electrical Construction & Maintenance (EC&M) Magazine
Comfortech365 Virtual Event