Page 3 of 3 FirstFirst 123
Results 27 to 30 of 30
  1. #27
    Join Date
    Jul 2008
    Posts
    20
    Quote Originally Posted by jimj View Post
    Is 70* the temp you want to maintain? If it's 72* thats a Hank R. do not do.
    I would cut a hole in my sheetrock and check R values before I would assume no insulation in my calcs.
    What does Manual J use for your area? don't add degrees to YOUR design temp!
    Go here and read Proctor info,http://www.proctoreng.com/articles/better.html
    Hank R.?, what's that mean?

    Based on my current system I am comfortable at 72 degrees so that would be the temp that I want to maintain. Again my current system could be oversized and with a hopefully correctly sized system I may not need to keep the stat at 72 degrees. More questions for the contractor I guess, thanks for your input.

  2. #28
    Join Date
    May 2007
    Location
    Naples, Fl
    Posts
    889

  3. #29
    Join Date
    Dec 2002
    Location
    Arizona
    Posts
    4,421
    Hank Rutkowski, he is the author of Manual J7 and J8.

    Your design temp at 1% is (88* DB/72 WB*). At 0.4 its (91* DB/73* B).What the means is the summer design temp will be exceeded only 1% of your cooling hours.

    Using 70* indoor and 95* outdoor would be considered oversizing to me!

    Here a couple of Manual J Don'ts
    Do not design for record breaking heat.
    Do not add a safety factor.
    Do not design for abnormally low or high indoor temps or humidity.
    Do not reduce known ceiling, wall or floor R-values "just to be safe".
    Do not apply "safety factors" during any stage of the load calc process.

    Here are a couple of does.
    Use the outdoor design conditions recommended by Table 1A of manual J.
    Use indoor conditions that are compatible with the comfort chart.
    Verify all construction details prior to calculating loads.

    These are a few of the reasons loads very from company to company. Manual J has a safety factor built into it already, Don't follow there guide lines and you mite as well use the square footage method.

  4. #30
    Join Date
    Jul 2008
    Posts
    20
    Quote Originally Posted by jimj View Post
    Hank Rutkowski, he is the author of Manual J7 and J8.

    Your design temp at 1% is (88* DB/72 WB*). At 0.4 its (91* DB/73* B).What the means is the summer design temp will be exceeded only 1% of your cooling hours.

    Using 70* indoor and 95* outdoor would be considered oversizing to me!

    Here a couple of Manual J Don'ts
    Do not design for record breaking heat.
    Do not add a safety factor.
    Do not design for abnormally low or high indoor temps or humidity.
    Do not reduce known ceiling, wall or floor R-values "just to be safe".
    Do not apply "safety factors" during any stage of the load calc process.

    Here are a couple of does.
    Use the outdoor design conditions recommended by Table 1A of manual J.
    Use indoor conditions that are compatible with the comfort chart.
    Verify all construction details prior to calculating loads.

    These are a few of the reasons loads very from company to company. Manual J has a safety factor built into it already, Don't follow there guide lines and you mite as well use the square footage method.
    Thanks for these suggestions, really helpful for when I review the load calc with the contractor. If I'm not being a pain I'm a little unsure of what this means:

    Your design temp at 1% is (88* DB/72 WB*). At 0.4 its (91* DB/73* B).What the means is the summer design temp will be exceeded only 1% of your cooling hours.
    What is the difference between using 88* DB/72 WB* or 91* DB/73* WB).Never mind this question I understand what it means now.

Page 3 of 3 FirstFirst 123

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