Page 1 of 2 12 LastLast
Results 1 to 13 of 20
  1. #1
    Join Date
    Jan 2008
    Posts
    196

    Sizing Frigidaire HP...

    I,m going with a Frigidaire 4 ton VS air-handler and either a 3.5 or 4 ton HP. The tech was telling me that he needs district aproval for the warranty if he is to install a different rated HP than the air-handler. Apparently a half ton smaller on the HP is as far a spread as they will go on the rating.

    The 2000 sq.ft. home has a duct system designed for 1600cfm (previously installed). The load calcs for the structure dictate a 2.5-3 ton HP. Though Frigidaire will not warranty such a spead in rating between the HP and air-handler.

    My concern is dehumidification, I am in a marine environment.

    Does this scenario sound normal?

    Any insight on a stat?

  2. #2
    Join Date
    May 2006
    Location
    Philadelphia, PA
    Posts
    1,391
    Get a matched 3 ton system with V/S air handler. If the dehumid profile of the air handler cannot keep your building humidity at the desired level a stand alone dehumidifier would be your best option. A 2 stage system might also help some with dehumidification (and noticeably increase comfort) since there will be longer run times in low stage.

    honeywell Vision Pro IAQ I think is the best stat out there.
    Climate Control Solutions for your Home or Office

    Serving Northeast Philadelphia and Surrounding Areas

  3. #3
    Join Date
    Jan 2008
    Posts
    196
    As I have no experience to base this on, would going with a smaller (less than 4 ton) air handler than would meet the 1600 cfm supply design, affect the comfortability of the heat?

  4. #4
    Join Date
    May 2006
    Location
    Philadelphia, PA
    Posts
    1,391
    Your load calcs determined 3 ton HP was needed. Why the need for 1600 cfm?
    Climate Control Solutions for your Home or Office

    Serving Northeast Philadelphia and Surrounding Areas

  5. #5
    Join Date
    Jan 2008
    Posts
    196
    To keep velocity acceptable in the ducts for good circulation?

  6. #6
    Join Date
    May 2006
    Location
    Philadelphia, PA
    Posts
    1,391
    Quote Originally Posted by mlo1 View Post
    To keep velocity acceptable in the ducts for good circulation?
    Obviously I cannot see your duct system. I'm going to venture a guess that it being a little oversized is not going to be a problem. Volume dampers at the takeoffs and adjustments to the registers should compensate.
    Climate Control Solutions for your Home or Office

    Serving Northeast Philadelphia and Surrounding Areas

  7. #7
    Join Date
    Jan 2008
    Posts
    196
    Thank you comfortdoc!

    I will know more tomorrow after the tech consults with the district manager. We just had a brief conversation over possibilities.

    We had not discussed going to a 2 stage HP yet with the VS air-handler.

  8. #8
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
    6,286
    Quote Originally Posted by comfortdoc View Post
    Get a matched 3 ton system with V/S air handler.

    A 2 stage system might also help some with dehumidification
    (and noticeably increase comfort)
    since there will be longer run times in low stage.
    Two-stage unit will not have much impact on dehumification in Seattle
    where heating is likely >> 85% of the annual HVAC energy use.

    Two-stage unit is desired/necessary
    if one is going to oversize the HP
    per the OP statements.
    Designer Dan
    It's Not Rocket Science, But It is SCIENCE with "Some Art". ___ ___ K EEP I T S IMPLE & S INCERE

    Define the Building Envelope and Perform a Detailed Load Calc: It's ALL About Windows and Make-up Air Requirements. Know Your Equipment Capabilities

  9. #9
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,038
    A 3 ton unit will have longer run times, so it will do better at dehumidifing.
    Good chance your duct was sized using .1 FR. So there is a good chance its not really sized for 1600 CFM.
    Have the tech check the Static presure of the existing air handler. From there he can tell if there will be problems going to a 3 ton unit.
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

  10. #10
    Join Date
    Jan 2008
    Posts
    196
    Quote Originally Posted by beenthere View Post
    A 3 ton unit will have longer run times, so it will do better at dehumidifing.
    Good chance your duct was sized using .1 FR. So there is a good chance its not really sized for 1600 CFM.
    Have the tech check the Static presure of the existing air handler. From there he can tell if there will be problems going to a 3 ton unit.
    A 3 ton air handler, then have them check static before choosing the HP?

    Thanks gentlemen.

  11. #11
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,038
    Have them check your current static.
    Then you will know from there what size Hp your duct system can handle. Doubtful its carring 1600CFM.

    If the load calc came up with 3 ton, strange that someone would want to go up 1 ton in size.
    If you go with a 2 stage, the oversizing isn't as bad, but you need to be able to move the air.
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

  12. #12
    Join Date
    Jan 2008
    Posts
    196
    My personal concern was that the HP type of heat coupled with a low velocity out of the duct system (via a smaller air-handler than the ducts designed cfm) would makes thing uncomfortably cool. Sounds like I am off base thinking like that.

    There is no equipment installed yet. How does one check static with-out having a air-handler hooked-up?

  13. #13
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,038
    You can't.

    But, if a room by room load calc was done. Then manual D, can be used to know what size the duct should be.

    Some people consider 12 x 18 duct as 4 ton duct. Some 12 x 24.
    Both those sizes would still have a velocity of 800+ FPM.
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

Page 1 of 2 12 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